I'm an amateur electrician thinking of installing an AC unit and was confused about the nameplate specs on the units. Just came across your video after digging across the internet trying to understand this logic breaking piece of electrical code. Wonderfully explained! No one explained that it's because the motor has a shut off to prevent itself from melting. Thank you Ryan
Glad Ryan is doing this. His training is far superior to more "well known" names. Accurate, concise, and well-spoken. Great vid. Learn to love 110.3(B).
Thank you so much for explaining the -WHY- I've known we can do this, but we have just sized the conductor on the breaker size regardless because I didn't understand that the motor itself is providing the overcurrent protection. We have just said the phrase "code is a minimum" and over-sized the conductors on principal. I feel so much more confident in my ability to provide a safe installation to the customer while also being more cost effective.
The manufacturers manual usually spells this out but it wasnt mentioned in the video, voltage drop. Be cognizant that long runs might have excess voltage drop and you need to bump up the wire size to accommodate. It might cost a few more dollars to install bigger wire but the customers compressor may last longer due to being able get up to speed faster vs having brown out conditions with smaller awg wire.
Hi Sir Ryan, thank you very much for the detailed and straight forward lesson, everything is on point and my confusion on "why the a/c have smaller wire ampacity than the circuit breaker's ampere trip rating" clears away! I think the secret there is, not everyone knows that the a/c equipment have an integral protection for an overload current, and most probably, everyone in this field must clearly understand the difference between short circuit, ground-fault and overload currents. I'll take note also the important thing from your video, when reading the a/c nameplate, the indicated Max Circuit Breaker size is NOT meant to protect the Wire feeding the a/c, which will be sized based from the indicated Minimum Circuit Amapcity. I would be watching more videos from your channel, thank you very much again, more power and God bless
I am a new subscriber and have fallen in love with the clear explanation, examples with photos and everything that you make understanding easy. I have been watching your videos for the past three days and like every one of them. So interesting and well explained. Thank you! Thank you!
I love learning from your channels. Learning why AC units and overcurrent protection are sized like their are. I always thought for example using a 14 gauge NM on a 25 amp breaker is a major fire hazard, in case there is a problem with the unit and it draws more than 15 amps, like back in the old days, especially with the Edison base fuses and to a lesser degree, circuit breakers, a 15 amp fuse keeps blowing due to overload caused by the homeowner running high amp devices like heaters, irons, vacuum cleaner, microwave ovens, electric skillets and hair dryers, to name a few. The fuse is replaced. . After a few times, the homeowner stops the trouble by using a 20 or 30 device. Or places a penny or wraps the fuse in aluminum foil. Over the years many homes have been destroyed & lives lost by such action. It's my understanding that part of the reason we went from fuses to breakers in the 1960s, aside from them being more convenient and practical, was because a breaker tends not to be tampered with as readily as a plug or cartridge fuse.
Ryan, thanks for making these videos. It spells out clearly the reasons we are allowed to size conductors and ocpd's the way we are. Great resource for young journeymen and apprentices. I suggest you do separate videos for motors, feeders, and transformer secondarys too.
Hi Ryan Been doing electrical 20 years. Literally wiring a new commercial building this weekend and helper asked to understand how to size air conditioners. Ive always max breaker, then wire based on that breaker This is great information and such great timing to randomly pop up on my Facebook to find your channel New subscriber. Thank you
thanks for the clear presentation and why HVAC//R has the exceptions.Also if people notice on the nameplates it mentions BREAKER (HVACR) these are special breakers for the hvac/r industry. Suppose to be able to pull locked rotor amps for a few seconds so the compressor and fans can get up to speed.
@@RyanJacksonElectrical my new Bosch unit is state-of-the-art and its Installation Manual still refers to an HACR breaker. Wonder how widespread the knowledge of the rating change has gotten in the HVAC industry. Or maybe some of them liked the distinction and want to hold on to it as long as possible.
As an electrician, using mostly, 430 and 440 for my work, I am very familiar with your subject. I used to get a kick out of showing "union" electricians how I could 'legally' put a 18 gauge wire on a 40 amp breaker for certain motor loads, because the overload was in the contactor, the breaker had to sustain the inrush current without tripping, the contactor would trip (very predictable) at a low current, below the breaker rating.
Motor loads allow you to size the wire based on the MCA, but the EGC should be sized based on the installed OCPD rating. The upsize of the EGC to match the breaker size may require you to size the phase conductors to a size larger that includes the code required EGC. Its a good thing to double, triple check before ordering and installing spool full of wires so the AHJ doesn't makes you rip them out.
Very good presentation. You have clearly demonstrated why ocpd is not sized according to the partial or full ampacity of the cable. Do you have any insights on how or what determines the max ocp values in these cases?
Thanks for your videos, watching and learning. I think you overlooked an important factor in this video. Motor internal overloads, compressors in particular, are usually thermal and auto resettable. Repeated overload conditions can cause conductor and motor failure. I would not use 14 gage wire to supply a 20A motor and air conditioner. Because the condutor in your scenario is undersized then it would overload and fail before the breaker trips. If the wire was 12 gage minimum the overload failure occur at the compressor terminals if if the 20A breaker doesn't trip. Speaking from experience, could you clarify?
Hello, Whatever does the NEC say about the disconnect box pertaining to outdoor ac condenser such as : distance from condenser( I have seen disconnect boxes 8 ft above a condenser, where a ladder is needed- that isn't safe) , within visible distance of the condenser(the box being around the corner of a building) being behind the condenser( in such a way where you can't stand in front of it, not exactly safe). A disconnect box being below snow line or to close to the ground. Is there a reference in the NEC for these items pertaining to AC? I have seen in homes built even 10-15 years ago where Romex is run from panel to outdoor disconnect box with no rubber conduit sleeve, and in addition Romex from box to condenser. We always change the Romex from box to condenser to a wire and conduit protector. What does the NEC say about that, do we know when that code was changed not allowing Romex to be run outdoors to ac's and disconnect boxes without a conduit sleeve? Also for electrical switches and outlets mounted to gas furnaces , requirements etc. Thank you very much for putting out this video if was informative and I have subbed.
Same would apply for large commercial air handlers with min circuit amps and max over current name plate markings? No hermetically sealed compressor motor. Only large fan motors that have overload protection. Also would the wiring compartment on a disconnect for an air handler stating ues 75° c or greater conductors imply that the terminals are 75°?
Great video training. How to know when choosing 60F or 75F? On the last example I have min amp 29, max fuse 50, max ckt bkr 50 In case that the existing breaker is 60 amps, can I leave the 60 amps breaker with a fused disconnect of 50 amps, and a 10awg?
@Ryan Jackson When the manufacturer provides their MCA, they have done all the calculations. The MCA tells you what wire size to use. Does that mean you do NOT have to correct for temperature and adjust for bundling? Thanks for your many excellent NEC videos.
The manufacturer provides the minimum ampacity of conductors. The definition of ampacity is the amount of current the wire can carry AFTER temperature adjustments and ampacity correction. So yes, you still need to factor that in. The nameplate won't state "use 12 AWG," it will state an ampacity.
Ryan, I completely understand and now I understand that the use of smaller gauge wire for condensers is allowed under 440. I also fully understand that wire sizing conductors for condensers is different than that of 310.16. My question is though the NEC code is the minimum requirement to be safe from fire and code violations. Can we run larger gauge wire using 310.16 as the base for wire sizing and over-current protection for a condenser install and simply use the correct amperage breaker for the conductor as per normal practices and still be code compliant? This is my only confusion! I get that an “MCA of 28.4A” with a max breaker size of 50A on a 10 gauge conductor using a 50A breaker is good with 440. That said would I be in code violation of 440 if I use 8 gauge wire following the 80% method which would be 32A using a 40A max breaker size?
The conductor has to be at least as large as the MCA. If you satisfy that it can be as large as you'd like. The breaker must be between the min and max overcurrent device rating.
@@RyanJacksonElectrical thanks Ryan, my a/c guy is installing a system for me and I’m just making sure the way I’m doing it will satisfy 440 while using 310.16 and the condenser tag for breaker size to do the work. Neither myself, the customer nor the city inspector are comfortable with using 10awg wire on a 40A circuit for this job as per NEC 440. We’re running 6/2 x 50’ for the wire and using a 40A breaker according to the max breaker size on the condenser tag. Also 18/5 x 50’ for the thermostat, air handler/furnace & condenser then a 20A breaker with 12/2 x 50’ wire for the air handler/furnace.
I’m assuming the 50 amp circuit breaker on 10 wire is only from the AC unit to the disconnect. A 30 amp circuit breaker would be used at the service panel for the branch circuit.
I had trouble with my first central air conditioner tripping the 30 amp breaker. Never pulled more than 17 amps. So I upped it to a 40 amp. Found out that my wife was what I called machine gunning the old mercury filled thetmostat. Would turn it on then off then on several times. Installed a 5 minute on delay timer then went back to a 30 amp breaker. Now have a high efficiency unit that runs on a 20 amp breaker. ( 2.5 tons ).
You nailed it. Every off cycle the Freon pressures begin to equalize in the system if the compressor tries to start before they equalize it tries to start under a load often exceeding the breaker amperage or the motor can't overcome the load to start and heats the windings which trips the thermal overload device embedded in the windings. All new electronic thermostats have a built in time delay so you can't short cycle the thermostat.
Great video, thanks! But I'm confused about disconnects and if they need to be fused or not? It seems it is not uncommon to use Both a breaker and a fused disconnect. Why would that be needed? And if so, would the fuse and breaker both be sized the same (per the HVAC label)?
@@RyanJacksonElectrical after some research I have learned a bit more on this. Though most condensers will say fuse/breaker max rating some might only be listed for a fuse and only say fuse max. In that case a fuse in the circuit is required and can be anywhere, so a fused disconnect becomes one easy way to meet that requirement. But a breaker in your breaker panel is also needed. Also, I checked my own home units and found fused disconnects were added when the units were replaced. Though I don’t know the rating of the old units we had I see the correct sized fuses are in the disconnects were the breakers are both larger. 35 fuse vs 50 breaker. And for the smaller unit, 20 amp fuse vs 25 breaker. So instead of downsizing the breakers they just buy the needed protection in with the correct sized fuses. So fused disconnects become an option to downsize the protection when needed for a unit replacement leaving the higher rated breaker for a possible future use of the circuit.
What if damaged or loose wires causes an additional load from arcing or current from a lightly conductive material that causes slight continuity between phases or grounding/grounded to ungrounded. Like say the material across the conductors creates 5 ohms of resistance across 120v. You will start pulling 24 amps. Or If a handy man comes along with out a permit and adds a condensate pump and heat tape on the circuit. The wires ampacity couldn't safely handle the over current before the breaker opens right? I can understand the max breaker size to handle the in rush current or a fail safe if the units over current protection fails. I understand the code implies that you if you are working with electric you will be knowledable of and following all codes accordingly. But I still believe it would be slightly safer to also size the wire to the breaker for freak scenarios like I mentioned.
@@erikolsen3611 If we were to wire everything based off of what if scenarios like you are describing then where does it end? I understand what you are saying but you have to stop somewhere
Ryan, I understand the concept completely. Been in the trade 40 years and you have explained this extremely well. I have encountered many a/c units wired with smaller wire. The reason leading to these encounters were the wires buzzing in the conduit upon unit startup. I work in a metallic code area around Chicago, no NM cable allowed by AHJ's, system must be pullable. This problem is always solved by upsizing the wire. I now always upsize because of my experiences irregardless of the circuit length. Maybe its overkill, but if the wires are rattling in the pipe, isn't this an indicator that the motor is potentially being power starved at start-up? Even if it isn't, the customer shouldn't have to here that irritating noise each time unit starts. "Code Plus" thinking can't be bad, correct?
I am assuming the rattling is caused by the strong EM field being peak on start up due to the approximate Locked Rotor condition present, causing the inrush current all induction motors have on start up, to be greater than normal. Increasing the wire size would just lower the extra load placed on the circuit by resistance, therefore reducing the start up inrush current load placed on the circuit. Correct me if im wrong.
@@MR-nl8xr Ohm's law says that if the load resistance goes down, the load current goes up. Since the load is a motor and the voltage is AC, there is an AC inductive reactance and some back EMF that would run counter to that, but basically the inrush current would tend to rise in stead of falling when you increase the conductor size, as the wire resistance goes down in both conductors. Correct me if I am wrong.
@@billcowhig5739 Ohms law also says that the circuit (load) resistance is equal to the current that will be used divided by the voltage. Current will not just go up because resistance went down if the load does not require it. There is a lot more to consider here since such planetary size of things are happening here all in the inversilly small time size of a second with AC. My reply was a quick attempt at trying to answer the OP's question, which looking back, probably confused him more. No such thing as easy or quick answer with Electricity.
@@MR-nl8xr No, nothing is easy or quick with Electricity in general. Ohm's Law can be expressed mathematically as E = I x R (Voltage across a load = Current passing through the load times the Resistance of the load). I believe you rearranged that equation to get R = I/E, when actually R = E/I. It's an easy mistake to make. Looking at the proper relationship (R = E/I) shows that if you make R smaller (using a larger conductor), either the current in the circuit will go up or the voltage will go down. Since voltage is the driver here, and is constant, the current will go up if the wire resistance goes down. That's the DC version of Ohm's Law. The AC version uses impedance (Z) rather than resistance. It's similar, but more complex . When you said "Current will not just go up because resistance went down if the load does not require it" I believe you were thinking about the way motorized equipment is frequently considered as presenting so much load (ex: 16 Amps for an HVAC compressor) to a given circuit, as if it's the motor that determines how much load it is going to present to the circuit, which isn't so wrong, necessarily, but it is like an estimate more than a calculation. To know the actual current, and it's increase, you have to consider the circuit as a whole, the resistance of the conductor leading to the motor, the motor itself, the resistance of the conductor leading back, and the circuit's driving voltage. The motor can be represented electrically (schematically), as a combination of resistances, inductances and capacitances which (as a unit) are in series with the two resistances of the supply line conductor resistances. You can work it out by pencil and paper, or let a computer do it for you, but the current will increase with a larger conductor.
Answering your question. Yes potentially, but it is not a clear indication that the motor is starved, it is an indication of the magnitude of incomplete cancellation of magnetic fields and the interaction with the steel conduit or other circuit conductors in the conduit (if present). I agree with you, electric switching sounds are only appreciated in movies for its dramatic effect . Code plus is not bad thing, unfortunately economics concerns ultimately govern every decision in our society.
In Germany I noticed they use 1.5 mm wire fused at 16 amps 1.5 mm is lighter than 14 awg since 14 awg is rated for 15 amps I don't think it's safe I also noticed they dot put a box above lighting fixtures so that's not code
In my 50 years never seen a three phase motor with built in overload protection. Explosion proof motors used to have something to measure when motor windings get too hot and have to be wired to motor starter coil. On single phase never saw overload protection on motors 7.5 HP & higher.
Is it max fuse or breaker? So I could install a properly sized breaker and a non fused disconnect? I thought when it says max fuse that the manufacturer is requiring a fused disconnect. Please respond. Me and another guy are having a debate on this subject.
Can I put a 20 amp condenser on a 30 amp breaker even if the nameplate calls for 20 amp protection as long as there is a 20 amp fused disconnect in between?
Please to electricians use the minimum circuit breaker on condensers it will provide protection for the compressor under conditions such as a clogged condenser coil. Compressors are expensive breakers are cheap. This is from 40+ years in the HVAC&R trade and as an industrial electrician
I recently discovered your channel and loved the quality content! We recently had a failed inspection due to having two 15 amp breakers (one for attic light and service outlet and the other for the furnace disconnect switch) and the inspector claims that both breakers HAVE to be linked or bridged???🤨 It doesn’t make any F$&#¥€g sense since the purpose of installing two separate circuits was to allow to be able to service and maintain the furnace while still having the ability of using the light and outlet while the braker feeding the furnace still off... if his argument it’s true then what’s the point on using two independent circuits if we can use only one with an SSU disconnect switch on the furnace! Any help with information on what can be used to allegate on this matter will be appreciated,thank you! This happened in San Jose,California by the way where I’ve had the worst experience with inspectors (I’m willing to comply with code as long as they make up their mind on what code they’re based on)!
Hi, Ryan . What about you don’t have that info in the plate and instead of that you get values of SYSTEM FLA , SYSTEM MCA and SYSTEM MFS. how can I size the conductors with this information only ??
Why does my Leeson 5hp pump motor say “needs thermal overload protection” and isn’t already built in? If I have a 30 amp breaker with 8 gauge 240 copper conductors, I believe I satisfy this?
Not every motor has inherent overload protection. You will need to provide separate overload protection, such as through the use of a combination motor starter, or you can size your ground-fault and short-circuit protection device to include overload protection. This is typically done by sizing it at not more than 115% of the nameplate current. The only problem with that is that it may not allow for the motor inrush current during startup.
A GFCI opens at 4-6 mA of current difference between the ungrounded conductors. An overcurrent device opens (quickly) at about 6-10 times its long time pickup rating.
thomas ipkiss Per Article 100 of the NEC, a GROUND FAULT is an unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit, and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth. When a circuit has been properly installed according to NEC rules, all of those "metallic" objects (enclosures, raceways, equipment parts, and the equipment grounding conductor) will have been "bonded" together, making all those metal pieces the same object, so if an energized conductor touches any part of that metallic super-object, ALL parts of it are energized at the same voltage. What that means is that you have another type of short-circuit, one between a hot conductor and the ground going back to the circuit breaker panel, where a regular circuit breaker would pick up this condition, and trip, because a hard GROUND FAULT has the same characteristics as a short-circuit. Infinite (so to speak) current will try to race from the hot wire directly back to the NEUTRAL connection at the breaker panel (the equipment grounding conductor goes to the grounding bus inside the panel, and the grounding bus is bonded to the neutral bus inside the panel), and once there, back to the utility transformer. It all happens so fast! GFCI breakers (Ground Fault Circuit Interrupter Breakers), as Ryan said, open at 4-6 mA current difference between ungrounded conductors, but GFCI breakers open due to an imbalance in current between the two circuit carrying conductors. One thing about electricity is that it is carried by electrons, and if X number of electrons are supplied in the hot conductor, then X will return to the source via the common (neutral) conductor, UNLESS they find another way to return to the source, which is the definition of a ground-fault. The opening of a GFCI breaker at 4-6 mA current is a way to protect people from being electrocuted, anyone who might touch whatever metal has come in contact with an ungrounded conductor that's causing a fault. 4-6 mA is not enough current to kill a person, normally. So GFCI breakers are intentionally designed to protect people, not equipment. A condition that can set off a GFCI breaker without having a full ground fault is leakage current, say between windings inside a motor and its case prior to its failure, usually due to its age. GFCI breakers have built-in GFCI protection, so will trip long before the ground-fault has been completely established, but are also normal circuit breakers as well, thus they will trip at their rated current, say 45 Amperes, absent any circuit fault going on.
So, who's responsible for this carve-out for the HVAC manufacturing industry. Seems to me that the NEC is asking us to put a lot of trust in the AC manufacturers for overload protection. I've seen multiple "built in" overloads fail resulting in melting wire and small fires (fortunately).
Why would it be pulling more than 15 amps? Did you watch the video? The motor is inherently protected. It is just like the cord for your disposal. You disposal is on a 20A circuit, the cord s 16 AWG. Why doesn't it melt? Because the motor will shut itself off before that happens.
Disagree. Worked in large industrial plants and always used the smallest fuse. I usually sized quality time delay fuses for 125 to 135% of nameplate FLA. Had some 5 & 10 HP air compressors that did not shut off until 150# and had to size them at 150% of FLA. Years ago would only purchase Chase Shawmut time delay fuses. Forget who last purchased them.
You are reading the code incorrectly and to say that if you short out 2 #14 wires it would trip an 800 amp breaker is ridiculous. Clearly the 14 wire will burn before it trips a breaker.
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Learned something today. Refrigeration tech for over 40 years. Thanks
I have 20÷ yrs. 10÷ non-union and 10÷ union. I learn something every time I watch one of your videos. Thanks
Thank you. I'm an HVAC tech and this has never been explained to me. It makes perfect sense now. Thank you.
Thanks for telling me that Dean, I appreciate it!
I'm an amateur electrician thinking of installing an AC unit and was confused about the nameplate specs on the units. Just came across your video after digging across the internet trying to understand this logic breaking piece of electrical code. Wonderfully explained! No one explained that it's because the motor has a shut off to prevent itself from melting. Thank you Ryan
Glad Ryan is doing this. His training is far superior to more "well known" names. Accurate, concise, and well-spoken.
Great vid. Learn to love 110.3(B).
Learn something new every day, thank you
Thank you so much for explaining the -WHY- I've known we can do this, but we have just sized the conductor on the breaker size regardless because I didn't understand that the motor itself is providing the overcurrent protection. We have just said the phrase "code is a minimum" and over-sized the conductors on principal.
I feel so much more confident in my ability to provide a safe installation to the customer while also being more cost effective.
The manufacturers manual usually spells this out but it wasnt mentioned in the video, voltage drop. Be cognizant that long runs might have excess voltage drop and you need to bump up the wire size to accommodate. It might cost a few more dollars to install bigger wire but the customers compressor may last longer due to being able get up to speed faster vs having brown out conditions with smaller awg wire.
Great video Ryan. This is a subject I love teaching. When they finally understand the concepts, its a great "Eureka" moment. Keep up the great work.
Hi Sir Ryan, thank you very much for the detailed and straight forward lesson, everything is on point and my confusion on
"why the a/c have smaller wire ampacity than the circuit breaker's ampere trip rating" clears away!
I think the secret there is, not everyone knows that the a/c equipment have an integral protection for an overload current,
and most probably, everyone in this field must clearly understand the difference between short circuit, ground-fault and overload currents.
I'll take note also the important thing from your video, when reading the a/c nameplate, the indicated Max Circuit Breaker size is NOT meant
to protect the Wire feeding the a/c, which will be sized based from the indicated Minimum Circuit Amapcity.
I would be watching more videos from your channel, thank you very much again, more power and God bless
Thank you! You explain very well and provide clear examples. Thank you very much.
I am a new subscriber and have fallen in love with the clear explanation, examples with photos and everything that you make understanding easy. I have been watching your videos for the past three days and like every one of them. So interesting and well explained. Thank you! Thank you!
Thank you!
I love learning from your channels. Learning why AC units and overcurrent protection are sized like their are. I always thought for example using a 14 gauge NM on a 25 amp breaker is a major fire hazard, in case there is a problem with the unit and it draws more than 15 amps, like back in the old days, especially with the Edison base fuses and to a lesser degree, circuit breakers, a 15 amp fuse keeps blowing due to overload caused by the homeowner running high amp devices like heaters, irons, vacuum cleaner, microwave ovens, electric skillets and hair dryers, to name a few. The fuse is replaced. . After a few times, the homeowner stops the trouble by using a 20 or 30 device. Or places a penny or wraps the fuse in aluminum foil. Over the years many homes have been destroyed & lives lost by such action. It's my understanding that part of the reason we went from fuses to breakers in the 1960s, aside from them being more convenient and practical, was because a breaker tends not to be tampered with as readily as a plug or cartridge fuse.
Ryan, thanks for making these videos. It spells out clearly the reasons we are allowed to size conductors and ocpd's the way we are. Great resource for young journeymen and apprentices. I suggest you do separate videos for motors, feeders, and transformer secondarys too.
great resource for old apprentice/journeyman/master electricians as well.
i really enjoy how you explain the code and know what to emphasize. Sorta cut to the chase as they say.
Thank you for making it clear!
I love Ryan knowledge and presentation.
Thanks Ryan. I'm learning a lot from your videos.
Your always give it in the point. Excellent video bro
Excelllent explanation !! Thank you.
You just spelled it out for me....KUDOS. Thank you Mr. Jackson
Great video...thanks Ryan!
Hi Ryan
Been doing electrical 20 years.
Literally wiring a new commercial building this weekend and helper asked to understand how to size air conditioners.
Ive always max breaker, then wire based on that breaker
This is great information and such great timing to randomly pop up on my Facebook to find your channel
New subscriber. Thank you
Thanks Eric, I appreciate you taking the time to leave a comment.
Thanks for the video Ryan
Great, very well explained,Ryan you are very good teacher ! I love the donkey example, very funny!!!
thanks for the clear presentation and why HVAC//R has the exceptions.Also if people notice on the nameplates it mentions BREAKER (HVACR)
these are special breakers for the hvac/r industry. Suppose to be able to pull locked rotor amps for a few seconds so the compressor and fans
can get up to speed.
That used to be the case, but now the "HACR" rating is no longer required. I definitely remember having to check for that though!
@@RyanJacksonElectrical good to know about the breaker change
@@RyanJacksonElectrical my new Bosch unit is state-of-the-art and its Installation Manual still refers to an HACR breaker. Wonder how widespread the knowledge of the rating change has gotten in the HVAC industry. Or maybe some of them liked the distinction and want to hold on to it as long as possible.
As an electrician, using mostly, 430 and 440 for my work, I am very familiar with your subject. I used to get a kick out of showing "union" electricians how I could 'legally' put a 18 gauge wire on a 40 amp breaker for certain motor loads, because the overload was in the contactor, the breaker had to sustain the inrush current without tripping, the contactor would trip (very predictable) at a low current, below the breaker rating.
Great teaching,thanks a lot Sir
Great video as usual. You may want to add a picture of the motor starters overloads to demonstrate better
awesome video thanks for breaking that down!
Thank you! Very clear.
Great video!
I think its important to mention this code pertains specifically to hermetic motor and compressor driven equipment
Very well done
Motor loads allow you to size the wire based on the MCA, but the EGC should be sized based on the installed OCPD rating. The upsize of the EGC to match the breaker size may require you to size the phase conductors to a size larger that includes the code required EGC. Its a good thing to double, triple check before ordering and installing spool full of wires so the AHJ doesn't makes you rip them out.
Very good presentation. You have clearly demonstrated why ocpd is not sized according to the partial or full ampacity of the cable. Do you have any insights on how or what determines the max ocp values in these cases?
Ryan love the new channel
Sorry to say I bet those AC units are now under water.
Thanks for your videos, watching and learning. I think you overlooked an important factor in this video. Motor internal overloads, compressors in particular, are usually thermal and auto resettable. Repeated overload conditions can cause conductor and motor failure. I would not use 14 gage wire to supply a 20A motor and air conditioner. Because the condutor in your scenario is undersized then it would overload and fail before the breaker trips. If the wire was 12 gage minimum the overload failure occur at the compressor terminals if if the 20A breaker doesn't trip. Speaking from experience, could you clarify?
Hello, Whatever does the NEC say about the disconnect box pertaining to outdoor ac condenser such as : distance from condenser( I have seen disconnect boxes 8 ft above a condenser, where a ladder is needed- that isn't safe) , within visible distance of the condenser(the box being around the corner of a building) being behind the condenser( in such a way where you can't stand in front of it, not exactly safe). A disconnect box being below snow line or to close to the ground. Is there a reference in the NEC for these items pertaining to AC? I have seen in homes built even 10-15 years ago where Romex is run from panel to outdoor disconnect box with no rubber conduit sleeve, and in addition Romex from box to condenser. We always change the Romex from box to condenser to a wire and conduit protector. What does the NEC say about that, do we know when that code was changed not allowing Romex to be run outdoors to ac's and disconnect boxes without a conduit sleeve?
Also for electrical switches and outlets mounted to gas furnaces , requirements etc. Thank you very much for putting out this video if was informative and I have subbed.
Great video. So why have both fuses in the disconnect and a circuit breaker.
Same would apply for large commercial air handlers with min circuit amps and max over current name plate markings? No hermetically sealed compressor motor. Only large fan motors that have overload protection. Also would the wiring compartment on a disconnect for an air handler stating ues 75° c or greater conductors imply that the terminals are 75°?
Thanks a lot!
Great video training.
How to know when choosing 60F or 75F?
On the last example I have min amp 29, max fuse 50, max ckt bkr 50
In case that the existing breaker is 60 amps, can I leave the 60 amps breaker with a fused disconnect of 50 amps, and a 10awg?
Yes you could and use DE TD fuses.
Is this true for 2020 NEC as well?
@Ryan Jackson When the manufacturer provides their MCA, they have done all the calculations. The MCA tells you what wire size to use. Does that mean you do NOT have to correct for temperature and adjust for bundling? Thanks for your many excellent NEC videos.
The manufacturer provides the minimum ampacity of conductors. The definition of ampacity is the amount of current the wire can carry AFTER temperature adjustments and ampacity correction. So yes, you still need to factor that in. The nameplate won't state "use 12 AWG," it will state an ampacity.
commercial 2 door or 3 door soda cooler is also a Motor ? that means need to go with ampacity conductor size and breaker size as per label ? Thanks.
Ryan, I completely understand and now I understand that the use of smaller gauge wire for condensers is allowed under 440. I also fully understand that wire sizing conductors for condensers is different than that of 310.16. My question is though the NEC code is the minimum requirement to be safe from fire and code violations. Can we run larger gauge wire using 310.16 as the base for wire sizing and over-current protection for a condenser install and simply use the correct amperage breaker for the conductor as per normal practices and still be code compliant? This is my only confusion!
I get that an “MCA of 28.4A” with a max breaker size of 50A on a 10 gauge conductor using a 50A breaker is good with 440. That said would I be in code violation of 440 if I use 8 gauge wire following the 80% method which would be 32A using a 40A max breaker size?
The conductor has to be at least as large as the MCA. If you satisfy that it can be as large as you'd like. The breaker must be between the min and max overcurrent device rating.
@@RyanJacksonElectrical thanks Ryan, my a/c guy is installing a system for me and I’m just making sure the way I’m doing it will satisfy 440 while using 310.16 and the condenser tag for breaker size to do the work. Neither myself, the customer nor the city inspector are comfortable with using 10awg wire on a 40A circuit for this job as per NEC 440. We’re running 6/2 x 50’ for the wire and using a 40A breaker according to the max breaker size on the condenser tag. Also 18/5 x 50’ for the thermostat, air handler/furnace & condenser then a 20A breaker with 12/2 x 50’ wire for the air handler/furnace.
[Thank you Ryan. Is there any other electrical equipment that this applies for?]
If a mini split has heating capability, does it still qualify under this provision?
I’m assuming the 50 amp circuit breaker on 10 wire is only from the AC unit to the disconnect. A 30 amp circuit breaker would be used at the service panel for the branch circuit.
Hi Jack. the feeder would be the same way, in accordance with 43.0.62(A).
@@RyanJacksonElectrical 430.62(A)
Ryan,does this apply when using Romex cable, example min. amp 18amps o/c 30amp.
I had trouble with my first central air conditioner tripping the 30 amp breaker. Never pulled more than 17 amps. So I upped it to a 40 amp. Found out that my wife was what I called machine gunning the old mercury filled thetmostat. Would turn it on then off then on several times. Installed a 5 minute on delay timer then went back to a 30 amp breaker. Now have a high efficiency unit that runs on a 20 amp breaker. ( 2.5 tons ).
You nailed it. Every off cycle the Freon pressures begin to equalize in the system if the compressor tries to start before they equalize it tries to start under a load often exceeding the breaker amperage or the motor can't overcome the load to start and heats the windings which trips the thermal overload device embedded in the windings. All new electronic thermostats have a built in time delay so you can't short cycle the thermostat.
If the breaker is only used for ground faults and short circuits, what could go wrong then if you go over the max circuit breaker rating?
Great video, thanks! But I'm confused about disconnects and if they need to be fused or not? It seems it is not uncommon to use Both a breaker and a fused disconnect. Why would that be needed? And if so, would the fuse and breaker both be sized the same (per the HVAC label)?
They are sized the same way. If the unit says "maximum fuse" instead of "maximum breaker" or "maximum overcurrent device," a fuse is required.
@@RyanJacksonElectrical after some research I have learned a bit more on this. Though most condensers will say fuse/breaker max rating some might only be listed for a fuse and only say fuse max. In that case a fuse in the circuit is required and can be anywhere, so a fused disconnect becomes one easy way to meet that requirement. But a breaker in your breaker panel is also needed. Also, I checked my own home units and found fused disconnects were added when the units were replaced. Though I don’t know the rating of the old units we had I see the correct sized fuses are in the disconnects were the breakers are both larger. 35 fuse vs 50 breaker. And for the smaller unit, 20 amp fuse vs 25 breaker. So instead of downsizing the breakers they just buy the needed protection in with the correct sized fuses. So fused disconnects become an option to downsize the protection when needed for a unit replacement leaving the higher rated breaker for a possible future use of the circuit.
What if damaged or loose wires causes an additional load from arcing or current from a lightly conductive material that causes slight continuity between phases or grounding/grounded to ungrounded. Like say the material across the conductors creates 5 ohms of resistance across 120v. You will start pulling 24 amps. Or If a handy man comes along with out a permit and adds a condensate pump and heat tape on the circuit. The wires ampacity couldn't safely handle the over current before the breaker opens right? I can understand the max breaker size to handle the in rush current or a fail safe if the units over current protection fails. I understand the code implies that you if you are working with electric you will be knowledable of and following all codes accordingly. But I still believe it would be slightly safer to also size the wire to the breaker for freak scenarios like I mentioned.
The example I used would be if you were using say 20awg 60c protected by a 25 amp breaker
@@erikolsen3611 If we were to wire everything based off of what if scenarios like you are describing then where does it end? I understand what you are saying but you have to stop somewhere
Yes, stupid happens therefore ... _insurance_.
How you wire size and breaker for air handler..
Ryan, I understand the concept completely. Been in the trade 40 years and you have explained this extremely well. I have encountered many a/c units wired with smaller wire. The reason leading to these encounters were the wires buzzing in the conduit upon unit startup. I work in a metallic code area around Chicago, no NM cable allowed by AHJ's, system must be pullable. This problem is always solved by upsizing the wire. I now always upsize because of my experiences irregardless of the circuit length. Maybe its overkill, but if the wires are rattling in the pipe, isn't this an indicator that the motor is potentially being power starved at start-up? Even if it isn't, the customer shouldn't have to here that irritating noise each time unit starts. "Code Plus" thinking can't be bad, correct?
I am assuming the rattling is caused by the strong EM field being peak on start up due to the approximate Locked Rotor condition present, causing the inrush current all induction motors have on start up, to be greater than normal.
Increasing the wire size would just lower the extra load placed on the circuit by resistance, therefore reducing the start up inrush current load placed on the circuit.
Correct me if im wrong.
@@MR-nl8xr Ohm's law says that if the load resistance goes down, the load current goes up. Since the load is a motor and the voltage is AC, there is an AC inductive reactance and some back EMF that would run counter to that, but basically the inrush current would tend to rise in stead of falling when you increase the conductor size, as the wire resistance goes down in both conductors.
Correct me if I am wrong.
@@billcowhig5739 Ohms law also says that the circuit (load) resistance is equal to the current that will be used divided by the voltage.
Current will not just go up because resistance went down if the load does not require it.
There is a lot more to consider here since such planetary size of things are happening here all in the inversilly small time size of a second with AC.
My reply was a quick attempt at trying to answer the OP's question, which looking back, probably confused him more.
No such thing as easy or quick answer with Electricity.
@@MR-nl8xr No, nothing is easy or quick with Electricity in general.
Ohm's Law can be expressed mathematically as E = I x R (Voltage across a load = Current passing through the load times the Resistance of the load). I believe you rearranged that equation to get R = I/E, when actually R = E/I. It's an easy mistake to make. Looking at the proper relationship (R = E/I) shows that if you make R smaller (using a larger conductor), either the current in the circuit will go up or the voltage will go down. Since voltage is the driver here, and is constant, the current will go up if the wire resistance goes down. That's the DC version of Ohm's Law. The AC version uses impedance (Z) rather than resistance. It's similar, but more complex .
When you said "Current will not just go up because resistance went down if the load does not require it" I believe you were thinking about the way motorized equipment is frequently considered as presenting so much load (ex: 16 Amps for an HVAC compressor) to a given circuit, as if it's the motor that determines how much load it is going to present to the circuit, which isn't so wrong, necessarily, but it is like an estimate more than a calculation. To know the actual current, and it's increase, you have to consider the circuit as a whole, the resistance of the conductor leading to the motor, the motor itself, the resistance of the conductor leading back, and the circuit's driving voltage. The motor can be represented electrically (schematically), as a combination of resistances, inductances and capacitances which (as a unit) are in series with the two resistances of the supply line conductor resistances. You can work it out by pencil and paper, or let a computer do it for you, but the current will increase with a larger conductor.
Answering your question.
Yes potentially, but it is not a clear indication that the motor is starved, it is an indication of the magnitude of incomplete cancellation of magnetic fields and the interaction with the steel conduit or other circuit conductors in the conduit (if present).
I agree with you, electric switching sounds are only appreciated in movies for its dramatic effect .
Code plus is not bad thing, unfortunately economics concerns ultimately govern every decision in our society.
In Germany I noticed they use 1.5 mm wire fused at 16 amps 1.5 mm is lighter than 14 awg since 14 awg is rated for 15 amps I don't think it's safe
I also noticed they dot put a box above lighting fixtures so that's not code
Is that true for ALL motors? Do they have overload protection built in?
For air-conditioners, yes. For other motors sometimes the case. It is more common for smaller motors.
Thanks
Can not remember ever seeing
In my 50 years never seen a three phase motor with built in overload protection. Explosion proof motors used to have something to measure when motor windings get too hot and have to be wired to motor starter coil. On single phase never saw overload protection on motors 7.5 HP & higher.
If a 5KW electrical heater kit calls for a min of 27 and max of 30 and say it's on a breaker for 40 amps would breaker need to be changed to 30?
What if the AC is continuously operating over 3 hours? Do you need to apply a 1.25 factor to the MCA to size the conductors/breaker?
That's already calculated
I have Forman that cannot rap this around their brains. I've been doing this for nearly 30 years residential and commercial/ industrial.
Is it max fuse or breaker? So I could install a properly sized breaker and a non fused disconnect? I thought when it says max fuse that the manufacturer is requiring a fused disconnect. Please respond. Me and another guy are having a debate on this subject.
If it says fuse, it requires a fuse. See UL Guide Card Category LZFE (iq.ulprospector.com/en/profile?e=209220)
What about size disconnect for a 35 amps max capacity condenser?
Doesn’t disconnect have to to readily accessible? Anyway, your the best at explaining these type of things. keep it up on RUclips...future is bright
FROM the heat pump, not the ground necessarily. If it has fuses the unit etc. can't block the disco.
Code states that you must have a 30" wide area and 36" clearance in front if all disconnects. Have to fight with other trades to keep away.
Can I put a 20 amp condenser on a 30 amp breaker even if the nameplate calls for 20 amp protection as long as there is a 20 amp fused disconnect in between?
Yes.
Overload protection is inherent in the motor.
Ground-fault & short-circuit protection if from the breaker or fused disconnect.
@@RyanJacksonElectrical what about same question , but on heater kit.
Please to electricians use the minimum circuit breaker on condensers it will provide protection for the compressor under conditions such as a clogged condenser coil. Compressors are expensive breakers are cheap. This is from 40+ years in the HVAC&R trade and as an industrial electrician
So true.
Can you do a transformer sizing for rooftop unit vfd motor.
Fair enough. Just pointing out that meeting just NEC requirements does not necessarily mean you end up with a good design.
Yep. That's why I started with Article 90.
I recently discovered your channel and loved the quality content!
We recently had a failed inspection due to having two 15 amp breakers (one for attic light and service outlet and the other for the furnace disconnect switch) and the inspector claims that both breakers HAVE to be linked or bridged???🤨 It doesn’t make any F$&#¥€g sense since the purpose of installing two separate circuits was to allow to be able to service and maintain the furnace while still having the ability of using the light and outlet while the braker feeding the furnace still off... if his argument it’s true then what’s the point on using two independent circuits if we can use only one with an SSU disconnect switch on the furnace!
Any help with information on what can be used to allegate on this matter will be appreciated,thank you!
This happened in San Jose,California by the way where I’ve had the worst experience with inspectors (I’m willing to comply with code as long as they make up their mind on what code they’re based on)!
There is no NEC that requires that.
@@RyanJacksonElectricalJust as I figured!
Thank you and keep on going with those videos,we really appreciate your work!
Were u sharing a neutral on the two circuits?
That’s the only reason they would need the handle tie.
Multi wire branch circuit
Hi, Ryan . What about you don’t have that info in the plate and instead of that you get values of SYSTEM FLA , SYSTEM MCA and SYSTEM MFS. how can I size the conductors with this information only ??
Should an AC disconnecting means require the same amount of working space as a service equipment panelboard?
Yes
That would be nice but in the real world it doesn’t happen. Example: Apartment complex with 16 AC units grouped together. Hard to comply.
Ryan do you have a video on motors??? Thank you
Not yet mate, sorry. I'll add it to my to-do list.
Thank you sir you are Tony the tiger great 👍🏽
Why does my Leeson 5hp pump motor say “needs thermal overload protection” and isn’t already built in? If I have a 30 amp breaker with 8 gauge 240 copper conductors, I believe I satisfy this?
Not every motor has inherent overload protection. You will need to provide separate overload protection, such as through the use of a combination motor starter, or you can size your ground-fault and short-circuit protection device to include overload protection. This is typically done by sizing it at not more than 115% of the nameplate current. The only problem with that is that it may not allow for the motor inrush current during startup.
My man went to the caribbean and while everyone was snapping away shots of paradise, he was snapping away shots of equipment & utilities😆😆😆😆.
^Fact^
Stupid question, Previous AC unit required a larger breaker and new Unit requires a smaller breaker, can you leave the older breaker?
No, you need to change it.
@@RyanJacksonElectrical what if there is a fused disconnect between them with the correct fuse size the unit calls for?
Can you please make a video on 440.22 and 440.33 ❤
If overcurrent protection devices detect for ground faults then why do we need GFCI breakers?
A GFCI opens at 4-6 mA of current difference between the ungrounded conductors. An overcurrent device opens (quickly) at about 6-10 times its long time pickup rating.
thomas ipkiss Per Article 100 of the NEC, a GROUND FAULT is an unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit, and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.
When a circuit has been properly installed according to NEC rules, all of those "metallic" objects (enclosures, raceways, equipment parts, and the equipment grounding conductor) will have been "bonded" together, making all those metal pieces the same object, so if an energized conductor touches any part of that metallic super-object, ALL parts of it are energized at the same voltage. What that means is that you have another type of short-circuit, one between a hot conductor and the ground going back to the circuit breaker panel, where a regular circuit breaker would pick up this condition, and trip, because a hard GROUND FAULT has the same characteristics as a short-circuit. Infinite (so to speak) current will try to race from the hot wire directly back to the NEUTRAL connection at the breaker panel (the equipment grounding conductor goes to the grounding bus inside the panel, and the grounding bus is bonded to the neutral bus inside the panel), and once there, back to the utility transformer. It all happens so fast!
GFCI breakers (Ground Fault Circuit Interrupter Breakers), as Ryan said, open at 4-6 mA current difference between ungrounded conductors, but GFCI breakers open due to an imbalance in current between the two circuit carrying conductors. One thing about electricity is that it is carried by electrons, and if X number of electrons are supplied in the hot conductor, then X will return to the source via the common (neutral) conductor, UNLESS they find another way to return to the source, which is the definition of a ground-fault.
The opening of a GFCI breaker at 4-6 mA current is a way to protect people from being electrocuted, anyone who might touch whatever metal has come in contact with an ungrounded conductor that's causing a fault. 4-6 mA is not enough current to kill a person, normally. So GFCI breakers are intentionally designed to protect people, not equipment. A condition that can set off a GFCI breaker without having a full ground fault is leakage current, say between windings inside a motor and its case prior to its failure, usually due to its age. GFCI breakers have built-in GFCI protection, so will trip long before the ground-fault has been completely established, but are also normal circuit breakers as well, thus they will trip at their rated current, say 45 Amperes, absent any circuit fault going on.
What about electric heat kits and air handlers? I believe all the examples you gave were condensers.
Good question, did you find your answer?
@@MR-nl8xr same rules. Use 60° column though for NM cable and for AC whip since it’s a wet location regardless of equip temp rating.
I want to see a discussion on that
Are you sure people can use 15 am wire for a 20 amp breaker??
Yes, under the right conditions. That is the crux of the video.
Shouldn't this be based on the 75degree column?
Only if the terminals are rated 75 degrees. See 110.4(C)(1).
? I THOUGHT that A/c conductors are sized for continus load which is 125% of the running load amps marked on the unit ???
The nameplate marking incorporates it.
I thought that was true for electrical heater kits.
I noticed my air conditioners are being installed near beach area,. Before, it was there breeze… California
Still the same requirement for 2020? You used the 2017 NEC
Yes
@@RyanJacksonElectrical thank you very much for your videos, happy 4th of July
Mike Holt says to use the 75 degrees column
U say to use the 60 degrees column
?
Electricians can’t agree on anything
Read 110.14(C) and (if using NM cable) 334.80.
So, who's responsible for this carve-out for the HVAC manufacturing industry. Seems to me that the NEC is asking us to put a lot of trust in the AC manufacturers for overload protection. I've seen multiple "built in" overloads fail resulting in melting wire and small fires (fortunately).
But what if the wire splicing become loose and the wire is pulling more than 15 Amp and it wont trip the circuit. It will burn the wire.😳
Why would it be pulling more than 15 amps? Did you watch the video? The motor is inherently protected. It is just like the cord for your disposal. You disposal is on a 20A circuit, the cord s 16 AWG. Why doesn't it melt? Because the motor will shut itself off before that happens.
@@RyanJacksonElectrical resistance due to a loose wire
@@noneyall2819 Then the rating of the overcurrent device is irrelevant.
Great instructions. I think your seven dislikes are professional jealousy's.
Always use the MAX fuse or circuit breaker?
Disagree. Worked in large industrial plants and always used the smallest fuse. I usually sized quality time delay fuses for 125 to 135% of nameplate FLA. Had some 5 & 10 HP air compressors that did not shut off until 150# and had to size them at 150% of FLA. Years ago would only purchase Chase Shawmut time delay fuses. Forget who last purchased them.
if its not my lucky day it will blow the 400 amp main HAHAHAHAHAHAHAHAHAHA
Running Utes
You are reading the code incorrectly and to say that if you short out 2 #14 wires it would trip an 800 amp breaker is ridiculous. Clearly the 14 wire will burn before it trips a breaker.
LOL okay.
So which section do you think I am reading incorrectly?