The good thing is you have everything you need in your phone. Once you can look at a schematic and understand all the symbols and flows and know the sequence of operation ( more complex systems) may require a manual. Even a factory tech needs manuals sometimes on as built systems. It takes time and dedication to learn and understand everything and nobody knows everything. The HVAC& R industry is now much more than a home split system to a 5-10 ton rooftop unit. It’s comms and logic which come in many forms and sizes. Asking for help when you don’t want to because of pride. Every tech wants to be the best or should, but also be humble.
Being in Arizona, I see 4 and 5 ton systems every day and very few 2 ton systems. This was a great video though, thank you for spending the time to make this amazing content! The technician community thanks you! 🤝
I agree. I don't use continuity that much and like to go off of the Ohms so that you can catch little problems that you might miss if you just went off of the audible cue. Maybe a nice use for it is when a compressor is overheated and you want to cool it down to get the safety to reset you can connect alligator clips in continuity mode and once you hear the beep you know it's finally reset. Thanks for the video!
The continuity beeping sound is good if you're trying to find a short to ground, You can go quickly through a system and listen for tone. Also, going through a circuit that has many points to see if it's open or closed.
This is imperative to understand especially when testing heating elements, and how you can aid in determining the proper BTU output of electric heat as the elements having resistance outside of its spec will lead to issues with high utility bills and or poor heating due to tripping limit switches.
Absolutely, understanding the proper functioning and testing of heating elements is crucial in HVAC work. Testing their resistance and ensuring they are within specifications is essential to avoid issues like high utility bills or poor heating performance due to limit switch tripping. It's important to pay attention to these details to ensure efficient and reliable heating performance for your customers.
The beep test is very useful when you are simply trying to find whether a switch is open or closed, or if you have a broken wire somewhere or something is plugged in to the wrong place or not fully seated. Also useful when tracing wires. In other words, sometimes a yes or no is more important than how much. This is the whole reason behind digital electronics and communications. On or off is easier and more reliable than precisely measuring the voltage.
@@shawnsgdoesn't seem like you read his comment. Sometimes you might not be directly in front of your multimeter testing the wire and a beep can tell you if the line is O.L or 0.0
If you guys are working with the power turned off due to some as yet undetermined fault being present, how do you supply the 24v to the relay coil? Do you carry a separate 24v transformer and wire that to the mains supply? Or do you isolated the out put of the units own 24v, and use jumpers to supply the 24v to which ever relay or CCTV your are currently testing?
My Fluke 116 has a “Auto V Lo Z” setting. It was useful recently in finding a faulty thermostat circuit board issue. Checking with regular voltage setting would show various AC voltages due to high resistance circuit board faults in the thermostat. Testing with the “Auto V LoZ” setting would shunt the noisy voltages on the line and the circuit would work normally. Maybe a video on that feature and the limitations of high impedance digital meters and their susceptibility to line noise might be helpful.
Baby steps! I think a lot of people would have a hard time wrapping their minds around that concept when they're starting. Were there any capacitors on the thermostat circuit board?
Thanks for an excellent video . I knew all of that , but this would be very useful for a lot of guys I used to work with , they didn’t come from an electrical background.
Thank you for saying something about standard wire resistance. While most applications will not have a run long enough to create significant resistance and voltage drop, there are going to be cases in which it does occur. There is even more resistance with stranded and thinner gauge wire. 0.0 ohms is perfect world resistance on short wire runs even.
hey can you explain a couple things further: 1) what is it about corrosion and melted wires (I'm assuming a different mechanism for each) that causes an increase in ohms and resistance 2) shouldn't even simple wires have resistance? Is anything really zero resistance? You said the door switch thing for the gas furnace should have 0 and those simple wires also should have 0. 3) What is so bad about some device having more resistance than it "should"? Can you explain a bit more in detail how more resistance leads to higher current and heat? This completely confuses me. I thought the higher the resistance, the more the current is being resisted and thus the less current gets thru! 4) Last question: What exactly does that door switch do?
@MathCuriousity 1. Corrosion causes higher resistance and higher resistance causes higher voltage drop. Since voltage is the electrical energy, you will develop heat wherever there is voltage drop due to resistance. The more heat that develops, the higher the resistance goes, and the higher the resistance goes, the higher the heat goes, so you can see that it's a catch 22 until the plastic or insulation melts or the metal contacts become burned and pitted. As you can see, corrosion and loose connections cause high resistance and they can cause a system to stop working or even worse cause a fire. One thing he said in the video that is NOT correct is that "current goes up when heat and resistance go up". If resistance goes up, current actually goes down. The melting of plastic on contactors and plastic insulation on wires, and burned/pitted contacts on switches are not caused by high current; they are caused by voltage drop in that spot that's loose or corroded. 2. You are correct. Everything has resistance. Except for superconductors but they're not used in HVAC so you don't have to worry about them. The ohmmeters we use are not sensitive enough to read the resistance value of 1 foot of 14 gauge wire. There are very expensive ohmmeters that will read and display the resistance of 1 inch of 14 gauge wire. For the purpose of HVAC, the multimeters we use are more than good enough. 3. Read answer #1 4. That door switch is held in the closed position whenever the furnace door is properly installed and allows line voltage of 120V to go to the circuit board and power both the 24V and 120V circuits so the furnace can operate. If the furnace is running, and you take off the door that is holding the switch closed, the switch will open, cut electrical power to the furnace and furnace will stop working. Also, if the door is off the switch will be in the open position and furnace won't have any electrical power going to it so it won't start. This guy is a gem. He's worth his weight in gold in my opinion. He puts out great content. I'm not in HVAC. I'm actually an airplane mechanic but I've learned so much from watching Craig. I like doing all my own repairs and installs. If you want to be the go to guy in your company, watch his videos and take notes.
@@bernardocisneros4402 Hey Bernardo, I had another question given that clearly you are a gad damn genius! So something’s been bothering me lately. I stumbled on someone on a forum mentioning that 1) If you take your hand and put pressure on a fan blower motor blade, it won’t start working harder, actually less work will be done and less current will be drawn. Is this true?!! If so why?! Intuitively to me it has to work harder and I would think more current will be drawn? Someone else mentioned “internal resistance” - no idea what that is or how that would play into this even if it is true. 2) In another area someone mentions that’s: centripetal fans will draw less current if blocked but axial fans will draw more current if blocked. Any idea if this is true and if so why?! Thanks so much kind soul!
@@MathCuriousity Thanks for the compliment but genius I'm not. I've just being doing this a while. My job working on airplanes deals a lot with electrical and electronic components, so you have to be on point with your electrical knowledge. You don't want to fry a $100K piece of equipment. If you hold a blower motor fan blade with your hand to prevent it from turning, it will do less work, but draw more current. It partially has to do with how "work" is defined. Work is defined as the product of force and distance. In other words, work is equal to the force applied times the distance it's applied, and since the fan doesn't rotate, there isn't any distance travelled when you're holding it still, so the distance portion of the equation is zero, and anything times zero is equal to zero. Let's not worry about that part because it doesn't really matter in the trades. It matters more so in engineering when they're designing these furnaces and air cond units. There's 2 types of resistance when dealing with motors. There's physical resistance: you holding the fan blade so fan won't turn and electrical resistance measured in ohms that opposes the flow of current. There's a lot that goes into properly answering this question, and I don't want to write a book, but just know that increasing the physical resistance on a motor will increase the current flow. The motor will draw more current. Increasing the electrical resistance on a motor or its circuit, will decrease the current flow to the motor. The impedance of a motor is the sum of its internal resistance and inductive reactance. In short, impedance is the total oppostion to current flow in a motor. Reactance also opposes current flow and is also measured in Ohms just like resistance but it's not the same thing. The internal resistance of a motor is composed of the resistance in its windings. inductive reactance is kind of like resistance but it's not. Inductive reactance in a motor is at its lowest when the motor is NOT turning. As the motor begins to turn, its inductive reactance starts increasing. This is why a motor will draw much more current at start-up than when it's up to speed. This current is called in-rush current. The reason it's higher at start-up is becasue the only opposition to current flow at start-up is the motor's internal resistance. As the motor begins turning, the inductive reactance starts increasing and helps the motor's internal resistance to oppose current flow. It doesn't matter what type of fan it is. If it's driven by a motor, it will behave in the manner I described above. Being axial or centripetal doesn't matter.
@@bernardocisneros4402 so if we hold the blade with our hand increasing physical resistance , the current draw will increase and just not to torment you further with questions but if you have a moment: is this current increase because: A) Torque increased? B) Impedance increased? If so was it internal resistance or inductive reactance to make the impedance increase ? (Since you mentioned impedance is a sum of them so one has to have had risen). Thanks so much!
@@MathCuriousity The current increase is because torque increased and Impedance decreased. The reason impedance decreased is because the resistive portion of impedance stayed the same but inductive reactance decreased.
There is a lot of this that is basic electricity and electronics theory that without some knowledge in that area first can be very difficult to understand. Even though someone might think they do. The condition described might be understood, but the underlying hows and whys that will enable deeper understanding in order to troubleshoot effectively are not. Not a criticism of your excellent video, just acknowledging the reality of what truly understanding this process in order to accurately and quickly find faults will require.
NCV stands for Non-Contact Voltage. This feature allows you to detect voltage without using your meter probes. I wouldn't trust it 100%. You can try it until you get comfortable with it but always double check the voltage with the meter probes before beginning work. NCV has steered me wrong a few times.
The thermal limit switch cuts power to the gas valve when it's subjected to an overtemp condition. For example, if the blower fan in a furnace stops working, the furnace temp will keep rising until the thermal limit switch trips and cuts off power to the gas valve. Without power, the gas valve closes, stops supplying gas, and the flames go out. A low/high thermostat will maintain a minimum temp and also maintain a maximum temp. Let's say we set it to a low/high of 65/85. The heater will come on when the temp drops below 65 and the air conditioner will come on when the temp goes over 85.
@@bernardocisneros4402 very cool! So how do these limit switches shut off the gas? Are they - how can I put this - causing an open circuit to shut it off or causing the electricity to be shunted somewhere else ?
Need advice. I have a unit that’s not blowing cold. The pressures look normal. The compressor is fine. Last guy replaced the fan motor. I said but the suction line still isn’t cold to the touch it should get cold to the touch within seconds. He said since it’s so hot it’ll take a while to start cooling. I knew better but still paid him and he won’t return my call. I knew better the suction line always gets cold within SECONDS of the condenser coming on. If I turn the unit off for a while and then turn it on, the suction line gets cold for about 1 minute but then that’s it, it goes back to ambient temperature and inside the it’s not blowing cold. I’ve now had 3 different people look at this unit. No one knows what’s going on. I’m already out $500. Any thoughts? Bad TXV?
Wrong video, i know. But, i was curious :Why in the video showing the vacuuming process of a system did you use 3 appion valve core tools instead of 2?
Have this question, always wanted to ask, thank you much: when measuring superheat, why taking the pressure/temperature at suction line and subtract from the vapor line copper's temperature? Pressure at vapor line yields the temperature of the vapor at that location, not the saturation of the liquid/vapor inside the evaporator coil..also what is temperature of the copper line? what does it represent? I thought the true superheat would be the temperature of the wet bulb minus saturation temperature, which is the temperature of the mixture liquid/vapor inside the evaporator coil because this superheat number represents how much heat/enthalpy is absorbed and removed by the refrigerant in the coil...this superheat has nothing to do with vapor temperature at the suction (derived from the measured pressure) or the temperature of the copper pipe...Appreciate if the host or someone can address. Thank you much.
I watched a video from this channel about heat strip circuits and one video from grayfurnaceman about changing a sequencer to a contactor about 20 times until I figured it out. Every time I watched, something clicked in my brain and I made a discovery. Repetition is key. Now I happily replace all my sequencers with contactors when working with electric heat.
Superheat, typically 12-15F taken near the compressor is important to make sure your not bringing any liquid back into the compressor (low superheat) but is not too high which will cause the compressor to run too warm or hot. Of course the proper charge and line sizes need to be correct.
Hello, I am subscribed to the Channel, but I understand a lot of English, we hope that the translation will be done into Arabic so that we benefit from the videos with thanks and appreciation
As an electrician, I can tell you beyond a shadow of a doubt, that the mm continuity function plays a vital role in determining certain electrical and communication shorts. All electrical and communication systems are NOT equal and thus that feature has its place from time to time; otherwise, why would mm manufacturers bother designing it into their products?
Off course it has its place but not in a video for techs just getting started in HVAC. After you get some experience and know how your meter works, then you can decide which feature to use, but for newbies the resistance feature is best over the continuity feature.
Contractor for 40 years stop just stop trying to give tutorials to average American citizens tutorials or no tutorials my experience after 40 years if you don’t have the skills for mechanics and troubleshooting you will probably fail at repair attempt and likely cause more problems. Stick to a blog where people have some experience.
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
Your channel is extremely helpful to many young techs trying to make it. Salute to you good sir 🙏 You're a great teacher
I used to be in awe when I watched guys trace voltage and ohm things out. I still think about that whenever I'm doing it. Love this trade
Super helpful. I need a big playlist of electrical help videos. It slips out of my mind from time to time how all these functions work.
The good thing is you have everything you need in your phone. Once you can look at a schematic and understand all the symbols and flows and know the sequence of operation ( more complex systems) may require a manual. Even a factory tech needs manuals sometimes on as built systems. It takes time and dedication to learn and understand everything and nobody knows everything. The HVAC& R industry is now much more than a home split system to a 5-10 ton rooftop unit. It’s comms and logic which come in many forms and sizes. Asking for help when you don’t want to because of pride. Every tech wants to be the best or should, but also be humble.
This is Very Critical to learn and know about electrical wires and Connections..... Thank you Teacher 👍
Being in Arizona, I see 4 and 5 ton systems every day and very few 2 ton systems. This was a great video though, thank you for spending the time to make this amazing content! The technician community thanks you! 🤝
I agree. I don't use continuity that much and like to go off of the Ohms so that you can catch little problems that you might miss if you just went off of the audible cue.
Maybe a nice use for it is when a compressor is overheated and you want to cool it down to get the safety to reset you can connect alligator clips in continuity mode and once you hear the beep you know it's finally reset.
Thanks for the video!
That's the exact use I have for the audible circuit tester.
Exactly what I use the continuity setting for. Just showed another tech that last week.
The continuity beeping sound is good if you're trying to find a short to ground, You can go quickly through a system and listen for tone. Also, going through a circuit that has many points to see if it's open or closed.
yep
Oh I always use the continuity function because I didn't know any better, thanks for correcting that!
No worries!
Im gonna send this to the new guy.
@daniel343ful I am the new guy.
I’m a new guy as well started in commercial ac as a helper I become a pm tech in October and I’ve been trying to learn as fast as possible
My thoughts too
😂
@@tiino4690same lol
Great information! When I try to teach other techs they scratch their heads! They’re thinking open or closed only.
This is imperative to understand especially when testing heating elements, and how you can aid in determining the proper BTU output of electric heat as the elements having resistance outside of its spec will lead to issues with high utility bills and or poor heating due to tripping limit switches.
Absolutely, understanding the proper functioning and testing of heating elements is crucial in HVAC work. Testing their resistance and ensuring they are within specifications is essential to avoid issues like high utility bills or poor heating performance due to limit switch tripping. It's important to pay attention to these details to ensure efficient and reliable heating performance for your customers.
@@acservicetechchannel Not to mention fires.
Excellent session.
Waiting for more videos
Thank you.
Wow, I’ve been doing it the wrong way this explains a lot. Thank you for sharing.
Thank you for watching, glad I could help!
Simples ...😊 plain English description. Subscribed 👍
The beep test is very useful when you are simply trying to find whether a switch is open or closed, or if you have a broken wire somewhere or something is plugged in to the wrong place or not fully seated. Also useful when tracing wires. In other words, sometimes a yes or no is more important than how much. This is the whole reason behind digital electronics and communications. On or off is easier and more reliable than precisely measuring the voltage.
It doesn't seem like you watched the video.
@@shawnsg why is that?
@@shawnsgdoesn't seem like you read his comment. Sometimes you might not be directly in front of your multimeter testing the wire and a beep can tell you if the line is O.L or 0.0
Great video and a solid explanation.
Thank you great explanation!!!! Just bought this meter can’t wait.
como siempre ,excelente en calidad y enseñanza ,saludos desde córdoba argentina ¡¡¡¡¡
what are the decent clamp meters for hvac testing and maintenance
I have used UEI my whole career!
awesome Craig!!!! thank you for sharing I love the book! and all your videos.
My pleasure!
Another excellent session
👍Awesome explanation and demo! Thank you!
If you guys are working with the power turned off due to some as yet undetermined fault being present, how do you supply the 24v to the relay coil? Do you carry a separate 24v transformer and wire that to the mains supply? Or do you isolated the out put of the units own 24v, and use jumpers to supply the 24v to which ever relay or CCTV your are currently testing?
I’m using this as a reference and educational tool.
This was an amazing video! Thank you for posting!
Loved your videos really helpful.
You guys recommend that multimeter for someone starting out in HVAC? Or is there a better brand
My Fluke 116 has a “Auto V Lo Z” setting.
It was useful recently in finding a faulty thermostat circuit board issue. Checking with regular voltage setting would show various AC voltages due to high resistance circuit board faults in the thermostat.
Testing with the “Auto V LoZ” setting would shunt the noisy voltages on the line and the circuit would work normally.
Maybe a video on that feature and the limitations of high impedance digital meters and their susceptibility to line noise might be helpful.
Baby steps! I think a lot of people would have a hard time wrapping their minds around that concept when they're starting. Were there any capacitors on the thermostat circuit board?
thanks for the tips very helpful with the understanding between the two will put it to use
Glad it was helpful!
@3:12 me on the field shaking around seeing random numbers on the screen 😆 🤣
Good explanation 💡
Excellent video
Thanks for an excellent video . I knew all of that , but this would be very useful for a lot of guys I used to work with , they didn’t come from an electrical background.
Glad it was helpful!
Nice channel any videos on automotive air condition?
Good ⚡️⚡️⚡️Stuff
18AWG solid copper wire has a resistance of .651 ohms per 100 ‘. FYI
Thank you for saying something about standard wire resistance. While most applications will not have a run long enough to create significant resistance and voltage drop, there are going to be cases in which it does occur. There is even more resistance with stranded and thinner gauge wire. 0.0 ohms is perfect world resistance on short wire runs even.
Thank you!
You're welcome!
hey can you explain a couple things further:
1)
what is it about corrosion and melted wires (I'm assuming a different mechanism for each) that causes an increase in ohms and resistance
2)
shouldn't even simple wires have resistance? Is anything really zero resistance? You said the door switch thing for the gas furnace should have 0 and those simple wires also should have 0.
3)
What is so bad about some device having more resistance than it "should"? Can you explain a bit more in detail how more resistance leads to higher current and heat? This completely confuses me. I thought the higher the resistance, the more the current is being resisted and thus the less current gets thru!
4)
Last question: What exactly does that door switch do?
@MathCuriousity
1. Corrosion causes higher resistance and higher resistance causes higher voltage drop. Since voltage is the electrical energy, you will develop heat wherever there is voltage drop due to resistance. The more heat that develops, the higher the resistance goes, and the higher the resistance goes, the higher the heat goes, so you can see that it's a catch 22 until the plastic or insulation melts or the metal contacts become burned and pitted. As you can see, corrosion and loose connections cause high resistance and they can cause a system to stop working or even worse cause a fire. One thing he said in the video that is NOT correct is that "current goes up when heat and resistance go up". If resistance goes up, current actually goes down. The melting of plastic on contactors and plastic insulation on wires, and burned/pitted contacts on switches are not caused by high current; they are caused by voltage drop in that spot that's loose or corroded.
2. You are correct. Everything has resistance. Except for superconductors but they're not used in HVAC so you don't have to worry about them. The ohmmeters we use are not sensitive enough to read the resistance value of 1 foot of 14 gauge wire. There are very expensive ohmmeters that will read and display the resistance of 1 inch of 14 gauge wire. For the purpose of HVAC, the multimeters we use are more than good enough.
3. Read answer #1
4. That door switch is held in the closed position whenever the furnace door is properly installed and allows line voltage of 120V to go to the circuit board and power both the 24V and 120V circuits so the furnace can operate. If the furnace is running, and you take off the door that is holding the switch closed, the switch will open, cut electrical power to the furnace and furnace will stop working. Also, if the door is off the switch will be in the open position and furnace won't have any electrical power going to it so it won't start.
This guy is a gem. He's worth his weight in gold in my opinion. He puts out great content. I'm not in HVAC. I'm actually an airplane mechanic but I've learned so much from watching Craig. I like doing all my own repairs and installs. If you want to be the go to guy in your company, watch his videos and take notes.
@@bernardocisneros4402
Hey Bernardo, I had another question given that clearly you are a gad damn genius! So something’s been bothering me lately. I stumbled on someone on a forum mentioning that
1)
If you take your hand and put pressure on a fan blower motor blade, it won’t start working harder, actually less work will be done and less current will be drawn. Is this true?!! If so why?! Intuitively to me it has to work harder and I would think more current will be drawn? Someone else mentioned “internal resistance” - no idea what that is or how that would play into this even if it is true.
2)
In another area someone mentions that’s: centripetal fans will draw less current if blocked but axial fans will draw more current if blocked. Any idea if this is true and if so why?!
Thanks so much kind soul!
@@MathCuriousity Thanks for the compliment but genius I'm not. I've just being doing this a while. My job working on airplanes deals a lot with electrical and electronic components, so you have to be on point with your electrical knowledge. You don't want to fry a $100K piece of equipment.
If you hold a blower motor fan blade with your hand to prevent it from turning, it will do less work, but draw more current. It partially has to do with how "work" is defined. Work is defined as the product of force and distance. In other words, work is equal to the force applied times the distance it's applied, and since the fan doesn't rotate, there isn't any distance travelled when you're holding it still, so the distance portion of the equation is zero, and anything times zero is equal to zero. Let's not worry about that part because it doesn't really matter in the trades. It matters more so in engineering when they're designing these furnaces and air cond units.
There's 2 types of resistance when dealing with motors. There's physical resistance: you holding the fan blade so fan won't turn and electrical resistance measured in ohms that opposes the flow of current.
There's a lot that goes into properly answering this question, and I don't want to write a book, but just know that increasing the physical resistance on a motor will increase the current flow. The motor will draw more current.
Increasing the electrical resistance on a motor or its circuit, will decrease the current flow to the motor.
The impedance of a motor is the sum of its internal resistance and inductive reactance. In short, impedance is the total oppostion to current flow in a motor. Reactance also opposes current flow and is also measured in Ohms just like resistance but it's not the same thing. The internal resistance of a motor is composed of the resistance in its windings. inductive reactance is kind of like resistance but it's not. Inductive reactance in a motor is at its lowest when the motor is NOT turning. As the motor begins to turn, its inductive reactance starts increasing. This is why a motor will draw much more current at start-up than when it's up to speed. This current is called in-rush current. The reason it's higher at start-up is becasue the only opposition to current flow at start-up is the motor's internal resistance. As the motor begins turning, the inductive reactance starts increasing and helps the motor's internal resistance to oppose current flow.
It doesn't matter what type of fan it is. If it's driven by a motor, it will behave in the manner I described above. Being axial or centripetal doesn't matter.
@@bernardocisneros4402 so if we hold the blade with our hand increasing physical resistance , the current draw will increase and just not to torment you further with questions but if you have a moment: is this current increase because: A)
Torque increased?
B)
Impedance increased? If so was it internal resistance or inductive reactance to make the impedance increase ? (Since you mentioned impedance is a sum of them so one has to have had risen).
Thanks so much!
@@MathCuriousity The current increase is because torque increased and Impedance decreased. The reason impedance decreased is because the resistive portion of impedance stayed the same but inductive reactance decreased.
Great info
Great vid
As always I like your videos nice videos
Glad you like them!
There is a lot of this that is basic electricity and electronics theory that without some knowledge in that area first can be very difficult to understand. Even though someone might think they do. The condition described might be understood, but the underlying hows and whys that will enable deeper understanding in order to troubleshoot effectively are not.
Not a criticism of your excellent video, just acknowledging the reality of what truly understanding this process in order to accurately and quickly find faults will require.
I might add that the meter or a better meter maybe measuring the OHM value of the probles also and that's why you may not be getting Zero Ohms!
Thank you helps me alot
Can you make a video about refrigerant heat exchanger , please?
Very niece sir ji 😘🇮🇳
thank you so so much!!!
That was awesome
Thanks for another great video. It would be nice to show a new contactor and how the resistance is 0 ohms.
What is the “NCV” mode on meter?
NCV stands for Non-Contact Voltage. This feature allows you to detect voltage without using your meter probes. I wouldn't trust it 100%. You can try it until you get comfortable with it but always double check the voltage with the meter probes before beginning work. NCV has steered me wrong a few times.
one other question: what's the difference between a thermal limit switch and a "low/high limit thermostat" ?
The thermal limit switch cuts power to the gas valve when it's subjected to an overtemp condition. For example, if the blower fan in a furnace stops working, the furnace temp will keep rising until the thermal limit switch trips and cuts off power to the gas valve. Without power, the gas valve closes, stops supplying gas, and the flames go out.
A low/high thermostat will maintain a minimum temp and also maintain a maximum temp. Let's say we set it to a low/high of 65/85. The heater will come on when the temp drops below 65 and the air conditioner will come on when the temp goes over 85.
@@bernardocisneros4402 very cool! So how do these limit switches shut off the gas? Are they - how can I put this - causing an open circuit to shut it off or causing the electricity to be shunted somewhere else ?
@@MathCuriousity The limit switches open their contacts and cutoff power. They do NOT shunt it to ground or anywhere else.
@@bernardocisneros4402 ah ok that makes sense I’m an idiot. I geuss all limit switches work that way right? At least fundamentally?
@@MathCuriousity All the limit switches that I know of work that way.
Sometimes you just want to ring something out though checking for the right wire
Need advice. I have a unit that’s not blowing cold. The pressures look normal. The compressor is fine. Last guy replaced the fan motor. I said but the suction line still isn’t cold to the touch it should get cold to the touch within seconds. He said since it’s so hot it’ll take a while to start cooling. I knew better but still paid him and he won’t return my call. I knew better the suction line always gets cold within SECONDS of the condenser coming on. If I turn the unit off for a while and then turn it on, the suction line gets cold for about 1 minute but then that’s it, it goes back to ambient temperature and inside the it’s not blowing cold. I’ve now had 3 different people look at this unit. No one knows what’s going on. I’m already out $500. Any thoughts? Bad TXV?
Thank you!!!!!!!
Wrong video, i know.
But, i was curious :Why in the video showing the vacuuming process of a system did you use 3 appion valve core tools instead of 2?
Have this question, always wanted to ask, thank you much: when measuring superheat, why taking the pressure/temperature at suction line and subtract from the vapor line copper's temperature? Pressure at vapor line yields the temperature of the vapor at that location, not the saturation of the liquid/vapor inside the evaporator coil..also what is temperature of the copper line? what does it represent? I thought the true superheat would be the temperature of the wet bulb minus saturation temperature, which is the temperature of the mixture liquid/vapor inside the evaporator coil because this superheat number represents how much heat/enthalpy is absorbed and removed by the refrigerant in the coil...this superheat has nothing to do with vapor temperature at the suction (derived from the measured pressure) or the temperature of the copper pipe...Appreciate if the host or someone can address. Thank you much.
More than happy to be the 250th like.
Sharing to Facebook.
I didn’t grasp anything but still watched
Now watch it again, it's all about repetition
I watched a video from this channel about heat strip circuits and one video from grayfurnaceman about changing a sequencer to a contactor about 20 times until I figured it out. Every time I watched, something clicked in my brain and I made a discovery. Repetition is key. Now I happily replace all my sequencers with contactors when working with electric heat.
Superheat, typically 12-15F taken near the compressor is important to make sure your not bringing any liquid back into the compressor (low superheat) but is not too high which will cause the compressor to run too warm or hot. Of course the proper charge and line sizes need to be correct.
Hello, I am subscribed to the Channel, but I understand a lot of English, we hope that the translation will be done into Arabic so that we benefit from the videos with thanks and appreciation
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As an electrician, I can tell you beyond a shadow of a doubt, that the mm continuity function plays a vital role in determining certain electrical and communication shorts. All electrical and communication systems are NOT equal and thus that feature has its place from time to time; otherwise, why would mm manufacturers bother designing it into their products?
Off course it has its place but not in a video for techs just getting started in HVAC. After you get some experience and know how your meter works, then you can decide which feature to use, but for newbies the resistance feature is best over the continuity feature.
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I think I knew most of that.
Wow
Corrosion Number 1 Connection Killer
AC SERVICE TECH, make a YT lesson about the top 20 most common problems in HVAC. Testing the start up capacitor and condenser capacitor.
10x 🧠
'Promo sm' 😍
Stop with the ads
Contractor for 40 years stop just stop trying to give tutorials to average American citizens tutorials or no tutorials my experience after 40 years if you don’t have the skills for mechanics and troubleshooting you will probably fail at repair attempt and likely cause more problems. Stick to a blog where people have some experience.
It's a free country.