Contactors Explained and Tested: Wiring, Troubleshooting, Problems, Ratings, and Visual Power Up!
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- Опубликовано: 25 авг 2024
- How HVAC Contactor Relays Work, Troubleshooting Procedure, 24v, 120v, 240v Wiring, Problems signs that they are Bad, Reading coil resistance, fla ratings, and visual checks. I will power one so that you can see the plunger go down. Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.
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I've been a journeyman for 17 year's and have been in the field for 21.Your video's are good to watch. Keeps your mind fresh and knock any rust off. Thank you'll.
Thank you very much for the Comment! Glad to hear you are enjoying them!
Thanks! I'd been systematically walking through all the things that could be wrong, replaced the run capacitor (which was bad), verfied the fan motor and compressor were good, but was still stumped why the unit wouldn't work. Turned out the contacts had to be cleaned. Using your video, I was able to get the contactor out, sand down the connection points, clean out the dirt & debris, put it all back together (without losing the spring!) and BAM, the unit fired up like a champ.
Nice, thanks. Contactors are pretty cheap it is best to have the smoothest surface on the contacts possible so if it were to happen again, I would say go ahead and replace it, thanks!
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Thanks for a great video. All these years in the trade and I thought contacts worked
electromagnetically but now I know they suck down. Never too old to learn something
new.
They do work as an electro magnet when 24v or another coil voltage is used. It sucks an iron core downward to close a separate set of contacts. Thanks
acservicetech yeah bro, it's called humor. Thank for the vid. ✌
Ha ha, ok you would be surprised the questions I am asked so I just went with it. i was thinking, man what did I say in that video! ha ha
Been looking for a good explanation of how contactors work. Thanks!
I truly enjoyed this video. Would you consider making a video explaining how you can make s 2 pole contactor work as a one pole contactor. Thanks.
you demonstrated exactly what I have been looking for.
That's awesome to hear Dave!
Yeah, did you enjoy that not being there or was it odd that it wasn't? I know the real long version was not appreciated ha ha
Good video!!!
Thank you for your time.
Thanks for the excellent video!!!
Glad to help Jorge!
To check inrush of your a/c would recommend placing the meter on the compressor common or compressor run wire to measure the hightest Amp reading? Thank you.
hi, i know the 24vac (for contactor coil) comes from the furnace control board. But for the 3 pole contactor (with 240vac coil) , where does the 240vac for the coil come from? thanks.
Ants like to die in the bi-metal disc portion of the armature as well. I have yet to pull a spider web out though lol.
What are the terminal connectors called on the two and three pole vs the ones on the single pole plus contactor Thanks 🙏🏻
Yeah it was a package unit not a split. What was weird is I checked reversing valve for 24 volts and it showed like 15 volts. I told her it may be an issue with transformer. Her unit is less than a year old and it was a new house so it was covered under builders warranty. I do not have any parts to fix stuff but at least I got some hands on. Hope you got some sleep. If you ever come across a package unit with service issues I would like to see that. Thanks man!
To check the voltage there, you can check one lead on one side and one on the other. Check the resistance on the coil or the rv, or
check the ground or c terminal with one probe on the power wire going to the rv. The thing is that it sounds like you didn't have voltage to the rv because you also didn't have voltage at the y terminal to the contactor either. I would work backwards and find where the low voltage signal from the tsat is not making it to the y on the contactor outside, thanks. You would verify if the tstat is correct by measuring 24v at the y to c and the o to c in the packaged unit, ok thanks David!
Do try and remember, something being sucked down requires vacuum to move it. A contacter works on electromagnets.
And now I understand. Thanks.
Thanks Nat!
Can't see where you connected your clips to the coil at 1:50
Awesome video. Thank you. Question I have Siemens "Single Pole" Contactor 45DG10AJA791R, VAC=277, FLA=25, LRA=150, RES AMPS=35. I have 2 of them in 2 different units which are about 14 yrs old(I'm sure that contact is pretty worn out after 14 yrs). I want to replace them with new ones, but apparently Siemens doesn't make them anymore. What high quality brand do you recommend as a replacement with sealed contact area? Also, can you go up on FLA number, let's say 30 or 40, compared to mine that's 25 FLA, same with LRA lets say 160 or 200, and RES AMPS let's say 50 , or should you stay at the same exact numbers as the ones I have when choosing different brand?
@AC Service Tech You put the contacter in front of the meter when connecting it. I couldn’t see the multimeters reading. My problem is when I tested my coil I got 17 ohms. Great but blew transformer fuse. Tested again and noticed that the multimeter reads 0 ohms and then a second later gradually increases in resistance to the original 17 ohms. Obviously my fuse blow immediately with 0 ohms as a dead short. What would cause this and do all coils behave this way. This seems strange to me so I thought it was my meter but the blown fuse tells me other wise. Any explanation you could give me would be helpful. Thanks great video.
So what if I apply 24vdc to a 24vac coil?
Hey man love ya videos, very informative
My question to you :
My unit don't blow anything out the vents and the condenser fan. Condenser fan refuses to spin unless the contactor has been pushed in manually...capacitor was replaced due to the fact that it was swollen on the top.....but the issues remained the same. I've noticed the auxilery heater would come on instead of the regular heat ....none of the wires are damaged
nice job!!!
I see a big spark after the connector/lever gets released….. is that a bad or good sign? Is it necessary to replace it? In another words: after being sucked…. It gets released and there’s a big spark. It is being use on a furnace at home. Thanks
Cool okay very nice
Only one question
in double pole
contactor where connect
a crankcase heather
Thanks
Well at the best you want it turned on when the compressor is off, at the worst you would have it on all the time. You would never just turn it on 5 minutes before the compressor turns on. Most are now sold with a self regulation feature based on temperature so these type get powered directly to the normally hot side of the contactor. If you get a 240v then you will wire the two hots together with the two hots that are incoming into the unit and are connected onto the contactor. Thanks
Question!
Does that 24 Volt have any negative or possible position and need to connect to correct side of connector, or we can connect either side of connector,
will does not make any difference.
The 24 Volts from the transformer is A/C. The polarity switches 50 to 60 times per second depending which country you are in.
thanks sir
Thanks Mukesh!
I tested a contactor and was only getting 24 volts on the one side. The other side very low voltage. Unit seemed to run fine. Any ideas?
Hello again Mr teacher I have an issue with a heat pump not pulling in contactor and I am getting 24 volts . also once I press in contactor manually the condensing part of my unit starts but my indoor blower doesnt.
You say you are getting 24v to the sides of the contactor but the indoor unit's fan is not running? Check the resistance of the coil on the contactor in ohms and make sure it is not 0.0 or 0.L or something close in mega ohms. You are going to have to see if you have 24v on the g wire from the tstat in the air handler. Thanks
Hi. I was wondering if can help me troubleshoot a contactor. It's being use for exhaust fan system. Thank you for any that can give me.it will be welcome
Is a single pole contactor like this is used for 220, won't there always be 110 flowing across from the non broken leg?
That is correct but they are connected to 240v motors so the circuit will not be completed. These are also used for compressors with crankcase heaters so that the power is not disrupted to the heater for the compressor oil, thanks!
I have some wires that have crimps and are connected to the old contactor via the screw. The new contactor doesnt has a screw but not
the size of the old crimp. Is it to cut the crimp off and then strip some of the cable off to connect to the new contactor?
That can be done or to cut the crimp connector down some, thanks!
When performing maintenance checks on AC units, say the contactor is still working, what rule of thumb do go by to say that the contactor needs to be replaced?
Hey Steve typically you would see pretty bad burn marks on the contacts which could weld shut in the closed position. The contactor will typically last a very long time though and is not replaced often unless you have ants getting into it, which you would replace with an enclosed contactor or electronic contactor instead, thanks!.
Just curious. Why while the coil is energized I only read 24 v to ground on one side of the contractor and 0 to ground on the other?
The other side is your common so you would always read 0 volts from any common to ground. That would apply to a light bulb or any relay , motor, or other load, thanks
Had a coil reading of 18.7 ohm resistance. Watched another video and this guy said that it has to be between 9-12 ohms resistance. He said anything over that, change it. I keep getting a blown fuse at my fan control board on a 2ton Goodman heatpump. Unit will run anywhere from 3days to 2weeks before blowing the fuse. Defrost board had some discoloration at the resistors where it looks like it was getting hot. Replaced the DB and the Tstat. Waiting to hear back from customer. Hopefully I don’t, though.
I have one doing the same thing. Have you heard from the customer yet? I hope not.
Yea I would replace the contactor also. . Just went to a check up this evening and mine was reading 18 ohms also so I recommended replacing it
What if you buy a new capacitor and the plunger sucks down but the compressor or fan doesn't come on? Is it still the capacitor?
It would depend on if you have 240v to the contactor in order to power the unit, thanks
So I was looking a friends heat pump package unit and it was not running. Went to t-stat and made sure it was calling for cooling and it was. So I went to unit and noticed contactor was not pulling down. I checked line voltage coming in and it was good when I checked 24 V at contactor I got nothing. I had 24 V from Red to common so transformer was getting power. What would cause 24V not to power contactor?
Hey David, I just got back in and couldn't sleep yet so yes it is 4:30am and I am answering questions. Check to see if the indoor blower motor is on first before checking outside. Make sure that the fan is at auto at the tstat and not at on. If the blower fan is running then that means the tstat is calling for cooling and the air handler is calling as well. Next pull the disconnect at the outdoor unit and check the low voltage inside. Check for 24v from y to c at the inlet of the defrost board. If you do but the defrost board is not allowing power through then it may be one of the pressure switches that have opened up the low voltage circuit. Also if it is not a ruud, rheem or weatherking then you should also have 24v to the reversing valve also. Check this video out- ruclips.net/video/fFL_ZSkAZM0/видео.html
If your resistance is to high on a coil is that a sign of being bad what should ohm reading be on 208/230 v coil
I would compare them to the fla contactors that you have in the truck in order to tell if it is high but basically the higher the fla, then the lower the resistance on the coil and the more work that is being done to hold the contacts together when powered, thanks Matt! If I mentioned high resistance in the video, I meant if you read thousands of ohms then it would certainly be bad and the windings are partially burnt apart. More often, you will read 0.L when they are bad which means that the coil is burnt apart, thanks
Great video Question, can you safely switch just one L lead on a 240 motor and get an effective switch? (Have a single pole 20a switch that I want to use to switch L1 of my 240v dust collector motor. Tx
As long as the switch is rated above the amperage draw of the motor, thanks!
@@acservicetechchannel Thanks. Was not sure if switching just one leg would do damage to the motor.
thanks for posting, do you do jobs that have 3 phase power?
Yes but not as much as residential. A lot of my commercial work is even single phase. I think it is just more so the county in which I live really. But yes some of the larger commercial buildings I work on or have in the past are three phase. You said that is mainly what you are involved with or at least commercial in general right?
I work for a comfort systems usa company in New York State, we only do commercial. I have been doing this for almost 4 years. I find your videos very helpful. I dont get to see much of the stuff you post. Thanks for taking time to post them.
Thanks Capitol, glad to hear!
alright alright OK OK OK alright SO SO SO Right-Here Right-Here OK alright So So alright
You rectify AC to DC, at least I though so? Am I wrong?
That would be a rectifier. In HVAC that would be found in the flame rectification process. A contactor is just powering a coil to close normally open contacts. Thanks Jason Lewis!
If you have a single pole contactor with a 120vac coil, can the same circuit being used to trigger the contactor (pole side) also be jumpered to the throw side to power whatever device is on the other end?
If you were to switch power off and on to the coil to power another load across the contacts, yes you could, thanks!
40 seconds into the video u said the voltage will flow through the contactor... Voltage does not flow, only current flows
James, yes old video and bad language, thanks!
Sir plz 4 ton units wairing me send
WTF did you say?
across NOT ACCROST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!