Carrier AC unit contactor replacement

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Old 09-30-20, 11:04 PM
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Carrier AC unit contactor replacement

I plan to replace the contactor in an older Carrier AC unit. The replacement looks similar but not exactly the same so I wanted to confirm if the wires on the original one will go to the same place on the new one. Honestly I’m not sure what all the different wire colors correspond to. For example the two black wires that go on top or the two brown on the bottom. I assume the black ones are the 24v? I appreciate any guidance. Thank you in advance.





 
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Old 10-01-20, 07:09 AM
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Hi, there should be some specs’s on the old contactor, coil voltage should be 24VAC which the new one is and 30 Amps should be fine, it’s a bit hard to tell which wires are which in the pic, if shut the power off to the unit and pull the old contactor out, leave all wires connected, install the the new one and just swap wire for wire you should be fine.

Geo 🇺🇸
 

Last edited by Shadeladie; 10-02-20 at 07:45 AM.
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Old 10-01-20, 07:22 AM
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I think the brown wires are for the 24v control. Trace them to verify as the 24v would connect to wires going to inside the house (Y and C thermostat wires - normally thin red and white).
 
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Old 10-01-20, 09:25 AM
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I added another pic to show more. So if the brown wires on the bottom of the contactor are the thermostat, wouldn’t they usually go on each side of the contactor (top and bottom)? What would the black ones be?
 
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Old 10-01-20, 10:54 AM
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Some contactors have both control tabs only on one side. Follow the brown and you see it goes down to the splice box. Does it not then connect to wires that go to the house?

Acordding to the diagram those black wires would be for a crankcase heater.
 
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Old 10-01-20, 02:39 PM
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So if the thermostat wires are Brown and go on the front two contacts of the contactor what purpose do the two contacts (with black wires) on the back serve? It would be good to know what each connector is for. I couldn't find much online. I understand that the screw on contacts on top are the 230 volt wires, one open and one closed until activated by the thermostat. I assume the ones on the side are for accessories.
 
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Old 10-01-20, 02:43 PM
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Look at the picture of your new contactor. We see two terminals on the side.
Are there two more on the other side ?

Post the part number of the new contactor.

I'll add more info as soon as you answer this.
 
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Old 10-01-20, 03:23 PM
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There are two terminals on the other side also. The part number is HN51KC024. Thanks.
 
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Old 10-01-20, 04:00 PM
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Thank you.

There are two connectors on each side. These are for the 24v contactor coil. One brown wire will go on either side of the contactor.... one on each terminal. There will be a spare terminal left on either side. There is no polarity with this.

The contactor is labeled L1 and L2 for the incoming power side. It's labeled T1 and T2 for the outgoing/switched side. Technically... only the L1/T1 connection is switched. The L2/T2 connection is just passed thru.

There is one black wire on L1 and the other on T1. As mentioned.... these are for the crankcase heater. The heater is in series with the L1/T1 connection so that it gets powered when the contactor is open. There is no polarity to this connection.

There are two yellow wires on T1. One goes to the capacitor (C) and one goes to the compressor (R).
There are two black wires on T2. One goes to the compressor (C) and one to the condenser fan (C).

It doesn't matter which actual terminal you use for which wire. Just make sure you have the proper colors on the correctly labeled terminal set. Each location has a place for multiple wires.
 
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Old 10-01-20, 04:06 PM
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Here is a better picture your current contactor in someone else's system: http://www.myhvacparts.com/store/med...contactor2.jpg 240v power comes in on the two wires on the right. motors are fed from the left connections. Two wires for the coil/thermostat that trigger the contactor are on the bottom. This is a single pole contactor - means the top power line is switched by the relay but the bottom wire just passes through to the other side.

The old one is different that the new one you have in that the coil connections (for thermostat) both connect on one side. Otherwise functionally the same.

The black wires are for a crankcase heater that connects across the contacts on the top. This means they get 240 volts when the system is not running and 0 volts when it is running. A trick that requires a single pole contactor like you have.
 
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Old 10-01-20, 04:20 PM
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Just to clarify.......
On the old contactor..... both 24v (brown wires) were on the same side.
On the new contactor.... there will be one wire on each side.
 
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Old 10-01-20, 05:23 PM
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Thank you both so much for all the info. Still trying to process it. So just to be 100% clear, the two brown wires (24v) that are currently both on the one side of the contactor will each actually go on both sides? Where will the two black wires go that are across from the brown wires on the old contactor? I highlighted the terminals in question. You may have explained with the L1 T1 etc but I thought those only represent the ends of the contactor where the 230v wires go. Thank you.



 
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Old 10-01-20, 05:38 PM
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Wait a minute...... you posted pictures of two different contactors. Which one is it.

 
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Old 10-01-20, 05:49 PM
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The one on the left. The one that has the two black wires on one side and two brown on other. So if I understand correctly the brown wires will be separated: one will go on one of The two connector on one side and the other will go on other side. There will be two connectors with no wire. So the question is where do the two black ones go?
 
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Old 10-01-20, 05:58 PM
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Yes..... one wire goes on each side of the contactor.

The four tabs in each area are all connected together.
You will connect those two black wires.... one to each end of the switched contact.
 
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Old 10-01-20, 06:07 PM
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Ok but I think all those terminals will already have wires connected to them when I move them over from the old contactor. In other words no empty posts for the black wires. So I will have to combine with one of the other wires on the T1 and L1 sides?
 
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Old 10-01-20, 06:12 PM
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Your old contactor had two tabs at each location. Your new one has four.
 
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Old 10-01-20, 06:24 PM
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Oh. I thought there were 4 also. Well that makes sense now. Still weird why they changed the design. I wonder how many just do a straight swap and what happens if you put the two 24v on the same side and the black on the 24 side too. Would prob fry something. Thank you again. You have been very helpful!
 
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Old 10-01-20, 07:04 PM
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When a condenser is designed..... they spec out a specific part like a contactor. Now you have many slightly different contactors. Too expensive to manufacture and stock many different parts. So now they're pretty much universal. Basically there are two types of 30A contactors that will replace many different models.
 
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