Heat Pump wiring 5 wires on thermostat 4 wires on heat pump

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Old 10-24-20, 04:10 PM
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Heat Pump wiring 5 wires on thermostat 4 wires on heat pump

What would be the best way to wire a heat pump? I have 5 wires for thermostat 4 wires to heat pump. I have a Ecobee 4 to 5 wire power extender that is suppose to be able to uses on heat pump to work as 5 wires. It would be next to impossible to change wiring.
Thanks for any help
 
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Old 10-24-20, 04:59 PM
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Welcome to the forums.

We cannot guess. You'll need to post a picture of the wiring on the existing thermostat
and tell us the model number of that stat.

How-to-insert-pictures.
 
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Old 10-24-20, 05:19 PM
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Sure Comfort heat pump

Honeywell RTH7600D1048 thermostat
Goodman air handler
Sure Comfort heat pump 5 wire same rheem, rudd
 
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Old 10-24-20, 08:27 PM
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No need to start a new thread. If you don't get a reply..... just bump this thread.
I've been unable to reply for the last three hours. Just got back on.

As I mentioned..... I need to see a picture of your wiring. If you can't take and post a picture.... pull the stat off the base and tell me what color wire is on which terminal.
 
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Old 10-24-20, 09:09 PM
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Can you make any digital thermostat work a heat pump and air handler with only 5 wires from thermostat? I'm not where I can take picture of unit.
 
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Old 10-24-20, 09:17 PM
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To run a basic heat pump system you need.....
1) R - 24v power
2) Y - compressor
3) W/aux - back up electric heat
4) G - blower control
5) O/B - reversing valve control

That would be a minimum of five wires.
If you're installing a wifi stat you need a C wire which makes six wires needed.
 
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Old 10-25-20, 07:31 AM
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Next problem my heat pump needs 5 wires if I want to use heat strip. I have 4 wires. What can I do or can I use a ecobee 4 to 5 wire power extender.
Thanks
 
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Old 10-25-20, 08:20 AM
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You would need 5-6 wires. A power extender will not help in your case. It’s for consumers with no common. That is not your problem.
How did this unit run in the past with only a 4 conductor bundle?
The use of electric heat is mandatory if you live in a cold climate. For normal unit operation.
 
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Old 10-25-20, 08:21 AM
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I think this hp is made by rheem. So rev valve would energized in heat mode. Could I use one of wire on comp to rev valve to eliminate a wire?
 
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Old 10-25-20, 08:29 AM
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You’d eliminate the cooling function in the unit then.
How did this unit run previously with only 4 conductors? How is it wired now? Post photos of the wiring.
 
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Old 10-25-20, 09:08 AM
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I'm changing out a ac to hp and there is only 4 wires there. Any ideas?
 
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Old 10-25-20, 09:21 AM
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Pull new thermostat wire.
Is your equipment installer unable to do so?
 
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Old 10-25-20, 09:45 AM
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It would be next to impossible to change wire. Would I get any energy savings to run both strip and hp at same time. And put thermostat on hp to kick out when too cold?
 
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Old 10-25-20, 09:53 AM
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Anytime your running electric heat, your elevating your electric bill tremendously. An efficient heat pump keeps electric heat off as much as possible.
If this is a new unit, does the installer have any suggestions?
 
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Old 10-25-20, 11:50 AM
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I'm installing it. And I'm looking for suggestions. I know I could put a dp switch inline to turn to hp or strip when it gets really cold.
 
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Old 10-25-20, 12:26 PM
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Thats not how heat pumps work.
You’ll simply need new thermostat wire with more conductors.
 
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Old 10-25-20, 01:19 PM
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Yes you could manually control the heat strips but you need to remember that the heat pump condenser needs to to defrost. It needs to bring the heat coils on un-attended.
 
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Old 10-25-20, 01:39 PM
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The handler is upstairs and there is no way to get to wiring with out cutting through several walls. Then I would have to have it run down the outside of wall from second floor. ugly
Is there any other way?
 
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Old 10-25-20, 02:03 PM
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No, there really isn’t.
I know of nothing for residential use for split systems.
 
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Old 10-25-20, 02:15 PM
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If you didn't already have the equipment you could opt for communicating equipment.
It communicates on several wires.
 
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Old 10-25-20, 03:28 PM
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What is communicating equipment?
Sorry I googled it.
 
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Old 10-25-20, 03:43 PM
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OK I been thinking I ony have 4 wires going to hp. You need 2 wires for comp and 2 wires for dev valve to heat. Why can't I jump from comp one side to dev valve. Of course I need to make sure I on opposite of trans for the wire going to dev valve? That would free up 1 wire I need.
 
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Old 10-25-20, 05:46 PM
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You need....
1) R - 24v power
2) C - common
3) Y - compressor
4) O/B - reversing valve.

So technically four wires will run your condenser BUT without a 5th wire..... when the unit goes into defrost.... the electric reheats will not come on. Defrosting a heat pump means running it in A/C mode where it uses heat from inside the house to defrost the outside unit. That would allow cold air to flow inside the house.

Communicating means to do many functions on two or three data wires.
 
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Old 10-25-20, 05:55 PM
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So will my scenario work? I'm saving 1 wire to use on rev valve.
 
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Old 10-25-20, 06:21 PM
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No, you’ll create a unit that will only run in heating mode.
 
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Old 10-25-20, 06:43 PM
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When it goes to ac the thermostat wont send power on the 1 leg to the dev valve. So it wont have a complete circuit of power to valve.
 
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Old 10-25-20, 07:23 PM
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The reversing valve is sharing the C wire with everything else 24V powered. So removing a wire means it’ll never receive 24V, and never switch to cooling.
R-24V Hot
C-24V Common for all components
O-Reversing valve
W-Auxiliary heat
Y-Compressor
 
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Old 10-25-20, 08:05 PM
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Finally I completely understand. OK can't I then use a small 24v trans and power it of the main power on relay to do r-24 hot, c-24v common.
 
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Old 10-25-20, 08:08 PM
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No, you still need a common off the source transformer to power the coils. Can’t use the transformer inside for hot and another for common.
And you cannot have 2 different sources of control power within the outdoor unit.
 
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Old 10-25-20, 08:15 PM
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Thanks soo much for the help. Do all hp need this many wires to operate?
 
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Old 10-25-20, 08:21 PM
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Yes, except for high end communicating models.
Have you thought out other details if your doing a DIY install? The power source for the air handler and electric heat? Special tools. How to properly size everything?
 
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Old 10-25-20, 09:10 PM
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What is this they are using. It looks to be on hp with 4 wire.


 
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Old 10-25-20, 09:12 PM
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I don’t know what that device is.
 
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Old 10-25-20, 09:16 PM
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Old 10-25-20, 09:19 PM
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I don’t think that device is for heat pumps. It’s for when there’s no C wire.
Look at the photo. There’s no O terminal.
 
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Old 10-25-20, 09:35 PM
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I'm going to call factory tomorrow and see if they make something for this. It's my last option.
 
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Old 10-26-20, 01:19 PM
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What is this they are using. It looks to be on hp with 4 wire.


This doesn't look like a heat pump. That's a "C" with enough of the letter blocked off it almost appears to be an "O".
 
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Old 10-26-20, 02:26 PM
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Do we need the R to have power for the control board? If so could I use a small 24v trans to connect R&C and still connect the C wire? That way I would free up the R wire.
R-24V Hot
C-24V Common for all components
O-Reversing valve
W-Auxiliary heat
Y-Compressor
 
  #39  
Old 10-26-20, 07:16 PM
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Yes, it needs 24V, but cannot be a secondary source of power from the air handler control power source.
You can’t put a secondary transformer in like that.
 
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Old 10-26-20, 08:05 PM
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It would be like a center tap trans. The R & C would power the board. The C with the wire attached from handler trans witch power therm and handler would a complete circuit for O W Y on hp. I hope I'm not bothering you just trying to make this work.
 
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