Can I disconnect the air handler heat strip for heat pump system ?

[RDuke]

Hi all,

In another post, it was mentioned that it is possible to disable the heat strips in an air handler so my generator can run the pump without the high
current heat strips causing issues. Now that freezing rain in eminent in my area, it is something I would like to understand better.

My system is a two year old 4 ton Rheem heat pump with 10 KW heat strip in the air handler. My assumption is that defrosting is time based, temp based or both. So how can I disable the heat strips, is it a matter of removing the 240V wiring to the heat strips ? Or can it be done using the control wiring to the air handler? I don't know what intelligence is built into the air handler, and whether it will fault if the coil is an open circuit. I guess it is one of those cases where a "dumb" air handler is an advantage.

Please advise if you have any thoughts. I realize the coils could freeze up, but I can monitor for that.


Thanks in advance

---Update---

I think I may have figured it out since I found the documentation in the attic with the air handler. The documentation says if blowing cold air is not an issue, you can run max efficiency by not connecting a wire to the W1 input on the air handler. I think that may work. If anyone thinks otherwise, let me know please. It is a two stage system so there is a W1 and W2, and a Y1 and Y2. I am thinking the W2 is not connected, but I have not taken it apart yet to verify.

 

[OzSolar]

The documentation says if blowing cold air is not an issue, you can run max efficiency by not connecting a wire to the W1 input on the air handler. I think that may work. If anyone thinks otherwise, let me know please. It is a two stage system so there is a W1 and W2, and a Y1 and Y2. I am thinking the W2 is not connected, but I have not taken it apart yet to verify.

What did you figure out?

W1 is usually heat the heat pump and W2 is the strips (AKA Emergency Heat)

It could be as simple as re-programming your thermostat to tell it there's only one heat stage. I'm no HVAC expert but I've helped a few friends do that so they could stay out of the strips until a much lower temp and/or use their portable generator during an emergency. They went from ~34F outside air temps to mid teens with thier basic older heat pump. Of course the run time increased.

 

[Supervstech]

A quick pic of the wiring inside the air handler would confirm, but yup, it should be that simple.

 

[bhbaker220]

My Carrier 4 ton heat pump has two 5 kW heat strips in it. I disconnected one of them (and wrapped it in electrical tape) so I could run it in an emergency with my inverter or my generator. Not sure if it would work if I disconnected both strips. I have not tried to disconnect the 24 volt wiring to the Emergency Heat Relay. I have Honeywell T6 ProSeries thermostat. It has an AuxHeat Lockout feature that can use the outdoor temperature sensor to control the temperature in which AuxHeat will be used but I have not tried it either. I'm a little afraid that if I disable both heat strips that I'll get too much cooling in the house during the defrost cycle. We had low temps this morning around 20 degrees F and the defrost mode lengthened to about 10 minutes. It typically only runs for about 2-3 minutes in defrost mode with ambient conditions of 25 to 30 degrees F.

 

[RDuke]

Fortunately we made it through the ice/snow storm only losing power briefly 3 times. I do have a fireplace so in a pinch I can burn wood. I will have to run some tests to see if it works disconnecting W1, but the manual actually says that should stop the heat strip from running.

 

[dreancestere]

If you have multiple heat strips, and you want to disconnect only some of them, make sure they come on in the order you think they will. When my installers disconnected one of mine, they tested that they were disconnecting the final one that would turn on. The wiring connection was not in the obvious order. I think they said the first one was connected to one side of the 3 connection points, the 2nd was connected to the opposite side, and the final one was connected to the middle one: [1 3 2] instead of [1 2 3].

 

[Philip53]

@RDuke, you will likely have a separate breaker in your panel for just the resistive heating elements, or if the AHU is fed with a large breaker you will have separater breakers in your AHU, usually one for each strip. If that is the case, just flip off those individual strip breakers. Job done.

Failing the above, is your heat pump a 2-stage compressor? If so, the W1 will be for the first stage, and the W2 will be for the second stage. In this case, you will have an additional wire (probably white), that is connected to the 'E' or 'Aux' connection in the T-stat - wired to the relay or controller for the resistive heat strips. Please note that T-stat wiring is not always universal between brands.

Good luck.

 

[RDuke]

I installed a single 60A circuit for the air handler back when I converted it from natural gas to a heat pump myself back in 2007, but when the system was replaced recently, I paid a HVAC company to redo everything including duct work at great expense. I am pretty sure Y1 and Y2 control the fan speed of the air handler for 2 speed control, W1 and W2 on this unit only control the heat coils. Since I only have one 10 KW coil it should only need a single control. I will test it out to be sure. I can easily tell when it is on by looking at my Sense.com power monitor. It works very well for that.