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Aux heat - install problem that's stumped both tech support and my local HVAC guy

NathanRNathanR South CarolinaMember

This album has the basic details and pictures of the relevant connections and components.

Here's the story:

I have heat pump system split into two zones, with a auxilliary electric heat strips. This is a bog standard system where I live, in South Carolina. 95%+ of the year, the heat pump is the only thing that runs.

After moving in a couple of years ago, I installed two Ecobee3 units, one for each zone. They've worked beautifully in almost every regard, controlling cooling and heat from the heat pump without issue.

However, during the first winter after installing them I discovered a big problem - they don't properly call for the auxiliary heat strips when the temperature drops enough to need them. This is only a few weeks a year, but of course they're some of the weeks when you need your HVAC the most.

What typically happens is that on a cold night I'll get an error message on the ecobee (or in my email) that it is calling for aux heat, but the temp is not rising. In fact aux heat never comes on. Even worse, when the ecobee calls for aux heat it seems to "crash" my HVAC system, or at least the heat pump. I have to power cycle the heat pump and air handler (and therefore the ecobee also) at the breaker to get regular heat back.

I called ecobee tech support, and they walked me through some tests and settings before concluding that there was a problem on my end, most likely with the heat pump. So I called a local HVAC tech. Unfortunately he knew nothing about Ecobee setup. He did, however, successfully reconnect my original Honeywell dumb thermostat, and with it connected I can successfully call for aux heat. That proves that the HVAC side of my system is working, so there must be some problem with how the ecobee is connected or configured.

He suggested I just keep the Honeywell, or get one of their wifi thermostats. I don't want to do that - I love the ecobees otherwise. His other suggestion was that the white aux/E wire should be connected to W2, not W1 on the ecobee. But this doesn't work - W2 can only be connected if W1 already is (W2 is for second stage heating, which I don't have). His other suggestion was to jumper Y1 and W1. I could try this, but I fear that even if it works, it'll mean my expensive aux heat comes on any time heat is called for.

Any advice here? Have I connected everything correctly, or is there another way to do so I'm missing? The attached imgur album shows the original Honeywell connections, my ecobee connections, the connections at the air handler, and some other details.



  • kevinmcckevinmcc Macomb, ILMember
    edited November 2017

    The install manual for the Zone Controller says that W1/E and W2 need to be jumpered on the the equipment side. That is only thing I see that could be an issue.


  • NathanRNathanR South CarolinaMember

    That could be it. I've noticed the original thermostat doesn't work (no hot air) on the Emergency Heat setting, though it does successfully call for aux heat when needed.

  • NathanRNathanR South CarolinaMember

    I did some work at the zone controller this evening. I didn't fix the problem, but I did get some additional info:

    As you can see in the 4th picture, there are three heat lights on the zone controller, indicating (I think) three different heat stages that could be hooked up to it - "Heat 1", "Heat 2", and "EmHeat".

    "Heat 1" is the heat pump. Both the Honeywell thermostat and the ecobee call for it correctly.

    "Heat 2" seems to be my resistive heat strips. Only the Honeywell can turn this one on.
    "EmHeat" I apparently don't have. When I put the Honeywell on its EmHeat setting, or press the Emergency Heat button on the zone controller, I get attic-temp air blowing out of the vents.

    I think what the ecobee is doing is somehow calling for emergency heat, and getting nothing because I don't have that.

    I tried correcting this problem by jumpering W1/E and W2 on the equipment side of the zone controller. The manual says to do this if you only have one source of emergency/aux heat. But this didn't have any effect.

    One thing I think this shows is that my system was never "crashing" as I originally thought - instead the ecobee was just calling for a heat source that I don't have. Flipping the breaker caused the ecobee to call for Heat 1 again, but manually calling for it (or just pulling the ecobee off the wall and putting it back) would have had the same effect.

    But nevertheless I still can't get aux heat from my ecobee. I don't know if I need to configure it differently in software, wire it differently at the wall, or wire the thermostat differently. Or perhaps my HVAC system is incompatible with the ecobee? That seems unlikely but I can't rule it out.

  • kevinmcckevinmcc Macomb, ILMember

    Ecobee should be single stage heatpump with single stage aux. If you put the thermostat in AUX only mode you should get AUX heat. You can test and see if you get signal at the zone controller.

    Emergency heat is same thing as the resistive strips in your case.

    If you hit the Emergency Heat button on the zone controller, measure on the equipment side and see if you get 24vac from W1/E and W2 to C. That means the zone controller is calling for your strips. If you do get the 24vac, then check at the furnace. Measure that you are getting the same 24vac from W1/E and W2 to C. could be wiring issue are furnace or problem with your strips.

  • NathanRNathanR South CarolinaMember

    I believe I've found a solution. I jumpered W1/E and W2 at the zone controller. Now when any thermostat (ecobee or honeywell) calls for either, I get both. Calling for aux heat in the ecobee Test Equipment menu now works. We'll see how it does in real-world conditions.

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