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I thought I knew at least the basics of how the Honeywell Thermostat worked, but testing with a multi-meter dashed those presumptions. I have another question posted, but until I get the basics straight, I am just confused.

I have a Honeywell TH6320R1004 Wireless Thermostat with the following settings - Changeover valve: O/B terminal controls valve in cooling mode - System Type: 2 heat/1 cool heat pump

I have a Taco SR503 providing power to R which is jumped to Rc. I presumed that with no power wire to Rh, there would be no power to Rh.

  • However, when in cool mode, I am able to get 24v from Rh to G and Y terminals. Why is this?

I disconnected the Rc and Rh cables to test continuity between Rc and the various Equipment terminals and the same for Rh and the various Equipment terminals.

I found the only scenarios where there was continuity:

In Heat Mode

  • Between (Rc and G) and (Rc and Y) when there was a call for heat

In Cool Mode

  • Between (Rh and W) and (Rh and W2)
  • Between (Rc and G) and (Rc and Y)

My presumption is that it is only in cases of continuity where the thermostat can make something happen. But this test does not make a lot of sense to me.

  • How does this thermostat run a heat pump if the Rh does not ever have continuity to any Equipment terminals in Heat Mode.
  • Why does Rh have continuity with W and W2 when calling for Cool (shouldn't it be Rc powering W and W2 with the setting: O/B terminal controls valve in cooling mode?)
  • Why does Rc have continuity with G and Y when calling for heat?

This test has shown my complete ignorance and my presumptions are way off.

Update I am beginning to suspect that this thermostat cannot be powered with 2 transformers in 2 heat/1 cool heat pump mode - this option is not shown in the manual.

I am wondering if I need to change it to 2H/2C System (2 transformers) and switch to "O/B terminal controls valve in cooling mode". Then I might be able to use W for heating and Y for the cooling mode.

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