1

When a low voltage HVAC unit cools a home do both W1 and Y1 circuits activate?

I've tested voltages when heating and cooling.

  • my brown wire is always cold but heat and cool work.
  • my y1 is hot on heat.
  • my y1 and w1 are hot on cool.

I'm trying to figure out what's happening.

Handler, Thermostat, and Outside Unit junction angle #1: Handler, Thermostat, and Outside Unit junction angle #1

Handler, Thermostat, and Outside Unit junction angle #2: Handler, Thermostat, and Outside Unit junction angle #2

Between Outside Unit and 3-Way junction (note reversing valve color change): Between Outside Unit and 3-Way junction

Thermostat: Thermostat

  • How are you taking measurements? When you say it's "hot", do you mean has voltage? if so, voltage to what? Where are you placing your probes to take measurements? Also, what is the make and model of thermostat? What is the make and model of air handler/furnace? – Tester101 Feb 28 '17 at 11:31
  • @Tester101 I'm using a multimeter from the appropriate wire to common and "hot" = 26v AC. Thermostat is a basic Honeywell wifi unit and the handler is a Trane. – acpilot Feb 28 '17 at 11:50
  • Is this a heat pump? – Tester101 Feb 28 '17 at 14:25
  • @Tester101, yes. It's a heat pump. – acpilot Mar 1 '17 at 4:18
  • What model is the handler and the 'stat? Also, can you get us photos of the wiring at both ends? I suspect W1 is being abused for reversing valve drive because the installer didn't know how to get the 'stat to drive O/B properly... – ThreePhaseEel Mar 1 '17 at 4:23
2

Your thermostat repurposes W1 (call for first stage heat) as O/B (reversing valve) when in heat pump mode, instead of having a separate O/B terminal that's unused in conventional mode and using W1 to control the emergency/auxiliary heat. (Instead, W2 (call for second stage heat) is repurposes as AUX/E (auxiliary/emergency heat) when in heat pump mode.)

So, what you are seeing is absolutely normal in your case, merely peculiar to your model of thermostat. See page 6/PDF page 8 of the manual for details.

  • would it do any good to reconfigure wiring per pg6 (8pdf)? – acpilot Mar 1 '17 at 5:10
  • @acpilot -- it's already configured that way, look at the row of labeling on the thermostat below the terminal block :) – ThreePhaseEel Mar 1 '17 at 12:34

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