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I got my furnace and A/C unit replaced last summer. The new furnace has 2-stage heating, the A/C unit is single stage. The installers put in a single stage thermostat, so as far as I could tell it was running as a single stage. I saw that the original wiring consisted of 4 wires, and wanting to make use of the 2 stages of heating, I ran a 5 wire cable, so I have 9 wires total.

For the thermostat, I have an Energate Foundation. It supports up to 2-stage heating and 2-stage cooling. Here are my connections:

enter image description here

This is the diagram pretty much as it is in the installation manual. (Edit: from the furnace installation manual)

The furnace is Carrier 59TP6A. A/C unit is also Carrier.

Then I go to test the system and when the thermostat calls for cooling, the blower comes on but on low speed. The A/C unit does not come on.

I am aware of the DIP switch to allow use of a 2-stage thermostat, so I switched that to ON. I did not touch the ACRDJ jumper, it is only to be removed if 2-stage cooling is present, at least that's how I understand it. (As an aside, I tried with and without and it didn't make any difference)

The A/C unit and furnace themselves are working fine, they were on a single stage thermostat just the other day, and worked. They are mechanically sound. To make sure my new wiring was ok, I removed the thermostat from the wall, and connected (jumped) R to G and Y/Y2, and everything worked as expected, ie the fan was on at full speed and the A/C unit came on. For some reason, the thermostat isn't energizing its Y/Y2 terminal which would turn on the A/C unit.

Since this is a smart thermostat, I did go through the software menu, and changed the settings so that it is aware that the equipment consists of 2-stage heating and 1-stage cooling.

Anyone familiar with the Energate Foundation thermostats and why it's behaving this way?

  • Is the thermostat putting 24VAC on Y/Y2 relative to C when it's trying to call for cooling? – ThreePhaseEel Jun 16 at 23:51
  • It was a bit tricky to get the multimeter lead onto the Y/Y2 terminal on the back of the thermostat. Did not get 24VAC there, but I will redo the test to be sure. It makes me wonder if the thermostat itself is either malfunctioning, or maybe it doesn't actually support multi-staging (even though its software makes me think it does). – Gaston Jun 17 at 2:22
  • I was a bit too rushed the first time that I was fiddling with probing the pins on the back of the thermostat. I had to create a few lengths of wire with alligator clips in order to get R and C to the thermostat, and had to wrap them in tape so they wouldn't touch each other (the pins are adjacent on the back of the tstat). Then I set the unit to operate in different modes and checked for voltage relative to C. See answer below. – Gaston Jun 20 at 14:25
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Ok so I figured it out. I probed the pins on the back of the thermostat to see which pins were being energized when it was calling for cooling. Turns out it energizes Y1, not Y2. Makes sense since it does support 2 stages for both heating and cooling. So I have my "cooling" wire at the Y1 terminal at the thermostat and Y/Y2 at the furnace. This wiring allows the cooling to work at the required high flow. Works as expected now. Final revised wiring diagram below. enter image description here

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