Trane 4TEE3F40B1000A Air Handler York YZB04211 3.5 ton Heat pump. Ecobee

Hello everyone,

Firstly, thank you for a fantastic forum, it has been hugely informative reading the threads so far!

I moved into my house in 2018. It has:

York YZB04211B heat pump
Trane 4TEE3F40B1000A Air Handler
Trane BAYHTR1415 or 1419 2 circuit electric heat
Trane BAYSPEK140B+ single point power entry kit
2 x Honeywell TH6220D Thermostats

There were several issues with the system when I moved in:

• The heat pump only had a 2-conductor cable going to it. One wire was hooked up the the reversing valve (O) at the heat pump, the other wire was hooked up to power and compressor (R & Y1) all connected together with a wire nut. There was no C wire.
• They had wired 2 thermostats in "parallel". One downstairs and one upstairs. They had the downstairs one to trigger the heat, and the upstairs to trigger the cool. Although BOTH were wired to O.
• All 3 W terminals are jumpered at the air handler. The Honeywell thermostat can only operate one stage of Aux, so this I guess I understand.
• As there were only 2 wire used to communicate between air handler and HP, there was no W coming back from the HP for the defrost cycle

Almost immediately after moving in I removed both thermostats and replaced them with 1 Ecobee.

This past summer I ran a new 18/8 cable from the air handler to the heat pump, and also from the air handler to the thermostat so that I could correct the wiring. I'm happy to get that done!!

However, there a several questions I still have about how to wire the system because the York HP and Trane AH are so different.

1. The Ecobee can handle 2 stages of aux heat. The Trane install manual gives conflicting info if I should jumper W2 and W3 together at the AH. Could someone help me out with the aux heat wiring? I have confirmed the wiring INSIDE the air handler, and there is NO wire into the heat strips for W3. However, there is definitely some sort of trigger on the board in the air handler for the fan if 24V is applied to W3 at the LV terminal block. If I apply 24V to ONLY W2 I do not get the fan at all. However, if I apply 24V to ONLY W3 I get full fan. W1 seems to behave properly were the fan kicks into full when 24V is applied. One one wiring diagram in the Trane install manual is says "W3 should only be connected if you are using a 3 stage heater", on another page it says W1, W2 and W3 should be jumpered.
2. The heat pump has a "Hot Heat Pump" mode that wants to control the fan of the air handler via sending 24V back to Y2 only after 10 minutes if the outside temperature is under 50. I don't think I need to use this. It's a single stage HP...
3. The heat pump also wants to control the aux heat to a certain extent. I understand that the HP would want to sent a W signal back to the AH for when it's in defrost mode. But the what the wiring diagram for this unit wants done is for W1 at the thermostat to go ONLY to "W" on the HP. Then the HP will send W1 back to the AH. Meaning that even if the thermostat thinks it needs Aux heat, the heat pump may override that and say "no". Aux heat will only come on if the HP says so. My question is: should I follow these directions, or set it up in the "normal" fashion where t'stat W1 -> AH W1 and t'stat W2 -> AH W2 AND HP W1 -> AH W1 but skip t-stat W1 -> HP W

I'm sorry for the long winded post with all the long questions! But I'd like to use the system to it's potential, using staged AUX heat, if that is possible, from the Ecobee.

Thanks!

source https://hvac-talk.com/vbb/showthread.php?2224103-Trane-4TEE3F40B1000A-Air-Handler-York-YZB04211-3-5-ton-Heat-pump-Ecobee&goto=newpost