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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Trying to replace my old lennox with a nest thermostat. blowing

Customer Question

trying to replace my old lennox with a nest thermostat. blowing hot air instead of cool
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.
Hello. My name is ***** ***** I'll do my best to help. Let's get started and see what we can do.In the Settings Menu, did you select HEAT PUMP as equipment type?
Customer: replied 1 year ago.
yes
Customer: replied 1 year ago.
you want the setting on nest to be heat pump?
Expert:  airheatman replied 1 year ago.
If blowing warm in Cool mode I suspect you have a heat pump. If you can give me model on outdoor I will verify but this is my suspicion.
Customer: replied 1 year ago.
model # *****
Expert:  airheatman replied 1 year ago.
Yes you have a heat pump we want equipment type to set to Heat Pump
Customer: replied 1 year ago.
ok
Expert:  airheatman replied 1 year ago.
Let me know if this corrects your issue
Customer: replied 1 year ago.
i am in a loop where i cannot get back to the setting screen stuck in wire missing loop that i cannot fix
Expert:  airheatman replied 1 year ago.
Try turning power off and back on to indoor unit and see if maybe it will reset and recognize equipment.Also tell me what wires you had to what terminals on old thermostat and what you have to the Nest.
Customer: replied 1 year ago.
efforting
Expert:  airheatman replied 1 year ago.
Not sure what that means. Efforting?
Customer: replied 1 year ago.
y1- yellow
g - green
r - red
l - not kind of a grey
t - blue
w1 - white
o-ornage
Customer: replied 1 year ago.
nest
y1 = yellow
g=green
ob=orange
rc=red
white=w1
grey'ish pink = rh
c=blue
w2=black
Expert:  airheatman replied 1 year ago.
I am a bit confused : l - not kind of a grey . and I do not see a black on old thermostat listed.Are you saying there was both an RC and RH on old thermostat?
Customer: replied 1 year ago.
no black was connected to w1
Expert:  airheatman replied 1 year ago.
Normally you will not have a wire to both RC and RH unless there is a second transformer in outdoor unit is why I am asking on the pink wire.
Customer: replied 1 year ago.
i have a pic of the original wiring
Expert:  airheatman replied 1 year ago.
THat would be great .If you see the paper clip icon, use that to attach the photo.
Customer: replied 1 year ago.
the wire in question was connected to the L on the lennox but I have connected to the Rh on the nest
Expert:  airheatman replied 1 year ago.
Thanks for the picture.OK that wire that went to L should be taped off and not used as well as the one that went to T.It appears that your C wire was BLACK on old thermostat so it should go to C on the NEST
Customer: replied 1 year ago.
ok, so leave do not use the rh and the y2?
Expert:  airheatman replied 1 year ago.
That is correct. Also if black was on C as shown it needs to go to C on Nest
Customer: replied 1 year ago.
wiring is happypic attached is my system screenstill blowing hot
Expert:  airheatman replied 1 year ago.
Show me pic of wiring currently on the NEST
Customer: replied 1 year ago.
attached
Customer: replied 1 year ago.
it also asked me if about a "O" wire and a "d" wire in relation the the heat pump
Expert:  airheatman replied 1 year ago.
OK looks like wiring is correct. Nest recommends the red to RH, but thi still should be ok.Let me ask this. Was unit working properly with old thermostat? And do you have a volt meter for troubleshooting? It sounds like your reversing valve is not shifting in the outdoor unit. WE need to see if we are getting voltage to the reversing valve solenoid on call for COOL
Expert:  airheatman replied 1 year ago.
WE want reversing valve selection to be O
Customer: replied 1 year ago.
yes, i do not a
have volt meter. it is O
Customer: replied 1 year ago.
i need to bail. thanks for your help
Expert:  airheatman replied 1 year ago.
OK thermostat is now wired fine. Heat pump settings is fine . Your unit reverses in COOL mode, so O is correct .From manual on unit"Upon cooling demand, the thermostat closes circuit R to O and Y. Closing R to O and Y energizes the reversing valve for cooling operation and closes the heat pump contactor, starting the compressor and outdoor fan. The thermostat automatically closes R to G circuit, which also brings on the indoor fan at the same time"It may be possible that we are losing the 24 volts at a connection between thermostat and reversing valve or the solenoid on reversing valve is bad. We would need a meter to check this.You can pick up an inexpensive one at Walmart for about 15 bucks if you want me to guide you in troubleshooting this.

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