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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
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: 2 years ago.
Category: HVAC
Expert:  airheatman replied 2 years 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 2 years ago.
yes
Customer: replied 2 years ago.
you want the setting on nest to be heat pump?
Expert:  airheatman replied 2 years 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 2 years ago.
model # *****
Expert:  airheatman replied 2 years ago.
Yes you have a heat pump we want equipment type to set to Heat Pump
Customer: replied 2 years ago.
ok
Expert:  airheatman replied 2 years ago.
Let me know if this corrects your issue
Customer: replied 2 years 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 2 years 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 2 years ago.
efforting
Expert:  airheatman replied 2 years ago.
Not sure what that means. Efforting?
Customer: replied 2 years ago.
y1- yellow
g - green
r - red
l - not kind of a grey
t - blue
w1 - white
o-ornage
Customer: replied 2 years ago.
nest
y1 = yellow
g=green
ob=orange
rc=red
white=w1
grey'ish pink = rh
c=blue
w2=black
Expert:  airheatman replied 2 years 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 2 years ago.
no black was connected to w1
Expert:  airheatman replied 2 years 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 2 years ago.
i have a pic of the original wiring
Expert:  airheatman replied 2 years ago.
THat would be great .If you see the paper clip icon, use that to attach the photo.
Customer: replied 2 years 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 2 years 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 2 years ago.
ok, so leave do not use the rh and the y2?
Expert:  airheatman replied 2 years ago.
That is correct. Also if black was on C as shown it needs to go to C on Nest
Customer: replied 2 years ago.
wiring is happypic attached is my system screenstill blowing hot
Expert:  airheatman replied 2 years ago.
Show me pic of wiring currently on the NEST
Customer: replied 2 years ago.
attached
Customer: replied 2 years ago.
it also asked me if about a "O" wire and a "d" wire in relation the the heat pump
Expert:  airheatman replied 2 years 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 2 years ago.
WE want reversing valve selection to be O
Customer: replied 2 years ago.
yes, i do not a
have volt meter. it is O
Customer: replied 2 years ago.
i need to bail. thanks for your help
Expert:  airheatman replied 2 years 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.