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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My Lennox Heat Pump M/N LPS13DC-024-230-01 is four years old.

Customer Question

My Lennox Heat Pump M/N LPS13DC-024-230-01 is four years old. It replaced a 9 year old Lennox whose compressor died. I have electric auxiliary heat. This winter when the temperature went to single digits for many days, the auxiliary heat worked very sporadic. Some mornings I woke up to 50 - 55 degrees. The thermostat said auxiliary heat was on, but cold air was coming out of the ducts.
After three service calls over 10 days and a new thermostat, they (the dealer that installed it) still did not find the problem. Out of desperation they said the auxiliary heat was probably undersized. I finally put it on Emergency heat for two weeks and it maintained temperature with no problem. Any possibility a bad temperature sensor on the heat pump could cause this?
Submitted: 2 years ago.
Category: HVAC
Expert:  Phil replied 2 years ago.
Welcome! We keep going until you have all of the information you need.[b/]. Extensive training & coaching also available.
Emergency heat comes no matter what, when ask for it...auxilliary heat only comes on according to how the thermostat is programmed
If you have the thermostat programmed for say 60F at night and the aux heat not to come on unit its 5F colder than the temperature in the house, then aux heat would be sporatic.
Look that over, check the programming on the thermostat and get back to me, we can go from there.
Customer: replied 2 years ago.
The thermostat is programmed for 66 degrees over night. I would wake up to 50 - 55 degrees with cold air coming out of ducts. It did this with the old thermostat which was 12 years old, and it still does it with a new thermostat. The repair technician replaced the thermostat on the first of three visits and could not find any other problems.
Customer: replied 2 years ago.
did not get a reply
Expert:  Phil replied 2 years ago.
Hello again,
I must come and go to answer the many questions I get, do research etc., and to eat lunch. and after 11 pm I go to bed for 7 hours.
I am back now however... unfortunately the fact of the tech replacing the thermostat with the same results leaves me somewhat a loss.
Lets try reprogramming the thermostat differently to see what effect it has........... as a test only.
Make sure you have not accidentally not programmed the system to go OFF at night.
Next reduce the night set back from 66F to 55F as a one day *trial.. perhaps there is a sensor error somewhere.
We can go from there.
Customer: replied 2 years ago.
The system is not programmed to go off at night. Can't do a test like you said. With the warmer weather here in Pennsylvania, my house is not going under 72F at night and my system is not even on. As I said in my opening statement, I had this problem when it was very cold ( 5F to 15F). No reason to proceed any further since we can't get anywhere close to duplicating the same condition.