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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7821
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My heat pump will not run when it is very cold outside but

Customer Question

My heat pump will not run when it is very cold outside but i hear a clicking sound in the area of the compressor (it is NOT the main contactor making the noise).
Submitted: 5 years ago.
Category: HVAC
Expert:  Phil replied 5 years ago.

Phil :

All work to be done by licensed professional. WE KEEP GOING UNTIL YOU HAVE THE INFORMATION YOU NEED, I come and go. This is step ONE.

JACUSTOMER-gqndmqq5- :

ok

Phil :

Look on the units wiring diagram for an outside low temperature limit thermostat....even though thenewer heat pumps will run a bit below 20F outside, some are set to go to back up heat in that range

JACUSTOMER-gqndmqq5- :

it has an LT thermostat set @ 30

Phil :

for a test, set it down, 5 or 10 degrees below the outside air temperature...

JACUSTOMER-gqndmqq5- :

ok. jjust a minute

Phil :

tell me in detail about the clicking sound...how often per second..is it regular or intermittent.

JACUSTOMER-gqndmqq5- :

I lowered it to 20. LT thermostat contacts clicked but unit did NOT start

Phil :

There is time delay in most of those circuits..give it 5 minutes, see if it starts.

Phil :

and tell me more about the clicking sound near the compressor.

Phil :

is it coming from the defrost timer control, how regular is it, how many times per second

JACUSTOMER-gqndmqq5- :

it is not clicking at all now. It was clicking last night and i shut the unit off with the indoor thermostat. Did not put it back on until we started chatting. The LT thermostat I adjusted is labeled "emergency thermostat". Same as LT thermo?

JACUSTOMER-gqndmqq5- :

The clicking last night was abot once per second and was a little irregular.

JACUSTOMER-gqndmqq5- :

Hey Phil, I hope I can continue this later? I have never used this service before. How do i re-establish our chat? Thanks.

Phil :

Hello again

Phil :

You will get reminder emails with each of my responses..you can click on the link in those to get back to me

Phil :

or...you can log into your JA account and click on this question you posted

Phil :

The LT and emergency heat thermostat are often wired to do the same thing, that is turn off the heat pump and turn on the emergency back up heat.... emergency back up heat normally consists of electric resistance heaters or a gas furnace... if you do not have a gas furnace... its electric resistance heat

Phil :

Tell me if your house is being kept warm in this 30F weather or not... if it is, and the compressor is off... the house is being kept warm with the back up heat... in the case of electric resistance heaters that is quite expensive to operate.

Phil :

These can be tricky controls issues even for an experienced heat pump technician.

Phil :

For a home owner, working on heat pump controls much beyond a few basics is not generally viable.

Phil :

Phil

Phil :

if you can get me the model number of the heat pump I can look up a diagram on it in most cases.