# Janitrol HPT18-60, change to electronic programmable?



## AU_Prospector (Feb 11, 2008)

Guys, 

I have a pair of heat pump/ac units.  One for the lower, larger area of my home and one for the smaller upper level of my home.  Both have Janitrol HPT18-60 thermostats and both units have aux heat coils in the blowers for "emergency heat". 

In a previous home i switched out old mercury switch dial Honeywells in favor of Home Depot type electronic programmable thermostats and this was a money saving upgrade to my old oil burner I believe. 

However in this case I have heard on home improvement cable shows that electronic programmables often DECREASE the effeciency of heat pumps with aux heat.  Is this true?  Any help is appreciated.  I want to save money, not throw it away. 

Thanks!
Prospector


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## glennjanie (Feb 12, 2008)

Welcome Prospector:
The home improvement cable guys are correct. Heat pumps run on such a narrow margin they can't 'catch-up' without using the emergency heat. In that case you're not using a heat pump at all but resistance electric heat. I have a ground-source heat pump and the electric coils are in 2 stages; one to 'supplement' and both to do 'emergency' heat. My supplemental coils have kikced in only 2 times this season. I keep the fan running all the time to mix the air we have, keeping the thermostat on its toes for when to kick in. The fan motor is a variable speed direct current motor that runs fairly slow when in the fan only mode. When the compressor kicks in the fan speeds up some. 
When the compressor kicks in with air conditioning the fan speeds up quite a bit. The fan continues to run faster even when the compressor kicks out to use the heat or cooling that is left over until the system equalizes.
I would strongly advise against the programable t-stat for your use.
Glenn


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