# Identifying heat pump



## sailor86 (Feb 18, 2009)

I had sort of an embarrassing situation the other day while installing someone's thermostat. The problem lay in the fact that what they had was a heat pump and not a furnace. Of course I didn't find this out until well after the fact. What's an easy way of identifying a heat pump vs. a furnace?


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## Stu_computer (Jul 7, 2005)

*Never assume that a wire color is correct for the function it should perform*


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## sailor86 (Feb 18, 2009)

Stu_computer said:


> *Never assume that a wire color is correct for the function it should perform*


Thanks, but the article never answered the question. How do I determine it is a heat pump I am dealing with?


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## Raylo (Feb 12, 2006)

A couple of ways I can think of to ID a heat pump... First, look at the existing thermostat. If it has leds for back up heat and emergency heat, it is a heat pump. The backup heat led usually lights up when the heat pump can't keep up with demand based on the delta in temp between set temp and actual room temp to indicate that the electric resistance coils are helping to close the delta. The emergency led should light up when the actual heat pump unit outdoors is not working and you are running purely on the resistance coils, that are installed in the air handler unit. In any case you should see wiring in the indoor air handler unit for the resistance heat coils that won't be there if the system is a separate furnace and a/c unit instead of a heat pump.

Also, look in the outdoor unit. A heat pump will have more "stuff" in there like a reversing valve and additional relays and wiring. A plain a/c unit looks pretty simple in comparison.. 

Another minor issue is that many folks these days are getting hybrid systems, i.e. a furnace plus a heat pump (instead of a plain a/c unit outdoors) that uses the heat pump for heat until the outside temps get low enough that it is more efficient to use the furnace. I'm not sure if these typically have the electric backup coils since the furnace can always provide heat if the heat pump fails.


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## Stu_computer (Jul 7, 2005)

a thermostat may control either. the article is very informative.

what you should have learned from it is *first* turn the power off before working on it, check both ends of the wires and which wires go to which terminals on the furnace circuit panel. a pump circuit will have additional wires for sensors.

the answer is you don't have the necessary knowledge to work on hvac so get a qualified person to do it.


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