Heat Pump Operation?

Archive Public Archive
#1

Originally Posted By: Kevin Blackwell
This post was automatically imported from our archived forum.


I am in search of understanding the heat pump operation.


When the thermostat has a red led light that is on (mark emergency heat)
is this normal operation for a heat pump and what dose this mean?
Thanks Kevin from Houston,TX

#2

Originally Posted By: dbush
This post was automatically imported from our archived forum.


The VERY basics on the heat pump is that in addition to the normal hot air, through the reversing valve from the freon, it also uses heat strips. The heat strips when you first turn the heat on goes into an Auxiliary Heat Source, which means that the air is going over the heat strips to heat up while the system is heating up. The Emergency Heat Source is, if I am not mistaken, using almost exclusively the heat strips. It is not a normal mode of operation for the heat pump. If the system comes on and stays in a emerg heat mode, that indicates a problem and should be evaluated.

–
Dave Bush


MAB Member


"LIFE'S TOUGH, WEAR A HELMET"
#3

Originally Posted By: Blaine Wiley
This post was automatically imported from our archived forum.


Quote:
When the thermostat has a red led light that is on (mark emergency heat)
is this normal operation for a heat pump and what dose this mean?


If the red light is on (most thermostats) you are operating only the electric strip heaters in the furnace. Emergency heat locks out the operation of the heat pump. If the green light is on you are using the strip heaters as auxiliary to the heat pump, which will happen when the set point on your thermostat is approximately 2 degrees higher than the ambient temperature.
#4

Originally Posted By: Kevin Blackwell
This post was automatically imported from our archived forum.


Dave & Blaine,Thanks for the reply


But if I have a heat pump with an reserving valve why would I have a furnace too?
Please explain

#5

Originally Posted By: Blaine Wiley
This post was automatically imported from our archived forum.


The heat pump is very efficient down to about 35 degrees Fahrenheit outdoor temperature. Below that, the heat pump looses heating efficiency significantly, and your furnace will kick on.

#6

Originally Posted By: ecrofutt
This post was automatically imported from our archived forum.


Quote:
If the system comes on and stays in a emerg heat mode, that indicates a problem and should be evaluated.


I can evaluate this one very easy. You have an air source heat pump. It's colder than hell outside, the heat pump portion won't function that cold, and it'll stay that way until it warms up enough for the heat pump to function again.

Look here:
http://www.serviceexperts.com/faqs/cooling/hp.html

and here:
http://www.srpnet.com/home/energy/heatpump.asp

--
Erby Crofutt
B4U Close Home Inspections
Georgetown, Kentucky
www.b4uclose.com
#7

Originally Posted By: dedwards
This post was automatically imported from our archived forum.


It’s really pretty simple. When the outside ambient temp is colder than the freon there is no more heat to be gained via transfer. At that point your heat pump calls for “auxillary heat” and calls for the heat strips to come on. These are usually on sequencers (staged heat) to augment the heat pump. At “around” 20 degrees the outdoor thermostat on the heat pump says to itself…Damn! its cold out here. Then your heat pump ceases to function as a heat pump and literally becomes a regulation electric forced air furnace. There are some dual fuel heat pumps out on the market that uses gas when it gets to the “damn, its cold stage.” but you rarely see one of them. A refrigerator is a type of heat pump…they all operate using same principle…

#8

Originally Posted By: dbowers
This post was automatically imported from our archived forum.


Everybody keeps talking about “heat strips” and electric furnaces. Please note that in many areas (north of the mason dixon line) your main setup will be the outside heat pump and the inside gas furnace. Since we don’t use oil in the midwest where I’m at, I don’t know if they use oil furnaces as backups or not.


One of the main reasons for the red light (emergency heat) to be on is that something malfunctioned at the outside unit and by putting the T-stat in emergency heat - you bypass the O/S unit. Another common reason is the T-stat is miswired OR the homeowner never got comfortable with the heat pump in the heat mode (it does not blow as hot as a gas furnace for example) SO they keep it in emergency heat mode ALL THE TIME.

Dan Bowers, CRI

#9

Originally Posted By: dedwards
This post was automatically imported from our archived forum.


I could have swore I mentioned dual fuel heat pumps.

#10

Originally Posted By: ecrofutt
This post was automatically imported from our archived forum.


I saw a 20 year old PowrMatic Heat pump just yesterday that was a dual fuel. It had electric heat strips and a wood burning heat exchanger box. Still pumping fine.


I've seen ones that use gas/propane and electric heat strips, but this was the first heat pump I've seen that included wood burning as a secondary heat source.

--
Erby Crofutt
B4U Close Home Inspections
Georgetown, Kentucky
www.b4uclose.com