Heat pump

[Gary Schering, II]

Is there anything special one shoud be looking for when inspecting a heat pump?

[Joe Funderburk, CMI]

If in the summer, test the AC mode as you would any AC. Do not test the normal heating mode, as it may damage the condenser (disclaim that in your report and say that the rule of thumb is that if it works in AC mode, it should work in heat mode). Turn on the emergency heat to make sure the unit is equipped with emergency heat strips. It should get to about 100 F.

[Gary Schering, II]

Joe
The emergency heat strips, do they work off the thermostat? How are u testing for this? Also, the temp here in Ohio has been in the 90's, so do not run in the heat mode, because the risk of damage?

[David P. Valley]

Gary,

You can test the auxiliary heat by placing the thermostat in the EM Heat position and it is not a procedure which may damage the equipment, and is often not performed during the summer months, but could be.



Use the following as a disclaimer in the summer months...

The heating portion of the heat pump system was not tested. Operation when outside air temperatures are above 75 degrees can damage the unit. The inspector, except under special circumstances, will not operate the heat pump when the outside air temperature is above 75 degrees. The system installation and other components are reviewed if possible. It is recommended that you call for reinspection by this company when the temperature is expected to be below 75 degrees. A reinspection fee may be charged. You may simply wish to have the unit demonstrated (if the temperature has been below 75 degrees for a few hours) during your final walk-through prior to taking possession of the property.

An HVAC contractor can always evaluate the heat pump in adverse weather conditions by temporarily modifying the system operation. They do this by controlling the outdoor fan as not to absorb too much heat in the summer months. Shutting down the outdoor fan in the heating mode during the wintertime (in order to test defrost control components) accelerates the time required and/or creates a frozen coil necessary to test the circuits when the weather conditions are not conducive under normal operation. Controlling the outdoor fan to test air-conditioning in the wintertime raises the head pressure which also raises the back pressure providing pressure readings similar to a 95° day.

So it's best if you left the testing of the heat pump (in the opposite mode) to an HVAC contractor.

[Joe Funderburk, CMI]

Originally Posted by nbhi

Joe
The emergency heat strips, do they work off the thermostat? How are u testing for this? Also, the temp here in Ohio has been in the 90's, so do not run in the heat mode, because the risk of damage?

David showed you the thermostat. I test the EM heat using the thermostat. The reason is because the aux. heat stips are sometimes not installed, especially in the South. They probably are not necessary in Florida, but certainly would be in Ohio. David's disclaimer is good. You need a disclaimer in your agreement, in my opinion, also.

I say this in my report: "The heat pump responded to a request for cooling, but was not tested on the normal heat cycle because the ambient temperature is too high and to do so could have damaged the coil. But generally speaking, if the unit works in the A/C mode, it should work in the heat mode."

And this: "We tested the operation of the emergency heat mode, and it was functional."

[Gary Schering, II]

? Why wouldn't you want to run the heat pump in the em mode when the heat is above 75f ?

[Mathew Hawley]

Hello Gary,

If the ambient temp goes below 40 degrees then the heat pump alone won't be able to properly heat the home. The electric heat strips will have to warm the home.

I always check the heat strips in emergency heat mode even here in Fl with the average temps in the high 90's. I amp probe the AHU conductor at the panel, get a quick temp and shut it off. We do have winter nights that get in the low 30's from time to time.

[Stephen W. Stanczyk]

Originally Posted by mhawley

Hello Gary,

If the ambient temp goes below 40 degrees then the heat pump alone won't be able to properly heat the home. The electric heat strips will have to warm the home.

My heat pump is 15 years old and has never come on until it reaches 30 degrees. The newer pumps are even more effecient and some don't rely on the EM heat until it reaches 25-26 degress. If you have strip heaters coming on at 35-40 degrees outside ambient, your system needs servicing.

[Mathew Hawley]

Stephen,

The balance point is between 15 and 40 degrees. Many units here in Florida have an outdoor thermostat that will not allow the strips to kick in unless it's below 40 degrees.

When in the "Heat" setting the electric strips should engage when the room temp drops 3-5 degrees from the desired temp on the thermostat.

[Gary Schering, II]

Mathew
AHU conductor, help me Iam brain dead.

[Joe Funderburk, CMI]

Originally Posted by nbhi

? Why wouldn't you want to run the heat pump in the em mode when the heat is above 75f ?

You would want to test the EM heat no matter what the temperature. I don't try to determine at what temperature they come on automatically, because I don't worry about system design. If they respond to the thermostat, then I'm happy.

[David P. Valley]

Originally Posted by nbhi

Mathew
AHU conductor, help me Iam brain dead.

Simply put....

Air Handling Unit Wiring(Conductor)

[Mathew Hawley]

Gary,

I amp probe the wire to the air handler unit/furnace at the electric panel. All this does is give me the system rating of the heat strips 20 amps=5KW 40 amps=10KW.

[Stephen W. Stanczyk]

Originally Posted by mhawley

Stephen,

The balance point is between 15 and 40 degrees. Many units here in Florida have an outdoor thermostat that will not allow the strips to kick in unless it's below 40 degrees.

When in the "Heat" setting the electric strips should engage when the room temp drops 3-5 degrees from the desired temp on the thermostat.

I agree with you to a point. I can force my strips into operation by manually adjusting my thermostat to 3 degrees more than the current temp. If someone has a newer model heat pump and programmable thermostat, the interior and exterior temperatures would be taken into consideration by the thermostat that would turn the unit on at a time that would have the room at the given temperature at the selected time. If the thermostat is not programmable and only has the levers and a choice between heat / cool as shown in David's picture, you would be correct.

The best use of a heat pump is in using more air flow with milder temperatures to bring the home to and kept at the desired level. The programmable thermostats, while more expensive initially, make a home more comfortable and energy effecient. While not necessarily mentioned in my report, I do verbally explain to my clients the benefits of the programmable type stat.

Nothing like keeping cool on a hot muggy day.