Auxiliary Heating Question

[Tom McDonnell]

During the past 45 days I have been unable to obtain heated air in auxiliary heating modes of 4 heat pump systems. This seems to be an unusually high number. Ambient air temperatures have been between 75 and 80. Systems tested are all five years in age or less. Testing periods were 5 minutes or more to allow for delays. I am wondering if newer heat pumps might not allow operation under these moderate conditions?

[Jim Luttrall]

Never heard of a lockout stat on the Aux heat, but it would be worth investigating. Have you tried doing a search under the brand name?
Were you using the manual "emergency heat" mode or just advancing the stat to call for second stage?

[Tom McDonnell]

Jim- Testing was by manual command at the T-stat.

[Nick Ostrowski]

Tom, I've seen some heat pumps with backup emergency heat modes that took a while to kick in (10 minutes or more some times). Some kick in almost immediately. Some take a bit of time but I'm not sure why. I'd give them at least 10+ minutes of run time to see if the auxiliary mode is operable.

Did you slide the selector switch on the thermostat to EMERGENCY MODE?

[Scott Patterson]

I would say that when I test a heat pump on the emergency or supplemental setting that they do not work 30% of the time. I have found that many the owners seldom if ever used the emergency heat mode, so they never knew that it was not working properly.

On the occasions that I checked back to see what the problems were I have found that a few times it has been a T-stat problem, other times it has been either a bad heat coil/strip or the system was never connected properly.

Based on what I have found I think that it is more common that we might think.

When I test the emergency setting, I first run the unit in the normal mode. Then I turn on the emergency heat. With the emergency heat, you should see a rise in the air temp over the heatpump mode. It is real easy to tell when you have one that is not working as the air gets cooler and cooler.

[Vern Heiler]

During the past 45 days I have been unable to obtain heated air in auxiliary heating modes of 4 heat pump systems. This seems to be an unusually high number. Ambient air temperatures have been between 75 and 80. Systems tested are all five years in age or less. Testing periods were 5 minutes or more to allow for delays. I am wondering if newer heat pumps might not allow operation under these moderate conditions?

It has been a few years since doing HVAC but do remember some heat pumps had an option installed at the outdoor unit. The thermal disk 'clicks-off' was 52 degrees, as I remember, and prevented the thermal strips 'aux heat' from coming on at ambient temps higher than 52 deg. It was to insure the use of the compressor and not use expensive electric heat if the T-Stat was moved more than three degrees.

[Jerry Peck]

On the occasions that I checked back to see what the problems were I have found that a few times it has been a T-stat problem, other times it has been either a bad heat coil/strip or the system was never connected properly.


Scott,

I had several like this in South Florida where many people simply did not use their heat - ever: I turned the heat on and nothing - no heat.

The seller was home and said he had replaced the air handler only 3 years ago and the same company had been servicing it since. The date on the AHU (which I had looked at previously) confirmed that it had been replaced 3 years ago, so I suggested he call his a/c company and tell them to get out there NOW while I was still at my inspection as it was THEIR problem - and it worked, they had a service guy there in about 20 minutes.

The reason there was "no heat" was because ... there was "no heater" ... the heating coils had never been installed. Billed for, yes. Paid for, yes. Installed? Nope. :)

The seller did not know because he had never turned the heat on. :cool:

[Vern Heiler]

"Not installed" as Jerry suggest, makes the most sense in Fla. If the T-stat is wired correctly, the option I was talking about would not keep the heat strip off when 'Emergency Heat' is selected.