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Quick Heat Pump Help Please


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Here in Chicagoland, I've seen about six heat pumps ever.  I am going to try inspecting one again this Sunday.

Can someone give me a quick checklist for this heat pump inspection (knowing that the high temperature this Sunday is going to be about 6 degrees above zero here)?

I'm thinking the heat will only work in *emergency/electric* mode?

Thanks much.

Edited by Jerry Simon
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Check that the reversing valve is still installed.  Some AC guys remove it if it gives trouble, instead of fixing it. The lower limit for heat mode operation varies with the manufacturer, so if only the back-up comes on, you can check with the manufacturer on that. Report the backup fuel source, delta temps, dirty coils, filters, etc. Nothing much to it beyond an AC.

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If it's 6 degrees outside, the heat pump won't be contributing much, if any, heat to the system, though it might still run. Feel the suction line with your hand. If it feels hot, then the heat pump is actually still heating (I'll bet that it just feels lukewarm). If it runs for a while before satisfying the thermostat, it'll go through a defrost cycle where the outdoor unit fan stops spinning and the compressor keeps running. After a minute or two, you'll hear a whooshing sound, the fan will kick back on, and a large billow of steam will rise up and out of the unit - that's normal, don't freak out. 

After you open the furnace door, you might have to remove a cover to see the heat coil connections and count the heat coils; they're generally 5kw each except for Rheem & Ruud, which are, I believe, 7kw each. If you turn the system to the emergency setting and crank up the thermostat, the coils should all come on in sequence. Use a clamp-on amp meter to make sure that they're all working. In the upper midwest I suspect that those coils get a heavy workout and it wouldn't be unusual to find that one or more are broken. Also just look at the wiring. I often find toasted wires and connections. 

You really can't test the heat pumpness of the heat pump when it's that cold out. I'd explain that and tell them to have the whole system serviced when clement weather returns. 

Also tell them that the single best thing that they can do for their heat pump is to keep the filter clean, keep the outdoor coil clean, and don't let dogs pee on it. 

Jim Katen 

 

 

 

 

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3 hours ago, Jim Katen said:

If it's 6 degrees outside, the heat pump won't be contributing much, if any, heat to the system, though it might still run. Feel the suction line with your hand. If it feels hot, then the heat pump is actually still heating (I'll bet that it just feels lukewarm). If it runs for a while before satisfying the thermostat, it'll go through a defrost cycle where the outdoor unit fan stops spinning and the compressor keeps running. After a minute or two, you'll hear a whooshing sound, the fan will kick back on, and a large billow of steam will rise up and out of the unit - that's normal, don't freak out. 

After you open the furnace door, you might have to remove a cover to see the heat coil connections and count the heat coils; they're generally 5kw each except for Rheem & Ruud, which are, I believe, 7kw each. If you turn the system to the emergency setting and crank up the thermostat, the coils should all come on in sequence. Use a clamp-on amp meter to make sure that they're all working. In the upper midwest I suspect that those coils get a heavy workout and it wouldn't be unusual to find that one or more are broken. Also just look at the wiring. I often find toasted wires and connections. 

You really can't test the heat pumpness of the heat pump when it's that cold out. I'd explain that and tell them to have the whole system serviced when clement weather returns. 

Also tell them that the single best thing that they can do for their heat pump is to keep the filter clean, keep the outdoor coil clean, and don't let dogs pee on it. 

Jim Katen 

 

 

 

 

Bless you

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The thermostat had an emergency heat setting, and the indicator light here was lit, and the heating elements were functional.  But. . .

There was another thermostat setting right next to the emergency heat setting, reading auxiliary  heat, and that indicator light was not lit.

I thought the emergency heat for a heat pump was/is the auxiliary heat???

 

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It is.  What you're seeing is some custom arrangement someone dreamed up, for whatever reason. Call it 'secondary backup'. As long as the set points for the two thermostat aren't too close, I don't see an issue.

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I have no idea why there's a second thermostat. 

In general, the thermostats use the term "auxiliary" when the heat strips are supplementing the heat pump. They use the term "emergency" when the heat pump is locked out and only the heat strips are heating the house. 

 

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10 hours ago, Jim Katen said:

I have no idea why there's a second thermostat. 

In general, the thermostats use the term "auxiliary" when the heat strips are supplementing the heat pump. They use the term "emergency" when the heat pump is locked out and only the heat strips are heating the house. 

 

That answers my question.  Thanks.  (I wasn't very clear, apparently; only one thermostat, with those two indicator lights next to each other.)

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How old was the unit?

I've been out of the loop for a while, so I don't know if they're out there yet, but a while back - probably about ten years - I read an article about new heat pump tech that was allowing heat pumps to work at far colder temperatures. I might have posted something about that here. Check the archives.

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  • 1 month later...
On 2/5/2021 at 6:30 PM, Jerry Simon said:

Here in Chicagoland, I've seen about six heat pumps ever.  I am going to try inspecting one again this Sunday.

Can someone give me a quick checklist for this heat pump inspection (knowing that the high temperature this Sunday is going to be about 6 degrees above zero here)?

I'm thinking the heat will only work in *emergency/electric* mode?

Thanks much.

My Mitsubishi heat pump will still operate at -5 degrees . This maybe brand dependant . Older systems will default to an electric coil in cold temperatures. 

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On 3/20/2021 at 10:36 PM, wedgren said:

My Mitsubishi heat pump will still operate at -5 degrees . This maybe brand dependant . Older systems will default to an electric coil in cold temperatures. 

This must be a mini split. 

A conventional heat pump that works at -5 degrees will be wildly over sized in the heating mode. 

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On 3/21/2021 at 12:36 AM, wedgren said:

My Mitsubishi heat pump will still operate at -5 degrees . This maybe brand dependant . Older systems will default to an electric coil in cold temperatures. 

At some point, the interior heat needed to operate the defrost (by switching into AC mode) will exceed the heat brought into the house during heat mode.

Edited by Marc
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