Heat Pump for cooling only

Hey guys, I inspected a home today that had an older Ruud heat pump. The data plate said “air conditioner” but the model number (UPKA-035JAZ) says heat pump. The label on the unit says “heat pump”. The thermostat didn’t have an emergency/auxiliary heat setting. This is the first time I’ve come across a heat pump set up for cooling only. When I tested the heat the furnace in the crawlspace came on. I didn’t test the cooling since it was 37 degrees outside. Now, I don’t know if the Ruud unit works. I can log all this in the report and recommend evaluation by a qualified HVAC specialist, but I’d like to know for future reference if anyone has come across this setup, and is it ok?

Did you see a reversing valve anywhere in the condenser? I could be wrong, but I feel like I’ve seen some units labeled with “heat pump” but no reversing valve and set up as AC only with a gas furnace.

Back when I was in the HVAC field, guys would buy dent and scratch units. On a couple of occasions, guys would go as cheap as possible and would buy a low seer heat pump and only use it just for AC.

Was there another heating system at the house?

Hey Michael, I didn’t see a reversing valve, although I didn’t look as closely as I should have.

Hey Brian, Yes, there was a Ruud furnace in the crawlspace. Same age as the heat pump.

Diagram on how a basic heat pump operates in cooling mode. Reverse the cycle for heating. Auxiliary heat is for additional electric heat strips or for a gas powered duel fuel unit.
heat-pump-2

Based on the climate of the area, you may see the heat pump used as both a heating and cooling system with no additional auxiliary heating components.

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You are a Home Inspector. Do you test a/c units in other houses at 37F?
Probably not. So it’s not a concern if you state “Not tested due to low outdoor ambient”.

Do you need an HVAC contractor come out?
Why? All he will do is turn on the thermostat.
Why didn’t you turn on the A/C from the thermostat and see if it responded? You can run a Heat Pump in cooling at any temperature. It has an “Accumulator”. You know what this is/dose?

Can you have a heat pump and only use it for A/C?
Sure, why not?

There is a set up called a dual fuel. Based on outdoor temps it will run the furnace or the HP whichever is best.

Is there heat in the house?
Yes, and it worked.

The thermostat is not for heat pumps but it works just fine because you have a furnace for heat.

If it says “Heat Pump” on the unit, that is what it is.

Look up: Ruud model upka-035jaz Does it say “Heat Pump”? Yup. You can get this information off your cell phone while on site. Then you know what your looking at/for.

If you don’t know HVAC (and you are not required to know) do what your state SOP required you to do and report.

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Hey Thomas, Thanks for the diagram. I’m aware of the operation of a heat pump, I’ve just never encountered one that was setup to be used for cooling only.

Hey Dave, thanks for your response. Back to my original question; I’d like to know for future reference if anyone has come across this setup, and is it ok? In reading your response I can’t quite tell if you’ve encountered this type of setup before, or if you consider it ok.

I have a heat pump duel fuel setup. I have rarely used the the heat pump for heating. It’s mainly my AC cooling when used.

Hey Thomas, I just moved into a house that has a heat pump with a gas furnace for “emergency” heat. I hate the heat pump heat so I use the furnace to heat and will use the heat pump for cooling. Similar to what I encountered in the inspection today, however, I’ve never seen it setup in this fashion; a heat pump without an “emergency” heat setting on the thermostat. As such, I didn’t know if there were any different ramifications I was unaware of or didn’t know existed. Thanks again for the feedback.

I have a heat pump with gas backup at my house and there is no auxiliary heat option on my thermostat. Mine switches to gas when the outside temp drops below 40.

I am an HVAC System Design Engineer, so yes I have seen about everything anyone could put together.

You have not collected enough information for me to be more specific for you, but if you follow HI SOP for your state you don’t need anything more.

If you turn on the heat and it comes on and there is a heat source in every “livable” room your fine.
If it is an A/C don’t run it when it’s real cold for 24hrs and it is still cold when your there. They do not generally have a crankcase heater in the compressor and the refrigerant migrates into the oil which erupts violently when it turns on. Compressors can’t pump oil in the liquid state.
If it is an A/C with a scroll compressor (if you learn to identify compressor type) you can run it for a short time to see if it runs with no problem.
If it is a heat pump, run it any time. It turns on the A/C every 45 min for defrost anyway so there is no reason you can’t too.

An A/C thermostat will run a heat pump so long as it has two stages of heat. You will not likely know this so just don’t talk about it.

Do not involve and HVAC contractor for things you do know or understand. If you don’t know it is really broken, least case you’ll look a fool, worst case may have to pay for the service call.

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For you guys that don’t like your heat pump and have a furnace, the heat pump has a changeover thermostat that you adjust for when it changes from Heat Pump to furnace. The Heat Pump can produce 80% more heat per watt, but this depends on the outdoor ambient for your region. It does not just have to do with air temperature, it has to do with enthalpy of the OA. That’s both latent and sensible heat.

Heat pumps have higher CFM rates than a furnace and regardless of the air temperature you may feel cool. This is often because the air duct is not designed properly. In the summer when it’s say 85F and you stick your face over the outdoor unit when it’s running, it will feel cool even though the air coming out is around 115F (if the coil is clean). Too much airflow is uncomfortable.

In the spring and fall when you need to take the chill off in the house, a HP can do it for practically nothing. You can make 800% more heat per watt/dollar. When it gets winter cold, heat leaves your house faster and there is less heat in the OA to properly heat the indoors, that is when things get real uncomfortable. The IA fan keeps running all the time and the auxiliary heat comes on and off and the fan just keeps running making you cold.
Also if you don’t switch over at the right time the HP has to run in the cooling mode to get the heat to remove the ice buildup off the outdoor coil. Your taking heat out of your house to melt ice. And this may only last for 10-15 min and the ice is back.

Thermostats on southern states HP’s does not need an EM / Aux switch because much of the time there is no 2nd stage heaters installed. They are an option, not a requirement. So if you find them missing it was likely intentional.

This is a lot of stuff to consider and is the main reason a HI is not required to know this stuff.

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Older heat pump compressors are labeled Air Conditioners on the cabinet. No worries.
You were wise and used the MN/Model Number.
Keep up the great work.

David. To put it plainly … You’re The Best! :grinning: