Carrier Heat Pump

[John Albert]

By "ground source", you mean geothermal, is that correct?

Is there a temperature range below which geothermal needs an "auxilliary assist" (i.e., electrical heat strips) as well? I thinking of an area like Pennsylvania, where temps can drop down close to 0 at least a few days of winter.

Also - I see plenty of homes with "regular" (non-geothermal) heat pumps installed around north/north central PA. When shopping for a home that has a non-geothermal heat pump installed, at what seasonal temps does it become impractical or non-economical?

[trader4]

My understanding is that geothermal systems are sized so they are all that is required. They're expensive enought without having the added complications of a hybrid system. That is the big drawback, the huge initial expense compared to other altermatives.

That depends on a lot of factors. One big one is the COP of the unit. Is it a 15 year old one or a newer, high efficiency one? How well insulated is the house? I think in most cases the problem isn't that it's not economic to run the heat pump. They have decent COP's down into the teens. The problem is that even though you're still getting heat produced at a reasonable cost, you just can't get enough heat to supply what the house needs, unless the house is exceptionally designed to need less heating than a typical home. I think for a typical house, with a relatively new higher eff heat pump, that point probably occurs in the

20s, to maybe teens,depending on how efficient it is, how it's sized, etc.

[krw]

No, though some people may call it that. Geothermal is passive.

The outside air temperature doesn't matter at all. If the ground gets cold enough to require such, then the ground "source" isn't big enough.

My brother had an air-source (the alternative to ground-source) heat pump in N. Philly. Around freezing efficiency falls off rapidly. At some point, probably above 20F, they stop working entirely without resistive heat.

[trader4]

At the risk of setting off another profanity laced response, why don't you answer the question and explain what exactly you meant? AFAIK, ground sourced heat pump for a house typically translates into geothermal. So, if it's not that, then what is "ground sourced", in this context?

It does matter to the extent that the geothermal system has to be large enough to deliver the heat needed at the lowest outside temps the house will experience.

I don't believe that's true. The curves I've seen, for modern high efficiency heat pumps, COP falls off gradually through a wide operating range. There isn't a sudden acceleration in loss of performance below 32F. COP might go down by 15% from 30 to 20. The problem is that while the performance is gradually decreasing, the need for more heat is also increasing.

[krw]

I did, dumb ass. I can't help the fact that you're illiterate, trader.

The heat is actively pulled from the ground (heat pumped from the ground), rather than passively (heat passively removed from the hotter ground). There *IS* a difference.

Not just the lowest outside temps, but the integral of the (delta) temperature over time. You are actively cooling the ground. That can't be done forever, unless you've tapped into an infinite heat sump, like a "river". If the heat source is too small, eventually you will cool the ground enough that the heat pump has no heat to pump. Unlike an air-source heat pump, this happens over a much longer time (over a heating "season").

Your religion is hardly important.

[makolber]

On

well yes, once you cross that "balance point" where the heat available can no longer match the heat needed, then the house will get colder.

And consider that when the outside temp falls such that the outdoor evap starts to ice up, the heat exchange efficiency gets even worse, so yes there is a sort of sudden decrease in performance when the outdoor coil starts to ice up.

Looking at performance curves is not the same is living with one.

Mark

[trader4]

And there you have it demonstrated again folks. KRW is incapable of answering any questions civily.

Again, you posted:

" Instead of wasting money on a solar assisted heat pump (daytime is not when you need the heat) why not do something useful and buy a ground-source heat pump?"

To which JA replied:

"By "ground source", you mean geothermal, is that correct?

And then you say:

"No, though some people may call it that. Geothermal is passive."

Some people? AFAIK, virtually everyone refers to a ground based heat pump system as one form of geothermal including experts in the field, eqpt manufacturers, companies installing it, govts, etc. Google and you will see. So, what are you talking about?

Around freezing efficiency falls off rapidly. At

As usual, no facts, just curt replies that don't address anything. Typical, when you know you're wrong, yet again. If you have COP data from a typical modern residential heat pump system that shows the efficiency falling off rapidly below 32F, I'm sure we'd all like to see it.

[jamesgang]

That's just silly there is no difference. Heat moves from warmer to colder. There's no "pulling" verses "passive" transfer.

[krw]

You're wrong, of course.

In your universe air conditioning doesn't work? Amazing.

[Ralph Mowery]

Sure it does, The cool room still has heat in it. When the refrigerant goes through those coils the heat in the room heats up the refrigerant and makes it boil into a vapor.. Then the vapor is compressed and that makes it hotter. It then goes outside and the hot vapor is cooled off by the outside air and it goes to a liquid. It is just a mater of what is actually hot and what is cool, or less hot.

[Ron]

Yes I would want the light on and if they installed the thermostat you could void the warranty by messing with it.

[krw]

[krw]

Now do you understand why you're wrong?