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Heat Pump question

Posted by matt.shaver (My Page) on
Mon, Jan 21, 08 at 10:49

Hey all, I live here in Spfld IL and as you all know the midwest has been experiencing some colder than usual temps. I've been searching the Internet for the correct answer and am finding some discrepancies so I thought to try here.

I have a band new heat pump that as installed this past summer and it's been a champ. However, during my list visit the HVAC guy told me during and ice storm and snow storm when the heat pump gets covered and cannot breathe, use emergency heat. Ok we've had to events for that to happen and it was OK.

Now that we are so very cold, the outside heat pump has run so much that I was worried about utility costs so I switched to emergency and of course the outside unit stopped and the inside air handler runs but much less.

What is the right answer here. I have read at HVAC sites that a heat pump will work up to -10 degrees but the emergency will also help, just keep the unit on normal heat. -OR- During this extended arctic chill, use emergency heat.

What is the right answer here??
Matt
Spfld, IL.


Follow-Up Postings:

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RE: Heat Pump question

You don't say what your aux heat is - gas or electric.

You should use your heat pump all the time. Once you switch to aux heat, your electric cost increases 3x (assuming you have electric resistance back-up).

If it is snowy out, the heat pump will defrost more often if you have demand defrost. If you have time-initiated defrost, the heat pump will defrost according to the pre-selected time (30, 60, or 90 minutes).

From Goodman's website, for my 14 SEER 3 ton heat pump:

Outside temp = 30, Delta T = 23.4 degrees, COP = 2.98
Outside = 20, Delta T = 20, COP = 2.65
Outside = 10, 16 degrees, COP = 2.26
Outside = 0, 13 degrees, COP = 1.84
Outside = -10, 9 degrees, COP = 1.35

This means that even at -10 F outside, the heat pump is putting out 79 degree air (70 room temp plus 9 from the heat pump) and is still 135% efficient as compared to electric resistance heat.

Along with a drop in output temp, the heat pump draws less KWs as the outdoor temp drops. My unit draws 2.64 KWs at 30F, 2.41 KWs at 10 F. 10% less power.

Many people turn off their heat pump at brutal cold temps because of concerns about wear-and-tear from it running non-stop.


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RE: Heat Pump question

matt

I am going to assume that you have strip heat backup not fossil fuel backup. If that is the case, then I agree completely with Gary. However, if you have ice buildup on your outside condenser fan/blades, then you might consider deicing the blades with warm water or going to emergency until ice on fan blades melt. You may want to contact dealer and get their recommendation on a situation like this.

IMO


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