Heat pump power consumption question

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Old 01-12-15, 04:14 PM
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Heat pump power consumption question

I've got a heat pump unit in my shop. the shop is 25x25 with an 18' ceiling. I have been keeping the tstat on 64 and just letting it run all the time - even on the weekend when I'm not there. Now, my last BGE bill was something like $170 - no sweat. It HAS been a little colder here but I got my BGE bill and it was $305!

I had posted a question about heat pumps here a while back and I remember someone suggesting removing the AUX wire from the tstat so that the AUX heater won't kick on. I did that a couple of weeks ago and one morning I came in and the shop felt cold. It was 57 but the tstat was set to 64. That means it had been running ALL NIGHT LONG to no avail. After this happened I immediately decided that I was no longer going to leave the heat up overnight. So, now when I leave the shop, I back the tstat down to 40 and in the morning, I run a large propane heater to get the shop up to temp, then the heat pump takes it from there. However, here's the kicker... Once the temp in the shop gets up to 64, the heatpump can maintain that but it runs all day long - continuously to do so.

So, my question:

Is it more cost effective to just let the heat pump cycle the AUX heater on and off to maintain temps and ultimately the entire system cycles on and off
OR
Am I better off doing what I'm doing and let the system run non-stop all day without the ability to cycle the AUX?

I'm totally stumped on this and I don't want to gamble with it - which is why I'd like experienced input from here. Like I mentioned, it has been colder, but not THAT much colder. To me, it seems like I unplugged the AUX wire and got a fat bill in the mail - but that may just be my perception and thus - somewhat anecdotal.
 
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Old 01-12-15, 07:20 PM
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There are a lot of things in play here. Cost of electric versus cost of propane. Size of the heatpump unit and the size of the electric reheat coils.

The heatpump needs to defrost. If the inside air is too cold it won't defrost properly.

I do have one big question..... 18' ceiling in the garage. Are you heating all that ? Is there any kind of fan to force the heat back down ?
 
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Old 01-12-15, 07:39 PM
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No fan. I mean I have a fan but I don't use it for that. But yeah, it's one big open shop. The heatpump freezes? So does that mean disabling the aux heat was shooting myself in the foot?
 
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Old 01-13-15, 05:57 AM
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CURVEBALL! I just went online to pay bills and I realized that my HOME bge account was the $300! My shop was again, $160. Damn kids leaving lights on.

But still - should I leave that aux wire disconnected?
 
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Old 01-13-15, 06:14 AM
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A heat pump system runs best with a set it and forget it temperature control. Let it run, if it can't maintain the temperature the heat strips should kick in for assistance.

IMHO - Put aux back into operation and let the system run. A ceiling fan will help push that warm air down from your high ceiling.
 
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