Posted on 11/07/2010 4:26:48 PM PST by plinyelder
As many here have said a heat pump (A/C running in reverse) is only effective down to the 40’s and only if it is charged correctly .. running in heat mode the accuracy of the charge is critical to poducing heat efficiently. below the temp where the heat strips (resistance heat) kicks in your power consumption goes WAY up.
Your best option is to make sure you fix any air leaks... to really save $$$ get a Franklin Stove or similar for heat.
Generally, the heat pump is cheaper because it gives you more heat than what ordinary resistance heating will give you (your electric fireplaces are resistance heating, as is your furnace's backup heat). Ordinary resistance heating gives you roughly 3.4 BTU per watt. A heat pump, in milder weather will supply much more heat than this, but as it gets colder, it loses efficiency.
More importantly, as it gets colder outside, the outside coil will need to defrost periodically, meaning that the resistance heating in the furnace has to operate while the heat pump is reversed into an air conditioner to thaw the coils. This is normal, and acceptable to a point. At some temperature, as the outside temperature drops, you will reach a level where it becomes more expensive to run the heat pump than it does to use basic resistance heating. I'm not sure what that point is with a modern heat pump - old rule-of-thumb (like 30 years ago) was 20-25 degrees or so. I think that with the higher efficiency heat pumps today, that temperature is lower even though the defrost cycle must occur from time to time.
Anyway, while the electric fireplaces are comfy and enjoyable, they are also less efficient than the heat pump most of the time and should be used somewhat sparingly.
Mrs gorush .. All home cooking .. would be welcome here! 8)
You are incorrect. We live in central Wisconsin and the heat pump was our only source of heat until adding a small fireplace for atmosphere recently. The geothermal system starts to struggle when the temp hits -20F.
If they're 12.5 amps, your math looks right to me.
Here in MN I haven't turned on my furnace yet this heating season (except for a 10 minute test a month ago). I've been using solar heating from a setup I designed and built and a small 1500 watt electric heater. That and the heat the computer and TV and cat and so forth throw off.
Great Stuff is great stuff, but be careful - it REALLY expands! I put some in a wall cavity when I was putting a shop room in the garage. I sprayed it into the crack in the corner cavity (used fiberglass in the rest of the wall but this crevice was too small to get into) and then went upstairs. When I checked on it a few hours later, I had a big 6" round, 8 foot tall blob of expanded foam sticking out of a 1/2 inch crevice! Had to let it dry completely before I cut it away with a razor.
I bet they do look nice. I’m no longer in a below freezing climate, albeit it did get down to 31 degrees last night. A bit early for that kind of weather down south. I like your idea, I could use them down here for a couple months to save money. Thanks.
I bought some of those foam-like insulators that you just take the faceplate off the wall and put those behind them.
Not to be too picky, but yes, ground source heat pumps DO extract heat from the ground in the winter and then put it back into the ground in the summer. The phase change of the working fluid is a way of storing more energy in the transaction, but heating and cooling can be obtained without a phase change in certain systems.
See the International Ground Source Heat Pump Association at http://www.igshpa.okstate.edu/
for more details and some good diagrams.
And, in tech-speak, there really is not any such thing as “cold”. Everything is heat. “Cold” is just less thermal energy than “hot” when compared to absolute zero.
BS in Mechanical Engineering, 1979
Thermodynamics/Energy concentration
NC State University
Moo.
Andy from Chapel Hill
All this talk about ground source heat pumps?
My outside unit sits on a slab while the rest is in my outside utility room?
Do I have one of those ground source pumps?
Thanks
I guess I did misunderstand. You mentioned the other two rooms as colder than the rest - not receiving enough heat - so I thought I’d add my 2 cents. ;)
All the best!
You mean like the little foam things you put over the outlets? That'll help a little.
If you're really serious about saving energy (and keeping the bills down) this winter, you should be looking for the big losses - uninsulated attic door, cheap windows, drafty door seals, uninsulated or poorly insulated walls and ceilings. There's plenty of places to find heat loss. Do some internet searches on heat loss and look for the biggest bang for the buck. Often, a cheap solution makes a significant difference.
When I bought this house, the garage ceiling (garage under the bedrooms) was not insulated, the AC/Furnace unit in the garage was blowing a ton of air out through some serious gaps where the plenum attached to the furnace, the wall between the garage and the basement had no drywall on the garage side (and since it was a 9 foot wall and the basement drywall was only 8 feet, had a gap above where the insulation was just flapping freely). The front door gasket was so bad that I could see light around the most of the door, and the thermal glass on the back door was missing the outside layer. The attic access had NO insulation, and no seal.
My highest summer AC bill this year (and it was a hot year here) was less than the previous owner's monthly budget electric bill. I didn't see their gas bills, but I'd bet that my heating bills are much lower as well.
It took some effort to get there, but I made it a better house in terms of energy usage, and I'm not done yet!
Absolutely beautiful! It must not be hard for you to get up in the morning. ;) What is the other building in the forefront of the pix?
No, you have a regular heat pump that uses the ambient air as the heat sink and source.
Geothermal and generic heatpumps are different animals. geothermal gets its temperature differential from below ground. Standard heatpumps use the outside air.
Thank You.
#1. Make sure your installer has done eight or ten geothermal systems before you take his bid.
#2. Get the heated floor option. There is absolutely nothing better.
$2/gallon propane = $22.00 MM/BTUs.
Slab mounted heat pump: $1,000
Geothermal heat pump $22,000
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