Mini Split Heating Efficiency vs Outside Temp??


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Old 10-07-12, 09:08 AM
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Question Mini Split Heating Efficiency vs Outside Temp??

I have rental duplex that is currently baseboard electric. I am trying to determine if converting to mini split heat pumps would significantly improve heating efficiency. I know efficiency drops with lower outside temps, but could not find anything quickly on the internet that shows at what temp would resistance heating have to take over from the heat pump. If I made this change, would I be well advised to leave the baseboard heaters as backup?
 
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Old 10-07-12, 01:08 PM
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I would leave the baseboard as a back up source of heat. Mini splits are very efficient even at or below 0F. The higher the seer and HSPF rating the more efficient the unit. I would absolutely choose mini splits over baseboard heat if I was having to pay the electric bill.
 
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Old 10-08-12, 05:31 PM
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Still Looking for More Info

Thanks for your reply. I spoke with a local contractor today and he said the efficiency of heat pumps plummets below 42 degrees. Apparently, Mitsubishi is using some method to capture compressor heat at low temps to improve efficiency. I am just trying to find some real numbers to compare. Resistance is simple: 1 KWH = 3415 Btu. With a mini split operating at 20 degrees, how many KWH do I burn to get equivalent Btu's.

I am not paying the electric bills, but am willing to upgrade the property if there is some real gain.
 
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Old 10-09-12, 07:54 AM
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I am confused. What comparison tool?

Dehumidifying is not a particular issue in our climate. Average outside temp ranges from about 29 to 35 in the 4 coldest heating months. One real plus from a mini split system would be vastly improved cooling costs vs the current 18,000 Btu window A/C. I just can't get my brain around whether spending $4k/unit would really improve the heating costs. Most of the glowing stuff on the internet on mini splits seems to be from milder winter climates than the front range of Colorado.

Thanks for you help so far.
 
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Old 10-09-12, 09:05 AM
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Forgot to add the link. sorry! Will add it when I get home tonight.
 
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Old 10-09-12, 09:07 AM
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I live in north Indiana. We use them all the time and our lowest temps are -5F.
 
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Old 10-09-12, 10:12 AM
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If they are effective in N. Indiana, that sound encouraging. Our climate is probably more variable than yours. The coldest I can remember in 45 yrs in Boulder is -27. Having said that we usually have a few golfing days even in the coldest months. Average lows in Dec, Jan, Feb range from 15 to 22, so that is what you have to heat in the morning warm up cycle. I understand that when we have record low temps, the heat pump would not be effective, but am concerned with avg performance over time. I should have never built this in 1977 when no new gas taps were available. Now the country is awash in gas, but there is no service on my street.
 
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Old 10-09-12, 05:11 PM
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Old 10-10-12, 11:02 AM
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For a mini-split to work well in a cold climate, it must have a variable capacity compressor which can ramp up in cold weather. The capacity of traditional single speed systems drops off significantly as the outdoor temp declines.

Check the spec sheets of the unit you'd like to purchase carefully. Some spec sheets may have a capacity/outdoor temperature chart.
 
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Old 10-22-12, 10:41 AM
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Thanks Mug

I have been out of town, but am back and ready to pursue. These data seem hard to find on the internet, so I'll contact manufacturers, probably LG or Mitsubishi.
 
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Old 10-22-12, 11:54 AM
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I don't recommend LG ... I have had bad luck with them annd their tech support. Just my 2 cents.
 
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Old 03-15-13, 08:36 AM
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Update?

I know this thread is old, but I'm curious if Handyman663 or anyone else has found additional info/experience with using mini-splits for heating in cold weather.

I'm based in NJ and looking to use a mini-split multi-zone system as the primary source of heat. I know multi-zones loose efficiency at colder temps but its hard to decipher exactly how much and if the potential loss in BTUs will still be enough to heat the house.

Does anyone have any real-world experience on how multi-zone systems perform with winter temperatures in the teens?

Thanks, Jason
 
 

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