Heat pump cold efficiency

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Old 12-04-19, 01:03 PM
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Heat pump cold efficiency

I have a new Mitsubishi mini-split heat pump. It is said to work down to -14 degrees F; however, I understand that above that temp, the efficiency decreases as it gets colder. I would like to see a chart or graph showing exactly how much the efficiency is affected by temperature. That way, I could make a better decision as to whether to use it (for example, at 0 degrees), or whether to use our wood stove or resistance-type electric heaters that I have. Can you help me with this kind of information?

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Old 12-04-19, 01:45 PM
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Search online for "heat pump efficiency vs temperature". It will give you a general idea. You'd have to contact the manufacturer for exact information on your heat pump.



In general, the last thing you want to do is use electric resistance heat. It is 100% efficient but it's also the most expensive for the btu's you get. If your wood is free then burning wood all the time would be the cheapest... after all it's free. But if you have to pay for your wood either with money or labor then you'll have to figure your own temp when it's better to burn wood.
 
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Old 12-04-19, 02:35 PM
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Thanks Pilot Dane. I did write to Mitsubishi but did not get an answer. Will try again.

I do heat with wood, but would prefer to use the mini-split as much as possible to go easier on the atmosphere. (We have solar electricity.)
 
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Old 12-04-19, 06:33 PM
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Whats model #.

Its best to just let heat pump run. -14 is great.
 
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Old 12-04-19, 06:59 PM
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Lawrosa--Here are the specs:

Outdoor unit, hyper/heat, will heat down to -14*F, R-410A, 2 ton, outdoor unit
M# MXZ-3C24NAHZ2-U1

Upper level, 12,000 BTU unit, l
M# MSZ-GL12NA-U1

Lower level, 12,000 BTU unit,
M# MSZ-GL12NA-U1
 
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Old 12-04-19, 07:58 PM
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Old 12-04-19, 08:03 PM
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page 34 shows 12000 btu at 17f outdoor. with an indoor dry bulb of 70F.

How many sq feet is the space your heating?

Shows at 5f it will only produce 9700 btus. so capacity starts falling off after 17f
 
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Old 12-04-19, 08:16 PM
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Im sorry, i see its multi zone..

Page 40 shows 25k btu at 5F. I would assume after 5 F capacity drops.

I assume thats about 12000btu per inside unit.
 
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Old 12-04-19, 09:05 PM
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Our house is 24'x36' (864 sq ft) and it's 2 1/2 stories tall including the walk-out basement which is finished as living space. It's kind of super-insulated so today, for example, I turned off the upstairs unit and heated the whole place w/ the lower level unit. (It was around 32 farenheit.) I'll probably use the wood stove when it's the dead of winter, like below 20, since the minisplit will be less efficient then...
 
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Old 12-06-19, 09:48 PM
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24000 BTU is the right capacity for your room. Ductless heat pump can efficiently heat up a room in freezing ambient temperature. Mine is 18000 BTU and I feel comfortable on 16 thermostat setting in 0 ambient temperature. You can find your own comfortable temperature by setting to different temperatures. Manuals and graphs cannot take into consideration all variables involved where the heat pump is installed. So find your own comfort level temperature.
 
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