ASHP real world performance in COLD climate..

[kenora]

Hi, I stumbled across this website and immediately signed up when I saw the discussions about mini-splits. I think they are the answer to my heating and cooling needs but would like a real world "been there, done that" opinion from someone that uses one in a cold climate.
My home is located N of Kenora Ontario Canada... according the the data I can find that's 10500 HDD with an average years winter low of -35c (-31f) with regular dips to -40c (-40f).

My 850 sq/ft home is reasonably well insulated (2x6 walls with R20 batts and roof at R40); I will be improving this during the summer by removing the vinyl siding and adding 3" EPS over the exterior sheathing and blowing an additional R40 on top of the existing batts in 1/2 the roof (1/2 flat ceiling, 1/2 cathedral that I can't change))

I will also be adding insulated removable exterior window shutters (R40 foam) that will be put on at night.

All with an effort to lower my heating bill. I am currently using an oil forced air furnace paying $1.21 Cdn a liter) but hope to use that as emergency and back up heat for a Fujitsu or Mitsubishi ASHP... I know there are units that produce heat to -25c (-13c).

Anyone in a similar climate got a real world experiance to share? Am I on the right track?

[NiHaoMike]

Have you looked into building a CHP system or even some Bitcoin miners? Those would do better in such cold weather.

[kenora]

Originally Posted by NiHaoMike

Have you looked into building a CHP system or even some Bitcoin miners? Those would do better in such cold weather.

Hi, I am at a total loss to understand what either of those are!

Google provided...

(never mind I guess I cant post links)


or how they relate to my post

[NiHaoMike]

CHP = Combined Heat and Power. For your use, it's basically a small diesel engine running from heating oil to spin a generator. You use heat exchangers to put the heat from the engine to good use and an induction motor can be repurposed into a generator.

Bitcoin (and some related projects like Litecoin) works by using a lot of computing power to establish a form of online currency. It's exactly the same energy efficiency as an ordinary heater, but the value of the "coins" generated offsets the cost of electricity, maybe even bringing profit.

[ecomodded]

All of the mini-splits i looked into can only produce heat down to -15 (not sure if its to the rated btu )

I suggest contacting your closes dealer of mini-splits to get more understanding of its usefulness in your climate, also they may have a good model for your climate.

[jeff5may]

The Mitsubishi Hyper-heating inverter units (and an increasing number of Chinese knock-offs) will do 100% of their rated capacity at -15 degC and 80% at -25 degC. Panasanyo, daikin, and fujitsu have inverter units that will do well down to -15 degC. Below there, they either rev up the compressor or fall off quickly in capacity. If they rev up, COP drops off at the expense of BTU output. If they don't COP stays high and power usage drops off with BTU output.

Quite a few fellow ecorenovators have been commenting on the operation of their various brands of mini-split units this year. It has been a long, cold winter so far, and many have been highly impressed with the performance of their relatively inexpensive systems. Just browse this forum and interact with others on their respective threads. Welcome and good luck!

Jeff

[MN Renovator]

Actually the 100% of rated capacity at x temp of an inverter unit is a point where it is already ramping up the compressor speed especially if the number matches at two temperature point or shows higher at a colder temperature, once you are looking at reduced output at specific temperatures with an inverter compressor, that's usually the compressor already at max speed and you are seeing the taper off of how much is can get while running at the speed at certain temperatures. All tests are in the lab, real conditions vary.

All inverter units can rev up to meet an increased load, but the matter is how much do they speed up and how well can they meet the capacity. ..in a similar light, how slow can they run with light AC loads in the summer to get the most dehumidification potential too. Compressor displacement isn't published but I think some guesses based on performance figures might give a decent idea. Either way a unit that tests with high HSPF and high EER/SEER AHRI ratings are what to look for. Then looking at the data provided by the manufacturer on how it performs at the super low temperatures below the 17f that AHRI tests to determine if a unit meets the needs should be a decent enough way to size a unit within reason if you know your load and temperature you want to design the system to work well for.

[AC_Hacker]

Originally Posted by kenora

...according the the data I can find that's 10500 HDD with an average years winter low of -35c (-31f) with regular dips to -40c (-40f).

My 850 sq/ft home is reasonably well insulated (2x6 walls with R20 batts and roof at R40); I will be improving this during the summer by removing the vinyl siding and adding 3" EPS over the exterior sheathing and blowing an additional R40 on top of the existing batts in 1/2 the roof (1/2 flat ceiling, 1/2 cathedral that I can't change))

I think that you are doing the right thing by getting quite serious about your insulation.

However, the weather as you are describing it would be an exceptional challenge to an ASHP. Honestly, I don't think that there is any commercially available ASHP that can supply 100% of the heat required to get you through your winter that has low temps such as you have cited.

The units like jeff5may described can do a very good job during the summer and spring and fall, and into the winter as well. But in my opinion, the severe low temperatures you are describing would be beyond the ability of those mini-split ASHPs to supply heat in those extreme conditions, no matter how well you insulated your house.

Now if you had a reliable backup heat source that could kick in (automatically) and completely take over for the ASHP, when the weather gets truly arctic, then you might have a workable system.

But to your original question of actual user experience, no one who has responded to your post, including myself, has operated a mini-split in conditions such as you have described.

If you had the means to install one, a ground source heat pump would be the best choice for you, because deep down in the earth, below the permafrost, there is a source of low-grade geothermal heat that a heat pump can use to easily supply you with a warm winter home.

Best,

-AC

[kenora]

Thanks for all the replies.. I appreciate the feedback. My intention was never to have the ASHP provide 100% of the heat; that's where either the heat strip in the ASHP or the oil furnace comes into play.
At my location there is only oil and electric, propane is as expensive as oil and would require a big cash injection to replace the furnace and buy a 500 or 1000 gallon tank.
Since oil is now pricing itself past electricity (I am on a tiered HydroOne plan with time of use billing) on a per therm basis I thought having the ASHP provide heat for 2/3 or so of the year at even a 2-1 COP would be better than paying the oil man. The balance of the year (Nov-Feb) would require either the existing furnace to take the load or since my panel has plenty of room I thought of adding baseboard heaters to replace that smog monster.
The baseboard heaters would operate at 100% efficiency at worst while my oil furnace is rated at about 77% at best.
A GSHP is out of the question, I priced one at $27000 and realized that money would be better spent on insulation, air sealing and a hybrid heating system to get me off the oil.
Not sure I mentioned it I am also adding insulated shutters (R20).
I figure I can do all the improvements including the purchase of the ASHP and baseboard heaters and foam for less than $10000.
I would also get the benefit of an air conditioner which woukd be nice for the few hot humid days we endure.

[NiHaoMike]

Skip the baseboard heaters and just use portable space heaters and incandescent or halogen lamps. Plan on a heat pump and/or Bitcoin setup to supply the majority of the heating load.