We had a Mitsubishi mini-split hyper heat 18000 unit installed in December to heat our ~1100 sq ft great room/kitchen area. We were hoping to be able to remove our old electricity-eating baseboard units, but decided to wait one year to make sure the mini-split could do the job. The mini-split's been great until we just had our first run of sub zero night weather. I was sure happy we kept in those baseboards! Under about -5 the mini was still trying, but couldn't quite do the job. Had to crank up the baseboards and our builder-box fireplace (saving to replace with wood stove in an alcove build) to stay warm. As soon as it warmed up to -5 (does that make sense?) the mini was on board again and all was well.
minisplit ductless heat pump
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RustyShackleford
Minister of Fire
Speaking of which, here in NC we've had what we consider brutally cold, high single digits, and my Fujitsu mini-split is handling it just fine.
That to me is a huge advantage of the mini-split: the simplicity of not requiring any backup heat source (in my climate, that is). It's going to be a tough call whether to try to get a couple of these for my main house (the Fujitsu is in a study I just added) when my main heat pump gives up the ghost, probably fairly soon.
Though, with my BlazeKing, and my newly encapsulated crawlspace, and my transfer duct cycling super-heated loft air through the room with the minisplit, I hardly use the heat-pump anyhow (in winter-time, that is).
semipro
Minister of Fire
RustyShackleford
Minister of Fire
Hello. Out of frustration and disappointment in my Mitsubishi "Mr. Slim" heat pump, I'm searching for forums for a sanity check. My story - I spent around 4K on a 13000BTU ductless unit. I have 1100 sf on 2 levels. I only expect to heat the downstairs. Recent cold snap, nights in the 30's. Heat pump not getting above 66 in spite of using the super fan and the super boost option. Service came out and determined unit was well below refrigerant or pressure (not sure term). They fixed that. Now, to get 68 degrees I have to set remote controller to 74 and can confirm the temp at the unit, up at the ceiling is constant at 77. The service guy seemed to figure this out on the fly. So far I am not at all happy with this setup. . I am in the habit of setting back at night, as the residual heat upstairs makes it too warm for sleeping. I cannot set back to 60 (which would be 66 on the controller) and get it back up to 68 (which would be 74 on the controller) within even 6 hours the next day. Hoping this makes sense and hoping someone on the forum can either tell me this is expected or advise me on some actions. Much appreciated.
A wild guess.....the unit is not powerful enough to heat your space without help.
Comfort will take a hit, and temp gradients will get bad when the unit is too small for the heating 'load'.
As for practical advice....if you can prevent the warm air from rising upstairs blocking it somehow, you will be better off. Can you close bedroom doors, etc?
Comfort will take a hit, and temp gradients will get bad when the unit is too small for the heating 'load'.
As for practical advice....if you can prevent the warm air from rising upstairs blocking it somehow, you will be better off. Can you close bedroom doors, etc?
It sounds like in one case you are trying in one case to have the mini-split function as an area heater and in the other as a whole house heater. 13000btus for 2200 sq ft is unrealistic unless the house is super-insulated. Can you close off the upstairs in some way so that the unit is only trying to heat up the downstairs in the morning? That should speed warming of the first floor.
PS: or am I reading this wrong and you have 1100 sq ft total. If so, how well insulated is the house?
PS: or am I reading this wrong and you have 1100 sq ft total. If so, how well insulated is the house?
Thanks for the quick response. Of course the sales people and the service tech both told me this was the right unit for my config. What can one do but trust the "experts"? Is not practical to close off the stair well; one bedroom door remains closed and unheated; the other has a zonal, "cadet" heater on a programmable thermo and it works very well heating the bedroom and hallway area. i will experiment with keeping ing that door closed for the day; thanks for the tip. I see no joy in owning ductless heat pump at this time.
1100 sf total. I live in a town house and share common walls on both sides of unit. Blown insulation in attic; none (yet) in crawl space. Not practical to close off stairwell, but can close off the two bedrooms upstairs for sure. Thanks!
One way to understand the heat output of the mini-split (or any heater) is to think in equivalent resistance heaters. The mini-split is putting out about 2.25 electrical heaters worth of heat. Could the whole place be heated with 2 - 1500w electric heaters? How long would it take them to heat up the whole place?
It is not efficient with a mini-split to have a large set back temperature. Try just a couple degrees cooler at night or try leaving the temp at the daytime temp setting and just close off the bedroom you sleep in around 7pm. It will get colder due to the lack of heat. Sleeping with the door just ajar may be just right for sleeping and you will wake up to a warm house.
It is not efficient with a mini-split to have a large set back temperature. Try just a couple degrees cooler at night or try leaving the temp at the daytime temp setting and just close off the bedroom you sleep in around 7pm. It will get colder due to the lack of heat. Sleeping with the door just ajar may be just right for sleeping and you will wake up to a warm house.
semipro
Minister of Fire
Even though you're trying only to heat the 1st floor I suspect you're actually heating both floors and 13k BTUs s is just not enough heat output.
According to the chart below for your unit it will only heat about 550 sq. ft.
I'd bet this unit is installed high on the wall as most are and that your heated air is hugging the ceiling until it reaches the stairwell and then moves upward to the 2nd floor.
The only option I see, other than adding more heating capacity, would be to close off the bottom of the stairwell at the 1st floor level somehow.
We installed some pleated cellular blinds at the bottom of our stairwell that do just that. Ours don't extend all the way to the floor but could I guess. We have a 10' ceiling there and the blinds only extend down about 4" but it does serve to trap hot air on the 1st level.
According to the chart below for your unit it will only heat about 550 sq. ft.
I'd bet this unit is installed high on the wall as most are and that your heated air is hugging the ceiling until it reaches the stairwell and then moves upward to the 2nd floor.
The only option I see, other than adding more heating capacity, would be to close off the bottom of the stairwell at the 1st floor level somehow.
We installed some pleated cellular blinds at the bottom of our stairwell that do just that. Ours don't extend all the way to the floor but could I guess. We have a 10' ceiling there and the blinds only extend down about 4" but it does serve to trap hot air on the 1st level.
flyingcow
Minister of Fire
we have a heat pump downstairs and one upstairs. very seldom use the one upstairs in the winter.but we keep the doors open at least 4 inches sometimes more to keep all the rooms upstairs relatively warm.
if you get good and bored.hang a few pieces of toilet paperaround the stairs or in certain areas and watch the air movement.
if you get good and bored.hang a few pieces of toilet paperaround the stairs or in certain areas and watch the air movement.
Retired Guy
Minister of Fire
My problem with the Mr Slim is that while I can set the thermostat to 60-62 degrees I can't get the bedroom to that temp. It stays 65-66 degrees.. We end up turning off the unit in the early evening and opening a window to get the "comfortable sleeping" temp..
No, you cannot blindly trust the experts. Some are excellent but some are crooks. You only find out which one you got when you run into problems.
Due to our 9 cent per kwh heat I have changed my mind on the ductless and will stick with plain old electric wall heaters for backup heat when the woodstove is unable to run. The minisplits are quite ugly, expensive, and in a backup heat application don't make as much sense as a wall heater. If I ever need to stop using wood heat then I can always switch to minis.
Ashful
Minister of Fire
I'll agree with the classic mini splits being less than attractive, but Mitsu sells all sorts of in-ceiling and in-wall options, now. I'm blown away by the idea of trying to heat or cool 1100 sq.ft. on two levels with only 13kbtu! I have 1 ton (12kbtu) just for my 300 sq ft studio over the garage. I'm being quoted 2 tons for a new 1200 sq ft space.
No they don't. Not in the units that are able to function at low temperatures. You're stuck with the ugly trailer looking wall warts. It's one of my peaves with the minisplit industry, that and they do not offer a water heating version. I wonder if it is a conspiracy. Lots of energy is spent heating water in this country.
I think they are ugly AND I have an old school BK. That's saying something.
I can burn wood in the shoulder season for primary heat just fine. So why would I spend any money on a minisplit? Cooling? Don't need it. The existing resistance back up heaters are functional, free, and don't look as ghetto.
The efficiency is wonderful and if you live in the city where you can't use woodheat and don't mind the looks then they are a great option.
I have a question similar to that posed by Gypsea above.
I installed a Caribou 12,000 btu inverter unit because it had quick connect lines for DIY, cost $1100 installed and was 110v so I can use it with my solar/battery/inverter or a generator. It is marginally sized for the Nova Scotia climate but I intend to burn wood in January and February. Cutting wood is getting to be too hard on my hands and wrists.
The room temperature never gets above 18C/65F even with the thermostat set at 77F. The problem is not undercapacity as this was the same Christmas day at 60F outside. The heat pump was only drawing 6.8 amps ( max is 11A ) but inside the temperature did not get above 18/65F. We like it at 20C/68F to be comfortable.
It seems to me that the mini split is reacting to ambient with the outdoor sensor and using this temperature to regulate capacity. The setting of the inside thermostat with the handset doesn't do anything.
I'll get back to the supplier next week ( this is the first chance I've had to document the information ) but I wonder if anyone has any ideas to help.
Thanks:
John
I installed a Caribou 12,000 btu inverter unit because it had quick connect lines for DIY, cost $1100 installed and was 110v so I can use it with my solar/battery/inverter or a generator. It is marginally sized for the Nova Scotia climate but I intend to burn wood in January and February. Cutting wood is getting to be too hard on my hands and wrists.
The room temperature never gets above 18C/65F even with the thermostat set at 77F. The problem is not undercapacity as this was the same Christmas day at 60F outside. The heat pump was only drawing 6.8 amps ( max is 11A ) but inside the temperature did not get above 18/65F. We like it at 20C/68F to be comfortable.
It seems to me that the mini split is reacting to ambient with the outdoor sensor and using this temperature to regulate capacity. The setting of the inside thermostat with the handset doesn't do anything.
I'll get back to the supplier next week ( this is the first chance I've had to document the information ) but I wonder if anyone has any ideas to help.
Thanks:
John
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