Limits to mini splits in cold conditions

[peakbagger]

I ran into a long term vented kerosene heater dealer this weekend. Since Monitors stopped being sold he had been planning to taper the business down. Lately he said he has gotten real busy selling rebuilt units to folks who went with mini splits. They are finding out that in Maine, the cold weather limits of mini splits is surprising folks so they end up needed a reliable heater for cold conditions.

I have been well aware of the practical limits of my mini split in cold conditions but apparently some folks aren't careful about understanding that yes a mini split can put out some heat down to about -10 F but its not a lot of heat.

He did mention that Toyo is apparently getting more aggressively back in the market and are even offering trade ins for old Monitors.

 

[pen]

I've had a mitsu mini split for about 6 years now. Good down to -13 according to literature. I have run it to -10 just to see how the unit would do, but normally shut it down if things are going to go below zero.

While mini splits are great, in the northern latitudes, not have a second option for heat is asking too much of the device and asking for trouble.

For us, the wood stove carries at least 90% of the heating duties. Mini split helps in the shoulder season or moderate winter weather, electric baseboards could cover the joint if needed, and help in the coldest of cold that we see.

 

[maple1]

There are a lot of mini-splits going in around here in new house builds as the primary heat source.

Have an Uncle and Aunt who put in a 4 head Daikin system 2 or 3 years ago (retro fitted to an oil baseboard system house) - I need to quiz them on their entire winter heating operation, not sure how far thru the winter the splits take them.

I'm not sure what everyone in the new builds does in the coldest of the winter, but I would think they wouldn't just have splits. We have a pretty moderate climate - but still have cold spells (meaning between -20c & -30c). Likely some electric baseboards? I would have a wood stove to supplement - after 22 years there's a few things I would do differently if I was doing a house build all over again....

 

[peakbagger]

There are lot of folks in Maine installing them but generally there is back up, it may be oil or it may be electric. As long as you have a wood pile and stove you should be fine as long as you are home to feed the stove.

My Mitsubishi unit does run down to -12F but its output is cut way down to around 6000 BTUS. What comes out of it is not very warm air and it cycles into defrost every 45 minutes or so. I have played with mine for a couple of years and the low end cut off I use is 30 deg F. Anything less than that at night I make sure I use the wood boiler or my stove. During the day if its clear and sunny out I can run down to 20 but if its snowing or high humidity it starts to frost up and the goes into defrost mode far more often.

 

[begreen]

I've had a mitsu mini split for about 6 years now. Good down to -13 according to literature. I have run it to -10 just to see how the unit would do, but normally shut it down if things are going to go below zero.

While mini splits are great, in the northern latitudes, not have a second option for heat is asking too much of the device and asking for trouble.

For us, the wood stove carries at least 90% of the heating duties. Mini split helps in the shoulder season or moderate winter weather, electric baseboards could cover the joint if needed, and help in the coldest of cold that we see.

Redundancy is good. Stuff happens and things break down, including humans at times. It's good to have backups.

 

[maple1]

I have a question. Not sure this is the thread for it or not but it is related at least.

Can the wall unit be mounted right up against the ceiling? If brand matters - Daikin preferred. The preferred spot in our main room is right above a door. The unit is 1/4" higher than the current space between ceiling and door trim. Which can be trimmed some (3" wide).

 

[peakbagger]

Not with my mitsubishi. It has a top inlet and the door hinges up.

 

[maple1]

Ya I dont think its looking good for those thoughts...

 

[pen]

My mitsu needs top access as well. I went for the unit I thought would best fit our needs, and had the installer that I trusted put it where it needed to be. As always, be informed and be honest with what your expectations are.

 

[maple1]

So another question but maybe more directly related to the thread topic.

I am looking at two heads, they would be almost right above each other, first floor & second floor. I am being advised that even though one outdoor multi-head unit would seem to be a good choice for that application, one separate outdoor unit for each head would actually give more efficient overall operation and also be (marginally) less expensive. Anyone have any input on that aspect?

 

[peakbagger]

My experience is dated but the early multihead Misubishi units were reportedly not as reliable as the single units. Two different HVAC techs steered me away from them. They are still actively selling multiheads so they must have worked out the kinks. Given that the vast majority of service calls for minisplits reportedly are for external damage on the outdoor units not covered by warranty I would expect two redundant separate units is the way to go. I am surprised that two single units cost less than two multi units as all they are doing is installing a set of remote valves in the upsized outdoor unit to route the refrigerant to the unit asking for it.

It could be that most techs just check the gas pressure on a single outdoor unit and yank it if it wont take a charge while they may actually need to diagnose and fix a multihead unit in the field?

 

[maple1]

That sort of supports what I was advised.

I just found it very odd (still do) that they have multi-head outside units, but even in a situation where it would seem to be the ideal choice, that the recommended (and apparently a bit cheaper) way to go is two separate ones. Which makes me ask why do they even have/make multi-head outside units if that is the case?

 

[peakbagger]

Real Estate. My local credit union apparently decided to go with mini splits instead of central system. They have a "farm" of various brands of minisplits out behind the building. Interesting to see that some brands use lower quality surface coatings on their units as cases are rusted and some look close to new.

 

[CaptSpiff]

Real Estate. My local credit union apparently decided to go with mini splits instead of central system. They have "farm" of various brands of minisplits out behind the building. Interesting to see that some brands use lower quality surface coatings on their units as cases are rusted and some look close to new.

That would make a good photograph with names, unless they are more than 10 years apart.

 

[CaptSpiff]

Can the wall unit be mounted right up against the ceiling? If brand matters - Daikin preferred. The preferred spot in our main room is right above a door. The unit is 1/4" higher than the current space between ceiling and door trim. Which can be trimmed some (3" wide).

Definitely need some room above, the brochure usually mentions the amount.
The other thing I ran into is the "header/king stud" situation above a window. You may encounter a similar situation drilling your 3" hole above the door.

 

[maple1]

Yes will see how this plays out. The brochures I found didn't have that listed - couldn't find spec'd anywhere actually, so far at least. This will be fully installed by them, not me. I think except for plugging a new breaker into my panel & screwing the wire onto it. Need to get him back out soon as he can get here to iron out the finer details - which I also have to balance out with what my other half doesn't like. Which is basically the whole mini-split concept & seeing those 'ugly things' anywhere on a wall. So have I still have some work cut out for myself with that aspect alone....

 

[peakbagger]

Its been while since mine went in but it came with full size template marked with all the options for routing the gas piping and had minimum distances from the ceiling and side walls.

 

[pen]

seeing those 'ugly things' anywhere on a wall. So have I still have some work cut out for myself with that aspect alone....

What is the attic like? I don't know of anyone personally running one from within the attic, but I believe they can be installed there.

 

[begreen]

I know of several local multi-head installations locally. Of them 3 are Mitsubishi, one is Daikin and the other is Fujitsu. They are all 4-6 yrs old now and to my knowledge have not had issues related to the multihead installation. And a friend just has a 2 head Mitsubishi Hyper-Heat installed, but has not gone through a winter with it yet.

 

[peakbagger]

What is the attic like? I don't know of anyone personally running one from within the attic, but I believe they can be installed there.

Various companies do sell ducted indoor heads but not sure much or how well they work. The standard indoor head would not work well due to the way the air flows.

 

[Tegbert]

Various companies do sell ducted indoor heads but not sure much or how well they work. The standard indoor head would not work well due to the way the air flows.

And they are huge too. Most I have seen are about 40-45” wide 24” deep and about 8-10” tall and weigh between 50-70 pounds. My neighbor just installed one earlier this year and he says it works great.


Lopi Rockport
Blaze King Ashford 25

 

[maple1]

The ceiling cassette did grab my attention at first. I think we have a spot that one would work good in as far as distributing & dispersing the heat & cool widely, in a hallway/stair landing spot between out kitchen & living room. But they need 24" o.c. spacing, whereas our spot is in a first floor ceiling with 16" o.c. joists. So no go there. I did find last night a minimum ceiling clearance spec for the Daikins of 1-3/16", which isn't very much. Not sure that is for the exact head unit that I was spec'd, but it puts us very close to being able to put it above the door we wanted to.

 

[Highbeam]

The multi head units were also much lower efficiency than the singles. Two single head units offers redundancy when one dies.

 

[begreen]

The multi head units were also much lower efficiency than the singles. Two single head units offers redundancy when one dies.

That was an early case but this has been improved on a lot with more recent advances. Often this comes down to yard real estate, looks and noise. I wouldn't want a bank of 3 individual compressor units sitting on the side of the house and if all 3 kicked on the collective noise would be defeat one of the nicer features of these units, quiet operation.

When we need to replace our AmStd. heat pump it will most likely be with a Mitusbishi, single large unit connected to an airhandler and the existing, well-insulated duct system.

 

[georgepds]

I've got 2 Fujitsu 12k units on the same side of the house, with a patio area between. Really can't hear a thing, even on the patio

If you stand in front of a unit you can tell it's working by the air blowing