Need Fujitsu mini split question answered ASAP please.

[Joe Leigh]

Practically every mini split manufactured in the last 8-10 years has inverter technology. It's nothing new.
I have a high end unit in my own home. Outside temps fall below 40 deg F and they put out very little heat.
They work well on 45-60 degree days to help take the chill out, but below that there's very little heating capacity.

Im not sure how cold it gets in your area, but I assume you have some secondary heat source?

P.s. the unit is located way too close to the house. Hard to tell from the pic but it appears to be only 12-14 inches from the house. Not nearly far enough to insure proper air circulation.

A quick check of the Fujitsu website shows the heating output for the 12-18-24k btu inverter heat pumps are all rated at 47 deg F. As the ambient falls below that the heating output falls.

[Brad Adams]

The new Fujitsu units maintain full capacity down to 20 degrees. They still work down to minus 15. 12" is plenty of room for circulation.

[Joe Leigh]

Sorry, but no heat pump works to full capacity down to 20deg F regardless of the manufacturer without a supplemental heat source. Even if it did that's a long long way from zero or below at which point the unit would produce little to no heat.

Also, I haven't seen a manufacturer yet whose inlet clearance was less than 18"
based on those pics I'd say he has less than 12"

Edit: I just checked the Fujitsu tech submittals on their Halcyon heat pump products and the entire line shows approx 50% reduction in capacity at 17 deg F. The capacities are not available below this number but you can bet they are much lower.

[David Weaver]

There are a lot of numbers thrown around with different units. My mitsu literature said the unit was 100% efficient at zero degrees. I would assume that means that I am getting the same efficiency more or less that I'd get from a coil heater when pre-heat current use is figured in. I believe it will deliver close to its rated 15k btu around 0 degrees, too, but at closer to 2kw than the 950 or so watts that the unit uses at temperatures where preheat isn't required.

Joe, presume you are saying that they lose their ability to work without any supplemental heat in the unit below about 45 degrees? Because they certainly will still generate a lot of heat at 20 degrees, or even zero, just not without supplemental heat.

[Raymond Fries]

We were told that we did not need a secondary heat source with this unit and the existing unit was disconnected to use the power for the mini split. I hope we were told the truth as I would hate to see all of my wife's garden be lost next winter. The salesman said they have a four head unit at their office here in Fort Wayne and it works fine all winter. They are coming back to install the dehumidifier and run the drain out the exterior wall into a french drain. They had to do the call before you dig thing. And it should be all finished.

[Brad Adams]

Don't worry, Raymond. The unit will work. The new extra low temp Fujitsu units are great. To someone who hasn't installed or used one, they just don't understand.

[David Weaver]

Raymond, as I mentioned, I got a mitsu - but it is very similar to the fujitsu in function, capabilities and efficiency. My unit will work down to -13F, and it's in an area on my house that can be closed off to supplemental heat (very very similar to yours, a converted porch that is a large room now with a lot of window surface.

My inlaws stay in there during the winter when they visit, and they close the door. This past winter, they stayed in there for the better part of a week where it was below zero most nights and had no issues at all. My electricity bill was a little higher than normal, but not much.

Your garden would only be in danger if the unit actually broke.

[Raymond Fries]

Well - They moved the unit today and both units are installed and operational now. It will be so nice to have A/C in the shop this summer. Will post a couple of pics later.

Thanks for the encouragement guys!

David - Good to hear you have a similar room and it works just fine. We do have a plan should we lose power. I have a couple of space heaters that we can run from the power inverter I got to hook up to the car.

Brad - Can you offer and advice on the dehumidifier that must be installed for the winter. The unit will be installed on the exterior wall just to the right of where the channel runs down. They plan to drill through the wall and run the drain pipe out of the wall and into a french drain. I have never heard of this but the contractor said it is a 2' deep hole filled with gravel. Since the hole is below the frost line it will not freeze. Someone told me this would not work but I do not see what he problem is. I guess I should just trust my contractor as everything has been just fine so far...

[Joe Leigh]

Joe, presume you are saying that they lose their ability to work without any supplemental heat in the unit below about 45 degrees? Because they certainly will still generate a lot of heat at 20 degrees, or even zero, just not without supplemental heat.

David, not sure if the OPs unit has supplemental heat, but a look at the submittals for that heat pump line show that the mechanical heating, that is compressor operation, at 17 deg F. drops to approx 50% of the rated capacity which is 47deg F. Same issue on the cooling side which is rated like most manufacturers at 95deg F. Once the ambient climbs above that the capacity drops.

The other consideration, if you look at the picture of the area in question, is the large amount of window/glass area. As the outdoor temperature falls the temperature of the air being delivered from the indoor unit also drops making the area feel drafty if no supplemental heat is used.

[Joe Leigh]

To someone who hasn't installed or used one, they just don't understand.

Actually we're one of the three largest ductless mini split installation contractors in the North East.

Anyway, good luck.

[David Weaver]

I don't know how his room will be - mine has 13 windows and a door and I have no issue. The other part of the house is more drafty.

I get what you're saying about the mechanical heating, but the supplemental heat makes up for it. You just have to pay the extra in the current used to run it like that.

My unit is a bit oversized for the space (15k btu for essentially 250 or 300 sq feet, but that space is on a slab with 13 windows and a door and only 4 inches of insulation overhead), so I've never had to push the unit and it's never struggled to heat it, even this past year when it was -5 overnight. The rest of the house was made in the 50s. The room the split is for is the most comfortable room in the house - maybe that will change when the windows are no longer so new and so tight.

I can't imagine the fujitsu unit wouldn't have supplemental heat. I had the same concerns, despite mine having supp heat, that it would get behind in really cold weather, but in the end they were unfounded.....as long as the outside temp doesn't drop below -13. If it does, it'll only be a concern for me if the inlaws are in town. For raymond, it'll only be a concern basically if he can't adapt any other type of heat to the room to avoid a hard frost in the greenhouse.

[Brad Adams]

Joe, you aren't looking at the specs for the right heat pump. The new Fujitsu extra low temp unit is a totally different animal than what you are thinking of. It WILL produce full heat capacity at 20 degrees. If you like I can send you the capacity charts. Above 20 degrees they actually produce more heat than labeled. I have installed a few of them, and with as cold as it was last winter I would have had complaints. I didn't believe it myself until we installed them. The rooms we installed them in, just like Raymond's, heated great with no back up heat.

[Brad Adams]

Also, I haven't seen a manufacturer yet whose inlet clearance was less than 18"

Not that you should install them that close, the Fujitsu specs for rear clearance is actually only 4".

[Brad Adams]

Brad - Can you offer and advice on the dehumidifier that must be installed for the winter.

Can't comment on that as I have never installed one like that. But I would trust your contractor, they now what is best in your area.

[Raymond Fries]

Our room is 14' x 16' with 22 windows, a door with glass, and 4 skylights. The rest is well insulated. I expressed my concerns about this winter and the installers told me today that the Fujitsu is more efficient than the 4,600 watt PTEC (sp?) unit we currently had. He said he has never had a call stating that the new units did not heat in winter. Guess time will tell.