Ductless heat pumps- Any experience out there?

[DaveOmak]

I live in north central Wa. where it is hot and cold. 100+ summers and 0 winters.
I have disabled my ducted elec furnace and heat with a pellet stove.
I found the ductwork in the attic lost/wasted too much heat.
At 10 deg. outside, with the pellet stove operating, when I plugged the entire ductwork system, the house warmed up at least 10 deg.
I had looked at installing a heat pump in the attic to replace the elec. furnace.
Realizing the heat loss thru the duct work, I am now looking at a ductless heat pump and filling the attic with more insulation since there will not be a furnace to service up there.
Everything I have read sounds too good to be true.
Are the new units really that efficient? Will they provide heat to -10 deg? (probably not a lot of heat but some)
Anyone out there with experience, chime in. I'm looking at Mitsubishi, Sanyo etc, what I think are top of the line.
I have a local furnace guy that can pretty much get any brand of unit.

Dave

 

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Dave
Heat pumps do not generally work well in extended cold climates. There are pumps that supposedly work better in this situation. I have no experience with these but they are called All Climate or Cold Climate pumps. I do know that they lose efficiency when asked to cool and are designed for heating more than cooling.

 

[DaveOmak]

Arrow, Thanks for the tip. I looked up cold-climate heat pumps and found a very interesting clip from the article.

Because they do away with costly and space-hogging duct systems, these units are often called ductless mini-splits. Refrigerant lines also move thermal energy more efficiently than ducts. The U.S. Department of Energy (DOE) estimates that ductless systems lose 1% to 3% of their thermal energy through distribution, compared with 30% distribution losses for ducted systems. This is from the "green building advisor"

This article confirms what I suspected about duct heat loss. So why do they still use it?
30% loss? At least my used beer can go in the compost bin. No waste there!
Dave

 

[texbaylea]

Dave

Stay away from LG. I have an LG mini-split that quit working. In a year I have not been able to get it repaired. In my area the repair techs do not like LG as they do not treat them well on warranty repairs. Mine is out of warranty now and the tech reported that the printed circuit boards had to be replaced but that he could not get them and he quit returning my calls.

I found the boards at the repairclinic.com and replaced them but this did not fix it so I am left doing further diagnostics on my own.

Vernon

 

[Sigarms]

Last I counted, there were over 70 ductless mini split brands sold in the U.S.

Out of that quantity, there is only one I can think of "made" in the U.S, and most, if not all their parts come from overseas.

Japan
Korea
Chinese

That is the order which you'll find both quality and price (highest to lowest).

Some time ago Sanyo had a ductless mini spit that also utilized LP for back up heat, but it was expensive and the lack of sales didn't keep it around.

Mitsubishi has their hyper heat system out in mini split heat pump, never used one (not needing it) being in NC, but my understanding is it was made for cold weather (my understanding was that it is VERY expensive).

This article confirms what I suspected about duct heat loss. So why do they still use it?

Air circulation
Fresh air
experience
price
warranty on equipment
parts availability

Most ductless mini splits are made overseas. I still remember waiting 6 months for a compressor coming off a boat from Japan (one PO'ed homeowner but the unit was still under warranty). Most ductless mini splits are now up to 6 year compressor, 2 years parts warranty. Take a new construction 2,000 square foot house with three bedrooms, and you could probably do it for the same with a "conventional split system" WITH duct work (I've never priced them out that way, so I don't know this for a fact, but a three ton tri zone ductless mini split is not cheap)

 

[czechsonofagun]

Search TBN, this topic comes up every two month or so.

 

[Kays Supply]

My son is in the HVAC businesss. When the homeowner will allow, they put the duct work under the sheetrock in a chase , in the tempered air. It all but stops the heat loss you talk about. Most women won't even start to listen about doing it. It is " UGLY" Another practice here in the midwest, is to put the duct work in the crawl space and seal the crawl up as treated air. They heat and air it like the house. No loss and no damp moldy space.

 

[Alan L.]

You can foam the entire attic envelope to bring the ductwork into the heated space. But, I don't think a heat pump would work well if it regularly gets close to 0. I have an LG minisplit that works fine after over 3 years, but it does not have heat pump.

 

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Dave
Ducts are not a bad way to transfer heat from a point source. The problem is in the installation. Ducts lose heat because of 1. convection, 2. leaks and 3. pressure imbalances within the heating space. The first two can be mitigated by putting insulation around the duct work and generous and careful use of tape. The third is careful layout of supply and return.
Typically, installers are content to just slap up duct work and move on. The nature of the put together being quick, also hastens the mentality. I have not seen many duct jobs worth their salt as a result. Once cfms get above 350 such as when a furnace is on, all the weaknesses of ductwork that has not been installed properly, come to bear.

 

[LD1]

I am not familiar with any of the systems you are looking at But I do have a regulat heat pump and duct work.

Which brings me to my point. Another good reason to use ductwork is if you have a basement. I have a basement and all the duct work runs through. It is a heated basement as well. So any losses in the ducting is not wasted energy because it still stays within the heated structure.

I would think having ductwork in a situation like this would be more efficent than a ductless because of air circulation. It will maintain a more even temperature through out the entire house instead of having hot spots and cold spots.