Thursday, July 19, 2012

Bleg on Minisplit Ductless Airsource Heat Pumps

Sources have told me that in the last few years it has become possible to heat buildings in cold climates (eg the US northeast) with the latest generation of ductless minisplit air-source heat pumps.  I am seeking detailed technical information on the performance of these kinds of systems that would allow me to evaluate the low temperature limits, thermodynamic efficiency, and cost-effectiveness of doing this in a retrofit context.  I haven't easily come up with sufficiently detailed information in Googling around - can any readers point me in the right direction?

9 comments:

Mr. Sunshine said...

Stuart,

I looked into them a few years ago and found that they work well as heaters on most days in my climate zone ("D" - Colorado Rockies)... there are a couple of good evaluations for one of the brands at http://reviews.younits.com/product-reviews/Ductless-Mini-Split-Systems/Single-Zone-1-Room/Wall-Mounted-Heat-Pump/Fujitsu/p/1320-12RLS-Wall-Ductless-Air-Conditioner-Heat-Pump-25-SEER-12000-BTU-1-Ton.html .... scroll down a bit for one particularly detailed eval.

jbsties said...

Stuart,

I see them occasionally here in my mix-humid climate of central Virginia. Your best source of information is going to be a local mechanical engineer who has specified them for buildings in your area. Best - Jb

Warren Smith said...

Using a reverse cycle chiller would seem to be the way to go.
Allows you to size for heating load, while still maintaining efficient cooling.
As a bonus you eliminate the chilled air from the defrost cycle.
http://www.ruralite.org/magazine/articles/hot-water-can-heat-your-house/

Don said...

Hi Stuart,

You may want to check into bivalent systems too.

Eric Thurston said...

On the Oildrum the poster HereInHalifax seems to be very knowledgeable about the mini-splits. You might shoot him an email.

I installed a minisplit a couple of years ago and it works great, although I haven't kept records on its efficiency. And the Pacific Northwest is a much more benign climate than Northeastern US.

Nick G said...

Ditto on HereInHalifax.

He seems to like the Fujitsu mentioned above, but I'd contact him.

I'd be curious to hear your evaluations.

Tommy said...

In the land of heat pumps, Sweden, these heat pumps are frequently used, with good results. In the mid winter they need a rest, as the can not be used below -5C to -20C, depending on model. The Swedish Energy Agency has a qualified test of a few REALLY made for heating, not just adapted chillers (also called "designed for nordic climate"). You find it here: http://energimyndigheten.se/sv/Hushall/Testerresultat/Testresultat/Luftluftvarmepumpar-2012-2009/?tab=1 The test is in swedish, use Google translate, it usually works OK :-)

I used to work with design of ground source heat pumps at www.eviheat.se (8 years), and in my opinion the air-to-air heat pumps are just noisy, anoying big hair dryers, giving a terrible climate in the house (warm at the unit, cold elsewere). In Sweden many houses have central water based heating, giving excellent heat spreading, but if your not used to that these heat pumps will give you good payback. I personally have a ground source solar aided heat pump with my superb under floor heating system, I'd never change ;-)

@TommyWalfridson

Tommy said...

In the land of heat pumps, Sweden, these heat pumps are frequently used, with good results. In the mid winter they need a rest, as the can not be used below -5C to -20C, depending on model. The Swedish Energy Agency has a qualified test of a few REALLY made for heating, not just adapted chillers (also called "designed for nordic climate"). You find it here: http://energimyndigheten.se/sv/Hushall/Testerresultat/Testresultat/Luftluftvarmepumpar-2012-2009/?tab=1 The test is in swedish, use Google translate, it usually works OK :-)

I used to work with design of ground source heat pumps at www.eviheat.se (8 years), and in my opinion the air-to-air heat pumps are just noisy, anoying big hair dryers, giving a terrible climate in the house (warm at the unit, cold elsewere). In Sweden many houses have central water based heating, giving excellent heat spreading, but if your not used to that these heat pumps will give you good payback. I personally have a ground source solar aided heat pump with my superb under floor heating system, I'd never change ;-)

@TommyWalfridson

Fred Unger said...

Marc Rosenbaum PE has a lot of experience with these http://thrivingonlowcarbon.typepad.com/thriving-on-low-carbon/

Also Coldham and Hartman: www.coldhamandhartman.com

This conferece is a great resource: http://www.nesea.org/buildingenergy/

Fred Unger, unger@hrtwd.com