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03/31/2011

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Margaret Dillon

Wonderful descriptions - especially of heat pumps, Marc - and blog, (dare I say Housebook?), in general! I'm wondering how low a temperature that COP3 will hold true? Have you seen the e-monitors at work? I suspect your usage hardly justifies the $/carbon investment, but for those of who love to measure. its minute by minute data logging by circuit matched up with hourly temps could be interesting. Can you tell us why you selected the Fujitsu?

Marc

Fujitsu makes the most efficient minisplit heat pumps, and I saw some independent test data that confirmed the performance. I'll say more at some point.

Christopher Yaun

Burning Down the House

Hello Marc, Chris of Heather and Chris with the low energy house in Portsmouth NH.

Is it accurate to compare the oil furnace at 290,000btu against the Fujitsu at 43,000btu? Will the electic grid have consumed 120,000 to a 160,000btu to deliver the 43,000btu consumed by the Fujitsu?

290,000(oil burner) vs 140,000 (electric heat)?

It is still a 100% improvement in efficiency.

Chris

Marc

Chris, that's one of the next posts - primary vs. site energy!

Paul Pimentel

This is a great idea. I predict a limited but engaged audience. Thanks.

NB: Pedantry times 2: When I think of boilers, I visualize steam as the product (pedantry times 3: must be vapor to visualize; one can't actually see steam). When hot water is the product, I think of a heater, as in domestic hot water heater.

Christopher Yaun

Burning Down the House

Heather asks me to tell you that her purchase of a heating system for the guest rooms are on hold pending your post on primary vs site. I think she is in a hurry if you don't mind:|

Chris

David Fay

Now that's something you don't see every day: three different heating systems all on the same wall.

I have one question about the mini-split: is there an efficiency reason to mount it high on the wall or is it just to get it out of the way of the furniture? Is there a price to be paid for this location?

David

Marc

Hi David
Great observation - a heat pump, baseboard fintube forced hot water heated by oil, and a propane stove heater!

We put the wall unit high up to make it more effective during cooling. The louvers on the outlet are adjustable up and down, and the unit on Auto aims them down for heating and up for cooling. If you were doing heating only, perhaps you'd mount it lower with no ill effects. It does protrude from the wall about 10 inches, so you do need to think about what is in front of it.

Scott Witt

Mark,

Great Blog.

We have a cheaper version of the Fujitsu mini slit, a Turbo Air installed in our studio building here in Austin. It is used irregularly - we use it only on the weekends. I have found that at certain times of the day the unit will drip water out of the bottom and down the wall. Dust accumulates on the coil and the blower pulls the water off the coil before it reaches the drain. It has been a real pain. Just a heads up with your painting beneath your indoor unit. I hope you don't have the same problem.

Marc Rosenbaum

Scott, that sounds like a very undesirable "feature"! Have you shown it to your installer or a Fujitsu rep?

Jacksonville Electrical

Thank you for the sensible critique. Me & my neighbor were preparing to do some research about that. We got a good book on that matter from our local library and most books where not as influential as your information.

crowdSPRING

Its minute by minute data logging by circuit matched up with hourly temps could be interesting.

WFG Canada

The louvers on the outlet are adjustable up and down, and the unit on Auto aims them down for heating and up for cooling. If you were doing heating only, perhaps you'd mount it lower with no ill effects. It does protrude from the wall about 10 inches, so you do need to think about what is in front of it...

Seth Downs

How's this logic? A Fujitsu 9 or 12RLS mini split heat pump has a HSPF(Heating Seasonal Performance Factor) of 12. Input that number into a HEATING FUEL COMPARISON CALCULATOR ( 205.254.135.24/neic/experts/heatcalc.xls ) I found online, that considers your local climate to give a more accurate HSPF. Take that "corrected" HSPF and multiply it by .293 to get your local climate adjusted COP. (Avg COP = Heat transferred / electrical energy supplied = HSPF * 1055 J/BTU / 3600 J/watt-hour = 0.293 HSPF.) I'm no engineer so please correct me if I'm wrong.

Orlando electrical contractor

Excellent idea and concept. Absolutely a noble post. Looking forward to see more of your post soon. Keep it up!

Marc Rosenbaum

Seth, I can't comment as to the accuracy of that calculator. I put 12 into it and it says 8.2 for Boston. You're correct that multiplying by 0.293 gets you COP.

Seth Downs

Marc, did you do computer simulations to determine the size of your Ductless Mini Split? I just had a HERS rater over today to help me with my road to NZE living. He is not familiar with Fujitsu heat pump performance numbers, but will be locating those and modeling our heating needs. On a related subject I will be insulating the exterior of our cement block bungalow with either 2" to 3" of Polyiso rigid board or Polyurethane spray foam, either of which with a stucco or EIFS exterior. Do you see any benefit if burying the refrigerant lines of a mini split (the outdoor compressor and indoor wall unit will be minimal distance apart)?

Marc Rosenbaum

No calcs, because I couldn't buy a larger Fujitsu and I wanted to try it. I knew peak heat loss when i'm finished would be under 20,000 BTU/hour and that the Fujitsu was likely good for 15,000, so I wasn't going to be far off. I wouldn't bury linesets if the condesner is adjacent to the house

Samantha L.

@Orlando electrical contractor

I couldn't agree more on your premise.

Heating and Plumbing

It was great to read th whole stuff, it seems that you are quite expertize in this field. Waiting for new such technological post to read up.

Jagadguru Kripaluji Maharaj

This nifty instrument shows when the burner is on and when it goes off - it logs it's "state".

Air to Air Heat Pumps

That air source pump looks really good above that painting! It almost looks like a light or something above it. Just goes to show how much some systems can be integrated into a home nowadays.

Tad Montgomery

Marc - aside from the propane stove, passive solar and the minisplit do you have any other space heating in the house? If not, are there uncomfortable cold zones in the winter? How about upstairs or in the basement? Or perhaps I've missed something, and the minisplit has ducts?

Marc Rosenbaum

No other heating. Basement gets quite cold, because even though I insulated the walls, I left the batts in the floor. It hit about 50F last winter. The 1st floor ell bedroom we didn't try to heat - we kept the door shut - and it floated in temp, getting heat through uninsulated interior walls, and potentially from the basement below if it got colder than the basement. The upstairs ran 2F cooler in normal winter temps (30F) and 4F cooler in severe weather. Remember this is not a superinsulated house! We've put the house on the market, and I've just finished installing a small (4.5 kW) electric boiler so that a future occupant could add heat to the two small zones that the heat pump only addresses by natural convection. I'd left all the forced hot water piping in place, so this was essentially a drop-in replacement for the oil boiler.

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