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Old 10-28-12, 06:22 PM   #1
ecomodded
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Default Low watt Heat pump Choices for PV systems

I have been reading up on heat pumps and energy consumption. So far to me it comes down to CoP and heating requirements.
With a well made/insulated 1,200 sg.ft off grid house I would hope a 1000 watts in PV panel would cover all but heating needs.
Now to find the most energy wise PV panel friendly heat system, Which is what I hope this thread will determine !


Any ideas or insights ?
Even other more suited heating alternatives,lets get the bottom of this

Thanks, Doug

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Old 10-28-12, 09:12 PM   #2
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Default Some reading

Dave Sparks uses PV for his ASHP..
Sanyo mini split AC (inverter/variable speed)

With your mild weather, there must be a lot of ASHP users up there.
Best Times to Visit Victoria & Vancouver Island | U.S. News Travel

If you were grid-tied, you could use any size BTUh and the amount of PV you could afford to buy..

But, being off-grid is a whole can of worms. (Since you can't go without heat when it's overcast all week).

You would need a good battery bank. Or maybe propane heat for back-up..
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Old 10-28-12, 11:51 PM   #3
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If a 9000 Btu Heat pump consumed 750 watts I would need enough PV panels to make a 1000 watts on a cloudy day.
And enough battery storage for say 6 hours of use ?

I think a 1 level seriously insulated 1200sq.ft custom house could be heated with a 9000 Btu heat pump, as 9000 Btu's is equal to 2,500 to 3,000 watts of baseboard heat. My current 70's house has 3,500 watts in upstairs baseboards that never run full tilt to heat this 1900 sq.ft (1000sq.ft upstairs) home in the coldest part of winter.

A closed loop copper coiled refrigeration filled system might be the best for this ? I will assume the air will get to cold to use a ASHP so ground/water source it should be, for this climate..
The house would have propane cooking and instant hot water.

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Old 10-29-12, 01:47 AM   #4
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Did you read any of the stuff that I posted above (wind-sun)? Those guys are talking about 9000 BTUh units running at 300 watts.
Of course, at 300w, they aren't making 9000 BTUh.. Maybe 1/4 to 1/3 of the full 9k.
These inverter units only go as fast as they need to.

Right now, my home is being heated by a 24,000 BTUh Sanyo (rated at 36,000 BTUh in heating mode).

It's switching off and on, using about 15w in standby and about 480 watts when pumping heat. (making around 4k to 6k BTUh).
http://i46.photobucket.com/albums/f1...r/NCL/F160.jpg

It's 53F (w/ light rain) outdoors right now and 72F in here.
If it were down around 20F, then it would use around 600w when heating.

If these are really the kind of temperatures you get up there, (Typically above freezing)?
http://travel.usnews.com/images/dest...rature_f_2.jpg
http://travel.usnews.com/images/dest...ature_c_60.jpg
Then you should use a mini-split ASHP (Inverter type).

Mine are old models and they work down to about 8F..
At 5F, I start thinking about backup heat.
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Old 10-29-12, 02:48 AM   #5
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Quote:
Originally Posted by ecomodded View Post
...I think a 1 level seriously insulated 1200sq.ft custom house could be heated with a 9000 Btu heat pump...
It's quite natural to think of a heating system (that is the title of your thread) when you are thinking about warming your house...

But if you are going to build your house, you should make every possible effort to design your house so that it retains heat. A BTU saved is cheaper than a BTU bought, and less environmental damage is done in the process. Another big plus is that insulation almost never malfunctions, or ever requires a service call.

I don't know if you are familiar with the Passive House concept, but there is a world of extremely relevant information. Don't confuse Passive House with Passive Solar Heating... different animal, but related.

The basics of Passive House construction are more refined than conventional building. It is not just a case of more insulation.

With Passive House, if you carefully attend to the details, it is possible to build a house that will need little or no heating system... however, it will need a sophisticated ventilation system.

The new wisdom is that if you carefully design and insulate, the additional costs of superior insulation will be approximately the same as a heating system... but no (or in the worst case, exceedlingly low) future fuel costs.

Think about it...

Best,

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Old 10-29-12, 10:49 AM   #6
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Ditto what AC Hacker said. Passive house is the way to go IMO. There is a house in Illinois designed to passive house specs, and it heats itself with a 1500W just electric heater, when needed.
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Old 10-29-12, 11:41 AM   #7
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Xringer I did indeed read your links, thanks ! , I like the idea of having a small system running constantly. Rather then a large system that cycles on and off.
I want to nix the large battery pack, meaning i will need to supplement the night heating from another source.

Easy fix is a wood furnace for back up and a large wind turbine for a energy generator.

AC
The house would be designed to retain heat more then absorb it. A house that will go up fast and be heated in a user friendly ,reliable manner. It should have a wood furnace for back up and require little battery storage, to make it semi passive. Going the distance of a fully passive house is a bigger endeavor then i want to take on.

In the past i lived in my own cabins for a few years, built on the west coast facing the ocean. For heat i used a wood stove for light kerosene lamps, cooking on the wood stove. I was in that cabin for a cold snap of -17 (freak weather) with the wood stove on full tilt bogie i staved off the cold enough to sleep/survive. That cabin had no insulation was made from hand split cedar boards over a pecker pole tarp covered frame.
That was ruff.

I have a ton of faith of constructing a off grid PV powered home, With only a $100,000 for the construction and power infrastructure I will be doing it mostly by myself but have tradesmen friends who will help out when possible.
My Dad was a journeyman Carpenter my Grand Dad a machinist, i leaned a lot from them as a kid including helping my dad build his house.

I have a friend who is a Steel worker , not just tying steel, he builds the footings for the buildings and bridges and has offered (with some compensation) to help make the structure. I was thinking of going with a tilt up design but am now thinking along the the lines of a steel and concrete framed structure.
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Old 10-29-12, 11:59 AM   #8
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The passive house concept really isn't that difficult. It has two basic principles:

1) air seal REALLY well
2) insulate really well (and eliminate thermal bridging)

If you do those two things you'll be 90% of the way to passive.
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Old 10-29-12, 12:06 PM   #9
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Quote:
Originally Posted by Daox View Post
Ditto what AC Hacker said. Passive house is the way to go IMO. There is a house in Illinois designed to passive house specs, and it heats itself with a 1500W just electric heater, when needed.
I love the idea, but the costs and construction time has me looking the other direction.
Its not so much as the work involved but the time and money that's involved.
If the land is suitable a passive house with the soil pushed around it and over the roof i would indeed like.
I am wanting a cement house to start with so covering it in soils would be a cinch.

I am going to look into some concrete passive houses and see what i can afford and build myself.
Combined with a 9000 Btu heat pump, it will heat better with only 750 watts of PV panel.
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Old 10-29-12, 12:09 PM   #10
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Quote:
Originally Posted by Daox View Post
The passive house concept really isn't that difficult. It has two basic principles:

1) air seal REALLY well
2) insulate really well (and eliminate thermal bridging)

If you do those two things you'll be 90% of the way to passive.
ok I was thinking under the ground passive..

I planned on air sealing really really well along with insulation.
For thermal bridging do you mean to separate the out side of the house from the inside ? with insulated contact points ?


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