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Old 08-15-14, 01:10 PM   #1
Theotilus
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Default Need cold climate solution

I currently heat my home with a 3 ton Unichiller RC supplying hot water for my radiant floors. When the outside air reaches about 30 degrees F or lower the btu output is insufficient. I need around 36000 btus/hr. My research indicates that I need a DC Inverter heat pump with EVI technology to produce adequate heat.
Our outside air gets down to 15 degrees F at the coldest. A Daikin Altherma system is not within my financial means. I have found a unit built by Macon in China that would meet my needs but there is the usual issues of parts and service that come with that. I am an avid DIYer. I purchased the Unichiller used a few years ago and connected it to my radiant floor system which I installed myself. I have considered buying an inverter ductless heat pump and using a flat plate heat exchanger to convert it to air to water but don't think I have the knowledge to pull it off. Any solutions you can offer I would be open to.

Thank here in Bellingham, Wa.

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Old 08-15-14, 08:20 PM   #2
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It sounds like a DIY geothermal system would be the way to go.
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Old 08-15-14, 08:37 PM   #3
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Although it would be fairly expensive you could add a buffer tank to store heat that can supplement the output at selected times. Heat input is more efficient during the day and usually heat demand is greatest in the early hours of the morning so the store needs to store something like half of the heaters output for about half of a day. The temperature range is quite limited so it makes the store requirement quite large but on the other hand the low temperature makes a DIY system easier.
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Old 08-16-14, 12:40 PM   #4
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Geo thermal is way to expensive and the ground at my location is way to rocky for drilling or digging. A thermal storage tank takes space I don't have. Since natural gas is not available I have to look at the most efficient heat source available. It looks like I need to sit tight until more inverter air to water heat pumps become available in the US.
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Old 08-16-14, 04:25 PM   #5
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Take a look at building a few Bitcoin (or similar - research first!) miners.
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Old 08-16-14, 05:36 PM   #6
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What about a solar thermal unit, but instead of heating potable water it heated your radiant floor fluid?

It shouldn't be too hard to DIY it and then connect into your system. You could even follow the blog post for solar heated air, just run tubes of water instead.
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Old 08-16-14, 08:04 PM   #7
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Depending on air for a heat source is always going to be a problem in cold weather. Drilling in deep rock for geothermal is supposed to be easier because the sides don't have to be lined. The heat pump for GSHP can be smaller nominal capacity. I had a 5 kW ASHP which was replaced by a 3 kW GSHP. The electricity use is almost the same but the GSHP produces about three times more heat in cold weather.
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Old 08-17-14, 01:55 AM   #8
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Never mind..... I just noticed you said no natural gas available. Call the utility and see if there are programs, like time of use, or all electric home rates. If the coldest time time (where heat pump is the least efficient) is during off-peak hours, you might get a better monthly cost.

I'll leave it in place as a reference for others however:

With natural gas available:
Your rates are at about $1.00/therm 29.3kWh/therm. Of this, the delivered cost depends on your combustion equipment. Using 90 to 95% boiler, you'll get a delivered rate of
26.37 @ 90% or 3.79c/kWh
27.83 @ 95% or 3.59c/kWh

So, using the average 68 therms and 80% efficiency, that's 5.44 million BTU of delivered heat.

So you'll be using 60.4 therms if you went with 90% equipment.

5.44 million BTUs of delivered heat translates to 1,593kWh.

each kWh at your area costs:
8.3 for first 600kWh
10.3 for portions over 600kWh

so, with first 600kWh probably needed for other stuff anyways and using 10.3cents/kWh, this means you start breaking even on utility cost at heat pump delivered COP of 2.71. (9.25 HSPF equiv).

90% gas:
60.4 therms: $60.40 @ $1/therm

3.5 COP Geothermal
1593kWh/3.5 = 455kWh @ 10c/kWh

Using 68 therm as monthly average given by the utility, and derating to 60.4 for switching to 90% gas equipment if you don't already have one, the 3.5 COP Geothermal over 90% gas system estimates to an whopping $179/year annual savings.

At PSE's rates, payback period is essentially never, forever.

http://pse.com/aboutpse/Rates/Docume...1_panel_pg.pdf

Last edited by ICanHas; 08-17-14 at 01:58 AM..
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Old 08-17-14, 03:19 PM   #9
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Theotilus

We have managed though winters quite nicely here in Canada with GSHP,s. They work extremely well saving us a lot of $$$. Before you dismiss the bore holes. Get a quote. It may surprise you. You having in-floor heat is already the pathway to nirvana.

You have already found the efficiency of ASHP's Can you imagine what a GSHP could do for you.

The money I saved within the first year more than paid for the excavation for the ground loop. You may find the same with paying a contractor just to install your bore hole loop.

I was going to suggest for the coldest days just plug-in some electric baseboard heaters but that's like going back to lighting with kerosene when you were considering LED,s.

Sometimes even with the DIY blood running in your veins, Sometimes you have to call in the guys with the heavy equiptment to get the job done.

Hack that Unichiller with either a brazed plate or coaxial heat exchanger, turn it into a water to water GSHP. Enjoy green, warm, heat starting at your toes as you stare out the window at the winter. Knowing its only costing you pennies.

I'll put out something else for you to think of. If a person installs enough solar panels (PV) you can heat and light your home for ZERO....

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Old 08-18-14, 01:42 AM   #10
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Quote:
Originally Posted by randen View Post
If a person installs enough solar panels (PV) you can heat and light your home for ZERO....
A couple of points on that.
First, if you need heat, a solar thermal solution will be much more efficient than PV (in terms of both heat per buck and heat per sq foot of collector).

Second, I doubt if many people could rely completely on solar for heat unless they had low heating needs or an unusual heat storage system. I have 100 evacuated tubes supplementing my heating system. They make a significant contribution to my heating needs and paid for themselves quite quickly but there is no way I could scale that up to make solar my only heating mechanism. Solar solutions don't work at night, and it would need a really huge system to collect and store enough energy during a winter day to last through a winter night. Also for about 3 months of the year the panels produce almost nothing. This is due to the heavily overcast conditions here during autumn & early winter. Conditions elsewhere may of course be different, but during any real winter I suspect solar power will struggle in most places.

Solar thermal is a good addition to a heating system, but think carefully before making it your only heat source.

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