Heat Load Calc & DX Geo Tonnage Required
Last Post 24 Jul 2008 09:22 PM by joe.ami. 8 Replies.
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SkiHawkUser is Offline
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24 Jul 2008 11:59 AM
I downloaded the HVAC-Calc v4.0 software and tried to do a very detailed assessment of my Heat Load needs.  I have  a couple of questions.

1) Currently I have an unheated basement, which I don't plan to heat in the future.  Does this need to be in the overall calc?  I'm thinking not.

2) I also have a whole-house fan that I try to seal very well in the winters.  Do I need to include this as some kind of window?

3) I have two fireplaces in my house.  One that I don't use, so I have seal with an outside and inside damper, plus some plastic inside.  I also have 42" wide fireplace that I do use in the winter.  In the HVAC Calculator I put "Average" and it adds about 7000BTU to the loss, if I do 'Poor' I loose about 14000 BTU.  This fireplace does have a damper.  Do I really need to put it as 'Poor'.  It seems to really raise my loss.

So when I add everything up (the way I have it configured now) I get 42,000 BTU as my loss.  (No Basement, "Average" Fireplace).   My house is 2100 sq ft of heated living space.  I have 2 year old Low E / Argon windows.  My house was re-Tyvek-ed, and sided two years ago, plus new doors.  So I think the seal is about as good as it will get.

A DX Geo Contract I had visit recently is currently calculating my Heat Loss, but gave a ballpark of 6 Tons for my DX Geo Pump.   Does this seem excessive, if my Heat Loss calculation is correct?

Basically How Many Tons for BTUs?    Is it 1-Ton per 12,000 BTU?  So if I need 50,000 BTU I should use 4 - 4.5 Tons of Geo Pump?

Thanks.
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24 Jul 2008 01:47 PM
Posted By SkiHawk on 07/24/2008 11:59 AM
1) Currently I have an unheated basement, which I don't plan to heat in the future.  Does this need to be in the overall calc?  I'm thinking not.

No. But you should treat the floor as 'Above Unheated Space'.

2) I also have a whole-house fan that I try to seal very well in the winters.  Do I need to include this as some kind of window?

I wouldn't.

3) I have two fireplaces in my house.  One that I don't use, so I have seal with an outside and inside damper, plus some plastic inside.  I also have 42" wide fireplace that I do use in the winter.  In the HVAC Calculator I put "Average" and it adds about 7000BTU to the loss, if I do 'Poor' I loose about 14000 BTU.  This fireplace does have a damper.  Do I really need to put it as 'Poor'.  It seems to really raise my loss.
That is toally your call.

So when I add everything up (the way I have it configured now) I get 42,000 BTU as my loss.  (No Basement, "Average" Fireplace).   My house is 2100 sq ft of heated living space. 
That sounds a bit low. Where do you live? Also, be careful with wall R-Values. They s/b treated as 'Whole Wall' and not just the value of the insulation. A stud is about an R-6 for a 2x6 wall. And they are every 16"

Good Luck!
....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building?
tuffluckdrillerUser is Offline
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24 Jul 2008 05:28 PM
Where are you located plays a big part.

What's the average ground temp., and what type of loop--horizontal or vertical?
Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com
SkiHawkUser is Offline
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24 Jul 2008 05:50 PM
I'm in CT.
I put Winter 7 Degrees, Summer 88 Degrees in the calculator.
DX Vertical/Angled Loop
geo fanUser is Offline
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24 Jul 2008 07:15 PM

design temp for hartford 100 degree's / 10 degree's

did you calc. for internal heat gain? I believe 2.5 watt's = 1 btu lights computers anything that uses power.

did you add for the frequency the doors are opened. I live in the area and you sound close but I do think your number is a little low

yes 12k per ton , and by rough estimate do you mean a guess before a calc was done. or did he estimate your house and gave you that as a hard number.

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24 Jul 2008 08:02 PM
Rough estimate of 6 Tons was based on 2100 sq ft, and just looking at my current config. which is two 2 1/2 ton air handlers.
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24 Jul 2008 08:16 PM
For CT, I'm guessing your ground is about 50 deg. F. If so, you'll get about 9500 BTUh per ton output under full load conditions. This would be when the heat pump is running 90% of the time. With a heating load of 42,000 BTUh, you'd be best off with a 5 ton, depending on the sensible and latent cooling loads. The cooling loads could recommend a 4 ton or a 6 ton, but without knowing the loads, I couldn't tell you.

As long as the loads are done correctly, the sizing of EarthLinked DX is pretty straight forward and easy.

Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com
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24 Jul 2008 08:35 PM
I re-ran my Heat Loss calculation with 'no' insulation in my walls. They have cavity insulation, but one of the posts said it was probably only R6 or so and the calculator only has R11 as a choice, so I want to be conservative. I came out with 60,000 BTU Loss. So based on tuffluckdriller's estimates of ground heat and BTUh output a 6 Ton makes some sense. I'll wait and see what my contractor comes up with.

My other problem now may be the size of my duct work. As I said I have two 2 1/2 Ton air handlers able to produce 44,000 BTUs at 140 degree water. At 115 degrees I probably need a new larger A-Coil.

Thanks
joe.amiUser is Offline
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24 Jul 2008 09:22 PM
It sounds like we're all fairly close, if that's true, i'll always yeild to the guy that has to back system performance.
Not quite clear on fireplace types, if masonry vs inserts your numbers are about right.
Some brands of A-coil are 30-36 ask your contractor.
If house is an old ranch, total makes more sense than a new colonial.
A slightly (1 ton) oversized system will pay for it self almost as quickly as the next closest size.
Good Luck.
Joe
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
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