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Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to prairiesky

Re: [HVAC] Manual J and heat pump sizing

The earth itself is what provides the extra capacity. If you make the loop big enough and at the proper depth you should never freeze the ground. It would be like dumping cold water in the ocean and worrying about the ocean freezing. Even in Antarctica if you dig deep enough you will find warm ground, granted it might be 20 miles deep. It's all just a matter of sizing everything correctly for the local environment.


prairiesky

join:2008-12-08
canada
kudos:2

said by Ken:

The earth itself is what provides the extra capacity. If you make the loop big enough and at the proper depth you should never freeze the ground. It would be like dumping cold water in the ocean and worrying about the ocean freezing. Even in Antarctica if you dig deep enough you will find warm ground, granted it might be 20 miles deep. It's all just a matter of sizing everything correctly for the local environment.

radiation only goes so far down. Most loops are 20 ft plus. For reference, our frost line is ~8-9 feet deep. The frost comes out naturally by mid July usually. That doesn't leave much time to replenish anything lower. Some of the loops go to 20 feet which will not see much replenishment and if it does get some, it's no where near enough. The ocean is a different story, it's a fluid which moves around and can you don't see the same water twice. pulling water out a lake does make more sense than the ground for precisely that reason, it's a bigger body and it's motion allows you to access it. The motion also allows natural convection in the summer which allows it to gain back more heat.

You have to answer the question, where does the replacement energy come from and how does it get there.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse

I am surprised that loop depth are so deep in your area. In Scandinavia loops are normally 1 - 1.5 meter down and the loop has a 1 meter distance to itself side ways. At that depth the loop get the replacement energy from the sun.

The medium in the loop is an ethanol - water mix that can handle temperatures down to -30 Celsius. A good loop might have a minim temperature of -1 Celsius or better.



Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to prairiesky

The earth itself is warm. Yes, the soil near the surface is heated and cooled by the air temperature based on the season, but below that soil, is soil that remains a constant temperature year round. If you put your loop in that soil, and size the loop correctly, geothermal will work indefinitely. This is the principle behind vertical loops.


iknow_t

join:2012-05-03
reply to Hagar

said by Hagar:

I am surprised that loop depth are so deep in your area. In Scandinavia loops are normally 1 - 1.5 meter down and the loop has a 1 meter distance to itself side ways. At that depth the loop get the replacement energy from the sun.

The medium in the loop is an ethanol - water mix that can handle temperatures down to -30 Celsius. A good loop might have a minim temperature of -1 Celsius or better.

Scandinavia is very far away from the U.S. as a matter of fact, it's in another country.. it has a different climate too. even comparing the climate of Canada and Florida there is a HUGE difference.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse

1 recommendation

Iknowit,
I am confused of the purpose of your post?
I know Scandinavia is far away from the US. Your post implies that my knowledge/experience of Scandinavia has no bearing on the discussion.
Ken is is Markle, IN average yearly temp 50.19°F, Stockholm Sweden average yearly temp 43.9 °F. I think that is close enough.

I replied to prairisky, his profile says Canada which has similar climate to Scandinavia.

I am surprised at the loop depth prairisky mentioned. Physics works the same regardless of county and I do not see the economic gains of a loop depth of 20 feet but I sure there is a reason for it, just trying to learns something.


iknow_t

join:2012-05-03

said by Hagar:

Iknowit,
I am confused of the purpose of your post?
I know Scandinavia is far away from the US. Your post implies that my knowledge/experience of Scandinavia has no bearing on the discussion.
Ken is is Markle, IN average yearly temp 50.19°F, Stockholm Sweden average yearly temp 43.9 °F. I think that is close enough.

I replied to prairisky, his profile says Canada which has similar climate to Scandinavia.

I am surprised at the loop depth prairisky mentioned. Physics works the same regardless of county and I do not see the economic gains of a loop depth of 20 feet but I sure there is a reason for it, just trying to learns something.

the type of soil and underground temperatures would make a big difference. above ground temperatures are a smaller part of it.


Hagar

join:2004-10-31
Sunnyvale, CA
Reviews:
·T-Mobile US
·AT&T U-Verse

Sorry for going off topic but I am curious about loop depth.

I agree that type of soil matters since heat transfer in different soils are quite different, strongly correlated to the water content of the soil. But that tends to effect how long loop length you have not how deep you put the loop.

Underground temperatures are usually correlated to average yearly air temperature unless you have an other heat transfer medium like moving ground water.

It is expensive to dig 20 feet down. It would be less expensive to dig less deep and have a longer loop. If the loop is divided in two or more parallel loops the flow resistance stay low and does not require a huge pump. I would have guessed that you put the loop at/just below the frost line but I am not a professional in the field.