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| In our 2800 sq ft one-story new house in southern Maryland,
we're planning to have geothermal heat (horizontal loop) using in-floor radiant technology. One third of the house will have a slab foundation, so it will use embedded piping. The remainder will be over crawlspace, so there we're going with engineered wood (tile in the bathrooms) above Warmboard, which was our architect's recommendation. For AC, I thought mini-split looked like a good solution, but the architect favors central, in essence telling me that the HVAC contractor will know how to do it right. So I'm deferring more pointed questions to ask prospective builders when they submit bids. I presume that details can be considered more fully at that time. We're going to live in this house forever, so
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Follow-Up Postings:
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| "So, anything above not to like?" YES - mini splits! Why would you combine this with geothermal? Better options would be either triple function geothermal or full function water-to-water geothermal heat pump (hot & chilled water) with Multiaqua fan coil units for A/C - WITHOUT ducts! Copy & Paste these links: Triple Function Geothermal Heat Pump: http://www.nordicghp.com/images/stories/PDFs/tf-series/tf-series-featu res-examples.pdf Liquid-To-Water Geothermal Heat Pump: http://www.nordicghp.com/images/stories/PDFs/w-series/001031slb-01-w-s eriestwo-stager410a60hz.pdf Hydronic Fan Coils (wall, ceiling, hi-wall): http://www.multiaqua.com/products.htm#MHNCCW |
Here is a link that might be useful: International Ground Source Heat Pump Association
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- Posted by david_cary (My Page) on Fri, Nov 16, 12 at 5:18
| While geo doesn't help as much with a/c, it still helps particularly with horizontal loops. The problem is hydronic heat makes it complicated. If you were just doing forced air heat, you would have a simple system. Of course it all can be done but you can't go the easy way out. |
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| "While geo doesn't help as much with a/c, it still helps particularly with horizontal loops." That requires an explanation... SR |
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| I looked at the links. One of the ads didn't make it clear how heating is done and the other didn't make it clear how cooling is done. I know what we want: heating from the floor and cooling from above (cold air descends). Therefore I'm willing to have the two systems be completely independent, if necessary. |
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| Again, see the link below for the triple function unit. This one unit does EVERYTHING you want, hot and cold forced air for heating and air-conditioning, full capacity hot water for in-floor radiant heating and desuperheater for pre-heating domestic hot water. See drawing # 1 minus the Pool & Ice Melt. ‘RA’ = Return Air, ‘SA’ = Supply Air. SR |
Here is a link that might be useful: Nordic Triple Function Geothermal Heat Pump
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| Resending because it came out weird. Again, see the link below for the triple function unit. This one unit does EVERYTHING you want, hot and cold forced air for heating and air-conditioning, full capacity hot water for in-floor radiant heating and desuperheater for pre-heating domestic hot water. See drawing # 1 minus the Pool & Ice Melt. 'RA' = Return Air, 'SA' = Supply Air. SR |
Here is a link that might be useful: Nordic Triple Function Geothermal Heat Pump
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- Posted by david_cary (My Page) on Fri, Nov 16, 12 at 20:45
| Geo doesn't help with a/c as much because the temp gradients with a typical air source a/c are not that great. The energy use for the pumps on a geo system really eat into that marginal benefit as compared to air source. The vertical pumps may eat into this even more than horizontal. |
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| David, you're in error on all accounts. Geothermal is in fact more efficient than air-source in the A/C mode in that it's easier to sink the extracted heat from an envelope into the ground at a temperature of about 43ËšF than the air at about 75ËšF and above. Secondly, geothermal heat pumps often have desuperheaters so that the heat extracted first goes into a domestic hot water buffer tank to assist in the production of virtually free hot water rather than just being expelled into the outdoor air and wasted. You mention geothermal heat pumps have circulating pumps. Just as the condenser fan (that doesn't exist in a GSHP) is taken into effect for the efficiency rating of an air-source heat pump or air-conditioner so too is the circulating pump taken into account for the efficiency rating of a geothermal heat pump with regard to a closed loop vertical borehole. You can verify this yourself by reading ARI/ISO 13256-1 Performance Ratings sections 4.1.4 'Power input of liquid pumps'. Furthermore, closed loop horizontal ground loops or vertical boreholes of any length or depth are balance systems requiring minimal pumping power due to lower head when compared to deep/long open loop systems. The point of least efficiency differential would be in heating mode when outdoor ambient air temp would be the same as ground temperature. SR |
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- Posted by david_cary (My Page) on Sat, Nov 17, 12 at 21:33
| I didn't say geo wasn't more efficient than air source it just isn't that significant. Ground temp of 43? - not where you usually need a/c. Of course the lower temp the better but the air is right there and the water needs to move around. Geo believers are hard to argue with because the idea is very sound. The practical reality is not always so great. Energy audits around me compare geo to basically a seer 18 ASHP for operating costs. Maybe they are wrong but either way, it is rarely worth the cost. They make great sense in cold areas when no NG is available. Great Great sense. |
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- Posted by energy_rater_la (My Page) on Sun, Nov 18, 12 at 14:04
| "Another thing that's making me nervous is whether the contractors in our area have sufficient experience in installing some of this technology." this would make me nervous also. reasons are: 2-lack of experienced installers. one company does 3-high efficiency of air source heat pumps you should consider hiring an independent energy rater check with www.resnet.us for an experienced rater invest in foam insulation in floor of the part best of luck. |
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