IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 06:05 PM |
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We are going to build an 1800 square foot house in May and will be installing Geothermal. We live in east central Iowa. We have 4 HVAC bids for geo, two 3 ton and two 4 ton. One 4 ton bid says that the 3 ton will cause us to run the electric heat all winter negating our savings. One 3 ton bid is vertical ground loop and the other 3 ton is a 20 foot deep horizontal loop. The 3 ton vertical bid says the horizontal ground loop is not a "proven science". We are getting really worried that a 3 ton unit might be undersized regardless of the ground loop. The insulation will R49 attic and R19 side walls (cellulose) with a geo caulking package. Can any one shed some light on the 3 vs. 4 ton dilemma and maybe some loop advice? |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 06:56 PM |
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Ask each of the contractors to show you the heat loss calculation for your home. If they don't have one then they are guessing. An accurate heat loss is necessary to properly size a system. I would not consider a bid from anyone who has not done a detailed heat loss.
Horizontal loops are a proven way of heat exchange. ( I have them on my house and they work great) Any body who says other wise is not being honest with you.
I can't tell you if your home needs a 3 or 4 ton unit with out knowing what the heat loss calls for.
I can tell you that horizontal works fine as long as it is sized properly. Even an undersized vertical system will cause problems.
Vertical systems usually cost more, so installers who can drill will recommend them over horizontal.
How are they going to do a 20' deep horizontal system? I have installed 9 horizontal systems, the deepest was 9'.
You need to ask some hard questions and verify the answers.
Keep in touch. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 07:11 PM |
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The 4 ton bid says 61,000 and the 3 ton bid says 46,000. All four have done the heat loss calculation. This is where we get confused. Can you do this heat loss math youself or is it rocket science for someone not in the heating business?
For the horizontal 20 foot loop they bore down 20 feet then lay out the horizontal loop with a horizontal boring machine. We are comfortable with the horizontal way. We didn't believe the "science" comment. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 07:26 PM |
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Heat loss calcs are done on a computer. You can buy a program here for $49. I use this program. It is not difficult to use plus they offer great support. You could probably do it your self then you would know. What is the price difference between 3 ton vertical bore and 3 ton horizontal bore? 46000 to 61000 is a big spread. Something is not right there. What design temperature are they each using? This might be where the difference lies. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Alton
Veteran Member
Posts:2164
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| 06 Feb 2008 07:28 PM |
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IowaGeoHope,
Maybe I have lived in the South too long, but two three ton units for an 1800 SF home. Is this a one story home? Why two units instead of one larger unit. Will the home have a split plan and the ductwork can not cross a vaulted great room? Does most of the glass face North? What size back up heat strips have been suggested (4 KW, 5KW, etc? If the calculations really call for this much tonnage, is there any way that you can lower the tonnage requirements by building differently? Talk to your HVAC bidders and share with us what you can.
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 07:32 PM |
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Alton, his house only needs one heat pump. He has four bids and each tell him something different. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Alton
Veteran Member
Posts:2164
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| 06 Feb 2008 07:43 PM |
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Geodean,
Thanks, I mis-read the original posting. Now it is obvious how many heat pumps he needs.
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 07:47 PM |
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It is a ranch with a full basement that will have an R10 blanket on the basement walls.
The price difference between the 3 ton vertical and the 3 ton horizontal is apporximately $3000.
The 4 ton and 3 ton bids are using the same design temperatures of -4 and 93 degrees. Also the average internal gains are very different. 3 ton is 7793 and 4 ton is 12692. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 07:52 PM |
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Which is $3000 more vertical or horizontal?
Looks like the internal gains need to be investigated.
What is the heat load and cooling load from each of the four bids? |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 07:59 PM |
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The vertical is $3000 more. This difference is for both 3 ton bids. The price difference isn't a big deal, it is the sizing. Iowa winters are kind of harsh and we want to be able to keep the house warm. We have read horror stories of not being able to get a house above 65 degrees with geothermal.
We only have data from two of the bids. The other two did not include these. The 4 ton heat and cooling loads were 61500 and 28900. The 3 ton heat and cooling loads were 46625 and 17485. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 08:18 PM |
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I was just curious about how horizontal boring compared to vertical. I have never seen a horizontal bore job.
Being undersized can be costly and uncomfortable. Being oversized means you spend more to install your system and humidity control can be a problem. Maybe humidity is not a problem in Iowa.
If sized properly, a geothermal system will keep your house very comfortable. Ours has been great for 3 years.
I am confused about your bids.
Most heat pumps have a heating capacity less than the nominal tons. For example a 3 ton climate master is rated for 26,700 Btuh on a ground loop.
Your bidders want you to install a 3 ton heat pump when the heat loss calls for 46,625 Btuh.
A ton is 12,000 btuh. So 3 tons of heat is only 36,000 btuh.
Any way you look at it, you come up short.
I really wonder if these guys know what they are doing. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 08:39 PM |
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I would ask the 3 ton guy how he expects to heat your house with a 27,000 btuh heat pump when his heat load calls for 46,000.
The same with the 4 ton guy. A 4 ton unit will give you 36,000 btuh and his heat load calls for 61,000.
I will be very interested in hearing what they say. I am pretty suspicious and you should be also.
What brand of heat pumps are they proposing? |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 08:44 PM |
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On page 7 of this manual you can verify the heating capacity of a 3 and 4 ton unit. Hope this helps. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 08:47 PM |
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Iowa can be very humid in the summer. It is what makes the corn grow so well.
Thanks for the information and help. Now we are going back to the bidders and ask these questions. We will post again when we get some hard and fast answers. It is just the advice we were looking for. We are also going to purchase the program you recommended. For $49 it may just give us more insight and answers. We used and survived Iowa's Res Check. This one is probably the same thing. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 08:50 PM |
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Posted By IowaGeoHope on 02/06/2008 8:47 PM
Iowa can be very humid in the summer. It is what makes the corn grow so well.
I would recommend a two stage heat pump. When running on the first stage, the unit will stay on longer which will remove more humidity from your house. Good Luck and please let us know.
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 08:53 PM |
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The 3 ton are one Water Furnace and one GeoComfort. Both 4 ton bids are Climate Master. |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 09:01 PM |
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One more question; The 27,000 BTUs are just the heat pump and doesn't include the electric back up, correct? |
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IowaGeoHope
New Member
Posts:15
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| 06 Feb 2008 09:09 PM |
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The 3 ton GeoComfort and WaterFurnace are both three stage heat and two stage cool. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 06 Feb 2008 11:17 PM |
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Posted By IowaGeoHope on 02/06/2008 9:01 PM
One more question; The 27,000 BTUs are just the heat pump and doesn't include the electric back up, correct? That is right. The third stage on heating is the electric back up. Good luck
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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tuffluckdriller
Advanced Member
Posts:630
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| 07 Feb 2008 12:09 AM |
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Those heating loads seem awful high to me for that size of house. What are the parameters they are using? Have they padded the numbers a lot as a safety on their load calculations, did they? What programs are they using, and can they really back up those numbers? What is the winter design temperature?
I'm in Utah, in the coldest part of the state (for this year). On a new 1800 sq. ft. home, I can't imagine the loads are really that high. You need to really scrutinize what they are telling you.
I'd really suggest you look in to a DX geothermal heat pump. EarthLinked is a good one.
Good luck. |
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| Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com |
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