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  1. #40
    Join Date
    Jun 2004
    Location
    Kathleen GA
    Posts
    236
    Todd S: Yes, I meant what I said and no, it is not necessarily ignorant if you think about it.

    The "sweet spot" on his units is when they operate at "low speed" so if the units run on low all the time he is getting the highest energy efficiency possible. Seems counterintuitive but it works. Also, I am guessing the contractor may have been conservative on the sizing but he was told that the goal was never to use auxillary heat. The downside to this apporach is he probably paid a higher first cost.

    Part of his success is he has a 7 ton system and 7 tons of loop. But his requirement is not really 7 tons. Thus he has an oversized loop making his units even more efficient.

    HVAC companies over size their coils to increase efficiency so he just did it with his loop.

    I think he could have gone with slightly smaller units but, I think the units he bought do not come in 1/2 ton units.

  2. #41
    Join Date
    Feb 2010
    Location
    The midwest.
    Posts
    663
    Quote Originally Posted by jdf123 View Post
    actually I think it is a 16" pipe on the return, but I don't think it is a 30x30 grill. more like 16x30ish. I'll have to measure it. What is a transfer grill? Is that just a hole in the wall?
    Recommended (return air grille) face velocity is 300-400 fpm. 30"x16" will give you about 900 cfm. To keep the system efficient and quiet your system needs about 1400 cfm. A 30"x24" will give you 1392 cfm @ 400 fpm.
    A transfer grille is a return air grille on one side of the wall and another grille (higher or lower, not across) on the other side of the stud wall.

  3. #42
    Join Date
    Jan 2010
    Posts
    55
    I just hate telling these professionals how to do their jobs. I will mention the transfer grills but he will most definitly tell me I don't need them. And he will tell me that the single 16" return pipe is enough on the top unit. But one of my main concerns going in was noisy ducts and he garanteed me that he would design them to be quiet so if they are not quiet he will fix it. We plan to test it before we do sheetrock.

  4. #43
    Join Date
    Feb 2010
    Location
    The midwest.
    Posts
    663
    Quote Originally Posted by dforster2 View Post
    I just hate telling these professionals how to do their jobs. I will mention the transfer grills but he will most definitly tell me I don't need them. And he will tell me that the single 16" return pipe is enough on the top unit. But one of my main concerns going in was noisy ducts and he garanteed me that he would design them to be quiet so if they are not quiet he will fix it. We plan to test it before we do sheetrock.
    He should not be offended if you ask him to put in transfer grilles. It's very easy to do and if the doors are closed, the air has a way to get out.

  5. #44
    Join Date
    Feb 2010
    Location
    The midwest.
    Posts
    663
    The return air pipe in the attic looks like its 14".

  6. #45
    Join Date
    Jan 2010
    Posts
    55
    It could be. I just remember seeing a 16 somewhere around the pipe or insulation. If it's noisy He'll be adding a return because it sits above our living room, there's plenty of room on the plenum to add one.

    He already explained to me that we needed to leave a 1" gap under the bedroom doors for return air. He thinks this is the best way.

  7. #46
    Join Date
    Feb 2010
    Location
    The midwest.
    Posts
    663
    Quote Originally Posted by dforster2 View Post
    It could be. I just remember seeing a 16 somewhere around the pipe or insulation. If it's noisy He'll be adding a return because it sits above our living room, there's plenty of room on the plenum to add one.

    He already explained to me that we needed to leave a 1" gap under the bedroom doors for return air. He thinks this is the best way.
    A 1" gap under the door is not enough. It's your house. I assume it's your money? Ask, and tell, if necessary, what you want. It is far easier to do the job right now than to come back later.
    If you've read any of the other posts, its not always easy to get the contractor back.

  8. #47
    Join Date
    Jan 2010
    Posts
    55
    Well he will be back because he doesn't require any payment until they come back to top out and test the unit.

    I don't know if there is room in the bedrooms for transfer grills. The interior walls are only 2x4 studs. how does that work w/ cutting through the top plate that is only 3.5" wide? Do you know the duct & grill size you might use for a standard size bedroom. If I understand right a transfer grill is a return in the top of the wall? why not in the ceiling?

    I wonder if it would be worthwhile to hire an inspector just to look over the duct work?? I usually don't like these inspectors because they are usually know it alls who don't even work in the field. But it would give me some backup to use when I talk to the contractor. Overall I've been very happy w/ the contractor, his work looks to be top notch and very thorough. I've just questioned some of the ducting decisions like we've been discussing here.

  9. #48
    Join Date
    Apr 2008
    Location
    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
    Posts
    1,411
    Quote Originally Posted by jdf123 View Post
    I'm not sure he was completely honest about the few hundered. ...

    Most people can't believe that ... Two of my conventional bids would have been more than the geo system after credits, they were high end 2 stage systems.

    There is a company in Tulsa that all they do is drill the geothermal wells. Environmental Loop I think they are called. I don't think I am violating any rules by saying that my contractor told me they are only charging him $2700 to drill the 1300' of well, 4 wells 325' deep, not including piping. .... My point is just that drilling and geothermal loops are not as expensive as many people think. My contractor told me roughly 40% more expensive than conventional and most of that is covered by the existing federal rebate.
    I think we should now understand why pricing discussions are an issue on this forum - too many permutations and people just go with what they "heard". Your cost per well isn't even half what I have heard in my locale, then yours are without pipe which I and others have no way of figuring.

    I just know that my gross cost of geo versus high-end DFHP was at least double. By gross I mean proposal cost without any rebates or tax or any other credits. My net cost of geo versus DFHP was closer to 2.5-3 times higher. By net I mean after my manufacturer rebate and tax credit. Your new construction changed these rebates and tax credits and you had additional credits from your utility. IMO all one can do is get actual proposals, apply tax/other credits and rebates from all sources and then compare net or bottom line costs. That said, I NEVER use lowest cost as the primary factor in a complex buy involving skilled installation, varying features and warranties.

    Thanks for you experience.

  10. #49
    Join Date
    Apr 2008
    Location
    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
    Posts
    1,411
    Quote Originally Posted by dforster2 View Post
    ...

    I don't know if there is room in the bedrooms for transfer grills. The interior walls are only 2x4 studs. how does that work w/ cutting through the top plate that is only 3.5" wide? Do you know the duct & grill size you might use for a standard size bedroom. If I understand right a transfer grill is a return in the top of the wall? why not in the ceiling?...
    Transfer grills are nothing more than passive holes in your walls to let air flow out of a closed door room. I added grills small enough to fit in the spacing between the studs with louvers to control air flow and to add the ability to close (6 such grills for 3 bedrooms cost like $30-40 total without install). The bedroom side grill is maybe 6' from the floor and 2' from the ceiling. I offset the bedroom side grill from the outside grill to minimize noise and light transmission between the rooms (I just hate sunlight when I am sleeping). The bedroom side grill looks like a return grill but it is just a pass through so that the blower has more area to suck air out of that room. One inch under a door to a good sized room with 2-4 registers (counting the master bath) is not enough surface for good exchange from the closed in bedroom/bath to the outside return.

    See the description of mine below.

  11. #50
    Join Date
    Jan 2010
    Posts
    55
    The without pipe figure I gave is just for me to see the difference in vertical vs pond loop since that is the only difference in the two. that might help some folks decide on which type to use. My contractor said they do both but for just that little more he would recommend vertical loops.

    I know generic pricing doesn't usually work, but for a specific area most contractors know about what they are going to get per ton, especially in a competetive environment like this. And most of them told me roughly how much extra the geo would cost /ton.

    I didn't go with the lowest bidder. I actually chose the guy w/ the highest bid because he had specified sheetmetal duct in the attics as well as higher grade flex & included all the low volt wiring and bath venting. He also seemed to be the most knowledgeable about the geo systems.

  12. #51
    Join Date
    Feb 2010
    Location
    The midwest.
    Posts
    663
    Quote Originally Posted by dforster2 View Post
    Well he will be back because he doesn't require any payment until they come back to top out and test the unit.

    I don't know if there is room in the bedrooms for transfer grills. The interior walls are only 2x4 studs. how does that work w/ cutting through the top plate that is only 3.5" wide? Do you know the duct & grill size you might use for a standard size bedroom. If I understand right a transfer grill is a return in the top of the wall? why not in the ceiling?

    I wonder if it would be worthwhile to hire an inspector just to look over the duct work?? I usually don't like these inspectors because they are usually know it alls who don't even work in the field. But it would give me some backup to use when I talk to the contractor. Overall I've been very happy w/ the contractor, his work looks to be top notch and very thorough. I've just questioned some of the ducting decisions like we've been discussing here.
    We don't cut the plate. There are two ways to do transfer grilles. One way is to have a 14"x6", or larger if needed, on one side of the stud (low or high) and one on the other side the opposite. Clear as mud? The other way, if a stud wall is not available, is to put a grille in the ceiling and duct it to another (transfer) grille in the "return air area". Understand?

  13. #52
    Join Date
    Jan 2010
    Posts
    55
    Yes. I misread another post and thought a transfer grill was a return duct on the wall. But it is just a hole in the wall. I'm sure he won't have a problem putting those in. My master suite has 4 supply vents all together so that is a good idea. My last house had the slamming door problem so the transfer grill would have been nice.

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