Ground or air source decision, and just any tips appreciated

[dforster2]

I have around 6 or 7 bids including a mixture of conventional air to air and ground source heat pump systems. It is for a 3100 sqft 1-1/2 story house in NE Oklahoma. I am pretty confident in the load calcs because just about all of them came up with about 4 ton downstairs and 3 ton upstairs. And surprisingly they are all about the same price for similar equipment, etc.

Considering the tax credits and rebates from the utility the ground source system will cost about 21% more than the conventional. this is for vertical closed loop system. My questions are concerning approximate payback and just general issues. Some geo equipement sites I've used that account for electric rates, etc give me a payback of about 3 years and the contractor claims no more than 5 years payback. the units I would use probably are climate master packaged units and claim around a 27 SEER. The conventinoal units I'm comparing to are about 15 SEER Lennox or Trane equipment. If I go up to 19 Seer the cost difference is almost nothing after credits and rebates.

So aside from the payback is the quality of the equipment comparable to the a high end trane or lennox, or any other higher end unit?

One technical question I had involves using antifreeze in the loop. One contractor says he won't use it because it decreased efficiency & isn't necessary. The other disagrees and says he never installs w/o it and that methanol doesn't decrease efficiency. Finally, one said he would drill 4 holes using about 183'/ton and the other said 7 200' wells, so 200' per ton.

Any general adivice or tips are appreciated. I think w/ the few thousand extra expense and rising energy costs the ground source may make sense. I just am not too familiar with it and wanted some advice.

Oh, another thing mentioned by a contractor is that he installs very small strip heaters because they are expensive to operate and the heat pump capacity will always catch up, it just might not catch up quite as fast w/o the expensive strip heaters. In fact he says he turns his off in his own home and just deals w/ the occaisional couple degree temp drop. Any thoughts on electric backup heaters? (we don't have gas or any other source)

thanks.

[dforster2]

Please excuse this post, I think I should have put it in residential, moderators please delete if so inclined..

[freonjohn]

I no nothing about where you live so this may be a little off base, but 7 tons seems like a lot to me. Do you have really cold winters? I believe that unless you are going to move in the next couple of years then the geothermal is the way to go. Climatemaster is excellent equipment as well as the Trane and Lennox. 5 year payback also seems a little wishful thinking, but even if you cost it on 10 year payback it will save you money. The systems should last over 20 years, so after the payback period you will be making money on your systems. If the costs were within 20% it really is a no brainer- go geo. As far as your loops you need to talk to the pros in your area because there are regional differences that I just cant answer for you. Make sure you talk to a contractor that has experience with the geothermal systems. You will be glad you went geo.

[dforster2]

Thanks for the input. The wells are actually my main concern as it seems like a bigger unknown and many variables can change the "rules of thumb" depending on soil type, water tables, etc. But in this area there is a single company that does all of the geothermal drilling for all hvac contractors and that is all they do, so that makes me a little more comfortable.

Sizing seems a little large to me as well. I've been told that we live in a cooling dominated area and that I have many west facing windows, large cathedral ceilings, etc.. Also, we have a very nice EPA wood fireplace that we plan to use extensively w/ 40 acres of free firewood..

One contractor actually claimed it was a tad undersized for cooling but would work.

That brings up another question. With my plans to use wood as a heat source, is just the cooling portion of a geo heat pump enough to justify the extra 20%. One of the contractors told me that these heat pumps are actually even more advantageous on the cooling cycle as compared to conventional air to air.

[virginiatech]

You would be fortunate to pay back in just 5 years on the geo installation, most likely you are looking at 7+ years. As far as the size of the equipment, I would agree with the existing proposals due to the fact that the 27 seer systems have 2 stage compressors and will operate in the stage 1 mode most of the time. Stage 1 mode decreases the capacity of the system by 30 to 35% and the fan speed will slow thus using less energy. When there is extreme weather or severe load on the system the thermostat will switch to stage 2 causing the sytem to run at full capacity, this helps to minimize the use of the strip heaters which can cancel out any energy savings in a hurry.

ClimateMaster is a very good line of Geo equipment and would compare in quality with the 16 seer and 20 seer Trane, I personally would not recommend Lennox to any one that I thought very much of.

Never install a geo system without some form of anti-freeze, methanol is great and has a minimal impact on thermal transfer. Glycol is not a good idea because at 40*f glycol will begin to thicken and by the time the temps reach 30* you will be trying to pump a slurpee through the loops. A freeze-up can split the coaxial heat exchanger and cause great expense and discontent. The increased cost of adding the methanol is only pocket change when pricing systems such as these.

Typically we average 250' per ton on the loop field design, you can go out to 250' u-bend loops without having to increase the sizing on the circulating pumps. So for a little more digging or boring you can have an additional buffer for little additional cost. Increased capacity on a loop field can give great comfort and confidence, it is very costly to have to come back and add additional loop capacity.

I agree with the small strip heater kits due to the fact that the systems are already sized a little on the large size for the load which is great for the 2 stage systems and they won't rely on the strip heaters to maintain temps in severe weather and will save you money.

Did any one explain how you can get free hot water from your geo system?

FYI: We operate in Central Virginia utilizing pond loops, vertical bores and horizontal ditches.

[jdf123]

Yeah, they all said the climate master would come with the hot water recovery and that was included in their bids.

What do they typically do when you have two heat pumps and just a single hot water heater? Would it be wasting heat if they only connected one of the units to the water heater? I considered using the second smaller unit to recirculate hot water through the house sort of like one of those hot water circulation devices.

[alex_in_fl]

Can't do payback calculations without data. Three years sounds like snake oil. Five years - maybe but I agree with the 7 years being more likely.

I am not a fan of oversizing. The reason is that the load is sized for the hottest/coldest days of the year (not "the coldest" but almost). You lose efficiency the remainder of the year. Can you stand to be 4-5 degrees colder than you like for a few hours 1 - 3 times per year? If yes then don;t oversize your unit. Also, you can increase the size of the ground coil and almost never have to use the aux heat.


Well depth depends greatly upon what is underground. If you hit a aquifer then your heat transfer rate is better. If sand then deeper wells are required. The 183 is from a program, the 200 is the rule of thumb guy (my opinion). I would add well not short change it - cost is minimal to go extra 10 feet in most cases.

Absolutely use antifreeze. Both lose some efficiency. I could get away without it here in FL but you cannot (unless you live atop a hotspring).

[dforster2]

When I say payback I am talking the difference between conventional and geothermal, and after the tax credits & rebates. Without getting too much into cost, I can say that the difference between a conventional system and the geo bids I have is about3500. That is compared to standard 15 seer units and the climate master tranquility 27 systems. If I assume I will save about 40% in heating and cooling the payback would be about 3.5 years. Even at 25% savings it would be less than 6 years.

Now if I compare with 2 stage 16 seer there is no difference in price after the rebates.

As far as sizing, he sized a 3.5 ton and a 2.5 ton unit for conventional but the climate master doens't come in half tons I guess so he upsized to a 4 and 3 ton. But he also explained that it would tend to operate on the first stage more often if it were a little upsize. It also comes w/ variable speed fans.

[dforster2]

As far as loop sizing, he claims the drilling company specializes in geothermal loops and thats all they do. He said they told him they were going to drill 183' per ton for my units and that would be 1281' of well, or I guess 2562' of loop for about 366' of loop per ton. He said this is what's required for this area and soil type. He didn't know exactly which pipe size they would use but said 1" to 1-1/2".

They install honeywell thermostats. Be kind of a techy, I was hoping to get the climate master thermostats with the sensors to tell me efficiencies and water temps. He said they believe firmly in the honeywell controls and don't usually install the climate master controls. Any thoughts on that?

[alex_in_fl]

If you really want to "watch" your sytem, buy a WEL instrumentation package. You can monitor everything - and then more.

Do you think energy costs are going up or down? If down then go with ASHP. If up then go with the GSHP. Here in FL, the power company just asked to increase rates by 30 percent (they got far, far less and more than their proposal actually deserved).

Seven tons for 3,100 SF would be grossly oversized here in FL. Most use one ton per 500 SF but multiple studies show that one ton per 700 SF is closer to the M J calculations. But rules of thumb are just wags and if you are buying an expensive system you should get the calcs.

One thing that might push you more toward the GSHP is that its easy to get hot water at a discount from the GSHP unit. But you will need a second water tank to get maximum benefit.

Good luck either way you choose to go.

Alex

[dforster2]

Well, we signed a contract for the geothermal unit. We chose the best guy for the job I believe. They've been doing it for 10 years they claim & have tons of references and been using the same driller and they have zero complaints in the BBB, if that matters much..

I would have questioned sizing more but they all came up with about the same 7 ton sizing, maybe because of the large cathedral, they say it's about like adding 500sqft of living area because it is over a 500sqft room. They also all claimed you want to operate in the first stage most of the time which would reduce the capacity quite a bit and runs more efficiently in that range. For conventinoal they actualy came up with 6 tons but don't have half ton increments on climate master equipment.

[jerryd_2008]

... It is for a 3100 sqft 1-1/2 story house in NE Oklahoma. I am pretty confident in the load calcs because just about all of them came up with about 4 ton downstairs and 3 ton upstairs. And surprisingly they are all about the same price for similar equipment, etc.

Considering the tax credits and rebates from the utility the ground source system will cost about 21% more than the conventional. this is for vertical closed loop system. My questions are concerning approximate payback and just general issues. Some geo equipement sites I've used that account for electric rates, etc give me a payback of about 3 years and the contractor claims no more than 5 years payback. the units I would use probably are climate master packaged units and claim around a 27 SEER. The conventinoal units I'm comparing to are about 15 SEER Lennox or Trane equipment. If I go up to 19 Seer the cost difference is almost nothing after credits and rebates.

...

Wow, would I love to see your cost comparison, but alas this is forbotten on this site. Live in extreme NW Arkansas which has got to be close to NE Oklahoma. Considering your 7 tons of capacity, I am amazed! Maybe I should say flabbergasted! Did they throw in the wells for free?

I got several 4 ton geo proposals, one was for Climate Master as I recall. Compared to a 17 SEER 4 ton DFHP after all credits and rebates for both approaches, the geo costs would have been 2-3 times the DFHP. I'm amazed!

In addition, our electric rates are quite reasonable, so a 3 or 5 or 10 year payback would have been a pipe dream for me given our energy lifestyle.

[dforster2]

I was surprised also. The federal 30% credit as well as a $300/ton rebate from my electric utility paid for most of the difference between geo and conventional. Otherwise it wouldn't have made sense to do it. If you want to see a comparison I guess you could Pm me, I don't know if that's allowed either. I could also give you the name of the installers, you're not that far away really.

[jerryd_2008]

I was surprised also. The federal 30% credit as well as a $300/ton rebate from my electric utility paid for most of the difference between geo and conventional. Otherwise it wouldn't have made sense to do it. If you want to see a comparison I guess you could Pm me, I don't know if that's allowed either. I could also give you the name of the installers, you're not that far away really.

Would like to see it but no email address I can find in your Profile. Not sure if rules let you post it in a thread. You can always remove it after I catch it. I could get more specific on my cost analysis also.

The $300/ton credit is nice but it doesn't exist in AR. You in an electric co-op? Even with that credit, my proposals were NOT even close to a high end DFHP.

[jdf123]

K, I put my email in my profile.

[dforster2]

Alex. I was wondering if you could explain the well instrumentation package you mentioned. My installer likes to install just honeywell controls but said he would check on the cost of installing the climatemaster thermostat w/ the sensors, etc.

thanks.

[Todd S 2]

Wow, would I love to see your cost comparison, but alas this is forbotten on this site. Live in extreme NW Arkansas which has got to be close to NE Oklahoma. Considering your 7 tons of capacity, I am amazed! Maybe I should say flabbergasted! Did they throw in the wells for free?

I got several 4 ton geo proposals, one was for Climate Master as I recall. Compared to a 17 SEER 4 ton DFHP after all credits and rebates for both approaches, the geo costs would have been 2-3 times the DFHP. I'm amazed!

In addition, our electric rates are quite reasonable, so a 3 or 5 or 10 year payback would have been a pipe dream for me given our energy lifestyle.

Jerryd.....I agree, I was surprised with the amount of A/C. I'm live in Iowa and we will size for heat. That's why our systems are so large. But 7 tons (I wasn't aware of such a size) seems excessive. Thank goodness for staging. people should ask for payback data. It's a easy program. Anyway, I would love to see the ductwork that will handle 7 tons.

[dforster2]

I will post some links to a few pics of the ductwork. It took two guys two weeks to squeeze all the ductwork into my i-joists and catherdral ceilings. We used 14" i-joists & rafters just for ductwork purposes, the structural design only called for 9" joists.

I may not have mentioned some other details, that it is 2 units, a 4 and 3 ton unit and that in addition to the 3200sqft I have a 24' cathedral ceiling taking up about 500sqft. As well as 10 large west facing windows. Also I have decided to eventually finish out a bonus room that is 500 sqft and we ran a return and supply to that room for the future expansion. So I am thinking it would be more equivalent to 4200 sqft for sizing purposes.

[alex_in_fl]

Hi Deforster2:

I do not have the Web Energy Logger (WEL) system but some of my online friends do. This website shows the WEL in operation: http://welserver.com/WEL0043/ .

FYI - He oversized his units to avoid ever using auxillary heat. It worked. To my knowledge neither unit has ever run in second stage due to the oversizing. Also, he has both units connected to the same groundloop.

For more information on the WEL see this website: http://www.welserver.com/

Let me know if you pursue it and if so how everything works out for you.

[Todd S 2]

Hi Deforster2:

I do not have the Web Energy Logger (WEL) system but some of my online friends do. This website shows the WEL in operation: http://welserver.com/WEL0043/ .

FYI - He oversized his units to avoid ever using auxillary heat. It worked. To my knowledge neither unit has ever run in second stage due to the oversizing. Also, he has both units connected to the same groundloop.

For more information on the WEL see this website: http://www.welserver.com/

Let me know if you pursue it and if so how everything works out for you.

That's ignorant to size the units so they don't stage. Surely you didn't mean that?

[dforster2]

I wouldnt say that it's ignorant. The first stage on my units claim a SEER of 31.5 and the second stage claims 23. Probably has something to do with the extra ground loop since the first stage woldn't really need the 400'/ton of loop required by the full capacity of the unit, but I don't know much about geo yet, still learning.

Anyway, I would think it would benefit you to oversize to operate 95% or more of the time in the first stage. Although it is probalby more expensive, my installer claimed it was just a few hundered more to go to a 3 ton from a 2 ton even with the extra few hundered feet of loop it required.

[Todd S 2]

I wouldnt say that it's ignorant. The first stage on my units claim a SEER of 31.5 and the second stage claims 23. Probably has something to do with the extra ground loop since the first stage woldn't really need the 400'/ton of loop required by the full capacity of the unit, but I don't know much about geo yet, still learning.

Anyway, I would think it would benefit you to oversize to operate 95% or more of the time in the first stage. Although it is probalby more expensive, my installer claimed it was just a few hundered more to go to a 3 ton from a 2 ton even with the extra few hundered feet of loop it required.

Yes, we size our sysems for 93-95% of the maximum heating requirements. Then, during the cooling season it will run mostly on low A/C for dehumidification. Beautiful. Seer, EER or AFUE means nothing if the equipment isn't designed to running properly. You'll lose efficiency and more importantly comfort.

[dforster2]

I'm not arguing, I don't even really know what I'm talking about. Just seemed that on a two stage system it would make sense to operate most of the time on the first stage. that would mean sizing the house to the first stage which is definitely more efficient than the 2nd stage. I always thought 2 stage was like having two units with the sencondary one not running unless the load demanded it. But maybe not..

[Todd S 2]

I'm not arguing, I don't even really know what I'm talking about. Just seemed that on a two stage system it would make sense to operate most of the time on the first stage. that would mean sizing the house to the first stage which is definitely more efficient than the 2nd stage. I always thought 2 stage was like having two units with the sencondary one not running unless the load demanded it. But maybe not..

We are discussing, not arguing. Your HVAC guy, hopefully, knows what he's doing. One reason, not to dramatically over size, is because the existing ductwork is too small (generally) for the existing system let alone the increase air we need to move. When we increase the geothermal size to heat the house we may go from a 2.5 ton A/C system to a 4 ton 2-stage (I never sell single-stage) geothermal unit. That's an increase of 60% more airflow to unload and take in (return air). This is not always easy to acheive.

[dforster2]

Ok, you understand a lot better than me. Hopefully he does too. Oh, this is all new construction so hopefully he sized the duct accodingly.

Anyway, here are a few cool pics & some boring ones. I promised these earlier I need to take some better pics of the plenums & the ductwork since they have finished. There are two very large sheetmetal plenums for the main unit that I need to get some good pics of. It looks very cool. My installer used all sheetmetal in the attic where he didn't have to go through joists, etc. he used flex in the floors where he had to cut through i-joists, although those are mainly in conditioned space so I wasn't too concerned about flex being in there.

The drillers just finished today w/ 4-325' wells. It took them two full days but I think they were wanting to do it in one day so they must have hit some rock or something.

3ton T27 in attic
http://farm3.static.flickr.com/2733/4382744011_f3593e2e1d.jpg

Pumps
http://farm3.static.flickr.com/2690/4383505282_a137344326.jpg

Large duct in cathedral
http://farm3.static.flickr.com/2803/4386221314_fdeed08c2a.jpg
http://farm5.static.flickr.com/4042/4369656455_7eff816278_b.jpg


some ductwork, not too exciting
http://farm3.static.flickr.com/2751/4358653915_3b9a6f7583.jpg


Well installation,they actually struck oil I think, cool maybe..
http://farm3.static.flickr.com/2687/4406459568_0b5fab611f_b.jpg
http://farm3.static.flickr.com/2791/4406461368_1cfc3425a9_b.jpg
http://farm5.static.flickr.com/4050/4405698139_cfe334ec7f_b.jpg
http://farm5.static.flickr.com/4025/4405698719_aaf7bfa5d3_b.jpg
http://farm3.static.flickr.com/2484/4405699829_8b9c72e0cb_b.jpg
http://farm3.static.flickr.com/2746/4406464386_0bbcd04383_b.jpg

[Todd S 2]

Ok, you understand a lot better than me. Hopefully he does too. Oh, this is all new construction so hopefully he sized the duct accodingly.

Anyway, here are a few cool pics & some boring ones. I promised these earlier I need to take some better pics of the plenums & the ductwork since they have finished. There are two very large sheetmetal plenums for the main unit that I need to get some good pics of. It looks very cool. My installer used all sheetmetal in the attic where he didn't have to go through joists, etc. he used flex in the floors where he had to cut through i-joists, although those are mainly in conditioned space so I wasn't too concerned about flex being in there.

The drillers just finished today w/ 4-325' wells. It took them two full days but I think they were wanting to do it in one day so they must have hit some rock or something.

3ton T27 in attic
http://farm3.static.flickr.com/2733/4382744011_f3593e2e1d.jpg

Pumps
http://farm3.static.flickr.com/2690/4383505282_a137344326.jpg

Large duct in cathedral
http://farm3.static.flickr.com/2803/4386221314_fdeed08c2a.jpg
http://farm5.static.flickr.com/4042/4369656455_7eff816278_b.jpg


some ductwork, not too exciting
http://farm3.static.flickr.com/2751/4358653915_3b9a6f7583.jpg


Well installation,they actually struck oil I think, cool maybe..
http://farm3.static.flickr.com/2687/4406459568_0b5fab611f_b.jpg
http://farm3.static.flickr.com/2791/4406461368_1cfc3425a9_b.jpg
http://farm5.static.flickr.com/4050/4405698139_cfe334ec7f_b.jpg
http://farm5.static.flickr.com/4025/4405698719_aaf7bfa5d3_b.jpg
http://farm3.static.flickr.com/2484/4405699829_8b9c72e0cb_b.jpg
http://farm3.static.flickr.com/2746/4406464386_0bbcd04383_b.jpg

What I could see of the supply, it looks good. I couldn't make out how the return air duct was run.

[dforster2]

I have to take some better pics yet, those were taken early on. The main downstairs unit is not installed yet because it is on backorder. But they have most of the plenums and ducting installed to it.

[Todd S 2]

I have to take some better pics yet, those were taken early on. The main downstairs unit is not installed yet because it is on backorder. But they have most of the plenums and ducting installed to it.

The unit in the attic looks like it has one pipe (size?) off the bottom of the return plenum. Are there any more return air pipes that I can't see? Size? How many return air grilles does the 2nd floor have?

[dforster2]

I think that there is just one on that unit. I asked the guy about putting another one but that space is open except for a bedroom and he said you don't want them in bedrooms. something to do with the thermostat not picking up the air temp correctly in the bedrooms (if they have their own return). In other words, you are after air circulation. I argued with him briefly about that but it is another standard answer to save money I think. They'll do it if I want. My last house just had a single return on the upstairs unit sort of central like this one. It worked fine as long as you have plenty of space under your bedroom door..

The downstairs unit has 3 returns though because there are 2 pretty separate living areas and a large master suite.

[Todd S 2]

I think that there is just one on that unit. I asked the guy about putting another one but that space is open except for a bedroom and he said you don't want them in bedrooms. something to do with the thermostat not picking up the air temp correctly in the bedrooms (if they have their own return). In other words, you are after air circulation. I argued with him briefly about that but it is another standard answer to save money I think. They'll do it if I want. My last house just had a single return on the upstairs unit sort of central like this one. It worked fine as long as you have plenty of space under your bedroom door..

The downstairs unit has 3 returns though because there are 2 pretty separate living areas and a large master suite.

I don't have a issue with the one return but the problem is it (the grille) has to be huge. I would recommend 2-24"x24" grilles feed by 2-14" round pipes. If he is only using one pipe, then the 3 ton H/P for the second floor
needs a 16" round (it doesn't look that big) to a 30"x30" grille. Normally, trusses are 24" on center. This doesn't work too well. Make sure to have them install transfer grilles to the bedrooms. He's going to love you. LOL

[jerryd_2008]

Jerryd.....I agree, I was surprised with the amount of A/C. I'm live in Iowa and we will size for heat. That's why our systems are so large. But 7 tons (I wasn't aware of such a size) seems excessive. Thank goodness for staging. people should ask for payback data. It's a easy program. Anyway, I would love to see the ductwork that will handle 7 tons.

Todd, this site has educated me a bit on avoiding geo tonnage. Never thought of it until reading posts here, but that extra tonnage and wells can probably be more economically offset with electric heat strips to cover the 5% of the time that the system capacity is a bit short. On the cooling side, IMO there are cheaper solutions involving the house envelope. Even if the house requires $1,000's for some new windows, geo costs are so high that I would really sharpen my pencil before assuming that more geo tonnage is the solution. Besides, buying more geo or any other system capacity to compensate for house inadequacies that can be corrected seems rather illogical and probably expensive in up front and on-going operating costs.

By the way, dfoster2 had a situation involving new construction, 2 systems, new ductwork and various rebates that don't apply to new construction. His email to me explained his reasoning. The 7 tons probably involved modularity issues (no 1/2 ton units). Just proves that you have to take your specific situation and run the numbers. I would like to know how he is doing since he was going into insulation and we were discussing using cellulose. Still wonder if a smaller geo tonnage could have been obtained.

[Todd S 2]

Todd, this site has educated me a bit on avoiding geo tonnage. Never thought of it until reading posts here, but that extra tonnage and wells can probably be more economically offset with electric heat strips to cover the 5% of the time that the system capacity is a bit short. On the cooling side, IMO there are cheaper solutions involving the house envelope. Even if the house requires $1,000's for some new windows, geo costs are so high that I would really sharpen my pencil before assuming that more geo tonnage is the solution. Besides, buying more geo or any other system capacity to compensate for house inadequacies that can be corrected seems rather illogical and probably expensive in up front and on-going operating costs.

By the way, dfoster2 had a situation involving new construction, 2 systems, new ductwork and various rebates that don't apply to new construction. His email to me explained his reasoning. The 7 tons probably involved modularity issues (no 1/2 ton units). Just proves that you have to take your specific situation and run the numbers. I would like to know how he is doing since he was going into insulation and we were discussing using cellulose. Still wonder if a smaller geo tonnage could have been obtained.

JD,
Of course there is no substitute for insulation. We ask if they will be doing any improvement but never know if they will follow thru.

[jerryd_2008]

... my installer claimed it was just a few hundered more to go to a 3 ton from a 2 ton even with the extra few hundered feet of loop it required.

Wow, I wish he had made a proposal to me! But excuse my skepticism, my experience that an extra ton of geo and the wells required are closer to 2 orders of magnitude more expensive than your understanding.

[Todd S 2]

Wow, I wish he had made a proposal to me! But excuse my skepticism, my experience that an extra ton of geo and the wells required are closer to 2 orders of magnitude more expensive than your understanding.

The differance should have been (roughly) $4,500.00. This is for the additional well and the extra ton of geo.

[jerryd_2008]

I... Make sure to have them install transfer grilles to the bedrooms. ...

Our house has 2 floors and only one return per floor. Had a contractor enlarge the return on the lowest floor to the largest filter size carried by Lowe's. Surprise, surprise. The darn return was half blocked by stud and plenum structure so the extra size was probably really needed.

Then I designed offset and louvered transfer grills the size of the stud width for each bedroom to eliminate noise and light. Had him block the top and bottom and caulk the heck out of it to prevent any airflow from above or below. This hasn't equalized the bedroom temps with the doors closed as well as I would like, but I am sure that it is much better than counting on only air flowing between the doors and the carpeting.

[jerryd_2008]

The differance should have been (roughly) $4,500.00. This is for the additional well and the extra ton of geo.

Not sure the moderator will like this discussion, but not in my neck of the woods. Add at least a third to get to my proposal cost/ton. Just in casual conversation with my DFHP contractor on his recent 6 ton geo install verifies this if I allow maybe another 10% for the duct work he probably put into new construction.

Maybe those oil drillers 100 miles or so West of me know how to drill wells cheaper.

[jdf123]

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?

[jdf123]

Wow, I wish he had made a proposal to me! But excuse my skepticism, my experience that an extra ton of geo and the wells required are closer to 2 orders of magnitude more expensive than your understanding.

I'm not sure he was completely honest about the few hundered. But looking at the price difference between the 4 and 3 ton unit I don't see a big difference. And I can say that I had one bid for a 4 & 2 ton unit and one bid for a 5 & 3 ton unit and the bids were all within $1500 of each other. Which I found pretty amazing.

Most people can't believe that with the unliminted geothermal credit & the coop credit I will get, the geo system was only a couple thousand more than the average bid for conventional. 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. That's about $2/foot which is about the going rate around here for straight drilling, it may be more in other areas. He only told me that becuase we looked at pond loop and I wanted to know how much more the vertical wells would cost. 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.

[jdf123]

sorry, I just realized I am posting as a different login from home. I guess I had two logins by mistake. one from last year and a new one a few weeks ago when I couldn't find my old account..

[alex_in_fl]

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.

[Todd S 2]

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.

[dforster2]

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.

[Todd S 2]

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.

[Todd S 2]

The return air pipe in the attic looks like its 14".

[dforster2]

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.

[Todd S 2]

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.

[dforster2]

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.

[jerryd_2008]

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.

[jerryd_2008]

...

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.

[dforster2]

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.

[Todd S 2]

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?

[dforster2]

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.

[dforster2]

My only concern w/ these transfer grills is that you are opening up your wall cavity to your living space. Do they use a pass through type of duct to close off the cavity? maybe that was already explained and I missed it.

I would think you would want the cavity sealed because of dust, etc.

thanks.

[Todd S 2]

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.

I was going to say that if your doors are closing on their own, then you have a problem. In our area, most systems are so short on return, the basement doors slam shut. This negitive (basement) pressure reverses the venting of the furnace and water heater. Does the inspector catch it? No. If someone hopes the inspector will make sure things get done correctly, they have another thing coming. Like I said in another post, most salesman wouldn't know a drive lock from a vapor lock. LOL

[Todd S 2]

My only concern w/ these transfer grills is that you are opening up your wall cavity to your living space. Do they use a pass through type of duct to close off the cavity? maybe that was already explained and I missed it.

I would think you would want the cavity sealed because of dust, etc.

thanks.

Let the heating guy explain it. But not to worry. It is just to let the air out of the room(s).

[jerryd_2008]

My only concern w/ these transfer grills is that you are opening up your wall cavity to your living space. Do they use a pass through type of duct to close off the cavity? maybe that was already explained and I missed it.

I would think you would want the cavity sealed because of dust, etc.

thanks.

DF, just think of it as cutting out the dry wall and inserting a grill on the inside and the outside of the room wall. But first, I believe I mentioned that I had the contractor put in 2 x 4 blocks the width of the wall studs above and below the grill openings. Then I had him caulk all around those blocks. This should completely seal the opening from sucking in any any dust, air infiltration, etc. Done!

I also mentioned that I offset the inside opening from the outside opening so that sound and light does not flow directly through 2 perfectly lined up grills. I highly recommend doing this. I also added grills that have open/close levers on each side so that I can pretty much close the pass through completely or redirect the air flow a bit on either side. This is not essential but it is not expensive.

[dforster2]

Well I had them install another return in the master suite so we don't have to do the transfer grills.

thanks.

[Todd S 2]

Well I had them install another return in the master suite so we don't have to do the transfer grills.

thanks.

Good, that will make a big differance. Hopefully, he didn't give you too much grief.

[jerryd_2008]

Well I had them install another return in the master suite so we don't have to do the transfer grills.

thanks.

Our last house which we built had returns in every room. Now we have a house which we did not build with only one return on each floor. Our first house had one return on the 2nd floor at the top of the steps. The transfer grills were a retrofit and not a preference. If I were to build another house I would insist on an adequate return in every room.

Good choice!:angel: