Which geo brand to seek to handle combination heating/cooling?
Last Post 18 Sep 2012 09:25 PM by Boontucky-girl. 55 Replies.
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Boontucky-girlUser is Offline
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30 Apr 2012 01:14 PM
We have hydronic radiant heat in the basement, currently with a boiler in an all electric house. 4 years ago when we built the structure, the plan ended up to use an air-source heat pump for forced air heating in main floor, and forced air cooling of the whole house, with the boiler doing just basement radiant since that was the option we could afford at that time. In the end we got as far as installing the ductwork and stopped there because of budget/financing reasons. So we have no heat pump/blower/ or AC. Just ductwork and basement radiant heat system. We live in the basement, main floor remains unfinished.

We're now currently collecting bids/estimates to finish the main floor/house all at once, and we thought we'd revisit the geothermal issue again and see if we should go that route. Planned insulation in walls is ~ R32, with attic insulation ~R80+, windows are marvin integrity, and a blower door test is planned for infiltration testing. We're not sure that geo would truly make sense since our rates are very low right now $0.046/KWH for heating, $.065/KWH for cooling, so I plan on requesting a cost comparison of going geo vs. air source and figuring out some sort of ROI to justify the geo investment, since it is a little higher than the air-source pump, even after rebates and credits.

We'd like to add hydronic radiant heat in the main floor, NRT Radiant would be handling the radiant design and I have an estimate of that cost, and it would be DIY install. It seems that forced air cooling is what would make sense since we already have the ductwork for that.

Option 1: Stick with original plan air source heat pump for main floor heating, whole house cooling, boiler for basement radiant. I have an estimate for this option.

Option 2: Boiler radiant heat basement and main floor, with just a central A/C unit for the cooling

Option 3: geothermal combination unit to run hydronic heat whole house and forced air cooling. I'd like to know some brands that could handle this so I can look for local reps/installers for said brands and collect bids/estimates. Would waterfurnace and hydron module be an option? Any others?

Option 4: Geothermal combination unit for hydronic radiant only in basement, forced air heat in main floor, and forced air cooling with geothermal. I wonder that if a combo unit can do option 3 above, why look at option 4? But this might have to be considered if because of budget we cannot have the main floor radiant that I want since all we'd be saving is the cost of the radiant parts.

Option 5: hydronic only in basement with boiler since system is already in place,  and only forced air heat in main floor, and cooling with geothermal. Would this mean a smaller geo vs. option 3 and 4 since it's only handling main floor load, depending on cooling load? Would this would be a direct comparison vs. option 1?

Not sure how feasible/possiblethese options would be, or which I should truly consider, but I'd like to compare if possible. What would be things to consider of one option vs. the others?

Once we get an appraisal ordered and bank approval, we will truly know what our final budget numbers will be, but I'd like to have this figured out before then.

Any feedback or guidance is greatly appreciated.

Thanks.
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30 Apr 2012 03:07 PM
Load calculations are a critical part to determining which system best suits your needs. Geography does as well since all systems perform better in some areas than others.
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01 May 2012 01:50 PM
Thanks Joe. My first question to anyone I potentially interview is if they do a heat load calculation. I am considering purchasing the H.O. Hvac calc to do my own to compare what they propose for sizing of each system option, just because of past experience where the load numbers I've received from a couple of HVAC contractors seemed way too high. Two instances I got quoted a 5 ton geo unit. But they would not show me their load calculations, just the final number, which is fine. Eventually one confessed that they really didn't do a heat load, and the size was merely based on past homes with similar floorplans. BUt that was 4 years ago. It seems around here because of city ordinances, heat loads are a must, so more contractors seem to do them.

I wouldn't expect to just get the heat loads to be freely handed over without some sort of fee or commitment to go with them, but I really want to have something that I can be fairly confident is close to what my loads should be to compare proposed sizing.

I'm in central Iowa, and assuming all contractors do the loads in similar fashion and come out to about the same number... with that in mind, how would I reasonably compare between options other than just actual cost?

I asked one contractor to do a cost analysis of geo vs air pump, and he compared a geo unit sized to do just the forced air upstairs + cooling, vs. an air pump sized to include the basement radiant as well. It took me a while to decipher the cost comparison to realize that was happening. In that case geo seemed like a no brainer, but including running the radiant with the boiler, the monthly savings didn't seem to justify the geo investment (based on his cost comparison).

If I wanted to truly compare between the options in my first post, how would I do a cost analysis to compare operation of each option so I'm comparing apples to apples as closely as possible? That would help us determine which option is worth the investment for our case.

Also, for a combination geothermal unit to do forced air and hydronic radiant, would those be waterfurnace and hydron module? Any others? I'd like to find local installers and I believe these two brands do have them around here. But I'd like to visit with more, if possible.

Thanks.
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01 May 2012 02:03 PM
With known load any contractor with the software can easily do op cost calcs. It would take me 2 minutes if I knew your load and closest major city + fuel and elec costs.
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03 May 2012 11:38 PM
Have a blower door test performed BEFORE drywall goes up so as to have a chance to find and fix air leaks rather than merely living with the result.
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The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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04 May 2012 03:41 PM
R32 walls doesn't always mean R32 whole-wall R- there is significant thermal bridging in a stick built. In another thread you wrote:

"1" of ISO on exterior, and I wanted to install 1-2" cc spray foam then fill the rest with wet spray or dense packed cellulose.

How does this compare to a wet spray cellulose? Installer said with the wet spray the the value would be R23 for the 2x6 wall."

With 1" of iso on the exterior and a flash'n'fill, with 25% framing fraction you're looking at whole-wall performance of ~R22, not R32, or a U-factor of about 0.045 BTU/hr per square foot of wall area per degree-F of difference.

From your basic building plan & R/U values it's pretty easy to do a quick & dirty heat loss calc with a spreadsheet.

If your outside design temp is about -7F (this is IA, right?) and the interior design temp is 68F, that's a 75F difference, so for every square foot of wall adds a heat load of (75 x 0.045=) 3.4 BTU to the heat load number. Look up your 99% outside design temp number for a nearby city here:

http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

But I'll use a delta-T of 75F just to make the arithmetic easy...

The Marvin integrity series varies with U-factors from 0.28 to 0.33, so call it U0.30. That adds (75x 0.30=) 23 BTU to the heat load for every square foot of glass.

Your roof-R gives you a U-factor of 0.013, or about 1BTU/square foot over the footprint of the house at a 75F delta-T

You'll have to fudge something for your foundation & slab insulation. If the foundation walls aren't insulated it could easily swamp the heat load picture. If you count just the heat loss of the upper half of the foundation (down to a couple feet below the frost line) based on the R value (U-factor=1/R) it'll probably make up for any losses to the ground through the slab, etc.

Then subract 250BTU/hr for every adult human, subtract some for your background plug-loads, add some for your actual infiltration/ventilation, but with an air-tight house and HRV 3000 BTU/hr would probably be more than enough margin.

My guess is that unless you have a HUGE amount of glass, with R22 whole-wall and R75- R80 roof you're looking at less than 3 tons for an average sized house, maybe under 2 tons.
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16 May 2012 12:24 AM
Thanks Dana1. How do you estimate the % of framing fraction for walls? I figure I can literally walk up there, count the number of studs on the exterior perimeter, and figure the square footage of lumber to get it exact. But I'm sure there's an easier way?

The basement is ICF, and manufacturer claims R28 (2.5" of foam on either side of concrete) and there's r10 under the slab, and perimeter of slab is against ICF wall. But it is a full walkout on the back, so counting the basement, there are quite a few windows. The stickers on the windows claim .29 for a U-factor.

Looking at the chart for design temperature, it says -7 for the 99% heating. Two of the HVAC contractors said they used -15 as design outdoor temp. for our area. Would those extra degrees make much of a difference? Also, I think they use 72 for indoor temp. Would that basically translate that you'd need bigger equipment to meet the load, since they are designing for an 87ºF deltaT?

Thanks!
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16 May 2012 08:55 AM
We have contractors around here who inexplicably lower design temp. (I think it's a CYA move). It absolutely affects unit and duct size.....all at your expense.
Manual J is designed with fudge factor in it to begin with.
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16 May 2012 05:26 PM
Framing fractions vary all over the place, it depends on the stud spacing, whether double vs. single top/bottom plates were used, whether code requires mid-level fire blocking, how window & door fraiming was detailed, etc., the number of bump-outs (that add corner framing) etc. A well thought out framing design attempting to minimize thermal bridging on simple rectangular footprint house might drop below 20%, a more complicated design with fire-blocking or seismic-resistance requirements might hit 30%. I tend to use 20% for simpler designs or for 24% o.c. framing, but the national average for tract-house builders at 16" o.c. framing is closer to 25%, so use 25% unless you did your homework on the framing design- it'll be close enough. If you think it's actually 20%, use 0.043 as the U-factor rather than 0.045- which is still not going to make huge delta on the whole house number.

The R28 ICF is a dynamic mass-effect fudge factor number, but adequate for use in system sizing. Steady state the 5" of foam is about R20 @ 75F +/- 25F, but rise about 5% for an average when it's 0F outside, the concrete, interior finish and air films add another ~R1 so call it R22-ish steady-state at design temp. The U-factor assuming the R28 is ~0.036BTU/hr per degree-F delta. If you used R22 (to worst-case it, adding unnecessary margin) it would be 0.045 BTU/hr per degree-F. For yuks you could split the difference and call it 0.040. Unless you have a LOT of above grade ICF using the biggest vs the lowest of those numbers won't change the whole-house number by very much.

R10 under the slab would be essentially zero heat loss if the slab wasn't heated, but it'll be some thing when used as a radiant slab. Precision isn't very good due to the variable conductivity of soil type and distance to the ground table, seasonal ground moisture and the slab temperature when it's heating the house at max load all make a difference. But it'll still be at most 10% of the heat loss of the rest of the house at design conditions.

Using a design temp fully 8F below the published ASHRAE/ACCA design temp and using 72F as an indoor design temp rather than 68F (which is pretty damned comfortable in a radiant-heating house) is malpractice. Using -7/+68 is a 75F delta-T, whereas using -15/+72 for the 87F delta-T, increasing the minimum size of the heating plant by 16%. I they do similar cheats elsewhere it's pretty easy to come up with 30-50% oversizing, not even counting the inherent 15%+ safety factors built into heat loss calculators.

At the upfront cost of geo, putting the thumb on the heat load scale practically criminal, adding thousands in unnecessary cost. Geo runs about $9K/ton in my neighborhood (sometimes more). If Manual-J done completely above-board, without any skewed inputs says 3 tons, odds are pretty good that even a 2.5 ton system would keep up. But with CYA factors adding 20-50% to the Manual-J, and they end up designing & installing 3.5-4 tons for what is actually a ~2.5 ton load it's more than 10 grand in unnecessary cost. It's bad enough when adding that much CYA upsizing to a condensing gas furnace, but it's financial abuse to upsize geo that way. If you can't find heating contractors who won't fudge the numbers, it's worth paying a competent third party energy-consulting (not HVAC) contractor to run accurate heat load numbers for you, even if it costs you several hundred (which it might, if they run a blower door test for higher accuracy.) It doesn't usually make sense to take it that far for sizing gas-fired heating, but it sure does with geo.

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16 May 2012 09:26 PM
I don't know the size of your house but if Dana says 2-3 ton, AND you already have a boiler for the basement, AND cost is an issue, use the boiler (unless it is propane or oil). Put the floor heating in upstairs, with a gypsum cement overpour and call it a day. I am sure your boiler has the capability to handle the heat loss , especially if it is a condensing boiler.

If the boiler is oil or propane, switch to an ASHP that heats water....yes they are available and will have an electric element as backup. We make them as do some others. With your electrical rates, you will be laughing.
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17 May 2012 02:27 PM
In an all-electric house, it's an electric boiler, so some form of heat pump is called for even though her electricity rates are well below the national average ($0.046/kwh is about 1/4 what I'm paying), but if only the basement zone is on the boiler, it would be very difficult financial argument to make. The whole house running on one heat pump has a better rationale.

Unlike in Europe where there are at least a dozen vendors to choose from, tere are very few ASHPs with hydronic output available in the US. The Daikin Altherma series is the only one with any number of installations, and it's still a very low number indeed, and the output a the design temp of -7F/-22C is limited. But NRT.Rob (who is doing her radiant design) has first-hand experience with that series in a similar winter climate, and would be better able to advise once valid heat load numbers are calculated.

I wouldn't make the call prior to doing the careful heat load analysis as well as the financial analysis. Places in IA with design temps of -7F usually have an average January temp of about +20F/-7C , so even pretty-good ASHPs would be only making seasonal average COP of ~2.5 and possibly less, unless the whole heating system can be run at a very low temperature (not just the basement zone. If it runs out of capacity at even 0F relative to what a careful heat load calc says it wouldn't be a good way to go. A GSHP installation is likely to average ~3.5 for a seasonal COP, can be designed to carry bigger heat loads, and has substantial subsidies available, whereas hydronic ASHP solutions do not, SFAIK. But if the radiant can be run at a low enough temp it's conceivable that the Altherma might average close to 3, and at 4.6 cents/kwh it may take forever to make up the cost difference in higher efficiency.

It may still be more cost effective to go with GSHP, but it's worth doing the math on the difference in final installed costs would be, and how much (also subsidized) photovoltaics that might buy, and whether the PV would more than make up the difference in seasonal power use between the ASHP & GSHP systems. At those very low power rates what's a no-brainer in my neighborhood would require a more careful look for her.

But it all starts with a better heat load calculation, since that determines the size & cost of the radiation (if all-hydronic) and the heat pumps.
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17 May 2012 05:10 PM
I must have missed the "all electric" part. Of course a proper heat load is called for first. There are some other questions such as ....is solar thermal desired or PV. It would take a semi-custom HP but solar thermal could be added.
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18 May 2012 07:06 PM
is the total cost of the electricity including all the transportation charges in everything else as a part of the bill is it your total kilowatt hours divided into the total dollars of the lower right corner of the bill ? or are you just going by that rate number in the middle after that 101 customers I have helped with rates found we have to divide by the total bill not go by the riate number then we even found air source heat pumps better and condensing gas was very close to inappropriately installed geothermal
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21 May 2012 11:10 AM
There are places in the upper Midwest where the whole delivered cost of electricity at residential rates are 7 cents or less, as hard as that is to fathom here in 15-22 cents/kwh land. The residential retail average in the state of Iowa is ~7 cents/kwh, with local markets within the state where it's less. Off-peak rates under a nickel are the norm.

In IA the moderating effect of the large installed base (and growing) share of wind power seems to be flatting out average rates and limiting price inflation. Since the marginal cost of wind is about 1 cent/kwh it can always under-bid fossil plants whenever the resource is available. Wind is currently delivering about 20% of the total annual supply for the state, and is cutting into the capacity-factor (time fraction at full output) of local fossil grid sources. Those plants can't compete on price even if the fuel were free, due to higher maintenance costs per kwh. The installation cost of wind per peak megawatt is high (but falling), but once it's up, the marginal cost of power is near-zero.

Electricity is likely to remain cheap in IA for some time to come, but that's not to say it makes heat pumps uneconomic, just not the slam dunk they are in my neighborhood.
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21 May 2012 11:46 PM
Wow! Great discussion. Thanks.

Joe - it's the reason I very much want 3rd party heat loads. Just today we visited with a general, and I said based on some rough numbers we could be looking at a 3 ton unit. He said he would not put in anything less than a 4 ton in because our house is so big, and we may be needing a 5 ton! I asked if his HVAC guys did heat loads, and he said that he always asks for an extra well/ton more than what he gets quoted to be safe! Then I explained what my ideas were on insulation, and he said no need for all of that, a simple BIB in fiberglass in a 2x6 is more than enough and wasting money on asking for anything else, and then I feel like an idiot for asking things that he wasn't even interested in even entertaining.

Dana1 - 4 years ago I tried to find a framer to do OVE, no one knew what that was, and no one would bid me framing with flimsy 24 o.c. the two willing to try it upcharged so much vs. normal that I could not afford it. I did my best to encourage less studs, but we still ended up with more than needed. At least I did convince our framer to do the corners like in the OVE details, and to ladder interior walls to increase some insulation space. Since I get stuck on small details, i will probably count each stud and rough how much sq. ft. of wall space I have in framing. If I had unlimited resources, i'd be buying those thermabloc strips made with aerogels to cut the thermal bridging even more. I got a sample from the manuf, and it's pretty cool! I'll keep scratching the lotto and maybe I'll win enough to afford those.

I will get heat loads done by a third party, but not until we finalize our loan and we are sure we are going forth! One of the hvac subs we priced said he uses 7th edition manual j and should be good enough for sizing. Then said if I want Manual S and D, I have to hire someone else since they don't, which I think is the norm around here.

On the ICF wall, I've used R24 in the past, vs the R28 claimed by the manufacturer. The exterior perimeter is roughly 206 ft, with 65 ft of that being completely above grade, and another 54 ft of basement wall the ground slopes upward. So there is quite a bit exposed, and it's more of a second floor, than a basement.

Your comments about the design conditions I've been told they use, and even with my primitive/basic understanding of the importance of proper heat loads, I am very concerned that I'm getting bids for systems that are oversized. But I'm getting really tired and feel like it's such an uphill climb to get things right. The one HVAC I thought was a winner, let is slip during a conversation that his software can't even go above R13 for walls, and R38 for ceilings so I'm not as confident now on his estimatet. And if as you say they fudge here and there, what am I truly getting vs. what I should get?

Mike - We have about 3850 sq ft. Our electric boiler is sized for the whole house, and budget is an issue. My dream home would have radiant heat everywhere, but then again, I can't get anyone local to bid anything above a 1 zone system without me having to go rob a bank to be able to pay them. It's the reason NRT designed our job in the first place 4 years ago. The compromise back then when budget ran out was to go ASHP forced air main floor and cool, and leave the basement with radiant. We're blessed that we're in a better position now that we can look at finishing the house all at once, but budget is still an issue. The time to visit about adding GSHP would be now, ideally to replace the boiler, add radiant in the main floor, and cool with forced air. But that's the cadillac, and I'm sure that if we have to pick between radiant vs. finishing the house, the radiant will not make it, and we'll get the chevy. But I do want to make sure that a GSHP is worth the extra $ vs an ASHP. Again, without proper loads it's all a guessing game right now.

Dana1, Rob at NRT talked about the Daikin ASHP to run a whole house radiant scenario (since I'm still very much exploring that option), but there a no local vendors/installers near me, not even in the whole State that I could find. When they did the initial heat loads 4 years ago, the max design temps were 115 for the whole house radiant option.

KnotET - on the heat rates the delivery fee is only $5/mo plus other fees is about another $8 so my $.05 rate is more like $0.06 on avg, but that's only for heating/cooling (via dedicated separate meter). Regular rates for non hvac needs are more in the $0.11 range.

I hadn't considered PV, since I have never heard of anyone in the area that does them, let alone seen a house with them. That usually means the one or two local vendors that do them probably charge a lot more since it's special market. But now I'm wondering if anyone does install them, and that I should get an estimate. Might be worth it (or add it to the future list along with adding a wind turbine to our small property to supplement, then switching to a wood fired outdoor furnace, and even a small hydro turbine in our river and getting off the grid). I'll keep scratching tickets.

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22 May 2012 06:57 AM
Posted By Boontucky-girl on 21 May 2012 11:46 PM
Wow! Great discussion. Thanks.

 
Mike - We have about 3850 sq ft. Our electric boiler is sized for the whole house, and budget is an issue. My dream home would have radiant heat everywhere, but then again, I can't get anyone local to bid anything above a 1 zone system without me having to go rob a bank to be able to pay them. It's the reason NRT designed our job in the first place 4 years ago. The compromise back then when budget ran out was to go ASHP forced air main floor and cool, and leave the basement with radiant. We're blessed that we're in a better position now that we can look at finishing the house all at once, but budget is still an issue. The time to visit about adding GSHP would be now, ideally to replace the boiler, add radiant in the main floor, and cool with forced air. But that's the cadillac, and I'm sure that if we have to pick between radiant vs. finishing the house, the radiant will not make it, and we'll get the chevy. But I do want to make sure that a GSHP is worth the extra $ vs an ASHP. Again, without proper loads it's all a guessing game right now.

Dana1, Rob at NRT talked about the Daikin ASHP to run a whole house radiant scenario (since I'm still very much exploring that option), but there a no local vendors/installers near me, not even in the whole State that I could find. When they did the initial heat loads 4 years ago, the max design temps were 115 for the whole house radiant option.

I hadn't considered PV, since I have never heard of anyone in the area that does them, let alone seen a house with them. That usually means the one or two local vendors that do them probably charge a lot more since it's special market. But now I'm wondering if anyone does install them, and that I should get an estimate. Might be worth it (or add it to the future list along with adding a wind turbine to our small property to supplement, then switching to a wood fired outdoor furnace, and even a small hydro turbine in our river and getting off the grid). I'll keep scratching tickets.


For floor heating, the most economical system is a single zone per floor. I like it because i find people set and forget the t-stats (which I stopped using a few years ago, for the most part I use just outdoor temps) and if the there is a lot of south side solar gain on a thermal mass floor, the heat can be moved to the cooler areas.

Personally, being on a budget, I would forgo the GSHP for a ASHP because, it is hard to retrofit a thermal mass floor after the fact but a HP can be upgraded. As far as the temps for the floor, 90F is doable with the right amount of tubing in the floor., given your attention to heat losses.

I wish our solar thermal/ASHP was ready but, alas, another year for that.
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22 May 2012 11:03 AM
But if there isn't a vendor support or an installer of hydronic-output ASHPs within 100 miles of her, that option may be off the table at any price. A wood fired boiler may be viable though.
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22 May 2012 11:56 PM
Thanks Mike. My problem wasn't really that normally they do single zone radiant installs in my area, my problem was that no one knew/was able to give me what I wanted, which was multi-zone radiant. And those who gave me estimates were so high it was ridiculous, and some of the answers were quite outrageous (like I needed double the tonnage in a system to handle hydronic because it was harder to get the heat to the water, or that I needed a pump per zone, etc. etc.)

I'm not quite sure I understand what you mean by upgrading thermal mass floor?
At the rates things are going, maybe next year we'll be ready to actually get our building going, and you get your distribution center here in IA and I'll try your system.

Dana1 - I do have enough timber in my acreage that maybe I should be looking at a wood fired boiler. If only they had auto-refill so I wouldn't have to go out to replenish the wood, that's be great. Not to mention the difference in amount of labor to keep a good stockpile of logs for heating, vs. wood pile for fireplace only. If this house ever gets done, maybe I'd have plenty of time to do that.

I got a copy of some heat loads that I got from one of the HVAC guys we're estimating. couple of questions, in the cost analysis provided, they have DHW compared between having a geo system and ASHP. Does that mean they are comparing the cost of the GSHP to run to produce some of hot water, vs. running our electric water heater to do full DHW needs?
So if they say with the ASHP the DHW cost is X, but with the geo is Y and the geo is handling 60%, does that mean then that the other 40% DHW load is still handled by the hot water heater? So to compare, DHW cost with ASHP is X, vs. Y+.4X for the GSHP? Or am I reading this wrong?

They also have the electric rate for heating with the GSHP at the correct rate, but the ASHP rate is twice as much. That doesn't make sense to me, since the electric rate is the same regardless of what system I use. I would assume the difference should be the KWH to run the GSHP to meet our load, vs the KWH to run the ASHP to meet our load. I also noticed the winter peak electrical demand is different for both systems (ASHP higher than geo) Is this right? This seems like an input parameter, so why would they be different between systems?
Just trying to learn more so I can read these cost comparisons right. Thanks.
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23 May 2012 08:00 AM
Posted By Boontucky-girl on 22 May 2012 11:56 PM


They also have the electric rate for heating with the GSHP at the correct rate, but the ASHP rate is twice as much. That doesn't make sense to me, since the electric rate is the same regardless of what system I use.

sounds like they are skewing the numbers in favor of geo.
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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23 May 2012 08:35 AM
The difference between multi zone and single zone from technology perspective can as simple as putting "telestats" on each loop of the manifold (which i don't like much), to create control for each loop, or having separate piping to each manifold (zone) with its own pump in the basement (I prefer this system because you design the zone as well as possible and the fluid flow matches the needs of the zone)

Telestats are powered valves that are tied to a thermostat so there is one pump whose flow is high when all the loops are open or lower when some ore open. It is not as controllable as separate pumps and supply piping.

This can account for a considerable cost difference and honestly, from a running cost point of view, there is not much difference. Many people say they want to control their zones differently but it rarely happens.

By upgrading to a thermal mass floor, I mean that if you did do forced air upstairs and had all your floor covering down, taking them up again would be expensive and a PITA. To me, planning it in, with tubing, from the beginning is the best choice.

Most North american heat pumps heat the water with a "desuperheater" which means that they can take some heat off the compressor while it is running. Using this method only produces X amount of heat and the balance must be provided by the backup heater. They are saying the HP will provide X times .6 for one method and X times .4 for the other (X being the if the DHW was heated entirely by electric resistance).

The way we designed our HP (air or geo), the primary DHW is done by solar (usually around 60% annually) and the balance is provided by the HP. Only on rare occasions is the electric immersion element doing any work. To me there is no point in running a HP in the summer if there is no cooling to be done and if there is cooling, we use all the heat taken out of the air and put it into the DHW (assuming it is needed) before dumping excess outside.

I understand the issues with the utilities. They have been told that Geo is the best thing going and because the drop in electrical usage is so high from a utility point of view, they should support it with a cost reduction. The issue is that ASHPs and don't get the press that GSHPs have so the utility doesn't put them in the same boat. For the utility, it is all about not having to import expensive peak power which is quite costly. Perhaps if an argument was made that an ASHP was still much more cost effective than straight electrical they might let them in on the savings. Who knows, but I don't see an ASHP lobby anywhere.

It is true that the ASHP will use more power than the GSHP on the coldest days but on other days it uses less. We tend to look at costs on an annual basis but utilities look at peak costs.



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