loghomebuilder
Basic Member
Posts:119
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| 10 Dec 2017 05:55 PM |
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I recently got a great bid for a 5 ton Geo system here in NYS. Two of the options he gave us was for heating Domestic Hot Water.
The first option is for $900, he can add a "Hot Water Generator" which would simply supplement hot water with a 40 gallon hot water buffer tank. How much it would supplement? I dont know.
The second option is for $3,250, he can provide full geothermal hot water with a 50 gallon storage tank.
I'm wondering if either option is worth it?? For $3,250, it would cheaper to have a heat pump water heater installed in my basement, wouldn't it? That would put less stress on the Geo system too. I guess if the Federal tax credit gets renewed, that would reduce the cost by 30%, but still more expensive.
With a quick online search I found this unit for $1,250. http://www.supplyhouse.com/AO-Smith-HPTU-50N-50-Gallon-Voltex-Residential-Hybrid-Electric-Heat-Pump-Water-Heater?gclid=EAIaIQobChMIkf3E4_3_1wIViUwNCh3DuAKEEAQYAyABEgJrTPD_BwE
If we do a geothermal system, we will be all electric FWIW |
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docjenser
Veteran Member
Posts:1400
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| 10 Dec 2017 09:10 PM |
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You certainly would benefit from a dedicated hot water solution with an extra heat pump for $2000 more compared to a low quality heat pump water heater. There is really not more stress on the geo system, since it is a dedicated geo heat pump. Don't know your hot water usage, but you probably save about $250/year compared to the desuperheater setup.
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| www.buffalogeothermalheating.com |
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loghomebuilder
Basic Member
Posts:119
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| 11 Dec 2017 02:07 AM |
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Thanks for your input. Why do you think the $3,250 geo unit would be a better option? I thought those air-to-water units were pretty respectable?
Saving only 250/yr it may be money better spent to get more solar panels installed with the desuperheater, no?
My hot water usage is.... normal? I do a lot of manual labor so I shower at the end of the day, every day. We have an infant daughter with another on the way, been running the dish washer a lot with all the bottles...so I'd say normal for a family of 4.... |
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mtrentw
Basic Member
Posts:128
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| 11 Dec 2017 03:32 AM |
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I have geo and a HPWH in Maryland. One questionable statement you made was the geo would have less strain with HPWH. Not so fast. If the basement is conditioned, every bit of heat that you remove from the space to the water needs to be put back in the space by the geothermal.
You can run some numbers and look at assumptions. Just some quick math with made up numbers.
Assume your geothermal is running at a COP of 4.0 and your HPWH at a COP of 3.0.
If you want to heat your tank, it may take 12.0 kWh of heat.
At COP of 3.0 that used 12/3 = 4 kWh of electricity at the water heater
Of the 12 kWh, 4 came from the electricity and 8 came from the house air.
Now to replace the 8 kWh of heat in the air at 4.0 COP takes another 2 kWh of electricity.
In this example, you just bought 6 kWh of electricity to generate 12 kWh of hot water. Net is a COP of 2.0. Better than straight electric, sure.
Figure out how much water you use and run the costs. Also determine how much you can accept additional cooling and noise from HPWH in your basement.
Trent |
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docjenser
Veteran Member
Posts:1400
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| 11 Dec 2017 07:10 AM |
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Lots of recalls on the air to water units.
But sure, get more solar panels and all odds might be equal again.
OK, with one infant daughter and another on the way, your water consumption is going up exponentially (not really, but more than linear for sure...). Wait until they want long baths and taking 2 hour showers by themselves.
You water savings are likely more like $350-400/year. For $2K more, for e it would be a no brainer.
The dedicated hot water solution does not take the BTUs out of the basement, it takes it out of the loop. It is a much more elegant solution. Pays back quickly, but takes some skilled installers. Make sure they look at the pressure drop and only use one single circulation pump for the loop to serve both heat pumps. |
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| www.buffalogeothermalheating.com |
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newbostonconst
Advanced Member
Posts:736
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| 11 Dec 2017 09:31 AM |
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If you have natural gas at the house I think that is the cheapest and best solution. It is nice to still have hot water when the power goes out, unless you have a well. Anything electric you are still having to pay for the electric to be converted from some other fossil fuel and those conversion inefficacy's.
I don't remember getting much heat out of a desuperheater. I think you only get significant heat out of it in the summer only. I had one on a unit and it took me a while to figure out that the pump was froze up from the factory. To get any benefit out of it you have to do the two tank hot water heater setup. I like the KISS method. Keep-It-Simple.
Also if your geo field is under sized at all the geo hot water option is going to put extra strain on it and possibly lead to other issues. |
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| "Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins |
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teshj314
New Member
Posts:39
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| 11 Dec 2017 01:55 PM |
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An Air to Water DWHP still needs a source, be it the need to dehumidify the area it is installed in, or a warm(er) space. I recall that the original intent for this equipment was de-humidification purposes. Either way, unless the installed environment supports this application, I often see these units running on hybrid mode, or all electric mode, and the homeowner is dissatisfied.
The desuperheater method is a great option, albeit you should install a buffer tank, or preheat tank, and then a finishing tank. And like another member said earlier, the most benefit comes when the geo equipment is running in cooling mode. I often have found that the limiting factor in how much desuperheater heat is available during the process is in the capacity of the refrigerant to water heat exchanger. The last I checked on one particular manufacturer, the most gained was in the neighborhood of 7,700 to 9,000 Btuh. That's not a lot all things considered. Also, the desuperheater can be operated during heating mode, but I do believe that put's a strain on the equipment/loop, as the heat energy intended to be delivered into the space is partially diverted to the desuperheater module.
If it is in your budget, I would go with the W2W geo heat pump to deliver domestic hot water. |
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ChrisJ
Basic Member
Posts:277
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| 11 Dec 2017 03:41 PM |
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I have a DSH on my 3 ton GSHP, has been operating since late winter. I am in RI/New England. Summer time contributions to the non-powered buffer tank (40 gal) was not as much as the late winter and now early winter contributions. My finish tank is a GE Geospring 50 gal.
I am heating dominated, 1) low loop field temps during early to mid summer. 2) Less run times in summer compared to winter, even though we keep the tstat at 70*F.
My situation is that 3 tons is a bit oversized, so I welcome the stealing of 10% or so of capacity for DSH.
I wish I had the budget for a separate w to w HP with a variable speed loop pump. |
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docjenser
Veteran Member
Posts:1400
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| 14 Dec 2017 02:35 PM |
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Posted By ChrisJ on 11 Dec 2017 03:41 PM
I wish I had the budget for a separate w to w HP with a variable speed loop pump.
This is the new best way to go.
Once you have the infrastructure (ground loop, lines coming into the building, to add a small w-w heat pump is really not that much more. |
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| www.buffalogeothermalheating.com |
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docjenser
Veteran Member
Posts:1400
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| 14 Dec 2017 03:27 PM |
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Lets clarify this. DSHs in heating dominated climate have the most contribution during the heating season. Due to cold loops in the spring and summer (relatively) there is not much heat in the ground. DSH output is so minimal that manufacturers turn off the DSH pump otherwise you would transfer heat from the hot water tank via the refrigerant cycle into the ground loop.
The heat exchanger for the DSH is on the refrigerant line right when it comes out of the compressor. The DSH contributes the most in A/C mode when the loop is the warmest, or in heating mode when the loop is the coldest. Essentially when the compressor has to work the hardest, also meaning when the system runs the least efficient.
Air to water heat pumps work the best when you are in a humid and warm climate, otherwise you are taking heat out of the conditioned envelope. So you steal heat from Peter to give it to Paul to give it to Mary....... |
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| www.buffalogeothermalheating.com |
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teshj314
New Member
Posts:39
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| 14 Dec 2017 08:58 PM |
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Doc,
I'm confused. In a heating dominated climate (very little cooling/mostly dehumidifying), are you inferring that heating mode is the only opportunity to benefit from a DSH? Seeing as how the DSH is in between the compressor and the condenser (for both heating and cooling), you would be losing heating capacity at the condenser coil in heating mode because of DSH operation. Unless you upsize your GEO HP to figure in this loss, energy intended to be delivered into your house is being slightly diverted into the buffer tank.
I agree about the A2WHP water heater, they should never be installed in a space that is conditioned. The design was intended to dehumidify basement/mechanical spaces, or where their is warmth and dampness.
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loghomebuilder
Basic Member
Posts:119
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| 15 Dec 2017 03:41 PM |
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I am near Rochester, I see you are near Buffalo, so almost identical to what you are used to. |
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geome
Advanced Member
Posts:987
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| 15 Dec 2017 04:33 PM |
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Posted By loghomebuilder on 15 Dec 2017 03:41 PM
I am near Rochester, I see you are near Buffalo, so almost identical to what you are used to.
Read Doc's informative posts in other threads. He knows his stuff. If I lived an hour or so away from him, I'd happily pay a travel premium to get a system installed by Doc, (provided he is willing to travel.) |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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ChrisJ
Basic Member
Posts:277
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| 15 Dec 2017 06:22 PM |
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Posted By geome on 15 Dec 2017 04:33 PM
Posted By loghomebuilder on 15 Dec 2017 03:41 PM
I am near Rochester, I see you are near Buffalo, so almost identical to what you are used to.
Read Doc's informative posts in other threads. He knows his stuff. If I lived an hour or so away from him, I'd happily pay a travel premium to get a system installed by Doc, (provided he is willing to travel.)
Aces Energy is in Rochester area he has worked with Doc I beleive. |
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docjenser
Veteran Member
Posts:1400
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| 18 Dec 2017 07:56 AM |
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Posted By teshj314 on 14 Dec 2017 08:58 PM
Doc,
I'm confused. In a heating dominated climate (very little cooling/mostly dehumidifying), are you inferring that heating mode is the only opportunity to benefit from a DSH? Seeing as how the DSH is in between the compressor and the condenser (for both heating and cooling), you would be losing heating capacity at the condenser coil in heating mode because of DSH operation. Unless you upsize your GEO HP to figure in this loss, energy intended to be delivered into your house is being slightly diverted into the buffer tank.
Yes, heating mode is the main source for the DSH performance in heat dominated climate, unless your loop temps and run time goes up in the summer due to high external and internal gains.
Yes, you steal heat from the HP capacity, about roughly 10%. DSH contribution in cooling mode is almost negligible, your compressor discharge temperatures will not be very high due to cold ground loops. DSH pump does not turn on until the loop is 45-50F, or more. Plus your run time is not very much either.
7 series is much better in cooling mode, since it runs much longer.
Still would go with a dedicated small w-w heat pump if this is my house (and budget).
ACES, Geotherm (Jesse Cook), VanHee, Moravec Geothermal and Dailey Electric are all A-Team installers in Rochester.
I'd be happy to help and advise, but you are really better served by someone close to you. They are all pro installers, you can't go wrong. |
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| www.buffalogeothermalheating.com |
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loghomebuilder
Basic Member
Posts:119
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| 20 Dec 2017 07:36 PM |
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Yes, Geotherm is who I'm talking to at the moment. Is there a water to water heat pump for domestic hot water I could ask them about? |
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loghomebuilder
Basic Member
Posts:119
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| 20 Dec 2017 07:54 PM |
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Maybe I should start a new thread but, does anyone in the know, know if the new tax bill has a provision to bring back the 30% tax credit for Geo? Because it was rumored to be in there, just want to see if it made it in. That would make this a no brainier. |
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loghomebuilder
Basic Member
Posts:119
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| 20 Dec 2017 07:54 PM |
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Maybe I should start a new thread but, does anyone in the know, know if the new tax bill has a provision to bring back the 30% tax credit for Geo? Because it was rumored to be in there, just want to see if it made it in. That would make this a no brainier. |
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Dana1
Senior Member
Posts:6991
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| 20 Dec 2017 09:34 PM |
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Posted By loghomebuilder on 20 Dec 2017 07:54 PM
Maybe I should start a new thread but, does anyone in the know, know if the new tax bill has a provision to bring back the 30% tax credit for Geo? Because it was rumored to be in there, just want to see if it made it in. That would make this a no brainier.
As of a week ago Bloomberg was reporting:
"Tax credits for fuel cells, small wind and geothermal heat pumps, which were left out of that 2015 legislation, will again be omitted. Thune said those credits may be dealt with in a subsequent “tax extenders” package. But it’s unclear that Congress will have the time or inclination to pass that legislation."
https://www.bloomberg.com/news/articles/2017-12-14/deal-reached-to-shield-renewables-from-tax-change-thune-says
But the way this thing got run through the sausage grinder behind closed doors, who really knows? (Its' not as if even those who voted for it really read the 1000 odd pages.) |
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icfbound
Basic Member
Posts:120
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| 21 Dec 2017 03:12 PM |
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Posted By Dana1 on 20 Dec 2017 09:34 PM
But the way this thing got run through the sausage grinder behind closed doors, who really knows? (Its' not as if even those who voted for it really read the 1000 odd pages.)
That is true. This tax bill was done for the Republican fund donors and benefit of the well off. Hint...if the wall street stock market is doing well the less well off are paying for it... |
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