Hot Water Heat Pumps

n3qikn3qik Solar Expert Posts: 741 ✭✭
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  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Hot Water Heat Pumps

    I'd be leery.
    "Makes use of ambient air temperature" - which could be highly valuable, and if it's pulling heat from heated interior space (in winter) it will cool that space requiring more heat from the source. You don't get anything for free. On the other hand, this might help with AC loads in summer.
    A standard ground-source heat pump makes use of the stable temperatures found a few feet underground. Thus you get predictable results. These "ambient' pumps would probably perform someplace between no extra heat source and a solar pre-heater.
    Just my 2¢ (CDN):p
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Water heater is in the basement, that's not heated or air conditioned. I would only use it in the summer to heat water and dehumidify the basement. In winter I would use the boiler/in-direct water heater for hot water.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,508 ✭✭✭✭✭
    Re: Hot Water Heat Pumps

    There are so many things in this world that are a challenge! My vote is to heat water the easy way like the big guy upstairs does. Of course I have not seen the system but I once heard on the radio (late at night) that he uses a flat plate collector outside the "big house" in the sun.

    If it is just for summer go open loop! Really easy and a totally homebrew project that you could do for under $500. If you are serious and want hot water all year in cold country, a drainback system is the best in my opinion.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
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  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Hot Water Heat Pumps

    I agree,, a simple DIY flat plate collector can be done for under ~$500,, and will heat a lot of water. The last system I built,, did about 50k btu in the summer,, 15k in the winter. (All while drawing 7 watts for the pump) This from ~30 sq ft. Latitude 50 N. (Just for comparisons sake,, a gallon of Propane has ~79k btu.

    Tony
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Hot Water Heat Pumps

    I like it - it fits in just fine with the "combined systems" suggestion I made on another thread.

    I would want to see one, and at this point I have no idea what the power consumption is, but just on general principles I like the idea.

    Also, it's been suggested on this forum many times to dump A/C heat somewhere, such as a swimming pool, so this might be a handy dandy way to accomplish exactly that. After all, you don't necessarily have to plumb the thing to a water heater. I suppose you could even plumb it to some pipe apparatus buried a few feet underground.

    Good idea, though of course the implementation/engineering/construction might be lacking, and naturally it'll be over-hyped.
  • FL SUNFL SUN Solar Expert Posts: 94 ✭✭✭✭
    Re: Hot Water Heat Pumps

    The idea of benefiting from sensible cooling and dehumidification is a good one, if there is a load. A basement (in the earth) has very little sensible load, but a lot of latent or moisture load. You might run a risk of mold and mildew in the basement if the walls reach dewpoint temperature with overcooling the space to get hot water. Also with low sensible load, there will be less available "heat" in the air for your heat pump to grab.

    Using some sort of desuperheater to grab waste heat from air conditioning would be a very good way to supplement any hot water heating system.

    I'm for solar thermal with some type of tankless back-up for heating water. The responses above for thermal HW I would agree with.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Some good points and ideals/suggestions.

    Was looking at other options, one is a direct-loop preheat setup. Having a spare 40 gallon water heater, I plumbed it in as a preheat storage tank when the indirect water heater was installed. Planning ahead does work, sometimes.

    Got to thinking the attic is always hotter then heck. Lets use that as a heat source.

    300 ft. of 1/2" Pex later. and 4-5 hours later we have heat !!!! Raised 40 gallons from about 65-70 to 98 deg. Not bad for the first try. Still room for improvements, but lets see how it works over the next week.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Hot Water Heat Pumps

    ken,
    good idea except is you attic hotter than heck in the winter too?
  • BB.BB. Super Moderators, Administrators Posts: 31,085 admin
    Re: Hot Water Heat Pumps

    40 gallons (8lb per gallon) and 70-98 F rise:

    40 gallons * 8lb/gal * 98-70F = 5,760 BTU heat gain in 1 day

    About equal to burning 1/10 gallon of propane? (~91,000 BTU per gallon). Of course, that is "free" heat every nice sunny day--can add up.

    For me--my attic got a whole bunch cooler once I installed my solar PV panels that covered the entire south facing roof/attic.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Hot Water Heat Pumps
    niel wrote: »
    ken,
    good idea except is you attic hotter than heck in the winter too?

    I was thinking that. Remember scenes of winter in PA, everything covered in snow ...

    If you flatten it out and fasten it to the rafters you can have a summer-only drain-back system.

    I really like the idea. I think I can adapt it to the inter-floor area of the cabin.:D
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Snow here, not !!!!!! It does get cold though. I do plan to remove it in fall/winter.

    BB
    With a indirect water heater, the boiler needs time to get to full temp. This is about 4 minutes plus. I have timed a complete cycle at 8-10 minutes.Now in winter, there will be little recover time if any. Plus attic today was 108 with outside of 80. Can't wait to the 90+ days.
    BB. wrote: »
    40 gallons (8lb per gallon) and 70-98 F rise:

    40 gallons * 8lb/gal * 98-70F = 5,760 BTU heat gain in 1 day

    -Bill

    I get 8,960 BTU. Plus we need to get 4 gallons for the boiler and loop raised from 70 to 180 deg. and the heater is rated at .82 AFUE.
  • BB.BB. Super Moderators, Administrators Posts: 31,085 admin
    Re: Hot Water Heat Pumps

    N3'

    You are just two holes and some mounts from bolting 40 sqft of solar collector on your roof. ;)

    Two-fer; More heat/hot water, cooler attic.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Already got 7 holes. One 10" x 10" vent hole under each solar panel. A panel on the roof is a option. I do not use that much hot water, so a roof mount panel is a long term plan. The cost of this was right, got less than $100.00 into this and all of the parts can be recycled to other projects.
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Hot Water Heat Pumps

    One note of caution regarding PEX. If you don't use PEX with an O2 barrier, you have to use special pump systems that are free of Cast Iron. There is something in the PEX that will destroy conventional cast pump impellers quite quickly. You can buy pumps with non-cast iron impellers,, or by O2 barrier PEX.

    Tony

    PS. Simple drain back systems are pretty easy to engineer. There are simple underground sprinkle drains that open at 1/2 psi and close at 2 psi, so once you releive the pressure,, a low point drain can be made to open automatically. I have used solenoid valves from Washing machines to serve as valves that let air in to relieve the pressure to allow a system to drain. Then you can use a simple hydronic heating float ball valve for a system vent to purge the air when it refills.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps
    icarus wrote: »
    One note of caution regarding PEX. If you don't use PEX with an O2 barrier, you have to use special pump systems that are free of Cast Iron. There is something in the PEX that will destroy conventional cast pump impellers quite quickly. You can by pumps with non-cast iron impellers,, or by O2 barrier PEX.

    Looks like more reading/research is needed.
  • BB.BB. Super Moderators, Administrators Posts: 31,085 admin
    Re: Hot Water Heat Pumps

    Here is a nice PexInfo.com site with a fair amount of detail on the various issues/recommendations associated with PEX..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,508 ✭✭✭✭✭
    Re: Hot Water Heat Pumps

    I hope they have fixed the PEX as when it was new it seemed rodents loved the taste of it.......
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Hot Water Heat Pumps

    One other PEX issue is that it lacks any ability to resist UV light,, and shouldn't be exposed to UV for more time than needed. It has been suggested to me that there will be problems in the future due to PEX lying about in wholesale yards in the sun. It will take a bunch of years to fail,, but fail it will. Where I have exposed PEX I sheath it in either pipe insulation or inside cheap poly pipe.

    My water line from the lake is PEX and a small portion is not covered by ice shield and can get sun, even under water,, so I sheathed that in Poly, just to make sure that I wouldn't have it come apart in the middle of winter!

    Tony
  • WisJimWisJim Solar Expert Posts: 59 ✭✭✭
    Re: Hot Water Heat Pumps

    My son is thinking of a heat pump water heater in his house, and looked at the AIRTAP and the Stiebel Eltron units. The AIRTAP is an add-on to an existing water heater, at around $700, and the Stiebel Eletron is a complete unit with tank, at about $3500. An idea that I remember from a book on super insulated houses many years ago, was to use a window airconditioning unit to cool the basement at night, when the cooling load was lowest, and use the basement to store the "cool", and then circulate cool air from the basement to the house during the day. Of course, it might take some work on the houses air circulation system. I think that one of these hot water heat pumps would be a good fit for this kind of use. A friend who is a full time PV installer and dealer, and also does solar water heating systems, said that if these heat pumps worked as advertised, it could be cheaper to put one in instead of solar hot water.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps
    WisJim wrote: »
    An idea that I remember from a book on super insulated houses many years ago, was to use a window airconditioning unit to cool the basement at night, when the cooling load was lowest, and use the basement to store the "cool", and then circulate cool air from the basement to the house during the day.

    Two problems with this, mold and radon gas. Both are problems in my area.

    Third day with the PEX coil. Tank was only at 89 deg. But it did rain, so that may be why. Going to be 90 on Saturday, so lets see how high I can get it.

    Non O2 barrier PEX I am using, pump is a Taco 007, it is cast housing with plastic rotor. Everyone warns about it with radiant heating system. Three things that may make my system a non issue are open loop, higher water pressure and lower temperatures.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Hot Water Heat Pumps

    For what it's worth, it's the oxygen (O2) that destroys cast-iron pumps. When used in a recirculating system, the pump is subjected to a continual influx of oxygen which causes the iron to oxidize, The oxidation is then worn off by the action of the water, and a new 'clean' surface starts to oxidize. Eventually this wears down the cast-iron parts until they are useless: cavitated. This also happens with aluminium pumps used in certain automobiles when the wrong anti-freeze is used.

    Meanwhile, I'm planning my "in ceiling" pre-heater with copper pipe because I need tight radius bends. This will probably be too expensive.:cry:
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps
    Meanwhile, I'm planning my "in ceiling" pre-heater with copper pipe because I need tight radius bends. This will probably be too expensive.:cry:

    Copy-cat:p:p

    How tight are the bends??

    Plus on copper will be shorter run for the same heat transfer.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Hot Water Heat Pumps
    n3qik wrote: »
    Copy-cat:p:p

    How tight are the bends??

    Plus on copper will be shorter run for the same heat transfer.

    I freely admit to being inspired by your genius! :p

    Basically, I'm trying to fit it between logs that support the ceiling. The space is roughly 5' x 15', and that's not a lot of room for the PEX to loop back in. Although I could possibly double it up.

    Worse, somebody here has voiced her objections to locating it directly above the wood stove where it would work best. Once again, aesthetics wins out over functionality!
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Hot Water Heat Pumps

    In our last house I used a setup very similar to the airtap. I used a small circulation pump and pumped water out of our indoor pool through the units and back to the pool. I had two 5000 btu units running in series. It worked out well in the summer. I bought the units used off eBay for about $200 each.

    In our new house I am heating the pool with a water to water geothermal unit. I can use the furnace coil as the field so basically it is the same thing on a much larger scale, a 4 ton heat pump with the heat going in the pool / hot tub and the cool side cooling the house. When I don't need house cooling I can dump the cooling to the geothermal field. The neat part is I can also circulate the geothermal field loop through the furnace without the heat pump on and somewhat cool the house with the 55F geothermal water, or at least help it to not heat up to much.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • BB.BB. Super Moderators, Administrators Posts: 31,085 admin
    Re: Hot Water Heat Pumps
    ...not a lot of room for the PEX to loop back in....

    Worse, somebody here has voiced her objections to locating it directly above the wood stove where it would work best. Once again, aesthetics wins out over functionality!

    Make it out of copper, paint it rough green or get a patina kit, and call it "Art". ;)

    And when it doesn't work, tell her you saved money by not spending $130,000 on a piece of "Wind Art" that does not work...
    A $131,000 piece of public art at Seal Point Park in San Mateo isn’t working properly and the artists who constructed it are not responding to the city’s requests to fix it, said Dennis Frank, landscape architect.

    The Wind Wheel, a giant structure sitting between two parking lots at the entrance of the park, is supposed to rotate and the city is holding back its final $10,000 payment to Manhattan-based artists Bill and Mary Buchen of Art Rail, Frank said.
    ...
    Considering the tough economic times the city is in, Councilman John Lee was bothered by the high cost of the piece.

    “I can tell you right now we wouldn’t spend that money today,” Lee said.

    And they wonder in the state capital how come they have run out of money... :grr :cry:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Hot Water Heat Pumps

    I think you should sell them on the idea of taking down the wheel that won't go 'round and replacing it with a big turbine that would help power the park! ;)

    I can't even get paid for putting up things that do work. It isn't fair! :p
  • mike95490mike95490 Solar Expert Posts: 9,042 ✭✭✭✭✭
    Re: Hot Water Heat Pumps
    BB. wrote: »
    Make it out of copper, paint it rough green or get a patina kit, and call it "Art".

    Paint is not a good thermal item. You want to give it the aged look, some salty water
    splashed on it will take the shine off, and jump start the natural patina .
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  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Update on the pre-heater setup.

    With a high temp of 83 degs and cloudy day.

    Tank is 40 gallons. I split the upper and lower temperature readings into two 20 gallon zones.

    Morning- upper = 83 degs, lower = 70 degs
    Night- upper = 98 degs, lower = 98 degs

    I did all calcs in watts to account for power the pump.

    Temp heat gain = 2150 watts
    Pump usage = 610 watts
    Total net gain = 1540 watts

    Between the pre-heated 40 gallons and the t-stat timer on the 60 indirect heater, my gas boiler only runs 5-7 min a day to reheat 60 gallons.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Hot Water Heat Pumps

    Just another update:

    Added two PT100 temp sensors to the PLC. This should reduce run time on pump.

    Below are the results. The ratio of watts used for pumping compared to heat gain watts is up !!!!:D
  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Hot Water Heat Pumps

    I just installed a Geyser 6000 heat pump water heater at my mom's house her basement is always damp and humid. it is basically an air conditioner but it dumps its heat into the water tank and i have to say it works very well and very simple to install. you would not want to run it during heating season as it does cool the building but for summer months how can you beat it. Dries out the basement and makes hot water for 20 bucks a month
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