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  1. #1
    Join Date
    Sep 2009
    Posts
    11

    Hot water generater

    I have not done enough research yet nor do I completely understand the efficiency gains for a second unpowered water heater tank. The manuel for the HTV 048 says duel tank is reccomended/most efficient. The question is how much more efficient? I only have one elec. 80 gal tank now should I wait to hook up the HWG until I get another tank?

  2. #2
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    Hard to say, but most manufacturers recommend it. The main reason is to prevent therm o siphoning from the water heater back to the unit. Personally I would recommend it.

  3. #3
    Join Date
    Jan 2004
    Location
    Sanborn, IA
    Posts
    191
    in my mind if you use 1 water heater you limit the work your ground source can do. your water heater will keep a minimum temp of water on its own (say 130 degrees) - and your ground source will boost that to it's limit (say 140 degrees). if you have 2 water heaters your first tank has a minimum temp of the entering water temp (say 55 degrees). your ground source can do a lot more with 55 degree water boosting it to 140.

    that is why i do it. i've even done 2 50 gallon water heaters and kept the minimum temp on the first tank at 90 degrees - this ensures that the minimum temp that will enter the second tank is 90 and the second tank has less work to do. this is helpfull if you have a large family needing more than a 50.

    my opinions.

  4. #4
    Quote Originally Posted by aaronforprez View Post
    that is why i do it. i've even done 2 50 gallon water heaters and kept the minimum temp on the first tank at 90 degrees - this ensures that the minimum temp that will enter the second tank is 90 and the second tank has less work to do. this is helpfull if you have a large family needing more than a 50.

    my opinions.
    I can see the benefit for a large family with 50+ gal needs. But, is there any effieciency benefits to this?

  5. #5
    Join Date
    Jan 2004
    Location
    Sanborn, IA
    Posts
    191
    Quote Originally Posted by ft_hvac-talk View Post
    I can see the benefit for a large family with 50+ gal needs. But, is there any effieciency benefits to this?
    the efficiency benefits are that your ground source heat pump has a chance to do some real work if you use 2 tanks. it can heat the water for 25% of the cost as your electric water heater can. having your ground source do more work is the benefit.

    in a perfect world you come home from work and your first tank is full of nice hot water your heat pump generated from air conditioning your house while you were gone. you take a shower and the water entering your second tank is already hot and your second tank doesn't need to heat the cold water.

  6. #6
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    238
    I have a single 50gal hooked up to my desuperheater. My bottom element is off and the top is on a remote control. In the winter my three ton Envision is able to produce all of my hot water needs for two to three months. During this time my water is completely off. During the summer and other times I only turn it on when i need hot water. The summer months it will give me warm water enough for a quick shower only opening the hot water valve. Keep in mind I am single.

    If you don't want to use up your real estate with another water heater. consider a tankless. There is a 30% tax credit (limited to $1500) for installing a gas tankless. You could include all cost of installing propane tank and lines. Another option would be to connect your 80 to the desuperheater(HWG) and buy the smallest tank you can get with at lease 4500watt element(s). Remember you preheat tank only helps out the main heating tank only when you are using water. At all other times it will waste just as much energy in standby losses as normal.

    Personally if I had a family I would go with a Rinnai tankless propane. But being single I cannot make the economics work out.

  7. #7
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257
    Have you seen the new heat pump water heater from GE. I ordered one and should have it in November. My largest cost even having a desuperheater is my Domestic Hot Water. In my GTHP I have a two 50 gal. water heater setup but the HP just doesnt run enough through half the year and my DHW is about 10Kw per day on average. The DHW is metered. The Heat Pump water heater from GE is the first I saw that also gets the rebate and for me it will help with humidity in the basement. I will leave both water heaters and add this one as a third. Google "GE Heat Pump Water Heater".

    Pretty neat unit.

    I probably should add for our PA PPL Electric customers that the water heater has a $300 rebate from the electric company besides the Federal rebate.

    John
    Last edited by jongig; 09-28-2009 at 09:21 AM. Reason: adding

  8. #8
    Join Date
    Sep 2009
    Posts
    11

    Hot water

    GE unit not out until Nov. Should I stay with old 80 gal eletric heater and wait? Should I install new 80 gal electric water heater to HWG on the unit? Should I wait to hook up the HWG?

    Man I am confused even more now. Thank god for copenhagen!

    Mike

  9. #9
    Join Date
    Sep 2009
    Posts
    11

    GE heat pump water heater

    During the winter won't this thing be "robbing peter to pay paul" so to speak?

    Summer - takes heat from basement to heat water = good?
    spring/fall - not a lot of heating or cooling = ?
    winter- taking heat from basement to heat water = bad?

    net result - I have no idea

  10. #10
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257
    Quote Originally Posted by mikeiss View Post
    During the winter won't this thing be "robbing peter to pay paul" so to speak?

    Summer - takes heat from basement to heat water = good?
    spring/fall - not a lot of heating or cooling = ?
    winter- taking heat from basement to heat water = bad?

    net result - I have no idea
    Probably depends on your situation. My basement is a zone on my GTHP and is insulated. Problem I have in the summer is the basement has more moisture than I 'd like so having the Hot water HP will be good as it will double as a dehumidifier. In the winter to some degree you're right but I get most of my DHW from the GTHP in the winter anyway so this will mostly be working about 6-8 months of the year and I don't see it making a difference at least for me. My basement is rather large anyway with 10 ft height and 2,400 Sq-ft.

    It really seems like a great product.

    I will make my purchase based on long term needs and overall costs and you should decide on what the house needs are and work from there. You may not know your costs for DHW and for me the cost in cash is over $30 per month and I could justify the DHW-HP. Maybe your situation is different. I have 3 people showering every day and we all seem to have trouble getting out of the shower.

    john

  11. #11
    Join Date
    Sep 2009
    Posts
    11

    hot water

    I guess I should maybe hold off on hooking up the hot water generator until I or my installer has a better idea of what to do

  12. #12
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    238
    Go ahead and hook it up can't hurt as along as you lower the temperature setting of the lower element to 90 or disconnect it. Also look into a Drain water heat exchanger. I bought the Renewability but have yet to find a plumber who will give me a reasomable quote much less a reasonable one for installing it. Waterfurnace also has a small gs unit that can be used for domestic water heating.

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