water heating plan


  #1  
Old 07-25-04, 07:02 PM
saltytom
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water heating plan

Hi,

I have sort of an unusual question. I have a house with an aging electric hot water tank. I am thinking about replacing it with a gas tankless setup. I also have a large aquarium that I possibly want to heat with the water heater. I would run a heat exchanger on the tank to heat the water with the hot water from the water heater. What would be the best and most efficent way to do this? I at first was thinking of a simple loop through the exhcanger and then teed to all the faucets and back to the water heater. But that would run heat through the tank when ever some on took a shower which probably would heat it up too much.

Can this be done with a tankless or would I need a tank? How would you set this up?

Any help on this would be great

Thanks

Tom
 
  #2  
Old 07-26-04, 01:11 PM
KField's Avatar
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To have good control over the temperature of the aquarium you will need to control circulation on one side of the heat exchanger. If you incorporated the heat exchanger into a circulating loop for the house, you could have hot water at all faucets when you needed it and also have constant flow through the heat exchanger. You would need to insulate the hot water pipes to prevent a lot of heat loss. Then on the aquarium side all you would need would be a small pump that was controlled by a thermostat to circulate tank water through the other side of the heat exchanger. I think a good exchanger for that would be a brazed plate. We use one for domestic that we get from the boiler manufacturer. There may be others you can use too. As for the tankless gas hot water heater, I'm, not familiar with them.

Good luck and don't cook the fish.

Ken
 
  #3  
Old 08-15-04, 04:52 PM
Homer Simpson
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Pipe Dreams

Tom,

A tankless W/H take about 100,000 BTU/H in gas imput. So you have the
gas supply available? They are usually direct vent through an exterior wall.
Is that possible? You mean Instant Tankless Hot Water Heater? Right?

The way they work is that there is a pressure drop in the hot water line (you
turn the faucet on). The hot water issues out of the unit to your faucet.
You turn the faucet off, the pressure in the line builds up and turns the W/H
off. There is no reservoir of hot water to draw from. There has to be flow,
why am I alway talking about flow, to heat your fish tank through the old
w/h.. Hot water has to flow into the old water heater and the only time that
happens is when you turn on a faucet. So, you get 50 gal of cold water
through the faucet before you get any hot water( you have to displace the
cold water in the tank before you get hot water out). It can't be done. but
the last time I said can't, my wife proved me wrong, much to her delight.
Say goodbye, Homer. Goodbye
PS: I am assuming
You mean Instant tankless W/H and not a tankless W/H in a boiler.
That you are going to disconnect the electrical and use the old tank as a
storage tank.
You weren't thinking of using the Instant Tankless W/H as a supplemental heat source for the old Tank, if so the above reasoning applies.
 
 

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