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Old 04-21-2011, 11:31 PM   #1
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Heat from domestic water heater


My computer room in the basement needs supplimental heat.
I heat with a forced air, natural gas furnace. The room in question has a duct and a cold air return, but the room doesn't warm up enough because the thermostat is on the main floor.
I have a h/e natural gas water heater and I'm wondering if I can use this to supply supplemental heat in my room.
I would use a standard baseboard heater with the flow controlled by a thermostat.
Is it possible to use a domestic water heater for space heating?

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Old 04-22-2011, 06:57 AM   #2
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Heat from domestic water heater


Most water heaters aren't approved for space heating. A small electric baseboard heater would work better.

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Old 04-22-2011, 08:03 AM   #3
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Heat from domestic water heater


Close the hot air registers elsewhere in the house partially so more warm air goes to the cooler room. But you may not close off too many registers too much or you may overload the furnace blower.
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Old 04-22-2011, 08:51 AM   #4
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Heat from domestic water heater


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Most water heaters aren't approved for space heating. A small electric baseboard heater would work better.
Thanks for your reply! An electric heater would be my obvious answer as the service panel is located in this same room.
I would like to avoid using electricity because our electrical rates are going to be going out of sight, in the near future.
Natural gas rates are reasonable and I would like to take advantage of this, if possible.
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Old 04-22-2011, 09:02 AM   #5
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Heat from domestic water heater


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Close the hot air registers elsewhere in the house partially so more warm air goes to the cooler room. But you may not close off too many registers too much or you may overload the furnace blower.
I don't have a balance problem, per say. When the furnace comes on, the room gets lots of heat.
Its the heat loss after the furnace shuts off that that is greater, that is the problem. This is caused because heat rises up, through the flooring into room above, where the thermostat is located.
Zone controlled heating would be ideal, but this is difficult to achieve with ducted, forced air heating.
A hot water heater would be easy to install as there are hot and cold water lines in the near vacinity.
I visualize tapping into the hot-water, a thermostat controlled pump that would move the hot water into the heater.
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Old 04-22-2011, 09:10 AM   #6
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Heat from domestic water heater


Is the space insulated?
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Old 04-22-2011, 09:12 AM   #7
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Heat from domestic water heater


You would have to run additional piping to use the water heater, so that hot water wouldn't be drawn from the cold water pipes when someone tapped cold water.

Using electric baseboard heat, would be that expensive, since it would only be supplemental heat, and not the sole source of heat.
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Old 04-22-2011, 09:24 AM   #8
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Heat from domestic water heater


I would use ( and use in my house) an oil filled radiator style 1500 watt heater. Has 3 settings, 750/1000/1500 watts. The complexity of putting in a circ pump, controls etc is a lot more than you can imagine and is expensive. Continuos flow thru the water heater will greatly shorten its life from erosion. Robbing Peter to pay Paul. The elec heater is the simplest way to go and requires no maintenance and causes no additional problems unlike using the water heater idea.
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Old 04-22-2011, 07:24 PM   #9
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Heat from domestic water heater


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Is the space insulated?
It has r12 foundation blanket on the outside walls. When the sunshines into the windows, there is no call for heat from the thermostat. The room cools at a greater rate than the main floor because there is no solar boost below grade.
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Old 04-22-2011, 07:37 PM   #10
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Heat from domestic water heater


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You would have to run additional piping to use the water heater, so that hot water wouldn't be drawn from the cold water pipes when someone tapped cold water.

Using electric baseboard heat, would be that expensive, since it would only be supplemental heat, and not the sole source of heat.
The present hot water tank is situated about 10 feet from where I would install the heater and plumbing isn't a problem for me, as I have been doing this for years.
Do you think that I would need to run both hot and cold water lines? I'm thinking that I could tap into the hot water, anywhere, but as you say, hot water could be drawn into the cold water line, so do you think a cold water line back to the tank would be all thats required?
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Old 04-22-2011, 07:53 PM   #11
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Heat from domestic water heater


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I would use ( and use in my house) an oil filled radiator style 1500 watt heater. Has 3 settings, 750/1000/1500 watts. The complexity of putting in a circ pump, controls etc is a lot more than you can imagine and is expensive. Continuos flow thru the water heater will greatly shorten its life from erosion. Robbing Peter to pay Paul. The elec heater is the simplest way to go and requires no maintenance and causes no additional problems unlike using the water heater idea.
Thanks yuri, I already have a 120 volt thermostat and most of the plumbing fittings kicking around. Even a 120 volt operated water valve. I'm a retired electrician so the control thing isn't a problem.
I would have to buy a base board heater and a couple lengths of copper pipe. And of course, I would have no labour costs.
What I'm unsure of is whether the domestic, gas water heater is capable of doing this job. Another question comes to my mind. The heater is a rental unit and would I cause extra wear and tear on the unit, and even perhaps be in contravention of the contract?
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Old 04-22-2011, 08:15 PM   #12
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Heat from domestic water heater


Quote:
Originally Posted by Wildie View Post
The present hot water tank is situated about 10 feet from where I would install the heater and plumbing isn't a problem for me, as I have been doing this for years.
Do you think that I would need to run both hot and cold water lines? I'm thinking that I could tap into the hot water, anywhere, but as you say, hot water could be drawn into the cold water line, so do you think a cold water line back to the tank would be all thats required?
Around here it is against code to heat with a domestic water heater.

You would need a circ pump,circ pump relay, zone valve, and a t-stat if you were going to attempt it.

And what about the water that sits in the pipes when you don't need heat. It gets stagnant, then when you do need heat it gets pushed into you system that you cook with and clean with.

I would't even think about it.....
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Old 04-22-2011, 08:22 PM   #13
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Heat from domestic water heater


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Around here it is against code to heat with a domestic water heater.

You would need a circ pump,circ pump relay, zone valve, and a t-stat if you were going to attempt it.

And what about the water that sits in the pipes when you don't need heat. It gets stagnant, then when you do need heat it gets pushed into you system that you cook with and clean with.

I would't even think about it.....
When you put it that way, I can see your point. Especially, since I do have a 1500 watt baseboard heater in the garage.
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Old 04-23-2011, 03:11 AM   #14
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Heat from domestic water heater


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Originally Posted by Wildie View Post
The present hot water tank is situated about 10 feet from where I would install the heater and plumbing isn't a problem for me, as I have been doing this for years.
Do you think that I would need to run both hot and cold water lines? I'm thinking that I could tap into the hot water, anywhere, but as you say, hot water could be drawn into the cold water line, so do you think a cold water line back to the tank would be all thats required?
You would need to run the return line into the bottom of the tan k where the drain is. And would still need to install either a spring check, or a bronze flow check, or use a bronze circ that is IFC, to prevent thermal siphoning.

Then after installing that, you will probably need to raise the water heaters temp to get the baseboard hot enough to get any heat from the baseboard.
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Old 04-23-2011, 06:33 AM   #15
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Heat from domestic water heater


The circ pump will probably flow the water too fast and at 35,000 BTUs it may be not enough to keep up with the pump. I worked in a hospital with LOTS of DHW domestic h/w recirc lines wearing out and the flow will wear out the tank soon and if its a rental they will void the contract and charge you for a new one.

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Last edited by yuri; 04-23-2011 at 06:37 AM.
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