Wiring HWT Elements together


Old 01-07-05, 07:32 AM
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Smile Wiring HWT Elements together

I want to re-post this in case it gets too far down and lost in the pile of posts.

I wonder if anyone can help with this. I am using a 40 gallon electric hot water tank to heat my garage floor. I have a 20 x 36', 6" thick concrete slab underlain with 2" of styrofoam insulation, and a total of approximately 750' of 1/2" pipe in the floor. The HWT is wired to a 30 amp breaker using 10/2 wire. Circulation is via a low volume boost pump (GPM unknown at this time). The problem is that the HWT cannot keep up to the loss of heat to the floor and the water does not get much warmer than lukewarm. As a result, the HWT top element goes continuously without the bottom element ever kicking in (the water doesn't warm up enough to flip between the elements). Even after eight 24 hour days of continuous running, the water does not warm up. As a result, the garage does not warm up enough for the in-line thermostat to be of any use. The only way I can get any heat out of the floor is to put the pump on a timer that circulates the water/glycol for 1/2 hour every three hours. This enables the HWT to "catch up" and gets the garage temperature up to 14 degrees celcius, regardless of the outside temperature.

A friend of mine has a garage that is only 200 square feet larger than mine running the same type of heating system. He is able to heat his garage to the point where the in-line thermostat will cut in and out and vary the flow of heated water through the floor (the way the system is supposed to work) and his HWT is able to keep up without continuous heating. The way he got around this is that he got an electrician to wire his HWT so that both elements heat at the same time and are controlled by one thermostat. Does anyone know how to do this or where I can get a schematic to show me what the proper wiring is? I can't get the info from my friend because he and his wife are travelling for the next three months and he lives on the other side of the country. Thanks in advance!
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Old 01-08-05, 12:37 PM
Join Date: Sep 2000
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I don't really understand how cycling the pumps helps any. You still can't get any more or less heat than the wattage of the element. It would seem to me like hot water circulated part the time or warm water circulated all the time would have the same net effect. You would however save the cost of running the pumps all the time.

You can certainly wire the water heater so that both elements will come on at the same time. All you have to do is separate the two thermostats (remove the wires that connect them) and connect a second power supply directly to the bottom thermostat. However, you'll need two double-pole 30-amp breakers and two runs of 10/2, rather than the one of each you have now. It should be fairly easy.
Old 01-09-05, 07:43 AM
Join Date: Sep 2004
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Just a thought...

In the past I had wondered about this type of system for myself. My thoughts wandered more toward a hot water heating system for a home, operating and maintenance costs, etc. I always figured if a fellow wanted to change the system over from gas fired to electric heat-or anything else- it would be easy enough since the pipe was all in place.

Questions I would have is this: does your system have an air bleeding point or does it even need it to help with circulation? Is it possible the water/coolant mix impedes the heating efforts?

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