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Question about a heat source for a dehumidifier system

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Novice Bob

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I'm building a dehumidifier system for my upright piano. The design is not my own, but it looks quite sound. The idea of the system is to use temperature to control RH. The system uses humidistat to control a heat source used to produce heat. The system will be put inside the piano, which is about 20 cu. ft (5' x 4' x 1'). The only thing I don't like much about the design is that it uses 100W incandescent light bulbs as a heat source. Even the bulbs are covers with a metal sheet which acts as a heat shield, I'm still concerned about fire hazard.

I need help with my questions as following:
1) Does the metal sheet provide enough safty for the light bulbs? The metal sheet is not touching the bulbs. There's clearance about 2" between the bulbs and the metal sheet, and about 2" between metal sheet and the piano boards. Am I thinking too much about fire hazard?
2) What are the alternate heat sources I should consider? One I have in mind is PTC heating element 110VAC 100W. Its design seems compact and safe. Any one can comment on this usage? What is the normal surface temperature of the PTC heating element 110VAC 100W? The system should switch off after it brings temperature up to certain level. I don't have the exact number, but my guess is 2-3 celcius on verage , and 4-5 celcius at most.

Thanks in advance for all inputs.


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Most Helpful Member
Welcome to ETO!
I think a safer and more evenly distributed heat source would be a couple of tubular heaters such as these (which include safety cut-outs). 60W each might prove too much, but you could connect them in series to reduce the heat output or use a simple lamp-dimmer as a heat control.

dr pepper

Well-Known Member
Most Helpful Member
Your right to be concerned, it looks like the purpose of the metal plate is to spread the heat out, so instead of a very hot point source you have a more even spread, which will most likely be more effective and safer.
A heat source that is lower in temp and more spread out sounds like a better idea, jp's idea pretty much covers that one.
I've used trace heating to keep industrial pumps from freezing, plastic ones have been good, but the metal ones for me have proved unreliable.
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