Heating question?

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Well-Known Member
Jun 9, 2006
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Leiper's Fork, TN
The sump for my wet pad is 30-40 gallons. The GH is only 8X14

I'm wondering if I would get more efficient heating (and humidification) by adding a submersible heater to the sump instead of running the electric space heaters that I'm presently using.

Any thermal engineers out there?
need a little more info to be able to picture you setup. Is your wet pad pulling air in from the outside? I shut my wet wall down in the winter and actually cover outside face of it up with plastic to keep the cold air out and the heated air in. I might have just figure out what you're thinking. You're running your wet pad, you just want to water reservoir as a heat sink. Correct? It could work. You would have to calculate the energy cost for both systems, that could be a factor. You could end up with too much humidity and introduce a disease problem. I know of an fellow grower that used a water heater to heat his GH. The water heater was outside of the GH and ran steel piping, zig zaged a long the GH walls. This was a closed system with a water pump somewhere in the piping to move the water. It worked great but no humidity from it.
Presently I am not pulling any outside air as you are. Its just recirulating interior air. The GH is pretty leaky though. I try to keep the humidity up to 70 - 80 percent, and it still needs to kick in the fogger when the dry north winds are blowing, otherwise it maintains a pretty stable 85% without the fogger when weather is coming up from the south. I really don't think you can have too much humidity for rain forest plants (maybe parvi's??), but my sangii would probably crater without it, and the more I increase it the crazier my bulbos go too.

Intuitively I think it should be more efficient because of the thermal mass issue as you're guessing too. But I'm wondering (without having to learn the math) if its a big enough difference to warrant spending the bucks on a submersible heater.
It takes a certain amount of energy to keep the greenhouse and its contents at a certain temperature. I would think that whether you heat the air or the water really makes no significant difference in the energy needed.

However, I suppose that air, having little mass, will heat and cool quickly, whereas having a large mass of heated water would keep the overall temperature more stable. But, I doubt that the volume you're talking about will have a sufficient amount of mass to make a significant difference.

You will certainly get better humidification, but do you want to boost it higher than the current levels?
That is also corect Ray. I could modify it by adding that wet air holds heat better than dry air. It may make more sense to look at the problem from an insulation and total energy lost standpoint than from focusing on the energy inputs.

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