Quote:
Originally Posted by RodFarlee  Well, actually, it's just the total heat loss.
Evaporation is small, when the R-18 closed cell foam insulated cover is closed. It seals pretty well. For example, my hot tub loses about 40 gallons/year to evaporation.
heat of vaporization: 970 BTU/lb * 8.3 lb/gal / 3413 BTU/kWh = 2.36 kWh/gal
40 gallons * 2.36 kWh/gal * $0.062/kWh = $5.85/year to evaporation
So in my case, it's roughly 4% evaporation and 96% conductive heat loss on a year-round basis. Mine is closed 99+% of the time. On the other hand, when it's open, nearly all the heat loss is evaporation.
All this is just ballpark/back of the envelope. A watthourmeter is the real way to know where you're power's going. You can buy consumer versions of these now. They're an inductive ammeter that clamps around either the hot or neutral lead (not both, they cancel) and integrator. So you have to open things up to use it, and most consumers shouldn't do that. |
You have a hot tub.... and you have not invited me over? And I thought we were friends.
Like I said, evap. is a small portion and is difficult to actually calculate in that water temp, humidity and surface area add to the cover on cover off part, but heck, probably only you and I care about stuff like that, so never mind.
So, what's that background that give you this knowledge my well educated friend who never invites me over to hot tub?