hot tub heat loss
hot tub heat loss
(OP)
hello, i was wondering if anyone would like to offer their input on hot tub heater control. assuming the hot tub is used every day and heating with a resistance heater would it be more cost effective to leave the heater on all the time so the users can hop in whenever and have the water ready to go? or to have the heater on only when it is used - just preheat it then hop in?
and if you can direct me to proper formulas i would greatly appreciate it.
thanks
and if you can direct me to proper formulas i would greatly appreciate it.
thanks





RE: hot tub heat loss
Besides conduction, convection, evaporation, radiation, and Joule heating?
Note that the answer depends heavily on factors you have not presented, i.e., insulation, temperature, duty cycle, etc.
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RE: hot tub heat loss
Thanks
RE: hot tub heat loss
http://web.mit.edu/lienhard/www/ahtt.html
Just bear in mind that Lienhard is a bit abstruse. Wikipedia articles on heat transfer can get you a long ways.
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RE: hot tub heat loss
RE: hot tub heat loss
RE: hot tub heat loss
Say the heat loss is L for 102°F and 65°F ambient. Then every day of heating incurs the same loss L. However, if you allow the tub to cool, each additional day results in a lower temperature, and hence, a lower L. So, for say, 20 days, with heat you incur 20L of heat input. but for 20 days of cooling, the heat loss is <<20L, which is what you have to make up to heat back to temperature.
So, that's why shutting off the heat is more economical.
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RE: hot tub heat loss
thanks
RE: hot tub heat loss
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RE: hot tub heat loss
Wow... That's smaller than the main burner on my stovetop.
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RE: hot tub heat loss
There is convection, conduction, radiation, evaporation and air velocity to consider.
RE: hot tub heat loss
You can mess around with some maths that you clearly have no prior experience with, making random assumptions for parameters that you have no feel for and getting results you can't verify...
...or you can casually observe the steady state heater cycle. If the heater on-time per day (leaving it on) exceeds the heat up and use time (when turned off), then you have your solution.
WIRT*, is the first time you go away for a week on holiday and leave it on will be the last time you leave it on overnight.
* "What I really think" - you heard it here first.