Split by moderator from HERE. Please start your own thread with your own questions. Thanks, jblizzle.
I'm going through this now. I have a 400 gallon in ground hot tub. I configured my hot tub so that is can run with the pool or by itself. I bought a 5.5 kw spa-pak from rheem. According to mfg specs the hot tub should heat up 5 degrees every hour. Starting off my hot tub is at 70 degrees. The first two hours the hot tub increases 5 degrees an hour as stated in the mfg specs. From there it tapers off. The third hour it increases 2 degrees, the 4th hour another 2 degrees. The next 6 hours it only increased to 2 hours.
1st hour 70 - 75
2nd hour 75-80
3rd hour 80 - 82
4th hour 82-84
The temperature only went up to 2 degrees over the next 6 hours to 86. A couple of factors I want to mention.
1. The heater is located near the pump which is about 15 feet from the hot tub.
2. Outside temperature in south Louisiana at the time was 74 degrees
3. I do not have a cover
4. It is an in-ground hot tub with over flow. However, I'm able to isolate the pump to just the spa when I run the heater.
I'm currently testing with a makeshift cover and will post the results.
I'm thinking that the distance from the heater to the hot tub is reason for most of heat loss but I'm still in the investigating mode.