'99 Hot Springs Sovereign, running 110V. Got the new replacement Watkins heater (PDR, 4kw version), piece of cake to install. I started with 47 degree water and after 6 hours I'm only at 55 degrees. What should my expectations be here. Based on some other old posts I was expecting about 4 degrees an hour, but maybe it will pick up steam once it's not so cold?

110 volt operation?

Wait 4 times longer.

24 hours to see what you want/need. Of course this is also influenced by how well your spa cover insulates, environmental factors, full supply voltage/ampacity at the spa, etc.

Remember you're heating a spa with a blow dryer at 110.

After 24 hours I'm at 76 degrees. So it's working, but only at a little over 1 degree an hour. The pace seem to be going slightly faster as the water gets warmer - it was probably working very hard to get past those first frigid degrees. I'll post final time once I get to 101, for anyone researching this in the future.

if you have a good cover and the cabinet is insulated well, you should have already met temp. I would do a voltage check across both terminals of the heater and see if you got juice there.

I finally reached temp, after 52 hours. So, 54 degrees took 52 hours. I'd love to check the voltage, as suggested, but I don't have the tools and have absolutely no knowledge in that area. I'l check with some friends and see if they can help with that.

Assuming I don't do anything, now that I'm at temp how do I know if I have an issue? What are the cons of doing nothing?

Sounds right, but why a 4 KW and not a 6KW PDR?

Too late now, if I should have ordered the 6. I bought on eBay, with limited knowledge - http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %3AIT&rd=1

Would 4 rather than 6 explain the slow heat up?

The 6 KW heater would have heated faster, especially since you are using only 120V. Figure a 4KW heater (at 240V) is only about 1100 watts (1.1 kw) at 120V. Not much at all. IMHO I think that only about 1 degree an hour is rediculous even for a 120V heater setup. I've had several tubs run off that voltage and never had one take more than overnight to heat. I usually got between 4 and 6 degrees an hour (depending on tub size) with 120V. The 240 was much faster at between 12 and 18 degrees an hour depending on tub size. Granted, I don't have experience with your particular tub, but I do believe one degree an hour is a bit slow. Even my 450 gallon tub I had once that was 120V heated faster without a cabinet or cover.

I'm going to get new filters and see if that helps. I think I should do that anyway, since I'm not sure how old they are. I suspect I could have a flow problem (would that effect heating?) since the "moto" jet isn't working. My plan, once I have the new filters, is to let the tub cool down 10-15 degrees and then see how fast it recovers those degrees. If that doesn't help, I guess I'll be back for more advice, or maybe I'll explore the previous advice on measuring the voltage some more - if the tool isn't too much.

I really don't see low flow being the culprit on this one. Generally HS spas (from what I know of them) are finiky with low flow, often reporting a fault or error or some other sort of wierd behavior. If this is considered "normal" heat up time for your spa, I'll just chalk it up to one more thing I've learned about HS spas. I'm still thinking that your heater isn't getting the proper voltage, or not running at all. HS spas aparently thrive on the notion that they are so well insulated, even just the running of the circulation pump will heat the spa, and that may be the only thing working in your situation.