Heat Pump for Spa in FL, experiences or experts?

BlueWave8

Well-known member
Mar 28, 2011
107
Space Coast, Florida
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
I'm in the planning phase of a pool/spa build on the east coast in FL. Pool and spa will be around 12,000 gal total. Spa will be "average" size, 6' circle or square. I'm trying to decide on what equipment I will choose for spa heat.

Efficiency is very important to me, so I am thinking hard about what a spa heat experience will be like with a heat pump. I'd be looking at the new AquaCal variable speed. Or another variable speed if someone is aware of one.

Comparing this, of course, to a propane heater. I don't have any propane at my house, so I would have to purchase and bury a tank somewhere, making initial cost of propane the same or more expensive than the variable speed AquaCal. Then there's the hassle of shopping for cheap propane at the right time and monitoring tank level...

I've never heated my pool in FL, so I know that would be an added benefit of the heat pump, but not something that is really important to me.

I also plan to install solar photovoltaic in the next couple years, so an electric form of heating would essentially become free.

Previously, I have had spas with gas heat, so I'm used to having a 102 degree spa in about 30 minutes, regardless of the temperature outside. I know I won't have that with a ~130k BTU heat pump, but I also know we are in an ideal climate for heat pumps most of the year with our FL humidity and temperatures, as 80/80/80 is actually lower than what we have for most of the year.

It looks like a newer heat pump might take about an hour to get a spa to 100 degrees most of the year in my zipcode in FL. I can deal with that.

What I'd like to try to get an idea of, is how bad will that be in January-March? How long would heating take, and what would my maximum attainable temperature even be?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,655
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
I am not sure what size heater you had before but a 130k HP will take about 3x longer to heat up the spa than a 400k NG heater. The problem with HP is that they don't come in very large sizes. I don't like waiting the 30 min to heat up my spa so waiting1.5 hours is a non-starter for me.

I am not sure how many gallons your spa will be but for a 750 gallon spa, 130k heater will raise the temperature about 20 degrees per hour (neglecting changes in efficiency). If the water is starting at 60F, then it will take 2 hours to get to 100F. You will have to plan ahead.
 
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BlueWave8

Well-known member
Mar 28, 2011
107
Space Coast, Florida
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Thanks for the response. The heater I had before was a 260k BTU propane, so you are correct about the rise time there vs a 400k. I was used to it taking about 30 minutes to heat up my old spa already.

Don't know the size on this spa yet, but yes, I am thinking it should be pretty average so around 800 gallons.

I agree that the waiting isn't ideal. If I had natural gas on my street I wouldn't even be questioning this, but I am really not wanting to deal with the hassle of a propane install if I'd only "need" it a month or two every year. (Need meaning having to wait over an hour to heat the hot tub up...what I'm really trying to do is quantify the pain of waiting and how often I'd need to do it. :LOL:

Here are some monthly averages for my town:
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Even in my coldest month, humidity is still 70% (pro for heat pump?).

Do you think a heat pump will really be able to get the hot tub from 60 to 100 in two hours? That's really a bit better than I was hoping for. I mean, its not adiabatic, right? It's got to heat all the concrete and keep up with whatever is lost to the 50 something degree air as well.

I just came across RayPak's line of E3T electric resistance heaters that sounds like they are okay to use with salt chlorination:


I'd almost rather add one of those to help out the heat pump than add propane :-\ It would definitely cost a lot less.
 
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