Electric Spa Heater for Spillover Spa?

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#1
Our pool has a 200 gallon spillover spa, which we'd like to heat so we can use it as more than a kiddie pool. There is currently a propane pool heater but it's obviously broken and according to our neighbors, the tank was above ground and removed before we bought the property. Our efforts to follow the propane line seem to confirm their information. Natural gas is not available in our neighborhood. So to get it up and running with the current setup we'd need to pay for both a new propane heater and tank, plus installation costs, and the initial propane fill up. This would be several thousand dollars and is more than we can currently afford, but the wife really wants a hot tub/spa she can use to help get over the pains and stresses from having 2 children in less than 2 years.

Since we're only trying to heat the spa and not the rest of the pool, would there be any problem with installing an 11 kw electric spa heater, like this, for this purpose? We would flip all the valves to spa only mode when in use so there would be no mixing of the water, avoid using the spillover during normal operation, and use a solar cover (or maybe a spa specific one?) which would help keep the heat in so we don't have to constantly start from scratch. In the reviews and questions of that product several people mention using it to heat pools of up to several thousand gallons effectively, so it seems doable to me.

I've thought about using solar heaters, and will probably install those for the pool, but I doubt they'd get the water temperature up to the 110 or so we'd want for the spa. Even if they would, would it do so quickly enough?
 

pooldv

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#2
The max temp a spa should be heated to is 104°F. Anything above that is unsafe. That heater would work fine. Most stand alone hot tubs use about a 5500 watt heater. Yes, adding a solar cover would help a lot. Any 8 mil solar bubble cover would make a pretty big difference in holding in the heat overnight.
 

gwegan

TFP Expert
Apr 19, 2013
2,769
Sacramento, CA
#3
That heater will work.

But this is an advanced dyi project.

Read the manual a couple of times.

It's 240 volts and draws 46 amps so it's not plug and play. It requires bonding and grounding.

They are very particular about how it's plumbed.
 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#4
For an 11kw heater you are going need at least a dedicated 50amp, but probably higher, electrical supply. Depending on where you pool and spa are in relation to you main service panel it could be expensive to run the cable.
 

pooldv

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#5
You might be better off with a smaller heat pump if you plan to keep it heated most of the time. The Hayward HP50HA operates on a 20 amp breaker and cost around 1500 bucks.
 

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#6
First off, thanks everyone for the responses and useful information. I love this forum!

The max temp a spa should be heated to is 104°F. Anything above that is unsafe. That heater would work fine. Most stand alone hot tubs use about a 5500 watt heater. Yes, adding a solar cover would help a lot. Any 8 mil solar bubble cover would make a pretty big difference in holding in the heat overnight.

You might be better off with a smaller heat pump if you plan to keep it heated most of the time. The Hayward HP50HA operates on a 20 amp breaker and cost around 1500 bucks.
We already have a solar cover for the spa :) . I think it's 12 mil? Anyway it helped a lot last summer even without anything heating the water.

They make a similar 5500 watt version which I presume would ease the electrical requirements. Do you think that would work for our needs? We don't plan to keep the heater on the whole time - I don't know if we could afford that - but we want to minimize the heat loss so that it can warm up to ~100 or so in a reasonable time, say 30-60 minutes, if we were to use it about 3 times / week.

That heater will work.

But this is an advanced dyi project.

Read the manual a couple of times.

It's 240 volts and draws 46 amps so it's not plug and play. It requires bonding and grounding.

They are very particular about how it's plumbed.
Thank you for the advice. We would probably pay someone to do at least the trickier parts of the install, if not the whole thing.


For an 11kw heater you are going need at least a dedicated 50amp, but probably higher, electrical supply. Depending on where you pool and spa are in relation to you main service panel it could be expensive to run the cable.
There is a sub-panel with its own breakers etc. about 10 feet from the pool equipment and maybe twice that from the spa. It powers the pump and pool light and has room for a couple additional breakers. I honestly don't know if it's got enough juice for this though. The main service panel in the garage is about 60 feet from the pool equipment and 90 or so from the spa. Unfortunately, I think it's maxed out on breaker space, though several are no longer in use.
 

pooldv

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#7
12 mil cover is good. 5500 watts is 18.7k btu. It takes 1 btu to heat 1 lb of water by 1 degree. How many gallons is your spa? A 250 gallon spa would work like this.

250 x 8.34lbs = 2085 lbs
2085 lbs ÷ 14,960 (18,700 x 80% efficiency) btu = 0.14 hours to heat 1 degree
0.14 hours per degree equals 8.4 minutes or a little over 7 degrees per hour.
 

gwegan

TFP Expert
Apr 19, 2013
2,769
Sacramento, CA
#8
Yes the 5500 watt version helps. Download the manual and have three electricians out. Give them the manual and they can give you bids for installation.

Whether either version will work depends on the capacity of the sub panel, the wire size from the main panel and the total load on the main panel. We aren't there so we can't help you much there.
 
#9
This is going to sound redneck, but if you want to go with the cheapest method, as I did, remove all the burners and electronics from your current (broken) heater. Then all you have to do is split some wood into small pieces and build a fire in the firebox. I was able to heat my 500 gallon hot tub from 70 to 110 in about 3 hours. When the desired temperature is reached, pull out some of the hottest embers, leaving enough to maintain the temperature. Considering that my original heater was rated for 300k btu, I deemed the wood fire as safe. If you want to play it safer, and with less work, you could use the burners from a donor BBQ grill and run it off a 20lb tank. Just a thought ;)
 

ps0303

TFP Expert
In The Industry
Jul 6, 2011
3,956
FL
#10
What do you expect your heat up times to be? Are you willing to wait a long time? Gas can heat it up so much quicker.

electric spa heater.jpg
 

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#11
What do you expect your heat up times to be? Are you willing to wait a long time? Gas can heat it up so much quicker.

View attachment 58351
I don't think we want to wait much more than an hour in most cases, preferably closer to 30 minutes, which is why I was going to try to keep the water as warm as possible when we're not using it. I know the benefits of gas, the problem for us is the cost. $1600+ just to purchase the heater, then we've still got to purchase a tank and have it filled. We may or may not have to pay someone to hook them up and bury the tank (above ground tank isn't gonna happen). Presumably we could do some of that work, but I can't see that getting it up and running for less than $2500 or so. Then there's the cost of running the propane 3 times a week at $4-6 / gallon. Now, we might not have to run it much to heat up 200 gallons for an hour or so... does anyone have an estimate how much propane would be used to heat 200 gallons 20 degrees and keep it there for an hour? I've seen calculators to get to the desired temperature but not to maintain it.

I was hoping one of these electric heaters might heat the water in 45 minutes or so, as opposed to the 8 it would take the propane, and that we'd be able to have it up and running for under $1000 considering I can buy the heater for < $500 (off brands for around $250). Then we'd have the ongoing benefit of cheaper use as well. But if the install is going to bring it into the $2k range anyway then that whole plan really goes out the window and we may have to wait another year before having a working spa :( .
 

ps0303

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Jul 6, 2011
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FL
#12
When you say "try to keep the water as warm as possible when we're not using it" do you mean ALL of the water including the pool? If you mean the spa only, then you have no circulation of the spa water for chemical treatment. If you mean all of the water, a heat pump is where you need to be. But again, the heat pumps have a draw back in cooler temps.

I understand your money issues but also consider if you ever wanted to heat the pool also for say a special event.
 

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#14
When you say "try to keep the water as warm as possible when we're not using it" do you mean ALL of the water including the pool? If you mean the spa only, then you have no circulation of the spa water for chemical treatment. If you mean all of the water, a heat pump is where you need to be. But again, the heat pumps have a draw back in cooler temps.

I understand your money issues but also consider if you ever wanted to heat the pool also for say a special event.
When I say that, I mean keeping it as warm as possible without running the heater. We don't want our bill going up by more than about $100 / month. And yes, it would mean no circulation of the spa water for stretches, but my plan was to still throw it in spa only mode for an hour or so a day (or whatever it takes to fully circulate the 200 gallons - I'll do the math when needed).

We're not concerned with heating the whole pool at this time. Yes, that would be nice, but it's not realistic by any means other than solar given our current budget. _maybe_ a heat pump would work for that, but would a heat pump really be able to raise the spa temperature 20 degrees in an hour or less? I haven't heard of any that can do that, and realistically I doubt we'll be able to keep the water temp sitting in the 90s for much of the year.

I do live in the Tampa Bay area where cold temps really aren't a problem :). The middle of our winter might have 1-2 weeks where the highs are in the low 50s and lows in 30s in the middle of the night. For virtually the entire year the highs are in the mid 70s to low 90s.



Some heat pumps can be set up to run a spa and will get water to104. You need to be able to circulate the water in your spa independent of the pool for that set up to work.
We do that already. How quickly do they get the water to 104 if it's starting at say 85?
 

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#15
Yes the 5500 watt version helps. Download the manual and have three electricians out. Give them the manual and they can give you bids for installation.

Whether either version will work depends on the capacity of the sub panel, the wire size from the main panel and the total load on the main panel. We aren't there so we can't help you much there.
The sub panel is powered by a dual 100 amp breaker on the main panel. Presumably the wiring is enough to support the maximum draw for that. The sub panel currently supports a dual 20 amp breaker and a 15 amp breaker. Unfortunately, I don't know enough about these things to know if that means there's enough juice / room in the sub panel to support either of the heaters or not. I could look it up, but does anyone know off hand?
 

pooldv

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#16
So, 5500 watts is 5500 ÷ 240v = 23 amps which would require a 30 amp dual pole breaker.
 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#17
If your panel is truly supplied with a 100 amp dual pole breaker then you should be all set wiring wise either for the 11kw electric heater or a 110kBTU heat pump.
With my heat pump and consistent use of my solar cover I managed a set temp of 87 on my pool the whole season in southern New England. I would say in the worst month I had my electric bill went up by about 80 dollars due to the heat pump. I am installing my solar panels this spring so they don't count for last year's results.

There are too many variables to a heat pump to say how long it will take to heat you spa but it should be in your 30min time frame. Also if you maintain your pool in the 80s it will take even less time for you spa to get to temp. Of course the problem with this route is heat pumps start around 2500 and the 110kBTU is over 3000 last I looked.
 

wsamon

Well-known member
Mar 16, 2015
94
Largo, FL
#18
So, 5500 watts is 5500 ÷ 240v = 23 amps which would require a 30 amp dual pole breaker.
If your panel is truly supplied with a 100 amp dual pole breaker then you should be all set wiring wise either for the 11kw electric heater or a 110kBTU heat pump.
With my heat pump and consistent use of my solar cover I managed a set temp of 87 on my pool the whole season in southern New England. I would say in the worst month I had my electric bill went up by about 80 dollars due to the heat pump. I am installing my solar panels this spring so they don't count for last year's results.

There are too many variables to a heat pump to say how long it will take to heat you spa but it should be in your 30min time frame. Also if you maintain your pool in the 80s it will take even less time for you spa to get to temp. Of course the problem with this route is heat pumps start around 2500 and the 110kBTU is over 3000 last I looked.
Thank you both for the info!

Yeah, unfortunately the heat pump is out of our price range. It might be possible in a year or two, at which point I'd have to decide between that or the propane, or maybe I'll get lucky and find a good one on Craigslist. Assuming that doesn't happen I'll look into the 11kw heater I think. I've sent an email to the pool company that did our resurfacing 2 years ago to see what kind of quote they give. Unfortunately, I don't know any electricians in the area so after this pool company and maybe one or two others I got bids from previously I'll be heading to Angies List.
 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#19
Before purchasing a heater you should verify for certain that your panel is wired with a large enough wire to handle that kind of load. It sounds like it is, but its not the kind of thing you want to find out the hard way.
 

gwegan

TFP Expert
Apr 19, 2013
2,769
Sacramento, CA
#20
I would respectfully disagree that your current panel subpanel setup is adequate. We don't know that yet. You need to determine current main panel load and subpanel capacity and load. If you are going to use the subpanel you need to make sure the wire size from the main to the sub is adequate. As Danny above points out that means a minimum 30 amp dual pole breaker.