Selecting the best pool heater for me

mwemaxxowner

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Apr 15, 2020
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I'm starting to consider the possibility of adding a pool heater to my setup at some point. I don't think it will be this year, I have a carport to build, but maybe next. Once I get an idea though it's hard for me to leave it alone until I have it figured out.

This is a 30,000 gallon in ground vinyl liner pool, 20x40 physical dimensions. It's in full sun all day. I've never had a thermometer in it. I have no idea what temperature it is when we like to swim, or anything like that.

I'm in SC and we do have a pretty long swim season. However, there is a good month or sometimes two before the swim season, *and* after the swim season where outside temps are warm enough swimming would be fun, but the water is too cold. Last year I went on a 3 day kayaking trip the second week in October, and the river water wasn't too bad. I was amazed it was so much warmer than our pool. My goal would be to use a heater to extend that swim season a little on the front end and the back end.

With that in mind, I believe my best option would be a gas heater? I imagine a heat pump would take quite some time on the pre season end to bring it up to temp.

I believe I've gathered that I need around a 300,000 btu unit in my case. Does that sound about right?

I have plenty of electricity available in the pool house to power a heat pump, and I have a natural gas tap right beside the pool house. There is no meter present but I'm sure I could have them put one in for me. I do not have bulk propane, but I have plenty of room out of sight to have them put a big tank it I decided to go that route.

I don't have any other gas appliances in the pool house, so that makes me hesitate to go natural gas. I hate to take on a minimum monthly payment for all those months I'm not running it. To offset that some, I'm sure I could convert my grill to natural gas, and I do have a desire to put a shower in the pool house, I could possibly use gas for a water heater for that shower. So I could potentially get some use out of the natural gas when I'm not heating the pool, but I would not have otherwise ever used natural gas for those things.

I think bulk propane sounds good, as it wouldn't be a monthly bill, necessarily. Just pay for a refill whenever I use up the tank. Isn't propane generally a good bit more expensive?

I gather that up front cost is a lot more for heat pumps, but the energy cost is much better. To a certain extent I'm willing to pay more up front, but I am afraid that it would take too long to heat the pool up in early spring.

Can you guys and ladies help me work through my options so I can make a good decision about what would be the best for me, given my variables?

Oh, also, I know a solar cover would be essential no matter what. I plan to do that even if I don't purchase a pool heater.

Many thanks!
 

mwemaxxowner

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Apr 15, 2020
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Pageland SC
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I've read that, and it doesn't do much to answer most of these questions.

For example, it says a heat pump can "take a while to heat the water compared to a gas heater", but in no way is "a while" defined. It's hard to make a several thousand dollar decision off of that.

It was a good article to give me some general ideas but that's as far as it goes. It also doesn't touch on propane vs natural gas at all.

I'm almost certain that I'll find the size heat pump recommended will be cost prohibitive up front enough so that I need to decide on propane or natural gas, but I want to be sure before I mark that off the list.
 
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ajw22

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Propane is about 3X the cost of NG. If you have NG available that is the way to go even if there is some minimum monthly cost.

From Calculators - Further Reading

Raypak Gas Pool Heater Sizer
Raypak has a Gas Pool Heater Sizer. It tells you the Temperature Rise/Hr and Natural Gas and Propane costs to heat a pool in your local area to selected temperature by month. Adjust the natural gas cost and propane cost in the lower left to your local gas prices for accurate costs.

Heat Pump Calculator
Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source.

Raypak also has a Heat Pump Heater Sizing App.

To get the most accurate cost comparison you should change the default electric kwh, natural gas price, and propane price to actual prices in your area.
 

YippeeSkippy

Mod Squad
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Jan 17, 2012
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Evans, Georgia
Ok, then gas is usually cheaper than propane. Many NG companies will change out meter for free to upsize it so you'll buy more gas.

Gas gives fast quick heating, but to *keep* it warm you 'd need to run it often ($),

Heatpump works on outside air to heat water. Works slower but better usually at maintaining heat level consistently. Some folks in hot western climes even get their heat pumps to reverse to chillers.

Covers are a must or you'll be wasting time and energy ($)

Check with energy companies if any are offering rebates.

That's all I got at this point.... maybe more later.

Maddie :flower:
 

mwemaxxowner

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Apr 15, 2020
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At the end of the day, one btu/hr is one btu/hr. Right?

So couldn't I roughly calculate my temperature gain with X heat pump vs Y gas heater?

I'd say outside temps would be around 80 before we'd be interested in getting in the pool.
 

ajw22

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At the end of the day, one btu/hr is one btu/hr. Right?

So couldn't I roughly calculate my temperature gain with X heat pump vs Y gas heater?

Heat pumps max out at 120K-140K BTUs. And read the specs, heat pump BTUS are for an air temperature of 80F and the BTU output declines as the air temperature drops until it shuts down around 50F. So when it is cold out and you want the heat the most you do not get maximum rated BTUs from the HP.

NG heaters can go up to 400K BTUs at 80% effeciency - so 320K BTUs into the water. They heat a pool a lot quicker and in colder air temperatures.
 
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mwemaxxowner

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Apr 15, 2020
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That reminds me of another question I had though. What size gas line and meter do I need to be using? The run won't be but 5 or 6 feet at most. The tap is right beside where the heater would be located.

Heat pumps may out at 120K-140K BTUs. And read the specs, heat pump BTUS are for an air temperature of 80F and the BTU output declines as the air temperature drops until it shuts down around 50F. So when it is cold out and you want the heat the most you do not get maximum rated BTUs from the HP.



NG heaters can go up to 400K BTUs at 80% effeciency - so 320K BTUs into the water. They heat a pool a lot quicker and in colder air temperatures.

I didn't know that. That's probably the final nail in the coffin then. I reckon 140k btus would be very slow. It would be 80 out I think,maybe 70 once we started it warming up, but I think those BTUs are still probably too low for us. Below 80 I don't think we'd enjoy regardless of water temps.


I believe I need to focus on pricing NG units in the ≥300k btu range. Thank y'all!
 
Last edited:

ajw22

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You need NG service sufficient for the BTU rating of the heater. Gas pipe size depends on the type of gas service you have. There is low pressure NG service and high pressure NG service with regulators at each device.
 

Homebrewale

Well-known member
Apr 21, 2020
428
Apex, NC
Propane is about 3X the cost of NG. If you have NG available that is the way to go even if there is some minimum monthly cost.

From Calculators - Further Reading

Raypak Gas Pool Heater Sizer
Raypak has a Gas Pool Heater Sizer. It tells you the Temperature Rise/Hr and Natural Gas and Propane costs to heat a pool in your local area to selected temperature by month. Adjust the natural gas cost and propane cost in the lower left to your local gas prices for accurate costs.

Heat Pump Calculator
Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source.

Raypak also has a Heat Pump Heater Sizing App.

To get the most accurate cost comparison you should change the default electric kwh, natural gas price, and propane price to actual prices in your area.

Interesting. I didn't know they had dual fuel (hybrid) heaters for pool heaters. I knew dual fuel gas packs have been around for years to heat a house. Using the Pentair link, it calculates I would save about $1882 per pool season using their hybrid heater. Currently, I have a heat pump because it is important to me to maintain consistent temperature for every day of the pool season.
 

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ajw22

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Jul 21, 2013
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Interesting. I didn't know they had dual fuel (hybrid) heaters for pool heaters. I knew dual fuel gas packs have been around for years to heat a house. Using the Pentair link, it calculates I would save about $1882 per pool season using their hybrid heater. Currently, I have a heat pump because it is important to me to maintain consistent temperature for every day of the pool season.

Price out the Pentair Hybrid Heater and you will find it saves you little over having a separate HP and NG heater. And it is a complex expensive unit. If either the HP or gas heater fails you may be looking at replacing the entire unit rather then an individual system. You can have a dual heater setup with automation and get the same benefits as a hybrid heater.
 

mwemaxxowner

Bronze Supporter
Apr 15, 2020
261
Pageland SC
Pool Size
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Chlorine
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That Pentair Hybrid sounds perfect. A quick Google shows it available for about $5500, which is less than I would have guessed. Having both options makes it seem well worth it to me.
 

Homebrewale

Well-known member
Apr 21, 2020
428
Apex, NC
Price out the Pentair Hybrid Heater and you will find it saves you little over having a separate HP and NG heater. And it is a complex expensive unit. If either the HP or gas heater fails you may be looking at replacing the entire unit rather then an individual system. You can have a dual heater setup with automation and get the same benefits as a hybrid heater.

Nah. I'll just stick with my heat pump. I don't have any interest in complicating my system. Once I open my pool in the spring, the heat pump takes a few days to heat the water to temperature but then it's fine until I'm ready to close.
 

mwemaxxowner

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Apr 15, 2020
261
Pageland SC
Pool Size
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Chlorine
Liquid Chlorine
Nah. I'll just stick with my heat pump. I don't have any interest in complicating my system. Once I open my pool in the spring, the heat pump takes a few days to heat the water to temperature but then it's fine until I'm ready to close.
What size pool do you have?
 

mwemaxxowner

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Apr 15, 2020
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Let me know if my math is wrong, but it looks to me like a 140,000 or 150,000 btu heat pump should be able to add 30 degrees (assuming outside air temp is high enough) in about 55 hours. I know this makes a lot of assumptions and doesn't take into account heat loss while it's also trying to heat.

Screenshot_20210219-064441.png

Also coupled with reading some first hand experience, it sounds like I could still heat this thing once the outside temps are 70, and of course it's covered with a thermal cover, in a week? I'd be okay with that amount of time. Running the cost figures on the link you gave me that still sounds a lot cheaper than heating with natural gas.

In a perfect world I'd have both, but if I'm okay taking a week to get warm it sounds to me like I can get by without it.
 

ajw22

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Your math is right but your assumptions are optimistic. Cost does not matter if the heater fails to achieve its objective. It all depends what your expectations are if you will be happy with a HP. If not you can always add the NG heater later.
 

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