Propane Heater Sizing questions

[forya]

I have a 25K Gal In ground Pool in South East Pa. I currently have propane for my furnace, Hot Water Heater, Stove/Burners, and 13Kw Backup Gen. I have a 500 gal underground tank, and could get the gas to my pad where the pool heater would go. I talked to the guy at the pool store and he said the bigger the better, but is there a point where the size of the heater becomes less efficient? I would like it to heat as quickly as I can. What size should I get

 

[JasonLion]

Get a 400,000 BTU heater. Even larger would be better, but above 400,000 BTU there is a large jump in price and drop in availability so that is the practical upper limit in most situations.

 

[ps0303]

A 400,000 BTU heater is really the largest residential unit you want. When you go bigger you are now getting into commercial heaters. A 400K BTU will be more than enough to heat your pool when you need it to.

 

[pooladdict]

My sisters pool had a 400,000 btu propane heater, man could that sucker heat a pool in a hurry...not to mention drain her wallet faster lol. I remember her saying of costs in the neighborhood of $800 a year, that was 20 yrs ago when propane cost $0.20 a litre.

 

[gwegan]

There is something you need to understand about heater size and efficiency to help you operate your heater at the lowest possible cost.

Heaters are dumb. They heat at a given rate to their capacity. So a 250K BTU heater puts out less heat than a 400K BTU heater does. Makes sense.

In a pool the only difference is with a 400 BTU heater you heat the pool up faster so you achieve your temperature goal more quickly.

So in the engineering world you use just as much gas to get your pool to a given temperature with a 250BTU heater as with a 400K BTU heater. But we live in the real world. And in the real world the pool is losing heat to the atmosphere at the same time our heater is adding heat. And the longer the pool is "heating up" the more heat it loses.

So a 400K BTU heater is more efficient because you lose less heat when heating up the pool.

Maintaining the temperature they should consume equally.

So when you are heating the pool up and between swimming you should always cover a gas heated pool. It significantly reduces fuel usage and overall costs.

 

[mas985]

gwegan,

One thing you neglected to mention is that a 400k BTU heater will also raise the water temperature going through the heater higher than a 250k heater by about 60% (400/250-1) assuming the same flow rate through the heater. Heat loss is proportional to the water temperature minus the surrounding environment temperature so while the 250k heater needs to heats longer for the same temperature rise, it also loses less heat per minute because the heater exit water temperatures are lower. This effect can reduce the advantage that a 400k heater might have over a 250k heater.

But a 400k is still a good idea especially for heating on demand.

 

[Kiss4aFrog]

Depending on your financial situation you might want to consider a heat pump. What you spend up front on the more expensive heat pump you save on the energy to run it. All depends on how $$$ LP is in your area and how much you think you'll burn. Nice thing about a heat pump is they can also cool but in PA I don't think you need to worry about that.
Here in Wisconsin LP is just too expensive for the speed the heater eats through the two 100 gal tanks.

:google: https://www.google.com/#q=pool+heat+pumps

 

[ps0303]

Keep in mind that with a heat pump the lower the outside temperature gets, 70's and 60's, the less efficient a heat pump becomes. A 250K BTU gas heater will burn approximately 2.5 gals per hour and a 400K BTU heater will burn approximately 4 gals per hour.