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# Pool heater size

Member Posts: 1,296
I have a customer with a 16,000 gallon pool, live in New Jersey, I’m trying to figure out how many btu it will take to heat the pool, thanks in advance.

• Member Posts: 17,762
Heat the pool from what temperature to what temperature? Or... continuously to keep it at a given temperature? The former is easy. The latter... not so much!
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 1,296
Wants 75 degrees let’s just say till September15, live in north east ( New Jersey)
• Member Posts: 7,117
edited July 2020
It probably going to come down to how fast you want it to heat up when refilled. I did a design for a winter use outdoor pool with design day of -10 degrees. It ended up with 500,000 Btu/hrs and a temp rise of 2 degrees per hour.

For a project like yours you would be good at 1 degree per hour if you can wait that long. 16,000 (gal) x 8.34 (# per gallon) x 1 (degree per hour) = 133,440 Btu/hr. There is really no efficiency penalty for oversizing so upsize from there as you please.
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein
• Member Posts: 15,392
edited July 2020
Surface area has a lot to do with the load, also a covering and wind block.
Plenty of pool calculators online
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 1,296
Thanks hot rod and z man, I installed a boiler for this guy down the jersey shore, now he has a house in Staten Island and wants to get rid of his chimney and at the same time heat up the pool. We priced out a boiler for house and an outdoor gas heater vs a larger boiler that modulates, here is what I think he wanted.
A NFB 200. That will modulate down to 20,000 for small load. And a Weil McLain pool heat exchanger. He currently has 3 zones. I want to see what his smallest zone is.
Or can I go with 2 NHB 110 so the smallest load is 10,000 btu
Or add a buffer tank on the NFB 200?
• Member Posts: 56
I like your idea, heat the pool separately, 250 kbtu's and size the boiler to the house
• Member Posts: 1,296
Sol, what idea are you talking about?
• Member Posts: 215
I like @hot_rod 's link with the engineering calculations as they provide guidance and show that most of the heat loss is through the surface area of the pool.

Energy Kinetics also has a Smart Pool Heater, which uses the winter heating capacity in an existing boiler to extend the pool season. Not trying to hijack this thread, I just thought I would provide a link to this brochure , which has a table with some common heat up times for pool volumes and boiler outputs (these assume minimal heat loss), and it also has piping and shows an example of clean trenching and sod replacement for a professional installation. We've been using plate heat exchangers for pool heating for over 30 years.

In general, the output is limited by the boiler or by the pool heat exchanger (whichever is smaller).

Best,
Roger
President
Energy Kinetics, Inc.
• Member Posts: 7,117
I like where you are headed on this. You can always prioritize the loads with controls. The pool heating would only occur when heating and DHW are satisfied. If you oversized the pool HX, the boiler will run at condensing temps all of the time.

As far as single boiler w or w/o buffer vs twin boiler, It depends on a host of things. Primarily I would be looking at the minimum heating loads. Some owners like 2 boilers for redundancy.
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein
• Member Posts: 542
You need the BTU's in the spring and fall ... use one of the calculators for a pool. Don't guess ... it's not just volume.

I own a house in same zone as the island -- 20x40 w/ diving area ... deep with almost 45k gallons. 400k heater -- they are only 80%. Use the heater the most in September. The pool is open as long as the weather is nice ... we have had it open way into October. W/O enough BTUs you can't recover when the temps drop -- you also can not oversize the heater past the pool equipments GPH through the heater. Many times the pool plumbing is larger just to get a bigger heater.

With 16k gallons you may be able to make it match up to the house -- typically a pool needs many times the house so you end up way oversized. The heat exchangers to isolate the pool are expensive and it often requires long piping. The numbers have never worked when I have investigated.

With a short swimming season in the mid-atlantic the heater is a necessary evil. You need 1 degree an hour .. that gets my pool up to temp in the spring and it can recover in the fall. One of my neighbors can't get the 1degree and he must leave his running and it will fall behind in the fall.

What's the cost of having a pool you can't use ...

• Member Posts: 11,122
You need to figure the heat loss from the pool. Below ground doesn't loose much it's mostly surface area and evaporation as @hot_rod mentioned
• Member Posts: 15,392
Some of the pool load calculators allow you to add a cover and or a fence/ hedge row to show the load difference.
Wind or air movement across a pool rips away quite a bit of temperature.

Got a solar option? Typically, a properly sized solar array can extend the season a few weeks on both ends.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 1,296
I think I am going with the navien 200,000 boiler.
Hot rod this is for you, what about a pipe layout of a navien with a buffer tank
• Member Posts: 3,013
@aicheatexchangers, you should add a little content, help someone out out a little, talk to people some, stuff like that before you start hawking your product. Really, if you're a nice guy (or gal), people will be asking you about your heat exchangers. Way better than an anonymous link.