One Boiler suppling pool and spa 2 different temps. 1

[Flamespread]

Hello all,I have a customer who wants to supply a 10500 gallon pool at 85 deg. temps and a 880 gallon spa at 105 deg temperature. The Boiler supplied should be around 800,000 btu,s. Would this be recommended with a plate or tube heat exchanger with the ability to control these seperate pools at two different temperatures? Any recommendations would be greatly appreciated on the set up and temperature control equipment.

 

[Flamespread]

Correction: To my Thread, Minimum 400,000 BTU needed!

 

[MintJulep]

Separate heat exchangers for each seems like a good idea to me. You'll want to keep all three chemistrys separate.

Pay attention to return temperatures under all possible operating conditions. The boiler may not be happy running cold. You might get condensation of the combustion gasses on the fireside. This is bad in a non-condensing boiler.

 

[willard3]

This can be done with simple piping/pumping arrangements. If you don't know about them, you should get help from someone who does.

 

[MechEngNCPE]

What about a thermostatic mixing valve for the 85 degree pool?

 

[MintJulep]

Mixing valves work by mixing hot stuff and cold stuff to make warm stuff.

Where are you going to get cold stuff?

 

[berkshire]

""Mixing valves work by mixing hot stuff and cold stuff to make warm stuff.Where are you going to get cold stuff?""

Right out of the pool. A lot of pool heaters work by injecting 140degee F water into a diluter/ mixer valve on the pool circulator pump.
B.E.

 

[KiwiMace]

This is a baby pool... 1400 cu ft and you can get off the shelf residential equipment for this job.

Typically (in CA anyway) a gas fired pool heater, integrated controls with two adj. setpoints, operates the spa and pool independently. The only crappy part of this deal is the manual valving changeover which is not user-friendly.

Personal experience is that in CA, we hardly ever ran the pool heater, except early season kickstart, and the spa will heat up in an hour. Where the spa overflows into the pool, as most do, heating the spa maintains the pool temp if the spa needs to be kept hot for long periods.

If these are separated and a commercial operation, the price of the heaters is much less than all the valving and heat exchangers. Just stick one on each.

 

[Drazen]

Mixing valves are standard solution for attaining different temperature regimes, and each of them is accompanied with its own pump that forms secondary constant-flow circuit with controlled supply temperature.

This is basic stuff of hydronics, and as Willard suggested, if you are not familiar with that already, discussion on level of these tips will not give you adequate answers for everything - you need professional help.

 

[MechEngNCPE]

Drazen +1

 

[msquared48]

I have a 2500 gallon swim spa with a 250,000 BTU boiler, and a 450 gallon hot tub with a 50,000 BTU boiler.

A problem I see here is one of providing a continuity of useage. If a primary component in the system breaks down, such as the boiler, they you lose the use of both pools. With separate boilers, that will not happen.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[AnotherEllis]

Be careful in your equipment selection. There is an NSF rating for pool equipment (any water used in public bathing may only go through approved products), and while most HVAC apps will exceed this standard, they aren't typically rated for it.

I have side-stepped this in a large 1,000,000+ gallon NCAA certified pool by immersing an HX into the collector tank. The HX was not rated, but as I pointed out to the building official: the water wasn't running through it, either. He went for that.

http://www.ellisconsultingengineers.com