Twin Heaters on one pump for large pool??

back_yard_lap_pool

Silver Supporter
Jun 16, 2016
263
Texas
Finishing up design on fairly large pool that I plan to owner-build.- ~85,000 gallon 2,064 S.F of water surface area. It will be located in Houston, so winters aren't terribly harsh - For example, it was 88 degrees today on Feb 8th (not normal - beat our previous record high by 4 degrees, but you get the point). That being said, I want to be able to use this pool year round. I am planning on a winter thermal blanket and reel like they use for outdoor swim team pools, but a 400K BTU heater doesn't appear to be enough at first blush.

Question: Can I use a 3-way valve on the inlet and outlet to tie two Pentair 400K BTU Master Temp heaters two one pump (Intelliflow XF)? I see minimum flow is 40 GPM per heater for the 400K BTU Master Temps., so if I'm running 100GPM plus while heating the pool, it seems like that would work. This heat side of the filtration system would feed into 12 floor inlets spread around the pool. Any problems with this theoretical scenario?
Screen Shot 2017-02-08 at 6.14.51 PM.jpg


Thanks,
JR
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,764
Pleasanton, CA
Why do you think you need two heaters? One heater running 24 hrs would raise the water at least 10 degrees. If you use a blanket, you should lose much less than that in a single day.
 

back_yard_lap_pool

Silver Supporter
Jun 16, 2016
263
Texas
Why do you think you need two heaters? One heater running 24 hrs would raise the water at least 10 degrees. If you use a blanket, you should lose much less than that in a single day.
Yeah - I'm on the fence... I'm going to plumb a 3/4" 2psi line back to the pad which would allow for about 1.8 MMBTU/hr and I might initially install just (1)400k BTU heater with space for its twin next to it - I just want to know that it is possible to manifold the two together if the pool and weather dictate additional "horsepower" in the heater department


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back_yard_lap_pool

Silver Supporter
Jun 16, 2016
263
Texas
I'm not qualified to give you an answer on the heaters but did want to say- Now that's a pool!!


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Ha! Thanks - I got the soil study and engineering back on it a few months back - it's a bit of a beast. 1/2" rebar @ 9" OC throughout with 12" walls top to bottom and a 9" floor. I was surprised - those thicknesses and spacing are not the typical build in this area.


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JamesW

TFP Expert
Mar 2, 2011
21,091
You can do it as long as the heaters are hydraulically balanced. I would add flow meters and flow switches to make sure that the heaters don't run with no flow.
 

needsajet

TFP Expert
LifeTime Supporter
Jan 4, 2016
4,731
Sydney, NSW, Australia
Welcome to TFP! Good to have you here :)

There's a triple pool cover and roller set up for sale somewhere around here (I can't find it anymore). Ya nevah know, maybe it fits :) It was 3 pieces, 13' wide each, and looked like it was in decent shape.

Awesome pool!
 

rahimlee54

Well-known member
Apr 8, 2016
121
Central nc
To save overall cost and cheaper replacements I'd get 2 300k heaters. cheaper operating cost same results.

If those values work.

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mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,764
Pleasanton, CA
cheaper operating cost same results.
Why would the operating costs be less? Larger heaters would run for proportionally shorter periods of time for the same added BTU so the net costs should be about the same. Plus larger heaters would require less run time so less pump cost.
 

rahimlee54

Well-known member
Apr 8, 2016
121
Central nc
Pump run time for filtration should be about the same. Assume the heater keeps the temp constant during that time they should run around the same amount. I am assuming pool heaters are either on or off like my basic understanding of home hvac tells me. I'd have to look a
up specifics to calculate energy usage for a period time of 600 k btu vs 800 k btu. Math says it'll cost 25% more to operate.

There are a large number of variables you could look at. My whole argument stems mostly from cost to buy. I'd expect parts on a bigger unit to be more expensive as well. Depending on the goals of OP the equipment choices could be more critical. On a quick look from earlier that was my initial thought. I am also not a huge fan of one unit just mostly hanging out because you'll pay for the deterioration of the unit even if not in use.

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mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,764
Pleasanton, CA
Yes heaters are either on or off but the time on depends upon the amount of BTUs required (i.e. temperature set point). No matter how many BTUs are required, A 200k BTU heater will be on twice as long as a 400k BTU heater but they will both generate the same amount of heat/BTUs AND consume the same amount of NG (assuming identical efficiency). This is exactly the same as in HVAC.

My whole argument stems mostly from cost to buy.
That part, I would agree with.

I am also not a huge fan of one unit just mostly hanging out because you'll pay for the deterioration of the unit even if not in use.
I would also agree with this statement.
 

JamesW

TFP Expert
Mar 2, 2011
21,091
ETiâ„¢ 400 HIGH-EFFICIENCY HEATER - YouTube

Pentair has a new heater. 400,000 btu/hr, 96 % efficient and a titanium heat exchanger.

Don't know if it's available yet or if it's worth considering.

Don't know price. Too new for reliability data.

A 96% efficient heater will put 384,000 btu/hr into the water vs an 84% efficient heater at 336,000 btu/hr.

That's 1.14 times more heat. A 96% 400k heater is equivalent to an 84% 457k heater.

Jandy also has a high efficiency heater. That gets mixed reviews.

Theoretically, a high efficiency heater saves in the long run. In the real world, higher up front costs are not always recovered. To be worthwhile, the heater has to last long enough with minimal maintenance and repair costs. That doesn't always happen.

There are also heaters that go over 400,000 btu/hr.
 

MarkTX

Bronze Supporter
Nov 15, 2015
342
Cypress, TX
I am not a pool heating expert by any means, but we have dual water heaters in our attic for our home. The home inspector told us that water heaters in parallel are for different hot water circuits, and water heaters in series are for added capacity in a single circuit. The trick for series heaters is to set the upstream heater's thermostat lower than the downstream heater, so the upstream heater does not do all the work. The inspector said ours were plumbed in parallel.

Not sure if this is applicable to pool heaters, but it is interesting.
 

back_yard_lap_pool

Silver Supporter
Jun 16, 2016
263
Texas
ETiâ„¢ 400 HIGH-EFFICIENCY HEATER - YouTube

Pentair has a new heater. 400,000 btu/hr, 96 % efficient and a titanium heat exchanger.

Don't know if it's available yet or if it's worth considering.

Don't know price. Too new for reliability data.

A 96% efficient heater will put 384,000 btu/hr into the water vs an 84% efficient heater at 336,000 btu/hr.

That's 1.14 times more heat. A 96% 400k heater is equivalent to an 84% 457k heater.

Jandy also has a high efficiency heater. That gets mixed reviews.

Theoretically, a high efficiency heater saves in the long run. In the real world, higher up front costs are not always recovered. To be worthwhile, the heater has to last long enough with minimal maintenance and repair costs. That doesn't always happen.

There are also heaters that go over 400,000 btu/hr.
The ETI400 looks interesting. Just called one distributor and it goes for $6k - so I'll need to figure out breakeven period - but definitely something I'll look into.


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back_yard_lap_pool

Silver Supporter
Jun 16, 2016
263
Texas
The ETI400 looks interesting. Just called one distributor and it goes for $6k - so I'll need to figure out breakeven period - but definitely something I'll look into.


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So... 96% efficiency vs 82% on the normal cupro-nickel is 14% savings. Assuming $4/MMBTU for natural gas, this is $0.56 per MMBTU. So in order to cover the $4k difference with just efficiency savings, one would need to have burned 7,143 MMbTU's of gas, or $28,572 in gas bill...

If this heater's lifespan was multiple times longer than the cupro-nickel master temp, that would help, but it would be hard to justify the difference by the energy savings on their own.

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rahimlee54

Well-known member
Apr 8, 2016
121
Central nc
I have found the same answer with all forms of efficient home appliances. Tankless water heaters and HVAC units in particular. After research one or two above base level is the way to go on most purchases as efficiency increases never seem to be even close on rate of return.

However, LED bulbs are great!

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