Pool Heating with Mod/Con

Paul Pollets

In this application, the better appliance would be a copper fin tube boiler(s). The high temp application puts a mod-con way out of condensation range. A CFT boiler(s) would not require a FPHX, either.

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Josh M.

I have an application problem. We want to give our clients the efficiency of a Mod/Con but we have to interface with a heat exchanger to protect the boiler from chemicals. I calculated the boiler size at 850,000BTUH output. In order to take advantage of the efficiency of the Mod/Con we need a $10K heat exchanger.

Does anyone have a better application or idea for my situation?

Andrew Hagen_4

Heat Load

Is 850MBH the heat loss or for a certain initial fill heating rate?

Josh M.

It is actually, I designed for a 1 degree per hour heat up rate.

Unknown

I must agree with Paul that a mod-con is not a good choice in this case.

ZERO need for modulation when you're talking one hour to raise heat a large quantity of water by 1F. Even with VERY tight control (plus/minus 1F) you're talking two hours of FULL fire to meet a load that is almost perfectly predictable and considering the extraordinary difference in water quantity between what's in the boiler and what's in the pool (think temperature transfer over time), a quality copper boiler will thrive and not require a heat exchanger.

Mark Eatherton

95% efficient Jandy pool heaters...

http://www.swimmingpoolsetc.com/JDY-EHE350NC.htm

Cupro-nickel heat exchanger. They claim it can handle the salt associated with salt based chlorine generators.

ME

tim smith

Nooooooooooooo dont go the Hi E......... Not the best option.

We have not been impressed with their serviceability and maintenance requirements. I for one think an oversized heat exchanger, shell & tube or cupronickel plate heat x and mod con is not a bad bet. Run low boiler temps, design heat exchanger water temp with close approach to pool side water temp and you will have less maintenance on your boiler, longer lifespan than copper heatx. We service pool heaters all the time and man do they take a beating. Gasses burning up through a low temp fintube copper heat x, always some chemicals in air, no matter how careful they are just spell disaster for open combustion heater and the sealed combustion units have not fared well either in my opinion, which I am not very opinionated as you can tell . Good luck, Tim

Josh M.

I agree Tim, boilers on a heat exchanger properly piped will go and go forever on a constant load.

After working for a copper fin tube rep and servicing hundreds of pool boilers, I am convinced that copper has no place heating a pool. The coating on the inside of the tubes wear out in a year or two. Also if chemicals are stored in the boiler room, as they always are, they will eat away at the copper as well from the exterior of the tube.

The other reason I like the idea of a Mod/Con is that the modulation is GREAT in a constant load application. The boiler will run full boar when you heat the pool at the beginning of the season and then just modulate on down to maintain the pool temp.

Mark Eatherton

Consider using Titanium...

Triangle tube makes a cute tube in shell heat exchanger that is made of titanium. Unfortunately, it has such a small surface area, it requires 180 degree entering water temps to kick out the btu's.

There are other titanium HXer's available. I had old man Weebler of W Cubed make me a flat plate heat exchanger out of titanium. Cost me an arm and a leg, but am certain he could do the same for you.

W Cubed Mfg & Engineering - 303-431-1180 Ask for Wonderful Walter.

ME

Mark Eatherton

Thanks for the feed back Tim...

I have zero experience with the HiE , only was it on a job that I had bid modcon w titanium HXer, and lost out to the pool guy using the Hi E. I will smile knowing that the cheap SOB will be spending twice as much money as he would have paid me to do it right the FIRST time...

What has your experience been with cupro-nickel HXers and the salt associated with sodium chloride generators? I know they are less expensive, just wondering about their life expectancy?

Also, I disagree with Paul and Mike T's post. Pool loads are just as variable as space heating loads, and I think that a properly applied modcon is an excellent idea, but that is just my opinion.

BTW, I have applied modcons, using multiple parallel titanium heat exchangers, and it works like a champ. Unfortunately, I can't track the fuel savings associated with the conversion because its bill is lump summed with numerous other city facilities, but the majority of the times I have been there, it is running at around 60% capacity.

ME

Home Depot Employee

Cupro-nickel heat exchangers all the way, unless you love changing them. Salts, chlorides or chlorine, the only way to go. Titanium for salt water pools if going with a exchanger.

AS for ME's remarks, properly applied a Mod-con with good flowrates at the exchanger end is perfect for full-fire condensing modes. (remember the water is 50-90? degrees)

Mike Thomas_2

400,000 btu / $2,000

I buy a 400,000btu poolheater for just under $2,000. It is designed to heat pool water and stand up to use in that environment. How much do you folks plan to spend for the systems you have described? Doesn't cost versus benefit come in to this equation somewhere?

Gordy

Whats their usage pattern?

I'm not a pro Josh, but I do own a pool with a hayward gas heater thats trated at 1/2* per hour. Do you really need to size for a 1* per hour rise? Unless they are the occasional user, and need to boost temps quickly.

If all you need is to get out of opening season, and keep at a desired temp you could get away with half the btu output. 1/2* per hour is not bad when you are trying to keep a desired temp range for the season.

BUT all this goes out the window if they don't cover the pool when not in use. Evaporation is the biggest btu hog of all.


Gordy

tim smith

Mark, I do not know what kind of lifespan they would have

in that application but cupronickel has been used in ocean going water cooled equipment for years and holds up well in that harsh environment so I would say they should hold up great. If you Look at marine heat pumps, or check with american standard heat xrs they all use cupronickel I think in their marine water cooled equip. So I would think if cost needs to be kept down that a steel shell & cupronickel tube bundle would be the way to go and low pressure drop also. If some more dollars could be thrown at heatx then maybe titanium as y'all said and I heard that is best way to go but don't have 1st hand experience with them. I have used the stainless brazed plates from a heat x co back east. They make titanium also, they were actually quite reasonable for oversized plate type 800mbh for each building. There titanium was not bad if I remember right also. I will find the name. Tim

tim smith

Reply to Mike, yes cost benefit does matter, but when std pool

heater only running at about 75% at best and I can get almost 20% more, then with large pools and or all year around pools, that savings is big!! So then cost benefit is there, if just summer std type pool, I agree you can't make it pencil out.

Mike Thomas_2

84%

StaRite heaters run at 84% efficiency. I would still like to hear some ball park figures on a mod con and heat exchanger big enough to take care of an average pool with about 30,000 gallons of water.....

Mark Eatherton

What's it matter???

When the new administration adopts the Kioto Environmental reforms, it won't be an option...

We have two counties here in Colorado that have adopted ordinances OUTLAWING the use of fossil fuels for the purpose of heating swimming pools, spas and water features.

Get ready for the new regiment, and it is expensive, but uses the least amount of energy possible.

ME

hot_rod

buy a mod con and flow right through it

Many years ago I visited the HT factory. I recall Dave mentioning he had a Munchkin connected to his pool, directly in the pool flow. I'd wonder if it still is in place? I'll bet that was 10 years ago, or more.

If the pool chemistry is kept accurate, stainless, and copper should last a long time.

Aren't pool heaters, Raypak, Laars, etc just regular copper hxers? Also those stainless header pieces to connect the PVC pool piping a few feet from the boiler connection, last as long as the heaters.

Strictly experimental of course

hr

Metro Man

pool heating

You would have to get the flow rates correct to flow straight through boiler. Pool water chemistry can turn south in a heartbeat with "dude" maintaining. But maybe a mod/con with an easy to change Ti H/E for the $$$? May be able to buy two boiler H.E. for cost of 1 external?

I know a guy who heats his pool w/solar flat plates running the pool water straight through w/no H.E. Been running for 15 years no problem. If you could get rid of chemicals and run straight ozonation with a contact tank that would be the ticket. Don't think it would work commercial code wise.

Check out... www.secespol.com "The polish heat exchanger". Think a US company now distributes.

Note: look for the "B-Line" for your application

Have used these with very good success.

BTW - Mark, Walt has retired. His son is still there as welder/ fab. under a new owner. They will still do all the things they used to though.

Metro Man

Josh M.

Hot Rod, I'd worry about a build up of chemicals on the inside wall of the heat exchanger. I've seen it may times on copper fin boilers used in this application.

tim smith

standard stainless and chlorine do not mix as far as what

I have gotten from Engineers. It will eat through them much faster than copper.

hot_rod

I've seem many stainless steel pool filters

over the years also. Same with hot tub filter canisters. Are all those Ti stabilized or titanium? Same with the connector tubes shipped with the copper pool heaters. those appear to be plain stainless tubing.

I suppose the quality of the water and chemicals is the key.

When I disassembled and filled in my pool last year, all the PVC piping was brittle to the point of shattering when dropped on the concrete. It had been in service for 20 years or more. I suspect it has seen some wild chemistry swings.

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Joannie_15

Don't Forget

Modcons that are made to be used as boilers may have ferrous parts in them, so if you decide to use them to directly heat a pool, you need to make sure they are good for potable water.....non-ferrous materials in the waterways.

And depending on where you are, an inspector may require the ANSI Z21.56 pool heater certification on the unit for directly heating the pool water (no heat exchanger between the pool water and the boiler). Boilers (with ANSI Z21.13 certification standard) are allowed to have much much higher temperature controls and high limits on them, to help protect against scalding. It's a local code thing, so some may allow it and some may not.

Just an FYI.


Joannie - Laars Heating Systems