Modulating boilers

Ken_8

calcs. need to consider not only the simple math of 8.3 BTU's per gallon of water per degree of rise - but more importantly, the BTU losses off the surface of the water that will be going on while the boiler tries to raise the water temp.

Weil McLain makes an incredibly simple HX for a boiler zone designed specifically for pool heaters.

I think you need to re-think the pool load numbers. Remember, allowing days for warm up may result in unforseen weather and cold snaps at night or cloudy days - adding lots of work to the boiler and HX. Unless of course the pool is indoors, where lots of use and long term heating is practical.

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J Matthers_2

Modulating boilers

I am looking at the various modulating boilers out there trying to decide what will work best for my situation.

I am adding two zones to my IF radiant system that uses Geo as the heating plant. The additional zones put the BTU demand just out of the Geo’s reach on a design day so I need to install an additional heat source. In addition, I need to provide a backup for the geo system and need a heater for my 22,000 gal pool.

Need for modulation: The new zones plus my garage which I want to take off the geo, totals 30,000 BTU’s on a design day. The pool would need about 200 btu’s for a 1* rise per hour if I want to heat it that quickly. The pool heating would be just to get the pool up to temp in the early season and then the heater goes off. So, 30,000 btu’s for space heating and as many as I can get for pool heating.

In looking at heaters I had planned on the Munchkin 80. This would give me a low output of 20,000 and a high of 80,000 or so. Plenty of heat for the space and about a 72 hour heat up for the pool.

Then enter the Buderus, and Ultra. Now the RTI Trinity with modulation of 1-8, which would work very well with the pool load (200 btus available).

Do I need the higher BTU output for the pool? As I see it, it is just a difference of how long it will take to heat the pool. If anything, a smaller unit burning 24/7 for 3-4 days will burn the same amount of gas as a larger unit burning less time...Right?

I need to make a decision on this soon or my wife will shoot me. Thanks

J Matthers_2

I've looked at that pool heat exchanger and plan on using it. My real question, I guess, is the sensibility of combining the use of a boiler to heat an area that only needs 30,000 btus and the pool with a much larger BTU appitite. The modulating units lend themselves to this to the extent of the modulation range. Can I heat a 22,000 gal pool reasonably with a boiler producing 80,000 btuh? It seems a waste to put in two boilers if I don't need them. The Trinity with a high end of 200,000 btuh and a low of 25,000 looks good but the warrenty is "soft".

Thanks

STEVE N

I would consider...

I would consider the Weil Mclain Ultra with a WM Maxi flow pool heater. As for controlling it, You can prioritize your home heat and DHW with a Taco SR series and a separate contactor to open the circuit to the pool heater until home needs are met. This would save you money, because you could use a smaller boiler. You would never have to worry about swamping your boiler with cool water to the point where your home heating and DHW would suffer.

Steve

Gordy

Pool

JMatthers,

I was in a similar situation last year with my pool. Do I use my boiler with HX, or do I just buy a pool heater. My pool holds around 13000 gals. so not as big as yours. I went for the seperate 150,000 Btu pool heater for 1000.00. It has the power to turn it into a jacuzzi ( just ask my kids, removed temperature knob). By the time I would have run all the pipe and bought an HX and controls it would have been a wash.

One other thing is how far away is the pool from your equipment, and how much heat will you lose in the transfer to the pool. I don't know when you open your pool or close it. But usually there is not much demand on the dwelling for heat, just hot water if you have an indirect.

Gordy

J Matthers_2

When we put in the pool I had an idea that I was going to run it as a zone off a boiler or use the pool as a heat sink for the GEO so the pipe is all in. I have since built a stone retaining wall and it would be more difficult to get the gas line to the pool than zone off a boiler.