Single large steam boiler or staged multiples

tim smith_2

Have a 75 unit building that has cracked old cast iron steam boiler. Load is appx. 1.4 million btus. What do you guys think? Sectional cast iron w/ power burner or multiple staged atmospheric gas boilers. Just trying to figure what is the most efficient and effective way of doing this job. Thanks in advance for opinions. Tim.

Al Letellier

staging steam

This doesn't usually work very well as you need the boiler to produce enough steam to heat the entire building...use two full sized boilers (if budget allows) for redundency, and use a weather responsive control for maximum efficiency.
A Heattimer control will cycle the boilers lead/lag and respond to outdoor temp changes. You will have equal run time on the boilers and always have back up in case of flame failure. You can do this with one full sized boiler and still use a Heattimer or Tekmar control, if you don't have the space for two.

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Mad Dog

Good advice al, but Noel has done it with great

sucess - staging steam boilers...oh Noel where are you??? Mad Dog

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Boilerpro_3

What if the sytem is zoned,

at any one time you are likely to have a much lower steam load than the full building. Wouldn't this really be a good place for modulars? Just speaking hypothetically here, I haven't ever installed a modular, step fired steam yet, just several hot water.

Boilerpro

Unknown

Most definately.

I wound caution and encourage you to carefully plan and understand the piping that you chose to do multiple, or modular (not the same thing) boiler systems.

I'm in love with the concept, after doing it both ways in different places.

The biggest advantage that I see is the ability to shed the pick-up load after the piping gets hot EVERY TIME IT RUNS, if sized carefully.

Same thing applies to shedding load when zones close, as BP said.

I can help with piping plans, if you like.

http://www.slantfin.com/spec-caravan.html

Noel

Al Letellier

staging boiler on steam

I didn't say it couldn't be done, and I'd love to give it try sometime, but how often do you see a zones steam system? Here in Maine it's quite rare and it usually is a problem system when you do see one. I think the key to Noel's answer is "if properly sized right". I respect his knowledge and the quality of his answers here on the Wall. I've just never run into a system where staging made sense. We did a system with Heattimer control staging two "full sized boilers and cut the fuel bill 65%......will staging save that much???

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Unknown

I'm with you, Al

Above a certain size, it can make sense. It depends on what your customers want. It isn't for everyone.

My experience is in the City, here, and at some larger buildings in NH. Here's the size I'd split up the load, especially since these buildings contained about 800 TRVs, which varied the load greatly. These were 2 pipe vapor systems. See the building sizes here.

http://www.colby-sawyer.edu/

Noel