Steam vs hot water

Jim Roberts

I am working with a 2.1 million low pressure steam boiler, it's output is 1.6MBH.. I was thinking of staging three 550MBH output boilers; question is this a smart move.. I know it is not like staging hot water boilers where the temperature is increased as needed, however steam is steam...help please......

Dave_4

The cost vs. benefit

of such a design is suspect. We have done a few "modular" steamers and as you might suspect, the three boilers run to get up a head of steam - then one or two drop out to maintain low pressure of ~ 1 PSI. The condensate feed issues become a nightmare and three receivers vs. one as well as the controls to make it work become hairy.

Having a 2.1 million (written as MMBTU, not MBTU as you wrote [for the output] @ 1.6 (sic) MBTU) suggests a power burner may be the boiler's burner design? It's much more effective to simply install a modulating burner. If atmospheric - easier to stage the combustion racks - than change to a new boiler system/design.

If on the other hand, the existing system is toast, I would opt for a single boiler with modulating burner. Easy to get what you want at a far better price and easy, straight-forward boiler feed options.

Before doing any design work, please check the amount of standing radiation to get a load number. Never size a replacement based on what's there. Always measure and calculate EDR based on existing radiation.

Let us know how you make out.

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Barbarossa

Mod vs. Lead/lag

The previous post on modulation has merit if the gun/boiler is reasonably efficient over the range. With modulation you eliminate the pre and post purge losses and long off times. Multiple units with lead/lag control headaches and flooding of the off units; something that can only be reduced not eliminated by header design. I have done both (more mod’s then lead/lag) and would certainly explore the modulation first.