Boilers in Parallel

[thewormz]

We have 4 buildings spread out over our campus and each one has its own boiler.
Our problem is some boilers do not supply enough to their own buildings on peak demand, and some break down.
We want to tie them together to better utilize all the boiler power we have, and provide redundancy in the system. We cannot go higher HP on the boilers we have otherwise we get into permitting issues, they don't care that we have 5X 20HP boilers they just don't want a 25HP.

Minor considerations/concerns:
Is it better to locate all the boilers into a single location instead of having them distributed throughout the facility?
The steam distribution part is easy, but should we put check valves coming out of the boiler so that one boiler doesn't feed into another?

Major Concerns:
How to handle condensate?
If one building demands a lot of steam, it will generate a lot of condensate and overwhelm the local boiler it is piped to. While the other distributed boilers will be starved of condensate and be pulling in makeup water.
Options: each building gets a condensate reservoir and a pump, and let a plc control what boiler needs it?

I guess what I am asking is does anyone have a reference on this sort of problem? Every option just seems to add complexity for problems, and will have to be built with lots of redundancy unless we relocate all the boilers to a central location.

 

[MJCronin]

Many campus facilities understand the advantages of a district heating system, which seems to be what you are describing.

Retrofitting such a system onto an existing campus can be expensive and difficult. It may be best to consider the shared use of other utilities (chilled & potable water, power etc) to develop a complete cost/benefit comparison.

If the boilers are at the end of their useful lives, this may be the time to consider such a bold scheme. Replacement of old equipment with modern, more efficient units can pay for the capital costs in a surprising time..

How far apart are the buildings ?

What is the fuel ?

Is there shared chilled water A/C and how is it executed ?

tell us more.....

MJCronin
Sr. Process Engineer
Venture Engineering & Construction

http://www.VentureEngr.com

 

[chicopee]

I am on line with MJCronin with district heating for a campus, however, in your case each 20hp boiler, (and by hp. I would make the assumption that you are referring to boiler horsepower (Bhp)and not the horsepower of each burner, the steaming hot heat outpout is equivalent to 670000 btu/hr which is small and essentially is for residential application.) would not warrant cross connections between boilers, and I would opt to install an addition 20 bhp in each building.

 

[StoneCold]

Maybe the question is why would you not want a 25hp boiler? Is the 20 hp boiler below the minimum size that requires inspection on an annual or biannual basis?

 

[chicopee]

Normally a properly maintained boiler should last the entire heating season, so may be that is an issue. Obviously for a campus qualified maintenance personnel performing routing boiler maintenance is also necessary.