Steam calculations

Jeremy_3

We have a customer with a Weil-McLain model H784-S, series 2 oil fired steam boiler. It is rated at 3190 sq ft of steam at 9 gph. It is downfired to 4 gph. How do I calculate how many square feet of steam it is producing?
Thanks for your help
Jeremy

Unknown

Count up the radiation

That's the right way.

However, to answer your question, Multiply the input (4 GPH) times the BTUH content (#2 oil is 140,000 per gallon)and multiply that by the boiler's combustion efficiency.

That's in BTUH; One Square foot of radiation uses 240 BTUH of steam, so divide the output by 240 for sq ft of steam radiation.


That'll be close, but it won't reflect jacket losses. Also remember to figure the house piping and pickup losses.

I'd not use this method on that grossly underfired boiler. The first thing I think I'd look up is the capacity of the steam main(s) leaving the boiler. The load won't be bigger than that, if the system is original and intact. It will be bigger than the next size lower pipe size would carry (or they would have used THAT size).

Noel

Unknown

Steam Calculations

You know that the boiler will produce 3190 sqft of steam at 9 GPM #2 oil.

The problem is is simple..

4/9 of 3190 equals 1416 sqft of steam..

That is less than half of the steam boilers capacity. You are burning less than half of the oil.

Do not worry about all the calculations that you are suppose know.

The question is why was the boiler down sized and is the building heating properly.

We can get into other details later.

You can e-mail me for information.


jake

Steamhead

First thing I'd ask is

why was the boiler down-fired in the first place?

To answer that we need to count up the radiation as Noel says. It's possible the boiler was grossly oversized for the load. I can no longer count the number of times I've seen this.

Also, if the boiler has a flame-retention burner now but did not originally, the firing rate would (should) have been reduced when the burner was changed- typically by 20 percent or so- to reflect the new burner's higher efficiency. This would account for part of the reduced nozzle size.

Noel and Jake are right, we really need to know more about the system to be more specific.

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