Historical Heat Load Calc/ Boiler Sizing methods

InTheLeed

I'm looking for information on some historical methods to both size total systems, and to size the boiler itself to these methods after results are reached for heating demand

Steamhead

The most famous one

was the "Mills Rule", named for John Mills, one of the pioneering geniuses of steam and hot-water heating. If memory serves, it went like this:



1. Measure the square footage of glass and divide by 2.

2. Measure the square footage of walls, ceilings and floors that are exposed to the outside and divide by 20.

3. Measure the volume of the room in cubic feet and divide by 200.

4. Add the results of 1, 2 and 3 to get the EDR needed.



There were other rule-of-thumb methods, but I believe all of them were based on Mills' rule.



Once you knew your EDR, you would then size your piping to carry the needed amount of steam or water at a very low pressure drop. On steam this meant a drop of 1 ounce in 100 feet for the smaller systems.



Coal-fired boilers were sized to be able to heat the radiation to its maximum capacity for at least 8 hours on the coldest day of the year, without having to add more coal during that time. This invariably resulted in some seriously oversized boilers, which made things interesting when it came time to convert them to oil or gas!

Mark Eatherton

I'm wondering....

Exactly how accurate was Mr Mills method? Has anyone gone and done a new style loss calc to confirm his numbers?



To the original poster, what exactly is it that you are looking for? Can you be more specific?



ME

Steamhead

Dan actually did that once

it's in his out-of-print book "Ye Compleate Workes of Dan Holohan" which is a collection of articles he had written up to that time. I'll look it up when I get a chance.



Hey Dan, while I think of it- how about "Compleate Workes, Volume 2"?

DanHolohan

Worth thinking about.

Thanks, Steamhead.



Mark, Mr. Mills' Rule will give you about 19% more than you need.

Mark Eatherton

Thanks Dan...

Them was some SMART Dead Men.



How did they know?? Like Gil Carlson, I guess they just "Got it".



ME