I=B=R Ratings

George T

After a heat loss is done, which BTU output rating is used? I have seen conflicting info on different websites, even from Weil-Mcclain themselves. Various people claim to use the I=B=R Rating others claim to use the DOE Rating, including Weil themselves.


CGI - 6 Weil Boiler Specs
Input - 167 MBH
DOE Heating Capacity - 140 MBH
Net I=B=R Water rating - 122 MBH
If you us the IBR its an almost 20,000 btu difference, so which is correct???

Brad White

For greatest efficiency

I would use the gross output rating when sizing a hot water boiler. Most boilers are over-sized to begin with. To add 15% on top of that (ostensibly for piping and pick-up) is folly.

The I=B=R 15% factor was originally conceived to account for piping and pick-up losses. These days with rational insulation and intelligent setbacks, few houses have to heat up from zero.

George T

calification

the house is 50 years of, has a single monoflo system which will be split to 2 maybe 3 zones. House is brick with full 2x4 inside constuction, and has some insulation.

So you are saying i should use the DOE not IBR??

Brad White

Yes

I would use the DOE rating.