Boiler Replacement Sizing Question

roc_rktec · November 4

Hey all, we currently have a Utica PEG187 from 1991, that I am finally in the position to replace along with all of its crappy near boiler piping.

Our system has is smallish at 343.5 sf (82,440btu) of radiation. Using a standard 1.333 pickup factor places our system in between the Weil McLain ED-40 & EG-45 boiler models based on AHRI rating (no one installs Peerless around here).

All of the mains, branches, and condensate return lines still have their original asbestos insulation intact. We have added insulation in our attic and storm windows to increase the efficiency of the thermal envelope of the house. Would it be a mistake to "undersize" the boiler by using a EG-40 (resultant pickup factor of 1.24)?

ChrisJ · November 4

Do not go larger than an EG-40.

If it was mine id probably go EG-35.

ethicalpaul · November 4

Don't worry about the BTU, don't worry about the pickup factor. Just compare your installed radiation to the Net Sq Ft of steam of the boilers you are looking at.

I wouldn't rule out Peerless or even Utica just because of what the contractors there like to install. There's no installation difference between any of the gas atmospheric steam boilers to speak of.

For WM, the EG-40 is rated at 321, that's the one I would pick. The 33% pickup factor that I advised you ignore is outrageously oversized so 321 sq ft is plenty large. 388 (EG-45) would be a crime.