Header advice, and other boiler replacement questions...

Fred

@Steam_Jon , you have to factor the boiler efficiency into the calculation, as per @KC_Jones' calculation above.

Steam_Jon

New England SteamWorks said:

The boiler you are considering does have 2 each 3" risers/tapings. And it is a fine boiler. If the installation is gas and in this size range, we use either your choice Weil McLain/GSA/Williamson, or Peerless. The gauges and controls are on opposite sides, so this sometimes makes the determination which we use.

You'd be safe with an EG-55 or GSA-200. But if it were us installing, we'd take a hard look at whether we could make the EG-50/GSA-175 work. Bigger is not better with steam.

You do need a new header. The steam supplies need to be piped into the header after the two risers, not one on each. Close, -but no cigar. And any contractor who didn't see this is not worth your time.

@New England SteamWorks I'm considering the Peerless 63-05L, rated for 533 SqFt, compared to my EDR calc of 501. The Williamson/Weil options are rated at 521 SqFt which is a better match, but it seems Peerless gets more praise around here. Is the difference of 12 SqFt between the two negligible?

New England SteamWorks

Yes, the difference is negligible, and as far as I am concerned, they are both equally fine boilers.

As previously stated however, if I were the contractor, I'd be looking to see if one size down could do the job better.