Attached EDR vs Boiler SF of steam

Well 233 * 1.333 = 310 so it's not TOO far off given the industry standard "pickup factor"

If the mains are insulated and/or the house has the typical oversized radiators, and/or the house insulation/windows have been updated, and given the higher design day temps since the house was probably built I would run it. You might not quite keep up with your setpoint if you had a cold snap, but you wouldn't freeze. Space heater would help. We're only talking about the coldest days where it might struggle I think.

As we all know, on a typical call for heat the radiators don't completely fill with steam anyway. It is the radiator vents that regulate which radiators get steam at what rate. The boiler doesn't know if you have 800 sq ft of radiation or 300 on a typical call for heat.

Isn't it true that a perfectly sized system should run 24 hours a day on the coldest design day? My boiler is only a little oversized and I have never even come close to a 50% duty cycle I think. Has anyone ever actually installed a system of any heating technology that actually runs 24 hours straight on the coldest day?

You'd hardly ever or never cycle on pressure, that's for sure, that's a plus. You could increase the gas regulator from the factory 3.5 inches of water column to like 4" to get more steam production.

You could buy a new burner tray from Peerless spare parts to upgrade it from 63-03L to 63-03 which would get you 308 sq ft of steam which is really 410 sq ft. Although my current understanding is that Peerless doesn't support doing that.

Finally, given that Peerless 63 series is now discontinued you might be able to find a buyer for it and get yourself a larger Weil-McLain or Utica.

How did you end up with Peerless's smallest steam boiler for this house?

OK in this case there is no "should" about it, this boiler will perform as good as any boiler you could pick.

Congratulations for getting one of the last 63 models ever produced

To quote one of my favorite movies, "it would be a shame to blow it up"

And congratulations for resisting going to the next larger one "just to be safe". You have somehow, some way, actually purchased the correct sized boiler, making you very rare around here!

Paul we don't know how if it is piped or skimmed correctly, so it 'should' work good. Since it is the correct size.

The EDR rating on a boiler includes the 33% pickup factor.

I'd never exceed that rating my self. IE. if the boiler's rating is a hair under, do not go to the next size bigger, it's a mistake.

Thanks for clearing that up. Umm, the boiler states sq ft of steam, not EDR. They have the same units, correct? Hmm, my current boiler is 450 sq ft, and my EDR is 404. I think the next boiler down was 350 sq ft.

Or go with a different brand boiler. For example the chart posted above the Peerless 63-04L is 383 Sq. Ft. if that makes you more comfortable.

My old 300 Sq. Ft. boiler and 347 of EDR works fine, even when it is below zero Fahrenheit outside.

450.

Lots of good options for a true 400sqft. I think a few % undersized could be a sweet spot for many homes. Your hypothetical example is 11% undersized if go the smaller route. There are many here that would probably say go for it. I'd say depends on how much you know about the performance history of that specific system and you perhaps as the homeowner are willing to manage the system such as insulating mains well, putting in adequate main venting and likely going through some trial and error balancing. So, depends. I think many professionals installing on someone else's house or business may not want to incur the risk.

So your bathrooms and kitchen were all below 32 degrees ?

I would not size a boiler on deficiencies with the building. I'd fix the deficiencies with the building.

If the heating system can't keep up to your satisfaction you may need more radiation and a boiler to match. or just improve the building (or strategic places) which is a one time cost, fuel is a continuous cost.

I don't know that it was cycling on pressure. I didn't check then. My pressure trol is set way down, like 1-1.5psi with a 0.5psi differential.

It was a once in 40 year event…. But yeah pipes froze in the exterior walls. It was a cold, cold night, and the wind didn't let up. Huge heat loss via convection of the wind. Inside, in our bedroom, it was about 69F. But obviously, the exterior walls were much colder. So maybe it's an insulation issue. The bathroom is cooler than my bedroom, maybe by 5 degrees. I haven't been able to balance that bathroom radiator as well as the rest of the house.

Had to raise the temp to over 85F in the rooms using heaters to slowly melt the ice in the pipes. Finally water started to run. Once it starts running again, the flow melts out the ice quickly.

I guess this shows that the boiler is capable of supplying the heat, but my insulation is a bit weak around those pipes. Or I have cold air leaks that I am unaware of.

Well, in an old house, all sorts of stuff is present. Including builder's short cuts, even ones made over a century ago. Like a short run in an unheated crawl space. Or short runs near an exterior wall. You don't know what bad or good things were done, unless it's out in the open, because the builder or renovator didn't leave you plans, or the owner threw them away. Only way you discover them is via an issue, or if you happen to be doing extensive renovation yourself. And even your discoveries can fade into the mists of time.

That freeze up was the only one that I know of. I've lived here 38 years, never had a freeze problem, save for that cold and windy night.