Boiler Replacement Sizing Question

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.

The EG-40 is good for 321 sq feet of steam. That is what I would use.

My boiler size relative to radiation is similar. The boiler is a WM EG-45 and my best estimate of the radiation (from the various charts) is, say, 345 sq ft. If I had to replace the boiler at this point, I certainly would go smaller.

However, the EG-45 can be pretty easily downsized to an EG-40 and I have had helpful discussions with @ChrisJ about doing this. Parts cost would be roughly $150. If the parts were not on extended back order, I would likely have already undertaken the modification.

With the system as it is, I do observe cycling on pressure (2-2.5psi), but generally only when recovering from overnight setbacks of around 4 degrees or more. Main and radiator venting is all adequate. Steam mains and near boiler piping are all insulated. All the radiators fully heat up after an extended runtime.

My question is whether you think making this modification makes any sense in terms of, say, potential fuel savings.

I expect that a downsized system would mean - for every boiler firing - a somewhat longer time for the boiler to begin making steam and the lower rate of subsequent steam production would increase the time to heat up all the piping to the radiators. How much of this would be noticeable to me can’t be known without trying it.

Your thoughts?

How much of this would be noticeable to me can’t be known without trying it.

it’s minimal. You might be able to time it to see the difference but you’d never notice it from your living room.

you can get a preview for free by blocking one of the burners with a small piece of aluminum tape over the burner supply orifice.

Don’t block the one that the flame proving rod is attached to 😅

Ok. Then what about the potential benefits from downsizing? Fuel savings, less cycling on pressure after setbacks, lower average steam pressure. Noticeable or minimal? Crime not to do it in your view?

@roc_rktec , if you're going with Weil-McLain, I'd use the EG-45 and downfire it a bit if needed. This would mean the cast-iron would run a bit cooler and last longer.

The only thing wrong with your present Utica is the installer. There may be some illiteracy issues there- proper piping is spelled out in the manual. I'd repipe it, in such a way that when replacement time comes you won't have to rip everything out.

That air vent in the first pic looks like it's in the wrong place. Steam from the header will reach it quickly and close it. The proper place for these vents is at the ends of the steam mains and, if this is a 2-pipe or Vapor system, at the ends of the dry (overhead) returns.

If you're not sure what type your system is, post pics of some radiators that do not have covers. We can tell from this.

The savings that would be even slightly more than negligible would only happen during the once a day during recovery from setback and even then would be tiny compared to the cost of replacement so it would never pay for the replacement cost. just do it right when it does need to be replaced.

since you commented on someone else's year old post, can you show us your near boiler piping? If your near boiler piping is as bad as the piping from the op and it affects the speed with which the system heats then fixing it could be worth it.

Thanks for having a look.

I have a Big Mouth at the end of the single 60-foot, 2.5” main and also a spare Gorton #2 midway (since there was a tapping there.)

One change I’ve made for this heating season is replacing my older thermostat with a VisionPro 8000. This model gives me the option for CPH setting of 2 instead of just 1 (or 3) like the older model. I’m expecting to see smaller temperature overshoots (and undershoots). So tighter temp control and therefore less boiler on-time opportunity for building the higher undesired pressures. Am interested to see the effects.

@Marc_18 , I'd move that Gorton #2 to the end of the main, teed into the location where the Big Mouth is now. You want all your venting capacity at the end of the main.