Downsizing 1 pipe steam boiler

Kjmass1

I have a 192k/152k 30+ year old Penco boiler in a ~1900 sf home in Boston. We’ve slowly been reducing our EDR as we lost a couple rads in a kitchen reno, attic now has a minisplit so is redundant, basement ceilings aren’t used, etc. we are currently at 303 EDR, and we can lose another 24 EDR as our bathrooms have heated floors.

I’m going to get a room by room heat analysis done to realign the radiators with their actual load as we have done a lot of insulation improvements. Whether it is swapping or finding smaller ones, I’m hoping to get my load down to 250EDR. The goal is to get the smallest boiler I can with radiators sized for the actual heat loss of the 1940s home.

What type of wiggle room is there on the pickup factor? I have a 40’ and 20’ main piping. I’ve seen 1.1-1.33?

Ideally I’d size only for the radiators on the 2 main living levels to keep it as small as possible. Trying to reduce nat gas usage as much as possible. Thanks!

Kevin

ethicalpaul

If you want to get real accurate with it (and it seems like you do), maybe manually calculate your actual pickup factor of your system and use the gross EDR ratings of the boilers, ignoring the manufacturer’s pickup factor

EBEBRATT-Ed

@Kjmass1
your probably headed for the smallest steam boiler available anyhow. so reducing the edr may cause you problems if you get to low you will end up with an oversized boiler.

If you want to keep steam, that's fine I love steam. But if all the heat is on the main floor you ay want to consider a hot water conversion for such a small load.

Pick up is 1.33 for steam. Others have used less. Whatever your calculated EDR comes out to be you can't buy a boiler with the exact EDR. Just make sure you have something in there for pick up

ethicalpaul

The smallest I’ve seen are about 200 net EDR, with about 75k btuh input. I think he’s going to need a little bigger than the smallest.

@Kjmass1 I like your thinking about resizing some of your radiators to be more appropriate to the room. People don’t seem to be willing to do this much, but I don’t understand why.

Kjmass1

Just a quick math on the mains and run outs is ballpark 100EDR, but those are uninsulated numbers and my mains have fiberglass on them. Like you said 80k is probably in the ballpark and the smallest I could go- and would be a huge improvement on what I have now.

I certainly don’t want to be oversized- and have 36 EDR in the basement in play if I really need it.

It’s tough finding a contractor who is competent in steam in the first place, and willing to run all these numbers. As a homeowner it’s fun to learn about it all. I’m pretty close to just doing the Manual J myself.

JUGHNE

Heated floors in bathrooms are usually consider supplemental comfort sources.
Unless you have a lot of floor space available.
Usually another source is needed for the really cold days.
I have floors and walls with heat embedded and can get by.
Without the wall heat the floor only would not cut it.

So my advice is to keep the steam in the baths.
Great towel warmers.

Kjmass1

> @JUGHNE said:
> Heated floors in bathrooms are usually consider supplemental comfort sources.
> Unless you have a lot of floor space available.
> Usually another source is needed for the really cold days.
> I have floors and walls with heat embedded and can get by.
> Without the wall heat the floor only would not cut it.
>
> So my advice is to keep the steam in the baths.
> Great towel warmers.

Thanks good to know- they are pretty small in the grand scheme of things so I like your thinking.

gfrbrookline

Sounds like a good job for New England Steam Works to figure out.

Kjmass1

You in Brookline,MA?

BobC

@Kjmass1 If you have electric heating mats in the floor they will fail in a few years so keep the rads in the bath's. i don't know what kills them but those mats just don't last and replacing them means tearing out the floor.

Bob

brandonf

Maybe I'm being too meticulous, but for remodeled rooms it might be a good idea to do a heat loss calc so you can find an ideal size radiator or know if you can eliminate one. No real downside to more accuracy. 🤔