Boiler Downsizing

Kjmass1

Let me know if my numbers are correct. My current, old boiler is 192k input/153k output. With the help of you folks I've calculated my steam radiator EDR to 471 for my system. I have 108 EDR's worth of radiators in my basement which is unfinished and are not in use. When we eventually renovate the basement we'll probably switch over to electric baseboard and remove the radiators from the ceiling to help with height clearance. The room won't be heated at all times, more on an as needed basis.

We have a kids playroom in the attic that is 60 EDRs. Rarely used but needs to function as designed.

With the attic heat turned on at times that would be 363 EDR. With it turned off most of the time we would be at 300 EDR.

Would I be able to downsize to an IN-5 140k input/86k output/ 358 sqft of steam output? Or do I need to have more pad than that? I've heard about the 33% steam pickup factor and didn't know if that is included in those numbers. The system seems to be running well and I wouldn't want to be undersized. On the other hand, would this equate to 25% less fuel spent, plus shorter burn times with the increased boiler efficiency?

Thanks.

BobC

If you insulate the piping in the basement you should be fine with the smaller boiler. It will be more efficient and probably not trip the pressure device except if coming back from a deep setback.

Bob

nicholas bonham-carter

Is this a 2-pipe, or 1-pipe system?
When you figure your EDR in square feet, just match it to the EDR of the boiler directly with no added. 33% pickup factor as that is already included.
Some 2-pipe systems can be sized below the EDR to a point closer to the building heatloss. Boilerpro/steam whisperer has done some tests on this.
Put a low pressure gauge, generous main venting, and proper piping on the new one. Don't forget pipe insulation as well!--NBC

Kjmass1

This is a one pipe steam system. Main and radiator venting is in good shape, and I recently insulated all the pipes.

Here's another wrinkle. When we renovated the kitchen we took out a small wall radiator. The kitchen is on the cooler side, but not by much. I'm looking in to possibly adding back in another 30 EDR in that room.


So if the system EDR is now 330 most of the time with a boiler putting out 358, probably not a problem.

What happens if I want to turn the attic on for a day or two, and now I need 390 EDR on that boiler? Will the radiators eventually fill up it will just take longer? Or will it just run and run not able to keep up?

Steamhead

Forget about electric baseboard. It's cheap to install but quite expensive to run, which will keep you from enjoying that room. A hot-water loop off the steam boiler is a much better way to go.

But, just how high are those ceiling radiators?

nicholas bonham-carter

Main and radiator venting must be in very good shape as you may dip below the EDR constant, and you want all the radiators to get steam at the same time.
It's not enough to have a vent which seems to work-you need enough main venting, to get to the open pipe point.--NBC

Kjmass1

Steamhead said:

Forget about electric baseboard. It's cheap to install but quite expensive to run, which will keep you from enjoying that room. A hot-water loop off the steam boiler is a much better way to go.

But, just how high are those ceiling radiators?

Thanks- that's good to know. The bottom of the radiators is about 76", the floor joints are at 82". I was hoping to get a bit more clearance, and get them down strictly for appearance.

What's the recommended BTUs/sf for Boston area?...in a basement? That part of the basement is probably about 800sf. The combined EDR of those two radiators is 108.