Oversize for uninsulated mains heating basement

curiousburke_2

Hello Heating Helpers,
I've been a frequent site visitor for the past 3 years since owning a home with steam heat and have found the advice here invaluable in getting my system working smoothly. Thanks also to Rod for lots of personal help via email. Unfortunately, now my boiler has sprung a leak above the waterline and I'm going to replace it.

I've calculated the total EDR of my radiators to be between 330 and 350 square feet, so between 79k and 84k. I have one odd bench seat radiator that provides the range. My old 4 series Burham produced 538 sq ft. steam, with a NET IBR rating of 129 BTUH. Dropping down by that much has me a little worried since my current system seems to run smoothly, especially if I don't use any nighttime setback.

I know a lot of old boilers were oversized, but I'm concerned that I do actually need a larger boiler because none of the mains in the basement are insulated. It's a finished basement, and the mains provide some heat, so I do not want to insulate them, but also at least half of the piping is above the ceiling so would be difficult to insulate.

My plan was to buy a Peerless series 63-04L, which has a net rating of 92k BTUH (383 sq ft steam) but I'm wondering if I would be better off with the 63-04, which is 110k BTUH(458 sq ft steam). This second unit is exactly the same size and weight, so I assume just has more burner tube, yes?

Any advice would be greatly appreciated.

Thanks you,
Mark

curiousburke_2

Yes, it would cycle on pressure if I had a nighttime setback of 8 degrees. I don't think I ever saw it cycle with no setback.

The steam mains are 2". The total exposed length is about 25'. Above the ceiling is harder to say, but I'd say around 40'.

curiousburke_2

Oh, I just remembered, I have another 17' of exposed main in the garage that I've been meaning to wrap heavily. The heat loss from that melted off most of the black foam that a previous owner installed.

I've had no problem getting heat to all my radiators.

BTW, this username is new because for some reason my old id was not being allowed to sign in. Erin, whom I assume is the site administrator, is kindly looking onto it for me.

ChrisJ

The Burnham cycled on pressure, but what pressure was that? 1 pound? 2 pounds?

curiousburke_2

I have a pressuretrol, set at it's lowest settings, so 0.5 plus 1, so 1.5 pounds I believe.

ChrisJ

Something to consider is whether or not that Burnham is actually running at it's rated output as well.

If it's oil fired, it could have easily been downfired.
If it's gas fired, it could've been downfired as well. Are all burner tubes present? Has the manifold pressure been checked?

This is actually very important if you want to use the current boiler to size the new one, i.e. go a hair smaller etc. If the current one has been downfired, you may want to go quite a bit smaller instead of a tad.

curiousburke_2

I'm not sure if it is downfired, but knowing the condition of the house, I doubt anything above a basic install was done. Could I tell by just looking at it?

I was thinking, one advantage of getting the larger boiler is that I could downfire if need be, but if I get the smaller one I could be SOL.

curiousburke_2

why is that?

curiousburke_2

The other thing I was wondering is: would an old boiler have reduced efficiency, such that it isn't really making 538 sq ft of steam

Ahhh, I just had a revelation. With a hole above the waterline, how much of that steam could have been going up the chimney?

curiousburke_2

curiousburke said:

Ahhh, I just had a revelation. With a hole above the waterline, how much of that steam could have been going up the chimney?

I guess not much if it goes by the ratio of area. The Burnham has 2 2" risers. hey must move a lot more steam than a waterline hole.

ChrisJ

Boilers always run less efficient when downfired.
You don't want to be downfired if it can be avoided.

curiousburke_2

Okay, it sounds like the 63-04L is the better way to go, but Hatterasguy you said "probably do setbacks". Is that just na understatement, or is there really any chance that I won't be able to do setbacks?

Since the 63-04L is the same size and weight as the 63-04, is it just a downfired version of it? Could this be modified, if need be, to be "upfired"?

curiousburke

Hello All, I am the OP. Erin fixed my account (many thanks) and I'm back to using my original user ID.

curiousburke

I'm still a little fuzzy on the whole short cycling thing. The Burnham never had very short cycles and it always got the heat to all the radiators. Is shutting down on pressure at some point during its operation fundamentally bad, or a sign of reduced efficiency, if the cycles are fairly long?

curiousburke

I'm sorry, I didn't mean to imply it short cycled; I just meant that shut down on pressure. I never saw anything like a two minute short cycle. I had wondered at times what defines a "short" cycle; I wish I had measured the cycle duration, but it was a lot more than two minutes

curiousburke

Hmmm, I wish I could remember better. I guess it doesn't really matter, the system worked much more smoothly with no setback.