gas fired steam boiler

Ficco

I recently had a new boiler installed. It replaced a 140,000 btu unit. the new unit is 87,000btu. I was told by 3 contractors of Burnham that the old unit was to big for the house. My house is about 1100 sq ft. The new unit works fine but some of my radiators are not getting hot. The thermostat is set at 72 deg. plenty warm enough to heat the house. All the pipes in my basement are hot but the heat does not seem to get to some radiators. Do you think the valves in these radiators are bad. They worked fine with the old unit. All 3 contractors took measurements of my house to determine the right size boiler

Jamie Hall

Well, without knowing the total EDR of the radiators one can't say whether the boiler is the right size or not -- total size of the house has nothing to do with it.

That said... no one ever said the radiators have to get hot all the way across with steam heat. The question is, can the system keep the house at the thermostat's set point? And that isn't clear. If it can, it's working.

You mention that the pipes in the basement are hot. They should be -- but they should also be insulated. If they are not, do it -- 1" fiberglass.

Ficco

They also measured the radiators.

KC_Jones

Sounds like a balance issue, we see this on a regular basis around here.

First thing kudos to the contractors for down sizing to what is hopefully a proper sized boiler.

What is your main venting like in the basement?

Ficco

Can you explain main venting? I'm not familiar with all the furnace terms. thanks

neilc

Main venting is the venting on the pipes leaving your boiler,
vs radiator venting.
Let's start with,
Are we talking Steam or Hot Water boiler?
One or 2 floor house?
Post a picture of your boiler, one shot, floor to ceiling, showing as much detail as possible, including the pipes above.
and post a picture of your radiators.
we go from there.

Douglocal638

Doesn’t really matter if they worked with the old unit of not? Are the air vents on the end of the radiators painted over? Are they old? Are the radiator pitched back towards the incoming steam pipe? are the main vents painted over, or old? Did the boiler ever get flooded by accident and you had water coming from radiators up stairs? Many questions to be answered.

neilc

nevermind my steam question,
just read the subject line , again.

Ficco

for Neilc. There is one vent installed by furnace people off a heating pipe in the basement. We are talking steam heat for 2 floors.
for Douglocal638. Air vents on radiators are not painted over. The radiators are pitched back toward the incoming pipe. No the boiler was never in a flood accident and no water ever came out of the radiators

Jamie Hall

Considering your reply to @neilc above, I would venture that you don't have anything like enough mains venting. That will make it difficult for steam to get to the farther radiators.

Ficco

Jamie, this is the same amount of vents in my basement when the old boiler was in use. And all the radiators worked fine. I really wish I could find someone that really knows steam systems

JUGHNE

But your old boiler was too large, the vents may work differently now.

Jamie Hall

The venting is part of a system -- as is the boiler. If you change one part (the boiler) you may need to change another part (in this case the vents). There is, however, one sure way to check if you have a low pressure steam gauge. Watch the gauge from a cold start. It should rise slowly to perhaps a couple of ounces, no more, and then just sit there -- possibly rising slowly, but much more slowly than the initial rise -- until all or most of the radiators are hot at least part way across. Then it will start to rise again, rather more quickly -- that's when you want your pressuretrol or vapourstat to cut out. If it rises fairly quickly on the initial warmup to a higher pressure -- say over half a pound or so -- you don't have enough main venting.

In your situation, although the boilers are of similar output, it is likely that the new boiler has less water capacity and better heat transfer, so it develops steam much faster at the beginning.