2 pipe steam problem

Fischetti · February 2010

Installed Utica 300,000 gas steam boiler

2" copper return reduced to 1-1/4 steel water being pushed out of end of line air valve by boiler also water pushed out end of the line air valve in garage 50ft away and 10ft high.

jpf321 · February 2010

when?

when was the boiler installed and when did you start experiencing problems?

nicholas bonham-carter · February 2010

2-pipe over-pressure?

check and regulate your pressure with a good low-pressure gauge [gaugestore.com 0-2 psi], as it looks like the high pressure is pushing water out of the boiler, up into the returns. this could be as simple as a clogged pigtail, or a faulty pressuretrol. if the later, consider replacing it with a vaporstat.

the maximum pressure you should have is 2psi, or for comfort,1.5 psi; or for more comfort, and economy, 8 ounces.--nbc

Jamie Hall · February 2010

Your pressure

as NBC said, is probably too high -- for starters. If the boiler is capable of raising water 10 feet, the pressure in the boiler has to be at least 5 psi -- which is about 3 times as high as it needs to be. There may be piping problems, or trapping problems, which can aggravate an already lamentable situation.

Get the pressure down first, then see what happens.

Nick_C · February 2010

A few things...

I think there is some misunderstanding about boiler pressure and the impact on raising the water level in the returns. First, pressure in the boiler does not cause the water level in the returns to "stack up" on a one-for-one basis. In other words, a boiler at 1 psi of relative pressure (27 inches of water) does not cause the water level in the return lines to rise by 27 inches. What matters is the difference in pressure between the boiler and the the pressure at the point where the dry return turns into a wet return. That pressure difference is what's most important and it will vary from system-to-system and will also vary during the cycle. If you have a massively oversized boiler, then this pressure difference will be strongest at the beginning of a cycle and can cause the water to literally shoot out of the boiler into the returns. (A properly sized equalizer helps stop this effect even in a massively oversized unit.)

Assuming the sight glass is working properly, if you aren't seeing a massive reduction in the water height in the boiler, then you aren't going to have a problem with water stacking in the returns (and this flooding a vent).

I know that NBC and Jamie know this - just think we need to be clear for the benefit of others.

jpf321 · February 2010

what about the case ...

of a system lacking both equalizer and check valve? how does that work? such as steam-rookie's system.

Nick_C · February 2010

It's the same...

It's still the same concept. What matters is the relative pressure difference between the two points. Just watch the glass tube. If it doesn't drop much, then, by definition, water isn't stacking up in the return. If the water level in the boiler goes down fast (ie not from creation of steam), then you might have an issue with a flooded return. But it takes a special kind of screwed up system for this to happen.

2 pipe steam problem

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