Flooded radiators

mfritzg

Struggling to find a solution, single level county building built in the 60's, steam boiler replaced in the last five years, radiator only heating, thermostatic valves and floats replaced on all of the radiators with in the last five years. On very cold days, when the entire building is calling for heat all appears to be working correctly, Once some of the areas satisfy and the overall load drops, the remaining radiators that are still calling for heat flood with condensate. Thank you in advance.

BobC

Several things to check-
Near boiler piping
Slope of mains and radiator piping
Possible failed traps

Does the water level in the sight glass bounce around a lot when making steam? Post pictures of the boiler and the [piping around it.

Bob

Jamie Hall

Is this one pipe or two pipe steam? Could make a big difference in where to look and what to look for.

What pressure does the boiler run at?

mfritzg

Thanks Bob, all piping appears to slope correctly, traps have been checked, I have not noticed the sight glass bouncing, I will verify and also post pic's tomorrow.
Thanks Jamie, it is a two pipe system and 5# pressure.

BobC

Why 5#? That seems awfully high, do you know if there is a specific reason?

Bob

mfritzg

Unknown, the facility engineer indicated it has always been operating around 5#. Too high possible?

Jamie Hall

The reason I asked is that you may be backing water out of the boiler into those radiators when the pressure rises. In fact, 5 pounds will raise water about 16 feet. You say that this is a one story building. Even if the boiler is in the basement, that's enough to flood all the pipes in the ground floor very happily, never mind their returns -- unless there is a really truly bullet proof way to keep that from happening (and note that check valves absolutely won't do it).

A scenario which I can envision is that the boiler runs very sweetly at a half a pound or less, and gets much of the radiation filled. Condensation slows, pressure rises, water backs out, radiators flood and there you are...

Jamie Hall

11.5 feet. Not 16 feet. I can't add...

But it's still enough to possibly cause a problem.

mfritzg

Gentlemen, thank you, we will drop the pressure down and monitor the performance, I will send pic's of the system tomorrow and let you know how it performs with lower pressure.

JUGHNE

From my limited experience, what I've seen is that lower is almost always better, as long as it heats the building....one exception being if the steam pressure is required to lift the condensate coming from an F&T trap, then some lbs are required. FWIW

nicholas bonham-carter

Jaimie, I think you hit the nail on the head! Oh the evils of over-pressure. That 11 feet of rise would certainly block the the dry returns, and flood the radiators..--NBC