Steam radiators

rodrigosanchez2

Hi all I’m having trouble with a steam heating system. Recently replaced 3 free standing radiators with 3 convector cast iron box and elements. The main steam manifold is piped out in the ceiling and it downs feed the steam to the radiators and fed through the top and in the bottom tap is where the return was connected to which is manifolded to the other 2 radiators originally they were 1-1/4” top tap and 1-1/4” bottom tap. The return line is 1-1/4” dry return. We connected the new radiators same way except these have a 3/4” tap on the top and 1-1/4” in the bottom. The problem is the whole supply pipe gets hot except for the radiators. What can I do to fix this?

Jamie Hall

What is keeping steam out of the dry return? And why is there an air valve, if the dry return is indeed dry and properly vented?

rodrigosanchez2

It is definitely a dry return because it is above water level. I was told to put an air valve because that’s how the original radiators were installed. Original radiators worked fine only difference now is that the top tap is 3/4” instead of 1-1/4” like it was before

Jamie Hall

There's something missing, either in the new install or left out of the old install.

Steam, as our leader says, cannot go where there is air. Conversely, it will happily go anywhere it can displace the air, unless there is a trap involved.

So. In theory, assuming the diagram shows everything, steam should get into those convectors and sail right through them into the dry return. The whole thing should get hot.

DanHolohan

Carefully unscrew the top of the steam trap and see if steam goes completely across the new radiator.

rodrigosanchez2

Yes in theory it should work but it doesn’t I even unscrewed the air valve to see if steam would start pushing faster. Everything gets hot except for the radiators. The supply all the way to the valve gets hot but it stops there. Do I need to install 1/2” steam traps under the radiator?

Jamie Hall

We'll see about the steam traps later — but I'm going to bet you need them.

In the meantime, I'm assuming from your comment that even with the air valve off the unit and the unit open to the air that steam gets to the inlet valve and stops? Is their any hint at all of steam getting past that valve? If not… um… the valve or something about the valve is stopping it.

Try this — but have someone at the boiler to shut it down immediately and a way to contact that someone. Disconnect the union between the valve and the convector and fire up the boiler. As soon as steam gets to the unit, you should get LOTS of steam out of the disconnected union. This is why you need a person at the boiler to shut it down IMMEDIATELY.

If you get lots of steam, your problem isn't the valve… but something else rigth at the inlet. If you don't, the problem is the valve or how it is installed.

DanHolohan

or a blockage in the radiator

rodrigosanchez2

Thank you guys for all your help , ended being a hidden zone valve in a storage room that I never had access to. That had its own thermostat at one point. The valve was left slightly open and that’s why steam was pushing very slow while the rest of the building warmed up fast

Steamhead

Is that the only zone valve on that system?

rodrigosanchez2

it appears to have like about 2 more zone valves that were in that room