Yet another radiator trap question

JimRafferty

Holiday Greetings!
Need a little wisdom here.
2-pipe steam with rad traps on returns.
Customer has one rad which will not heat (Rad #1) and one nearby rad which heats just fine (Rad #2).
The customer likes to tinker and pulled the trap cage out of the cold rad (Rad #1), left the trap cap off and only then we have great steam coming up the supply and heating the rad so the supply side is good and the supply valve is open. He then took the trap cage out of the good rad (Rad #2) and installed it in the cold rad (Rad #1). The cold rad is still cold even with the "working" trap cage unit.
He then took the trap cage from the cold rad (Rad #1) and put it in Rad #2 and it heats just fine.
What am I missing here?
Would appreciate any and all suggestions.
Thanks!

Jamie Hall

Is one of those two failed open, by any chance? If one is failed open, the radiator on which it is installed will usually heat just fine -- and none of the other radiators in the vicinity will heat at all.

Sailah

Blocked return pipe on Rad 1?

JimRafferty

Thanks for your responses.
The return pipe appears open. With the the trap and cap removed, we do get some pressure pushing up the return while condensate from the rad does drain. It spits and sputters but it does drain.
As for one of the traps failing open, what's a good way to check? And there are gobs of other radiators.
New 2,000+ sq ft. boiler last year. Properly sized, rad count etc. Per customer, rad problems unrelated to new boiler.
Thanks!

steamhouse

> @JimRafferty said:
> Thanks for your responses.
> The return pipe appears open. With the the trap and cap removed, we do get some pressure pushing up the return while condensate from the rad does drain. It spits and sputters but it does drain.
> As for one of the traps failing open, what's a good way to check? And there are gobs of other radiators.
> New 2,000+ sq ft. boiler last year. Properly sized, rad count etc. Per customer, rad problems unrelated to new boiler.
> Thanks!

Just draining is not good enough. I bet there is a sag in the return causing standing water. If the air cannot get out the radiator will not heat.

Jamie Hall

You should not be getting pressure pushing up from the return. Somewhere pressure -- probably steam pressure -- is getting into that return, and it may be a bit tricky to find it.

Fred

@JimRafferty said: As for one of the traps failing open, what's a good way to check? And there are gobs of other radiators.
Can you find a radiator where the pipe under the trap is about as hot as the supply pipe?