A Messed up 2 Pipe system

BernV

If you have a two pipe system, with a gravity return, no vent at boiler, and vents on radiators w/ thermostatic traps, what kind of problems could I see?

Checked out customer house today and that is what I found (In part of the house anyways). When boiler cycles on, I get air from vents on radiator. This is coming from the return line, not the steam line. Even when I disconnect the thermostatic valve on the rad inlet, I get no steam but this is due to a low spot in the lateral before the riser.

I don't know what was there prior to my visit. All the rads have air vents and suprise....on rad they couldnt repipe has the tell tale valves at both ends. (It doesnt heat either...imagine that.)

My main question is....should I remove and plug all the air vents on the radiators?

The main (50 ft) is sloped away from the boiler towards a condensate pump with a F&T at the end of the main. The lateral I mentioned comes off the main and runs for 10 feet before the riser. It slopes towards the main. (except for about 2 feet at the end which slopes away because of some improper piping) One problem I am having is that even though the end of main F&T flows condensate, (Disconnected a downstream union), the main is backing up with condensate, so much that it is keeping steam from reaching two radiators near the end of the main.

Should an F&T be installed before the riser at the end of the lateral?

 

Jamie Hall

You do have

The Lost Art, don't you?  I hope... if so, reread the whole section on two pipe steam with gravity returns.



And no, with very rare exceptions vents are not used on the radiators on a two pipe system. 



It sounds as though one or more of your predecessors working on this system has managed to really mess things up, and it would be hard to say just where to begin.  The mains do have to be vented somewhere, somehow.  The condensate pump (which really shouldn't be needed on a gravity system, unless water levels got messed up sometime -- which is possible) should have a receiver, and that receiver needs to be vented to the atmosphere.  Is it?  If not, then how would the air which gets by the F&T from the main into it get out?  And if the air doesn't get out, how does the condensate get in?  So that's one place to start looking anyway...



If the air coming out the vents is coming from the return line, something is seriously wrong -- the return should not be pressurized.  Until that is fixed, nothing else is going to work as advertised -- so I think I'd start there.



Sounds to me like you have a longish, but potentially very interesting and rewarding job ahead of you! 

Jamie Hall

You do have

The Lost Art, don't you?  I hope... if so, reread the whole section on two pipe steam with gravity returns.



And no, with very rare exceptions vents are not used on the radiators on a two pipe system. 



It sounds as though one or more of your predecessors working on this system has managed to really mess things up, and it would be hard to say just where to begin.  The mains do have to be vented somewhere, somehow.  The condensate pump (which really shouldn't be needed on a gravity system, unless water levels got messed up sometime -- which is possible) should have a receiver, and that receiver needs to be vented to the atmosphere.  Is it?  If not, then how would the air which gets by the F&T from the main into it get out?  And if the air doesn't get out, how does the condensate get in?  So that's one place to start looking anyway...



If the air coming out the vents is coming from the return line, something is seriously wrong -- the return should not be pressurized.  Until that is fixed, nothing else is going to work as advertised -- so I think I'd start there.



Sounds to me like you have a longish, but potentially very interesting and rewarding job ahead of you! 

Jamie Hall

On further condiseration

is this system very old?  Like around 1900?  It could have been a two pipe air vent type of system.  The double valved radiator suggests that.  See Lost Art, pages 228 and 229.



If so, you've got a ways to go here -- but they can be straightened out.