steam condensate trap?

gerardlem · February 11

I have a Dunham (condensate vent?) not sure what this is. See pictures. The inlet comes from the condensate return lines from about 3/4 of the radiators with 1-1/2" pipe then goes up 20" with 1" pipe into the 2" gravity return (so as to avoid doorways) which catches the rest of the radiators then into the boiler feed tank. There is a lot of banging and I suspect that this is the issue. The system used to have a vacuum pump attached to the returns but that was another nightmare. Any help would be greatly appreciated. Thanks

EBEBRATT-Ed · February 11

I don't know what that is, @Pumpguy

Steamhead · February 11

Lift fitting?

EBEBRATT-Ed · February 11

Yes. I thought that after he mentioned vac pump. That is probably why the riser is smaller than the horizontal to increase velocity

Steamhead · February 12

That would explain the banging. It needs vacuum to operate.

Pumpguy · February 12

https://forum.heatinghelp.com/discussion/comment/1887501#Comment_1887501

Thats what I'm thinking. The difference in vertical and horizontal pipe sizes is a good clue.

That said, I've never seen a cast iron lift fitting that looks like this one.

Sounds like this OP needs someone that really knows about 2 pipe vacuum return systems.

Let start by asking what is the operating steam pressure on this system? Also, what is the height of the lift in these pictures?

Not having any vacuum on these returns means we need the water column height in back pressure to move condensate up that lift pipe.

gerardlem · February 20

I believe that EBEBRATT and PUMPGUY are correct. The riser goes up about 18" and with vacuum it increases velocity. System pressure now is 4-5 PSI the system heats up but a lot of banging. I think that without a vacuum pump I will need to pipe the return gravity all the way back to the boiler room.

Thanks for your input.

Gerardlem

mattmia2 · February 20

i;m not sure i see the difference between the mains being at 5psig and the returns at 0psig vs the mains at 0 psig and the returns at 10 in hg vacuum. either one will push the water out of water seals and lift condensate. the boiling point of the water is the only difference that i see. seems that it is likely some bad traps or pitch somewhere.

Jamie Hall · February 21

@mattmia2 is absolutely correct. What matters is pressure differentials, not absolute pressure (absolute pressure does affect boiling point, though).

gerardlem · March 5

Yes there are bad traps. But in order to get the air out of the system the pressure needs to be elevated more than necessary then if there is one bad trap it allows steam into the return which in turn causes water hammer which causes more bad traps. Vicious circle. The system does heat but noisy.

Thanks

mattmia2 · March 5

https://forum.heatinghelp.com/discussion/comment/1890563#Comment_1890563

increasing the pressure with steam in the returns doesn't let the air out, it just compresses it some so some steam can get in and heat the radiator a little.

mattmia2 · March 5

but you are using steam to lift condensate so you need enough differential between the main and return to lift the water that height.

gerardlem · March 9

Yes I do have enough differential pressure and there are some air vents on the system. The system does heat but not like it should and is very noisy.. I'm going to recommend to either repipe the returns or add a condensate pump prior to that contraption.

Thanks for the input.

steam condensate trap?

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