Considering returning system back to gravity return if possible.

Double D

This one is close to the number depending on what I want to call the lowest steam carrying pipe. In the pics of the dry return and the piping above, there are steam carrying pipes drilled between joists leading to convectors. Those pipes are 30+" above the water line of the boiler. Directly above the dry return there are steam carrying pipes leading to crossover traps. Those pipes are only 24" above the water line of the boiler. Which pipes should I be calling my lowest steam carrying pipes? The condensate return pump is located directly under the the master BR and they hear it cycle during the night. I would like to be able to tell them I could shut it down and operate the system with gravity return if possible.

Steamhead

It should work on gravity return if you keep the pressure low with a Vaporstat and proper air venting, and if the dry return is high enough above the waterline that it doesn't flood. Remember, if this is the typical 2-pipe system, the air from the convectors goes into the dry return and is vented near the boiler. In the present setup, the condensate tank may be serving as the vent.

Double D

Thank you for your input @Steamhead . Yes, typical 2 pipe system. The system was operating on a pressuretrol at 2-1/2PSI. I installed a vaporstat. The lowest dry return is 12" above the water line.

Steamhead

That's cutting it close. I've seen it work, but you'd have to keep the pressure down to 6 ounces.

The dry return is a "B" dimension rather than an "A" dimension. There is no leftover steam pressure in there to help the water return, so all you have left is gravity. The weight of the water stacking up in the return lines forms the pressure that pushes it back to the boiler. My guess is this system once had a Return Trap to help things along and someone took it out.

In a "B" dimension, you need 30 inches of height for each pound of boiler pressure so the water can return. You only have 12 inches here, which is 40% of 30. 40% of 16 ounces = 6.4 ounces. That's all the boiler pressure you can have when using gravity return on this system.

Try setting the Vaporstat to 6 ounces. Install a low-pressure gauge so you can verify that the setting is accurate- some Vaporstats have come through with poor calibration. If the system heats properly at this pressure, go ahead and make the changes. Be sure to vent the dry return well, as well as the steam mains.

Double D

This is a Webster system, no doubt it had a return trap. The original radiators on the first floor were cast iron wall hung leaving plenty of height for water to return by gravity. The convector piping is an extension of the piping which once supplied the wall hung rads. The convectors are all the way down to the floor. The condensate return pump most likely went in at the same time the convectors did.

I will first try as you suggest, try operating at 6oz. The system has been performing very well set at 8oz. for almost 2 months.

Venting the dry returns is straight forward but the mains and branches all use crossovers.

Jamie Hall

Double D said:

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Venting the dry returns is straight forward but the mains and branches all use crossovers.

And should. Make sure they are working and properly let air into the dry returns, then vent the dry returns like mad. You should be fine.

Double D

@Jamie Hall the system hammered pretty good, there were several failed crossover traps, one of which was failed closed. The originals are 1/2" Warren Webster 02H. Rather than repairing existing I've been replacing them with 1/2" B&J 122 traps.

Steamhead

B&J makes a 1/2" Big Mouth trap for use as a crossover. We've used quite a few of these. How long are your steam mains and what pipe size?

Double D

I have not yet used the B&J crossover version of the big mouth but I have considered it if I ever came across a main the right size. When I go back to the job I will check to see if I have enough space to fit the big mouth. I have 2 air vent type with me to use as reference for spacing. If I have the space I would prefer to use the Big Mouth. The 2 mains are 2-1/2"and they run 40'. At the end of the 40' they reduce to 1-1/4" on the drop to the location of where the original wall hung radiator used to be, then they reduce to 1" down to the basement an pick up 2 convectors. The pictures of the red brick wall in the basement shows the 2 crossovers just above the dry return between the return piping and the brick wall.

EBEBRATT-Ed

Just a suggestion.

Pipe a 3 valve bypass around the condensate tank. In case it doesn't work you can go back on the tank easily just by opening and closing valves. What is now the pump discharge may not be large enough for gravity return. However use full port ball valves or gates you can't afford any restriction in the gravity line.

Don't know the layout but possibly you could relocate the tank to a less objectsional spot or enclose the pump in a insulated sound deadening box although the motor needs some airflow for cooling