two pipe steam problem

[Deleted User]

I have been trying to fix a two pipe Barnes and Jones steam system for a couple of weeks now. Customer complained about high gas bill and banging pipes. WE changed the steam traps that were not working and changed the main air vents that were on the condensate returns, they were all plugged up. The one thing that i am not sure of is the thermostat. It is programable and we spread the differential as far as it would go 4 degees. If she doesnt use the programing the system is super quiet and no problems occur. If it is programmed there is total chaos and the pipes are banging. Also there has not been a change in fuel consumption. Any help would be appreciated.

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gerry gill

is the banging

because of a long extended coming out of setback run?

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[Deleted User]

possibly

It only happens at night when the thermostat is set to come on.

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Fred Harwood_2

Steam problem

Got a Vaporstat on it?

Jamie Hall

check in Don's book

for all the problems to give rise to water hammer towards the end of the run -- they're 'too numerous to mention' here! But from your description (does it at the end coming out of reset) that's what you've got...

gerry gill

i think Freds on to it..

your pressure may be to high on setback recovery mode..two stage gas valve could work too, if its a gas boiler.

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Mad Dog!!!!!!!!

Programmables are NEVER a good choice with high-mass

systems like steam or radiant. With The Steam, its either a Honeywell T-87 or the program. set at one temp. Cruise control modulating around the desired room temp works best. Me thinks you have other issues with this system, i'e,: I have yet to see a steam system that works poorly because of a programm. t-stat, or lack of insulation, et cetera. Mad Dog

Christian Egli_2

The spill pipe for spilling the guts

BJ radiator traps, return lines, this must be a two pipe vapor system. The totally silent heat.

All system air goes through the main, then through the radiators, then through the BJ traps, then through the separate return lines to the boiler room, then... and this is important... through a plainly wide open hole, a real hole, in direct connection with the atmosphere. (Just like the obviously open to the atmosphere condensate return tanks are)

Adding air vents that shut on heat here at this location causes the double trap disasters, with noises and radiator trap busting hammer. I would remove the air vents you have there. Then clear open the breathing hole as big as you can and
pipe it a short way to the ground somewhere where the owner can keep an eye on it and somewhere any water can spill out. End it with no threads, just like the safety valve piping of a hot water tank.

Measure the altitude of the return main hole, that's your B dimension. Set the vaporstat for that maximum and no more. Beyond 1.5 PSI, these vapor systems get in trouble - there used to be the return traps to deal with overpressure, but a modern vaporstat is better. Your system will work like a charm and heat up real fast.

The spill pipe will evacuate any emergency overfill or overpressure water without flooding the system and perhaps the leaky valve stems upstairs - no big deal. Plus, any spilling steam will indicate a faulty trap to be fixed imperatively.

Your system might also have a crossover trap - these are not always necessary, there is loads of venting going on plainly across the radiator traps. If you have any, make sure they are working. Replacing them with standard one pipe air vents is possible but not as good as keeping the crossover scheme. Functions between one and two pipe solutions are not entirely similar.

Return lines also have to be in good pitch.

I suspect with the short differential that your system air vents remain shut on temperature. This would not help on the initial morning warm up (as air gets out, though with some difficulty) but then it remains out and the system seems to work better - but that's not so. Give it a longer pause, and you're restarting the morning warm up all over.

I also suspect you might have too much pressure building up. This pressure does not build quickly, it takes all the radiators to be fully hot first, which would happen on lengthened cycles... and as the pressure passes beyond the B maximum you get B-banging in the returns - most particularly with shut air vents and no alternate return trap.

Summary for the two pipe system:

Get rid of air vents
Get pressure set real low, in ounces
Eliminate return sags

I hope this all makes sense.

Steamhead (in transit)

Check the WET returns

These drain the steam mains. If they are plugged, water will eventually back up into the steam mains and cause banging.

Oh, and I'd keep using dry return air vents but maybe make them bigger ones, like the Gorton #2. These will keep steam from leaving the system and possibly scalding someone if a trap goes bad.

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