Hoffman Differential loop

Steamhead (in transit)

you will want to use at least one Gorton #2 in place of the Hoffman #15.

That #15 was a vacuum vent. Vacuum worked great on coal, not so well on oil or gas. With the latter two, it's way too possible to get vacuum before all the air is out of the system. The remaining air will expand as vacuum builds, possibly blocking steam circulation.

Remember that the steam mains on this system were likely vented with crossover traps. These must be working properly or they will mess up steam distribution.

Is this one of the later Differential Loops that was made up of just one large vertical pipe instead of two smaller ones?

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Scott Kneeland

Hoffman Differentional loop

I Have a situation that I would like your help on. I have a customer that has a 2 pipe vapor system with a Hoffman differentional loop. the boiler has been replaced about 20 years ago but ran dry and cracked. I am replacing it and have removerd the Hoffman loop it was 27" above the Utica water line I have a Hoffman #15 vapor valve at the start of the return. the system has no radiator traps it has orficed hand valves. I believe that I need to replace the vapor valve with standard main vent? this is the first Differentional loop I have run into since 1981. should I have of just left it?
Thanks
Scott Kneeland
Scotland Heating


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DanHolohan

You can leave it

or take it out. It was there to keep water from backing out of the coal-fired boiler. Get a high-capacity air vent if the one that's there isn't working.

Scott Kneeland

Hi Dan, I remember you telling me that but was not sure about the vent it is a Hoffman # 15 Vacuum Valve. I believe I should install a conventional main vent to let the condensate back thru the return. I have already cut the Hoffman loop out due to leaking piping.

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Scott Kneeland

Yes this is the later one, when the boiler was replaced 20 years ago it was just hacked in and not piped correctly. I took out the loop and plugged that end of the return. I'll change the vent, and yes their are crossover traps on the main (under much asbestos I'm going to fire the system up and see if all is working. The crossover traps are in a nasty location too and would not be fun to play with.

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