Model K System

NewEra

Im a contractor located in CT. I recently was tasked with changing out a steam boiler. After doing some extensive research im fairly confident I have a vapor system referred to as "the model k system" outlined in Dan Holohans book "the lost art of steam heating companion" starting on page 146. Ill attach a picture of the piping diagram. The 1 and only difference is on the boiler we removed there was a quanity of 2, 3" long black nipples and a swing check where the wet return comes back into the tee at the boiler (commonly referred to as the hartford loop, or part of it) every piping diagram ive ever seen shows a close nipple required there. Radiators are all heating evenly top to bottom, with the swing check at the bliler removed and a close nipple on place. Not feeding any water, but were coming out of winter and I haven't been able to tax the system. Im wondering if removing this swing check is gonna cause returning issues when the system gets longer run times.

I still have the air vent, and swing check on the where the dry return drops down to the wet return.

Jamie Hall

The checks do no harm — but on the other hand if you keep the pressure down where it belongs you don't really need them either. That being not more than 8 OUNCES per square inch.

The air eliminator is really a big fancy main vent. If it's working, leave it alone. If it isn't you need it for sure — but a couple of Gorton #2 vents will be ample.

mattmia2

usually the check valves in the return at the boiler were to allow the boiler return trap to equalize the main and return pressure to allow the water to return to the boiler if a hand fired boiler built pressure. usually there were a couple and the return trap was connected between 2 of them.

as @Jamie Hall said, if the boiler is sized to match the load or controlled with a vaporstat so the pressure stays low you don't need the check valves, they were for a coal fire that was too large.