2 pipe steam with F/T's and hoffman 75 main line vents.

Scott McGuire

I worked on a job today in a warehouse with a zoned steam heating system. We have radiators that are downfeed from a main above, then each radiator has a steam trap and drains to a return line to a condensate pump.

The two floors above have ceiling mounted steam blowers. each blower is feed with its own branch and the return goes through a F/T trap and drains to a common return which goes to a condensate tank.

The end of each zoned steam main has an F/T which drains to a common return and then to a condensate tank.

At the end of each steam main is a Hoffman 75 main line vent before the F/T.

The common return lines also have a Hoffman 75 vent on them prior to dropping to the condensate tank.

My question is are the Hoffman 75 vents even needed. (I don't think so.). Since all the returns drain to a vented to the atmosphere condensate tank. These vents are loud when they vent and spit out water at times.

I can see leaving the vent on the return main after the F/T before in drains to the condensate tank to vent the air before it drops to the tank. But the other vents at the ends of the steam mains and prior to the F/T at the end of the main make no sense.

Looking for any insight on this.

Scott

Steamhead

The vent you might not need

is the one on the return before it drops to the tank. If the return goes into the tank without forming a water seal, the vent on the tank will vent the return.



As for the others- keep them. The faster the system vents, the faster it will heat up, and the less fuel it will use.

The Steam Whisperer (Formerly Boilerpro)

The need for vents

What seems to be a very little known is that most F&T traps have very little air venting capacity so when venting mains they rarely have even close to the capacity needed to vent quickly.  A quick walk through Gerry and Steve's newer vent tables demonstates this problem.  If the vent are making a lot of noise and spitting, you probably need alot more venting capacity, or a much lower capacity boiler.



Boilerpro