One pipe main venting using F&T trap

JUGHNE

I have a one pipe system with 165' fm boiler to F&T at cond pump.  Most rad removed.  Pipe starts with 6" down to 2 1/2".  How much main venting is needed in addition to  the 1" series H F&T trap.  Does the usual fast main venting rules apply?  Thanks for any input.

JStar

Venting

I've looked at a system like this before. We have 100ft of 6" main. I came up with 20 Gorton #2 vents. Instead, I opted for a very large thermostatic trap rather than having a monster vent tree.

JUGHNE

Actually short steam main...

Thanks Jstar for the reply.  With so much rad removed.  there is only 414 EDR  (4 CI rads) connected to the first 70' of 6 & 4 " steam main.  The remaining 55' of 4" & 40' of 2 1/2" is actually dry return.  Doesn't the Hoffman F&T 1" H series vent a 1" open pipe until steam hits it.  The F&T is right at the cond pump.  Also above the pump/trap is a Hoffman 75 and another at the end of what was previously the steam to cond return reducer fitting.  Would moving the two 75's vents closer to the end of the "new" steam main improve things?  Thanks again and good luck with new help.