how much venting

bubbad

first timer,i have 11/4 main running 27' from header to furthest rad,it goes up to rad,throuh a t the t reduces int a 3/4 -28' return what size main vent would I need. never had mains before,i don't want to fix what ain't broke but I keep thinking effiecieny,would addind mains improve my small system

Fred

Is this a 1 pipe steam system? 1-1/4 inch main is really small. How many radiators are fed off of this main? Are there vents on the radiators? Do they all heat? If it is a 1 pipe and the rads are vented, I'd put 1 Gorton #2 on the end of that main, if you have the head room to get it up there.

Mad Dog_2

Fred's right. In general, you should add enough main vents to purge The main trunk line in a 5-10 minutes from an off cycle (most systems) Gerry Gill has a chart for exact capacities. Mad Dog

bubbad

1 pipe system,no noises anywhere,installed heat timer adj.varivalves on all 6 rads.no banging,or surging in glass,new peerless 63/64 boiler,skimmed 3 x,no insulation,plan to insulate in next couple of weeks

system appears to be running well would I still benefit from main venting,i had guessed at the gorton #2 as well

I will add vents if you guys think it is helpful,

from the hydronics inst,I calculate 210 edr

Fred

You definitely need to add Main vents. If your Radiator EDR calculation is correct @ 210 sq. ft. your boiler is about 30% over-sized which can cause pressure to build and some short cycling, all by itself. Inadequate Main venting will only aggravvate that situation. I suspect when the temp gets a little colder outside you will see some short cycling. If it gets to be a problem, you may want to have a Pro try to down fire the burner or maybe even install a 2 stage gas valve to get your boiler more closely matched to your radiator EDR. Wait and see how she runs during the colder days this season.