Main Line Venting & Branch Venting ?

greengiant

Two mains come from the boiler. One is 28 feet long, feeds 3 radiators that are relatively close to the main (the one furthest from it is on an 8 foot branch), and it ends back at the boiler with a Vent-Rite #31. The other main is not as simple. It also feeds 3 radiators however two of them are very far away down a branch off the main. The main extends 10 feet from the boiler. It then turns 180 degrees and goes straight back to the boiler, ending with another Vent-Rite #31. I believe that these vent are functional. If you hold a thread over the orifice you can see the air coming out. Branches from this main originate at the 180 degree turn. One branch travels 10 feet to a small radiator. The other branch travels about 25 feet to a T with 5 foot branches that feed 2 more radiators. There are no vents on any of the branch lines in the system. The only other vents are those on the radiators themselves, Vent-Rite #1's. I've got all the radiator vents open all the way. The cut in is set at 1/2 psi and the pressure guage on the boiler goes up to 2.5 before it cuts out. When the boiler cuts out, the pressure drops quickly and then the boiler refires. I hope this info is helpful. This system has 2" mains and 11/2 inch branch lines.



My question is, should I be putting different main line vents where I already have vents and should add vents to long branches like the 25 foot branch? Also, how should I calculate for the addition of those vents. My radiator vents hiss loudly now when the boiler runs. They all currently shut off though so it seems to me that there is just too much air that they are venting.



Any advice would be greatly appreciated. I'm trying to decide how to spend a few bucks that I have.

[Deleted User]

vent issue

The purpose for a main vent is to eliminate air in the mains first to allow steam to travel evenly to radiators. Steam like water is lazy and takes the path of least resistance. It will travel back to the boiler if it cant be vented. I would add a main vent to the end of the line that is not heating those radiators. It may be a balncing game at that point because that should make those radiators cook! Also the main vents are supposed to be a minimum of 15 inches before the return drops, and atleast with 6" nipple off the main for it not to get damaged. Also is the piping insulated, is it in a crawl space?? Steam will condense!

greengiant

vents

Some of the piping is in a crawl space but all of it is insulated. The two main vents that are there now are on the elbows where the pipe drops to the boiler. Even though they're in the wrong spot I think they work but if I replace them I'll move their location back from the elbow and up as you've indicated. Any idea how to figure out the sizes of the vents I need?

crash2009

6 tips if you have an oversized boiler

I looked back at some of your threads and now I remember why your story sounds familiar.  You have the oversized SGO.  Don't feel bad as it is not the end of the world.  It's just a pain in the neck.  I have 377 EDR hooked up to a 510 EDR boiler.  What's that, about 25 or 30 % oversized.  I have been improving and adjusting for some time now.  I can imagine your boiler acts up like mine. 



The first thing I did was have my low water cut off probe maintained and tested every year.  These oversized boilers go off on low water often.  You and I should both have a secondery.



Second was to add a vaporstat.  This is to shut it down before it builds pressure and runs out of water.  It also buys you a little time for the condensate to return, before you run out of water.



Third I shut off the valve to the water feeder.  Mine was constantly adding fresh water before the condensate came back.  After the condensate came back the boiler would be over filled.



Forth insulation, the more the merrier.



Fifth maximize your main venting.  Get the steam around the mains as fast as you can, without creating water hammer.  Start building one of those antler deals, and keep on adding Gorton 2's until you get water hammer or you have maximized the tapping.  Antler picture enclosed.



Sixth look into downfiring.  maybe you should do this first, then you might not need the first four tips.



There is probably more but I am out of time.  See ya next time.

Abracadabra

hissing radiator vents

"My radiator vents hiss loudly now when the boiler runs"







This is a clue I think that more main venting is required.