Main vent sizing

danmasri

2.5"  single main with an approximate 50' run. Single family home with single pipe system. What main vent/vents should I install. Not sure will have clearance for larger vent like gorton#2 so please help with sizing with multiple #1 or #2 options.

ethicalpaul

I would perform a timing test with an open pipe at the vent point to see the fastest possible venting. Then start putting Maid O Mist #1 (supplyhouse link here) or Gorton #1 (if you like to spend more money) vents on there until the time is similar to the "open pipe" time.

To get the open vent time:
- perform a call for heat, and use your hand to determine when steam has reached the point in the main where the main vent is/will go. This is just to get the main hot because a cold main obviously takes longer to fill with steam than a hot one.
- Shut down the boiler.
- remove any existing vent, or remove the cap or whatever depending on your current situation
- Perform another call for heat, this time set a timer when the boiler fires up and time how long it takes for steam to be visibly escaping from the open pipe.

This is your fastest possible venting time for a hot system. There is no point in adding more venting after this time is achieved or nearly achieved with vents.

- Put one #1 vent on the pipe and call for heat, timing the duration between flame on, and steam at vent
- Add another vent to the antler if necessary
- stop when the time gets close to the "open pipe" time (close is within let's say 15 seconds)

This will get you plenty enough venting, probably too much venting because in a normal call for heat, the main will be cooled off some (even an insulated main) which will slow the speed of the steam to the vent anyway.

danmasri

Do maid o mist #1 go on with Teflon so easy to change like radiator vents?

dopey27177

You have small pipe with a relative short run.
A Gorton D vent which is small in size will vent 4 cubic feet of air per minute is much cheaper than a Gorton # 1 vent that will vent the same amount of air.

The 2 which is in my opinion overkill and very expensive is a waste of money, the same goes for Maidomist.

Jake

ChrisJ

Just figured I'd mention my 2" 29' main has five Gorton #1's on it.
3 wasn't enough and 4 barely got by when the system was good and hot (below zero outside and 3 cycles per hour).

So I settled on 5. With this setup it takes under a minute from the time the boiler lights until steam hits those vents on a cold night.


2.5" pipe is roughly 1.5 times the size of my 2" pipe but it also depends on the size of your boiler which is why Paul made the recommendation he did. You need to do those tests, but I'd expect to need several vents.

ethicalpaul

dopey27177 said:

You have small pipe with a relative short run.
A Gorton D vent which is small in size will vent 4 cubic feet of air per minute is much cheaper than a Gorton # 1 vent that will vent the same amount of air.

The 2 which is in my opinion overkill and very expensive is a waste of money, the same goes for Maidomist.

Jake

Respectfully, the Maid O Mist #1 (about the same capacity as the Gorton #1 and #D) is $18 which I believe is less than any Gorton vent available anywhere

ethicalpaul

danmasri said:

Do maid o mist #1 go on with Teflon so easy to change like radiator vents?

Yes. It is dimensionally and operationally equivalent to the Gorton #1. It has the same combination 1/2" and 3/4" threads on it.

Steamhead

If you have the clearance, I'd use a Gorton #2. You need at least 6-1/2" above the fitting to install this vent.

I've used pipe nipples and elbows to move the vent location to where there's more clearance. If you do this, make sure the pipe slopes down from the vent toward the steam main, so water won't accumulate in it.

Fizz

I have small single pipe parallel system, with 2 supply lines each about 30'. When we moved in the system had Gorton#1's, but system took awhile to heat, so I got MOM #1's which were about the same,so I replaced with Gorton#2 and a Bigmouth, no different. Changed back to MoM's, switched from old mercury t-stat to Emerson 1E3ON-910, and removed jumper to by=pass steam/hot water setting so now t-stat turns on-off heat 2-3xhour with much better balance, no overshoot or air vents on rads getting steaming hot or water in them to have to remove.