Constructing the vent antler

Emeliza

I am adding 3 #2 Gorton's to my two mains ( it's a split main, one going one direction and the other going the other direction). My current vent is 3/4", the Gorton is 1/2". My question is: in constructing the antler should I use 3/4" pipe between the tees and an elbow that have 1/2" threading (on the top riser) to accept the Gorton's or can that antler portion be all 1/2" pipe, tees and elbow? I've looked at GW Gill's blog and pictures on his maximizing venting article. I'll have one vertical tee, a horizontal tee and an elbow to accommodate the 3 air vents. My new system is in and now all that remains is to install the main vents, balance the radiators an finished insulating the pipes, especially all the new near boiler piping. I am just using the boiler for hot water now, too warm for heat, but the cold will be here soon enough

Fred

1/2" pipe for the antler will work fine

JohnNY

First, it just so happens I ate a lot of paint chips as a child.

Second, I feel like I read or perhaps made the comparison that a Gorton #2 vent basically vented at the same CFM as a ¼" hole.
If that's the case, I'd think that 3 Gorton #2s would be choked by ½" pipe and that ¾" pipe would be perfect.

However, I'm not ruling out that the previous two points are not related.

gerry gill

two gorton #2 max out a 1/2'' pipe... four gorton 2's pretty closely maxes out a 3/4''..use 3/4''

Fred

My Bad. The way I read it, there are two mains and I assumed the intent was to put 2 Gorton#2s on an antler on one main and the other main would have just 1 Gorton #2

JStar

We've noticed, through endless timing of steam travel, that even if the pipe size of the antler is correct, the smaller sizes can reduce airflow by a noticeable amount. I have a rule of thumb that only exists in my head at the moment...

1/2" = 2 Gorton #2
3/4" = 3-4
1" = 5-6
1-1/4" = 7-10
1-1/2" = 11+

Adding vents outside of this range can slow down the venting rate. Even if the manifold is reduced on the same antler, some of the vents will be slower.