Measure Mains for Vents.

ST140

Hi Everyone. I just ordered two Gorton No. 2's for my mains because from what I've read, they will vent the mains the fastest... But then I started getting curious about my mains, and how much venting they actually need. I've seen requests for people to measure their mains, and give the pipe diameter, and then they end up recommending main vents. OK, makes sense. Now here's my dumb question. I have 1 pipe parallel flow steam. 2 mains coming off the boiler, one to the front of the house, one to the back. When you say, "measure the mains" does that mean the entire main, going away from the boiler, and coming back? I guess I get confused as to what is considered the main, and what is considered the return. I think I understand that it's a dry return, but is that still considered part of the main? Or do I stop the measurement where it turns 180 degrees back to the boiler? Sorry if this doesn't make sense... but Thanks!

AlexR

measure separately to last radiator takeoff

You should measure the two mains (one to the front, one to the back) separately.  Measure the length from the boiler to the last radiator takeoff (probably where it turns 180 degrees around).  You'll figure out how much venting each main needs separately since a vent will only let the air out of the main it's installed on.



The vent will end up venting the dry return too (if it's installed at the boiler end of the dry return), but that's less critical and you probably don't care how long it takes (if your dry returns are like mine, they're smaller pipe than the mains, so they'll vent faster.  Also, I think it doesn't matter if they're vented at all until condensate starts coming back).



Alex

ST140

Thanks Alex.

That makes sense. Each vent is currently installed right above where the return drops down towards the boiler, they're both installed in the T off a ~6" nipple with a union... I think it'll probably be better to "Antler" the Gorton's off to the side of the T when they get here in the mail. What do you think? I'll measure the mains to the last takeoff...



The reason I'm asking about the main vents is because there's a ton of air coming out of my radiator vents, and I'm really hoping it'll help and be an improvement over the Ventrite 35's that are clogged and installed on there now...

Charlie from wmass

The Gorton is

8 times faster than a properly working 35. Roughly I left the venting book in my truck. In my area 35's are actually pretty big compared to many installations I see. They are too small but better than nothing for sure. I think off setting the Gortons is a very good idea.  

ST140

Measurements

Front of House Main: 14ft long x 2"

Rear of House Main: 20ft long x 2"



The outside diameter of the pipe measures +/- 2 3/8", but all the fittings are marked "2"



Let me know what you think I need for Main Vents. LIke I said before, they're at the end of the dry returns where it drops down to the boiler at a T fitting. As Alex suggested, I measured to the last takeoff.



Thanks for your help. -Steve

Dave in QCA

Venting Calculations

Your 2" mains have a volume of .023 cu ft/ linear foot of pipe.  One of your mains is 14' long and has a volume of .322 cu ft.  The other main is 20' long and has a volume of .46 cu ft.  The Gorton #2 vents that you ordered will vent 1.1 cfm (cubic feet per minute) at 1 oz of pressure, and 1.74 cfm at 2 oz.  Assuming 1 oz of pressure, the Gorton 2s will vent your mains in less than a 1/2 minute.  Gorton #1 would have been sufficient, but excessive venting of the mains will NOT cause a problem.  I think I would have made the same choice.

ST140

Thanks.

Thanks everyone for your help and info, looks like the 2 gorton's should be enough for me.   -Steve

AlexR

very similar to mine

It sounds like your setup is very similar to mine.  I did the same thing- put a Gorton #2 on each main, up on an antler.  Just make sure you size the antler to leave enough space to install the vents, since they're pretty big and you want some clearance to the ceiling or rafters.

Charlie from wmass

Personally

I would return the #2 vents and get #1 vents. and maybe a new 35 and a 75 to balance the mains in speed.