Mains venting calculation help

SchenleySeven

Fine tuning the main vents on the old girl, and have replaced a Hoffman #6 and a #4 with Gorton #2's:



Main #1- 2" 20 feet long w/ a Gorton #2.



Main #2- 2" 20 feet long no vent. It runs parallel to main #1 and it's return connects to that of main #1 as both connect to the wet return on the floor.



Main #3- 2" 22 feet & 1.5" 7 feet long w/ a Gorton #2.



Once the header is hot, it takes about 4 minutes for main #1 and main #2 to get hot at their ends, and about 7 minutes for main #3 to be hot.



More venting needed?



Thanks for the help, Dave

Abracadabra

venting

2" pipe has .02 cubic feet per lineal foot.

1.5" pipe has .012 cubic feer per lineal foot.

Main 1 + Main 2 (since they are vented together) = .88 cf

Main 3 = .44 + .084 = .524 cf

It doesn't make sense to me that Mains 1/2 get hot before Main 3 if you are venting both with the same vent. Are you sure the "unvented" main is really a main? and that it's not getting hot by the steam from Main 1 returning back onto Main 2?

A Gorton #2 should vent Main 1/2 in under a minute. A Gorton #2 should vent Main 3 in about 30 seconds at 1 oz.

ChrisJ

venting

I have a 29' main and a 11' main.

I have three Gorton #1s on the 29' main and I originally had a single Gorton 1 on the 11' main.



The 11' main is first on the header and every time the boiler fired up that main and its 3 radiatiors would steal all of the steam.  This caused an annoying delay and made it so the front of my house got warm far faster then the rear of my house.



I swapped the Gorton 1 out for a Hoffman 40 on the 11' main and all is happy.  This causes steam to spill into the second main right away.  In my opinion (which isn't worth much) more venting won't always help you.  Sometimes you just need a little less.

malex

same problem

Chris, I had the same situation but (I had a #2 on the long main and #1 on the short) I opted to add add a #2 to long main after advise from Gerry. We bot will probably solve the same problem, but hopefully faster in my case and worth the extra money for the #2.

Hap_Hazzard

It's all about balance.

You only have so much steam pressure to push the air out of both mains, and proper balance can be achieved by either increasing the venting on the slower main or decreasing it on the faster one, as long as your main vents are adequate overall and none of the radiator vents are excessive.

SchenleySeven

more info on mains

The picture of the boiler shows Main # 1 off to right. On the left side at the T, Main #2 tracks to the rear around the chimney and then parallels Main #1, and Main #3 tracks forward.



Picture of pipes shows on right side Main #1 with a Gorton #2 vent and the return pipe down. On the left is Main #2 with no vent and a return that connects to the other return.



So yes, I'm sure Main #2 is a main. I'm amazed it seems to vent so well, because of the interconnected return from another main that is vented?

SchenleySeven

More info on mains

Thanks for the calculations for c.f of air in the mains.



The picture of the boiler shows Main # 1 off to right. On the left side

at the T, Main #2 tracks to the rear around the chimney and then

parallels Main #1, and Main #3 tracks forward.



Picture of pipes

shows on right side Main #1 with a Gorton #2 vent and the return pipe

down. On the left is Main #2 with no vent and a return that connects to

the other return.



So yes, I'm sure Main #2 is a main. I'm amazed

it seems to vent so well, because of the interconnected return from

another main that is vented?

crash2009

Dave

I am going to ask you a couple real stupid questions.  Could you just play along with me and give me a straight answer?  I could be making something out of nothing, but it might be important to your solution.



The first picture that I drew on in red, is what I think you are saying, but I just wanted to clarify this.  Is the main on the left venting down-over-and up through the gorton?  Does that horizontal pipe down by the cement sink get steam hot?



The second picture that I drew on.  If the boiler was sitting on the floor over there by the cement sink, and you were looking at the sight glass.  Would the water level be closer to 1, 2, 3, or 4?

SchenleySeven

stupid answers

Crash, not stupid questions- I appreciate your good eye.



I will guess that the main on the left is indeed vented by the Gorton #2 attached to the main on the right by the down-over-up return piping, because the ends of both got hot to touch at the same time.



I will check the horizontal "over" to feel if it gets steam hot tomorrow, because I ripped off some crappy fiberglass wrap & plastic insulation for the picture and as prep for new sleeve insulation, and have never checked it's temp.



That "over" pipe is at about your #3 elevation. The basement floor is not level and I do not have a laser level, so I put a laser pointer on top of a level on top of a tape measure to "shoot" the elevation:-) It's definitely below your #2.



Thanks for your thoughts, Dave

crash2009

water level

So, the water level of the boiler would be somewhere between 2 and 3 on the picture above.  That's what I thought you were saying.  You need to get a professional opinion on that.  When you had the old boiler the water level was probably up around the 1 mark.  The steam was unable to travel through water, it couldn't get through there and up into your new Gorton 2.  That main to the left should have its own vent.  If that little horizontal pipe, the one at the 2 mark, gets steam hot when you check it tomorrow, you might have to have it lowered.  So its lower than the water line of the boiler.  Steam is not supposed to move back and forth like that if it is. 

Hap_Hazzard

Wow!

I think you nailed it. Nice piece of troubleshooting there!

nicholas bonham-carter

why a picture is worth a thousand words!

crash would have taken longer to figure this out, without pictures. what a valuable tool is the digital camera!--nbc

SchenleySeven

Yes he did nail it

So I checked those returns, and really interesting how what got hot when:-)



The right main gets steam hot, and the left is at room temp. Then 20-30 seconds later the diagonal down pipe on the right gets hot to about half way down it's length, and the main on the left is hot, but that horizontal "over" pipe is RT. Another 20-30 seconds later, the left down pipe is hot most of it's length, the diagonal pipe on right is hot down to the over pipe, but the horizontal over pipe is still RT. More seconds, and then the over pipe is steam hot. Steamy indeed!



So, mystery solved, and Crash gets the "Broken Steam Vent" award.



Now I have to tap that 2" left main. I assume a Gorton #2 is overkill to vent  about 0.5cf of air. Recommendation for a vent?



Thanks for ID-ing a problem I didn't even know I had!

crash2009

Gorton 2

Not sure what size to use.  I would tapp the hole using 3/4", that way you can use any brand or size.  I like lots of venting, so I would try a Gorton 2.  If the Gorton 2 caused too many problems, I would pull them all off, and rethink my whole main venting strategy.  Gorton 2 is very popular, and would be easy to sell.



I just did some rough calculations for all the 2" pipe you have.  I didn't count the 1.5".  I calculated 60 feet of 2" @ .023 of air per foot to end up at 1.380 cubic feet of air in all your 2" pipe.  There is a chart that we all have, that tells us what to put where.  http://www.heatinghelp.com/products/Steam-Heating-Books/25/146/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-by-Gerry-Gill-and-Steve-Pajek  According to that you have too many vents right now.  If we had of known about this steam jumping before, we would have recomended 3 Gorton 1's, or 3 Hoffman 75's to begin with.