Question about main venting

Christian Garibaldi

Hi guys, this may be a simple question, but I havent really been able to find an exact answer for it up here in my searches. Perhaps you could point me in the proper direction of help answer it for me.



I have a 1 pipe steam system, building is 2 story, 25x100, boiler in basement, with a 5 inch main riser that comes up about roughly 16 ft to the ground level ceiling, splits into to main loops, one towards the front , the other the rear. The boiler is located about 70 ft back in relation to the building footprint, to the front and rear loops arent equal, the front is a longer run.

The second floor rads are fed from below along this loop at the ceiling, and the ground floor rads are fed from drops from the main loops at teh ceiling. Returns at the end of the loops at the ceiling drop back to basement, as well as returns that run along the ground floor to the basement as well.



When I first got the place, I knew jack about steam. There were two old clogged up kelly main vents (if you called them that) at the end of the front and back loop right before the dry return vertically to the basement.



I replaced them last year each with a gorton #2. It helped, but I still notice that when my boiler is running, the rear shorter loop hits with steam pretty quick, while the front loop that has its end sitting right next to it, takes a loooooong time to get hot.



It seems that I still have inadequate venting, esp on the front longer main loop. So I was reading up on the antlers, menorahs, mezzuzahs, or whatever you want to call them, and was considering ganging up some more #2's on that vent branch.



My question is is there a method to calculate how many I should get based on my system? The front longer loop if I had to guess would be: including the riser from the basement- 130ft or so, feeds 8 radiators on the second floor, and 4 in the ground floor. The rear loop (again, guessing ballpark) 115 feet, feeds 5 rads.



As cool as it may look to have a giant hebrew style menorah of #2s gracing my tin ceilings 12 ft up, I havent the slightest clue if a) I need more than the 1 each I have at the end of the mains, b) how many I would add on if I needed more or could benefit from more of them. Is there a rule of thumb? At $62 a pop, they can add up, so figured Id ask before I just threw a dart at a board :-) Thank you in advance

nicholas bonham-carter

How much main venting?

Take the vent o ff the slower loop and fire the boiler until steam comes out the tapping. Is it quicker to get steam without the vent in place? With no vent installed, the resistance to the air escaping is almost zero. You want to add vents until you get as close to this low back-pressure (as measured with a 0-3 psi gauge), as possible.

With an antler, you can keep adding gorton 2's, until the venting resistance/back-pressure is 2ounces.

The vents have a cost, but then so does their absence, or inadequacy have a cost. If you can hear the vents now, then you need more main venting, and lower pressure.--NBC

BobC

Also

Make sure both mains have adequate slope and that there are no dips along the way that might trap water and collapse the steam.Don't trust your eyes use a level and perhaps a taught string to check each leg.



Bob

MTC

What size are the tappings?

Is the Gorton #2 screwed directly into the fitting/tapping, or is there a reducer on there? Gorton 2s are 1/2" tapping, often you'll find vents on 3/4" tapping.



The capacity of a 1/2" tapping is basically 2 Gorton #2s. The capacity of a 3/4" tapping is pretty much exactly 4 Gorton #2s and 1 Gorton #1. By capacity I mean that with this number of vents, you'll get essentially the same venting as if you had a wide open pipe. Any more, and you're wasting your money.



If you want to balance your mains, we'll need an actual length of each one. If you can tell us how many feet there is of each pipe size (if it reduces, we need to know that), all the way down each main, we can calculate how much air is in each main, then figure out how much venting you need to fill them quickly and at some degree of balance.



I like to target emptying the mains in about 1 minute after the header fills with steam, at around 1 oz of pressure. This can mean a number of vents on each main, but it balances the system and reduces operating costs.

Christian Garibaldi

thank you for the reply

I will gather all of that information and try to take some pics as well in the next day or so s you can get a better idea of what I have

STEAM DOCTOR

5" main

Are you sure that the mains are really 5"? Did you measure the circumference or the diameter?Also what is the length and pipe size of the mains after they branch out? What type of radiator vents do you have? If you have varivents they may be throwing the system out of balance due to their high venting rates? Do you have any steam leaks? Steam leaks can also be a form of oversized air vents in a sense. Anywhere that steam escapes from is a form of an air vent and can through the system out of wack. Do you have anything that is causing wet steam? If there is too much water being carried out off the boiler the steam will move slower. Very often the water is carried in one direction and not the other and the result will be that steam moving in one direction will be slower then steam going in the other direction.