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# main air vents

Member Posts: 66
The short main coming from the boiler is a 2.5" and 23' long. The problem is that it is inside a crawlspace that I don't have access to.

The return line from that main protrudes from the wall and I was thinking of putting an air vent on it, as from what I can see there is no air vent. The only problem is that the return is 2 ft below the main line and 5 ft away from it as you can see in the diagram.

1) What air vents should this main have?

2) Can the air vent be put on the return?

3)Should the air vent be on position A or B?

And what size pipe should be used to connect the main vent to the return, 1/4", 1/8"?
Burnham Independence IN8

• Posts: 2,067
Main Vents

Hi- Adding a main vent should really help the performance.

A few questions :

1. Is the 2 ft and 5 foot pipe in your drawing also 2 ½ inch?

2. What is the distance between the height of the return pipe where it drops down and the boiler’s waterline?

3. What is the maximum pressure that you are operating your boiler? (It shouldn’t be more that 2 ½ PSI)

2 ½ inch pipe has a volume of .03 cubic ft. per every lineal foot of pipe. Your 23 foot main equals 0.69 cubic feet. A Gorton #1 main vent at 1 ounce of pressure will vent .333 cubic feet of air per minute and would vent your steam main in about 2 minutes. Gorton #1 main vents come with a combo 3/4 male or ½ female pipe thread. I would use ½ inch pipe for the vent pipe.

The vent should be placed in the “A” position of your drawing though the feasibility of this is dependent on how much the distance is in question #2

- Rod
• Member Posts: 66
main vent

The 5 ft return in the diagram is the 1.5" return and it looks like the 2 ft one is also that size.

Now that I looked at it again the only place for the vent would be on B because there are ducts in the way of A.

'B' is 22" above the boiler waterline.

The max pressure is set at 3 psi but on the 0-3 psi gauge the needle just rises a little above the 0 mark.

Also looking at the picture it looks like I would have to drill into the 1.5" return in the nipple at point B and tap it.

The pipe on the right side is the return from the 2.5" main. (The left is a return from a different part of the house.)

What type of drill bit to use?

I would like to make a smaller hole that's why I'm thinking of using a 1/8" pipe on point B and screwing the air vent into that.
Burnham Independence IN8
• Member Posts: 14,414
Is the tee fitting in the picture

above or below the boiler's water level?
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 66
It is

around 20" above the water line.
Burnham Independence IN8
• Member Posts: 15,736
The real question is

how does air get from the steam main into that return?

Assuming that this is a two pipe system, If it is through radiator traps -- plural -- or through a crossover trap at the end of the steam main (can you even see in there?) putting a main vent at either A or B should work just fine (it will be best with a crossover trap).  If, on the other hand, you are dealing with an orifice type system with no crossover trap, it really won't do much for you, as the orifices will restrict the air flow to the return and thence to the trap.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 66
One pipe

It is a one pipe system.

That was my question! Since the return at point B is 2 ft lower than the 2.5" main, can the air vent downwards through that pipe?
Burnham Independence IN8
• Member Posts: 14,414
A vent placed at this point

will vent air from both mains whose returns come into that tee. You may find that one main vents more quickly than the other because of this.

The cure will be lowering the tee below the boiler waterline. Then there will be water standing in it and the air won't be able to go thru the tee. Now you can put a properly sized vent on each return and the two mains will heat evenly.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 66
edited June 2013
main vent

The pipe on the right is the return from the 2.5" main.

The pipe on the left isn't a return from a main from rather from an individual radiator. (I'm not sure why the contractor installed it.) There is another long main on the other side of the house.

The 2.5" main is 23' long so that would be = .69 cubic feet.

The return from the radiator is 1.5" and is probably 25' long from the radiator = .364 cubic feet.

Is this the right way to calculate the return from the radiator?

Looks like a total of 1.05 cubic feet. So I should use a gorton #2?

Thanks
Burnham Independence IN8
• Member Posts: 14,414
Is there

an air vent on the radiator that returns to the tee?

If so, that radiator will have air coming at it from both directions- the steam connection and the return connection. This will make it heat rather slowly.

The cure, again, is a water seal.

I ran into this a long time ago- read about it here:

http://www.heatinghelp.com/article/325/Piping/246/Steam-Stumper

It pays to wander off the Wall.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 66
steam supply

Thanks

Now I'm thinking that it may be a steam Supply valve to the new addition on the house so it should be above the water line.

Anyway, is Gorton #2 the appropriate valve?
Burnham Independence IN8
• Member Posts: 14,414
Assuming

that it is a steam line to the addition, you'll want to put the Gorton #2 in the addition near the end of the steam line. That way it will vent all the piping.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 66
edited June 2013
There

is no access to the end of the steam line in the addition.

So I guess i will just vent the main which has .69 cubic feet with a gorton 1.

Or can I drill and tap a 1/8" pipe into the return line and use a gorton D which has the same venting as gorton 1 according gerry gill venting capacity chart?
Burnham Independence IN8
• Member Posts: 14,414
The D will work

and there's room for a second one if you wish.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Posts: 2,067
Connecting Returns

Hi- Here is a great video done by Gerry Gill which shows the crossover problems that can happen when your return lines or drips are connected together above the waterline.

- Rod

• Member Posts: 66
edited June 2013
main vent

Rod - thanks for the link

Steamhead - I think I'll use a 1/4" pipe with a D, thanks.

So now that I have figured out where to put the air vent on the short main, thank you for that, I would like to know what air vent to put on the long main.

It has a radiator valve.

Long main - 3" pipe 70 feet ?? which main vent?
Burnham Independence IN8
• Member Posts: 66
edited June 2013
tap a 1.5" return

Now that I am going to drill and tap the 1.5" return (the right side in the picture),

which size should I tap it with

should it be a 1/4" 3/8" or 1/2" hole?

I plan on using two D air vents as the main vents as per the discussion above.
Burnham Independence IN8
• Member Posts: 14,414
Use

a Gorton #2.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 14,414
1/4"

will work fine.
All Steamed Up, Inc.
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
This discussion has been closed.

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