Installing main vents

Jeffrs

Hello, I did a brief search but didnt find exactly what i was looking for.

Ive attached 5 pics of my mains. Lemme describe each pic to give an idea how its setup and then ill get to my questions.

The first and second pictures are the main off the header. About 15 feet in length and has 3 tees at the end. The middle tee in the second pic branches off and goes 11ft to the right of the house. See third pic. This is that branch.

Closer to the header there is another branch off this main, if you look at the first pic again you can see the tee closer up to the header in the picture.

This goes 11ft out to the left of the house and then bends 90 degress toward the back of the house and travels another 7ft. See 4th pic.

Finally the last pic is a seperate main off the header. This travels to the back of the house about 29ft to the kitchen through crawl space. Not the best pic I know to describe that main.

Its 1.5" pipe for all the mains.



With that being said, Where should I put my mains and how many do I need? I was thinking about 10-15" back from the end of each horizontal branch of the system.



And how do I install them? I originally was planning to cut and put tees in but now im reading people are drilling and tapping the pipe?

I know the main vents come in 3/4" but I dont think ill be able to drill and tap for a 3/4" hole on a 1.5" diameter pipe. Can I drill for 1/8" size and use an antler with a couple "D" vents? If so how many "D" vents would I need to equal a 1 main vent and a 2 main vent?



Thank you very much all for the help.

Rod

Main Vents.

Hi- If I understand this right  you probably need two main vents. One on the "Kitchen main"

and one at the end the pipe in picture #2.  In picture #2 just before it turns down and runs back underneath the other pipe, on the top of the upper pipe there seems to be a "bump" in the yellow insulation. Check this out as it maybe a plugged tee where you could install a main vent.   The common main vents used are the Gorton #1 and the Gorton #2  (The Gorton #2 has 3+ times the venting capacity of a Gorton #1)  Both will attach to 1/2 inch pipe and are available at your local supply house or Pex Supply on the internet.  (A "D" vent has the same venting capacity as the Gorton #1) . A Gorton #1 on both of your mains should give you plenty of main venting.  You can tap the mains for 1/2 inch and if necessary, reinforce the vent pipe attachment with a filet of JB Weld.

- Rod

Jeffrs

Only 2 needed?

You think I only need 2 main vents? Would it be a problem to vent the other branches aswell? Can you Ever have too much main venting?



My other question is After I plan to install the main vents, I want to replace my radiator vents. They're all either a size C or D. How can I tell if these are too large? I read that your supposed to size the vents by the size of the radiator, but how do I know what size vent how big the radiator is? Is it just trial and error until the system is balanced? Would have to buy a bunch of different valves then just to get it right.



thank you very much all for help.

Hap_Hazzard

Can you Ever have too much main venting?

Not usually, but there is an exception, and it may be pertinent in this case. You mentioned that your mains are 1½" pipe. That's on the small side--usually they are 2" or larger--but you don't say what your boiler's output is. The boiler generates steam at a rate measurable in CFM, or cubic feet per minute. When you force it through a pipe of a given cross-section area, measurable in square inches, it moves at a velocity measurable in feet per second. Since you divide the output by the cross-sectional area of the pipe to obtain the velocity, the smaller the pipe the higher the velocity.



One of the pros here (I think it might have been Gerry Gill) mentioned something called critical velocity. This is the speed at which water droplets entrained in the flow can't precipitate out. Unfortunately I can't remember what that velocity is, but I would need some information from you to calculate your velocity anyway. Hopefully one of the pros will weigh in on whether or not this is a potential problem. Most of them have done the calculations so many times they just know what size pipe and what size boiler would be problematic.

Jeffrs

Pipe is 2"

I apologize, I was wrong. The kitchen main is 1.5" but the main that feeds the rest of the house is 2". I could not find a CFM rating but the sqft. Rating for my boiler is 392.

I don't know if this is of any help.

Thank you again

Hap_Hazzard

Then go for it!

That sounds pretty run-of the mill, so I would vent the heck out of it. =:^o