main venting - how much?

lizg

We have a new boiler, Burham IN9l 280 input BTU, and--for the first time ever--we now have a main vent (a Gorton #1) on the system. This one vent serves 130 ft of main piping that runs around the perimeter of our basement: 110 ft of 2” main and 20 ft of 1.25” main. Plus 21 feet of 1.25’ risers serving 14 radiators.

I don’t know whether the venting is working as it should. I timed it after turning the thermostat up a couple of degrees. It took ten minutes before I actually heard air exiting the vent, which it did for 2.5 minutes.

The radiators don’t all heat up at the same time, but in general we're happy with the steadier heat delivery than we got from our previous (over-sized) boiler. Should we leave well enough alone, or could we heat more efficiently by adding more main venting? Headroom is an issue, so I think our option would be an antler of Gorton #1s.

Thanks in advance for any thought and advice.

EdTheHeaterMan

As a rule you can't have too many vents. The faster you can get rid of the air, the better. However, there is a diminishing return with each additional vent. If one vent gets the air out of your main is 120 seconds a second vent may cut that time in half to 60 seconds. The third may only cut the time by 10 more seconds and the fourth by 5 seconds. So there is a point where adding another vent is not worth the expense of the vent. But if you are getting adequate heat with the vents you currently have, then you may have the correct amount of vents.

If it takes more than 2 or 3 minutes from the start of boiling water in the boiler (which may take a few minutes or up to 10 minutes or more*), until the end of the main is hot with steam, then you may need another vent.

You will know when your boiler starts to make steam by placing your hand on the cold, uninsulated main just above the boiler. When the steam reaches that pipe, you will remove your hand very quickly. Then you can follow the colder main pipe just ahead of the steam around the basement. I remember the first time I did that test. It was fascinating to move across the basement touching the cold steam main waiting for the arrival of the steam at the next fitting, then moving 10 feet and waiting for the steam to arrive there. and so on...

* Every boiler has a different amount of time before it starts to make steam. depends on water volume and BTU Input.

Steamhead

@lizg , you will need more venting. Can you post a pic of where the main vent is so we can see how more vents would fit?

KC_Jones

You’re not even close to enough. I have 3x that on 25’ of main.

You’re going to need multiple Gorton #2 vents, but as Steamhead said need to see what you’re working with.

lizg

@Steamhead and @KC_Jones , Here are images marked up with ceiling clearances. The one vent is currently installed in the hallway outside the boiler room, right after the last takeoff. There’s more clearance on that pipe once it enters the boiler room.

dabrakeman

Is there any other location possible back at the boiler where the main extension drops down into the wet return? Maybe a picture of the boiler from that doorway shown in the last photo.

A Gorton #2 is 6 1/2" top to bottom.

Waher

A B&J Bigmouth vent is 4-1/2" from the tip of the threads to the top.

Steamhead

lizg said:

@Steamhead and @KC_Jones , Here are images marked up with ceiling clearances. The one vent is currently installed in the hallway outside the boiler room, right after the last takeoff. There’s more clearance on that pipe once it enters the boiler room.

If you take out the pipe nipple and coupling that the #1 is mounted on, and screw a 3/4x1/2 bushing into the tee, a #2 should fit.

lizg

@Steamhead , Many thanks for describing how replacing #1 with #2 can be done in that tight spot. I’ll talk with our plumber about doing this.