Adding More Main Venting Later?

cubicacres

We were wondering what type of pipe section is best for putting a main vent on just past the last radiator to allow a few additional vents to be added easily if needed. We have a Gorton #2 main vent on each now, and can add more if needed or they aren't working anymore. Would this be a T that has additional tappings that are plugged and can be unplugged to add some more main vents later if needed to allow fast main venting? Ideally we'd figure this out on our install, but if we can't, is there a second best option?

We currently have a 4 inch main pipe out of the header for about 5-10 feet, reducing to 3.5 inch for another 10 feet or so out the boiler room before T splitting into 3 inch & 2.5 inch mains. The 2.5 inch is only about 15-20 feet before going back into the boiler room as a condensate return pipe at 1.25 inches, and the 3 inch splits off about 10 feet past the T split and becomes two 3 inch mains that run the perimiter of the house, another 40 feet or so for the shorter one & 70 feet for the longer one until they both return to the boiler room as 1.25 inch condensate return pipes.

KC_Jones

If you search on here for vent tree you should find some good information and pictures of what others have done. Here are a few things I picked up on while hanging around the wall.
1. Use a union where it connects to the main, this allows you to easily remove the entire vent tree to change or add vents as needed.
2. Yes use tees to allow for adding more later if needed.
3. Whatever you do make sure the pipe slopes back towards the main. You will get condensate in there and it needs to be able to get back to the main.
4. Get the vents as high as you possibly can. You want to keep the steam from slamming into them so get them up high.
5. With as much main as you have I promise you are going to need a lot more than 1 #2 vent. The general rule is 1 #2 vent for ever 20' of 2" pipe. Sounds like all your pipes are bigger than that so you will be really short of venting.
Did you buy the venting book from the bookstore here? If not I highly recommend it, fantastic information and it's only 10 bucks. By my very rough calculations based on your approximate pipe dimensions I am guessing you will need somewhere around 6-8 Gorton #2 vents. To be more accurate you will need to measure pipe lengths and diameters accurately and determine their volume. If you buy the book it is all outlined in there (that's were I am getting my info from).

cubicacres

Thanks-we'll try and get the added capacity for vents this week so we can add them later as needed.

Per Dan's "Greening Steam" book, it looked like the Gorton #2 vents were the largest that are still made today. Any thoughts on a good way to test if we can still use our 3 Gorton #2 vents and just add a few more as needed? We blew in the radiator vents to see if they were still good, but I don't know if that's a good test for main vents as well.

KC_Jones

As long as the vent closes when steam reaches it the vent is fine. If the vent is hot and still open it's not working. Also as you have tried if it doesn't flow at ambient temperature it's bad. So you have one test done. Gorton #2 is the largest vent currently available that I am aware of. As to your question about "as needed" that is sort of a matter of preference. Will the system work with what you have? Yes it will work. It comes down to efficiency and balance. The efficiency part is that you want that steam to get down the main as fast as possible, every second of delay is seconds of gas you are burning to do essentially nothing. So every second faster it goes is a second of gas you don't have to burn. Save 10 seconds on every heat call, average of 12 calls per day times 6 months of heating that's about 6 hours of gas saved. Multiply that by the firing rate and gas price, well it can add up. With proper main venting you can balance the rest of the system, without it you have a difficult time balancing the system because you end up with radiator vents trying to vent the mains. This is due to inadequate main venting. A test that a lot of us have used is to remove all the vents and fire the boiler, put your hand on the header and as soon as it's hot start a stop watch. Then go to the end of the main at the last radiator take off as soon as the steam reaches that point stop timing. That is your baseline. Now you put the vents back on and keep adding vents to get as close to that number as you can. The other option as I stated before is to do all the calculations and vent according to the venting book.