Venting Mains - Single Pipe Steam System

tcapron

I've been reading lots of the threads here and they've been very helpful to me as I try to get my system working better.
I'm in a 5 story townhouse with a natural gas boiler firing a system that was originally coal, converted to oil and converted to natural gas 3 years ago. The top floors are not getting significant heat and so I'm working on balancing the system.

I spoke with the folks at Gorton last week who were very helpful. I had called to discuss the radiators and which size release valves to use on each floor and was told that I should check my main venting before messing with the radiators. I spent some time in the basement and it appears that I have NO vents on my mains (one goes to front of building and the other to the back). The return lines appear to have a vent on them that looks fairly old and I cannot find any writing on them to determine what they are (photo attached). My questions are as follows:

1) Main to the front of the building travels approximately 25 ft before splitting off to the two runs up the building. The mains have outside diameter of approximately 2.5-3". I assume I should add Gorton vents just before the split to the runners but what size and how many?

2) Main to the rear of the building travels about 5 feet from the boiler and then has one small pipe (maybe 1.5" diameter) that splits off and runs direct to a radiator in the first fl bathroom. The main continues for another 12 feet before splitting to the runners that go up the rear corners of the building. I assume I should add Gorton vents but am unsure where (before the first split to the single radiator or before the split to the main runners) to add them and how many??

3) I've attached an image of one of the old return vents. Any clue what this is and whether or not I should replace them?

Over the weekend I changed the 5th floor release vents to Gorton Ds and the first and second floor release vents to Gorton 4s and this made a nice difference. My hope is that adding lots of venting will help get the heat moving more quickly into the system and then I'll be in decent shape. I've also taken care to add insulation to the mains in the basement to the few areas where it was missing.

Thanks for any/all insight and I apologize if much of this is redundant from old posts!!

KC_Jones

If I am interpreting your description correctly it sound like the pipes that go up through the building may be express mains to feed all the floors. If that is the case genereally those need to be vented as well to truly get even heat distribution. To verify, do all the radiators connect to the main in the basement? If they don't then those pipes that split off the end of the basement main are technically still "mains". All mains need to be looked at separately from the rad vents. The idea of vent the mains fast and the rads slowly counts on getting steam to all the radiators at roughly the same time. Or getting it to the radiator take off from the main at the same time. A pipe that feeds a single radiator is a radiator take off, a pipe feeding multiple radiators is technically still a "main". Since this was an old converted coal system it is generally accepted that the venting needs a complete revamping because modern boiler function completely different from the coal boilers of the past. Perhaps someone with more experience on systems this size can comment.

tcapron

Hi KC - I'm pretty sure there are 4 risers coming off those mains. The main to the front of the building has 2 risers coming off of it - one to run up each front corner of the building. The main to the rear has 2 risers coming off of it for the rear corners.

However, there are a couple of radiators on the first floor (one in the middle of the building and one at the rear) that appear to have their own direct line coming off the rear main. One starts about 5 feet from the boiler (as described in my first post) and another is at the split to the 2 rear risers and goes directly to service a radiator in a bedroom at the rear of the building on the first floor.

Fred

Do those 4 risers all go all the way to the top floor? Are there Take-offs or run-outs from those risers to the individual radiators? It sounds to me like the best place for Main vents would be at the very top of each of those risers. Do they, by chance extend up into an attic space?

tcapron

Thank you Fred. I think each riser ends at a radiator. The back/right riser ends at a radiator on the 4th floor. The back left splits just before it ends, serving 2 radiators on the 5th floor. Front/right ends at a radiator on the 5th floor as does the front/left.

I just spoke with Gorton again and was advised to essentially get some #1s or #2s anywhere I can but perhaps at the end of the 3" OD mains just before they split to the risers and then again at the very top of each riser between the main valve of each end point radiator and the radiator itself. Then, those end point radiators would have a release valve in front of the radiator venting the full riser and another after the radiator to vent the radiator itself slowly.

Any additional thoughts would be fantastic!!

Fred

As long as you can get enough vents somewhere along the top of those risers before the last radiators you will push the air out quickly. If those risers are 2" pipe and you are going up about 40 feet to get to the fifth floor, you will need 2 Gorton #2s on each of those to vent like you need to. You can put them on a Tee if need be.

Abracadabra

Some radiators have a boss for attaching a vent to the supply side of the radiator. I have often attached a Gorton D on the valve side to vent the riser, and then a Gorton 4 or 5 on the far end of the radiator away from the supply valve to vent the radiator.

tcapron

Thanks Fred, Abracadabra and KC!

I'm pretty sure I can add Gorton #1s and/or #2s on the supply side of the terminal radiators up on the top floors myself with a little help from my local plumbing supply.

If I do that, do you think I should still add Gorton #1s or #2s in the basement just before the mains coming out of the boiler meet the risers? Or, just start with venting the ends of the risers and see where that gets me? As I said, I think I can do the tops of the risers myself. Probably need a professional if I'm going to add something to the larger mains in the basement.

Last, I'm a little unclear about what to do with the return lines (per the photo I attached in the first post). Just replace what is there with Gorton #2? From what I have read on this site, I take it that I cannot over-vent the outbound mains but is that also true of the returns??

This has been incredibly helpful so thanks again.

Jamie Hall

Can't overvent the returns, either. In fact, in some old vapour systems the dry returns went through a condenser radiator in the basement, to catch any stray steam (with a nice drip to the wet return), and then through an open pipe to the chimney!

KC_Jones

I feel like a broken record because I recommend this so much, but here goes again. There is a venting E-book available in the store here and if you haven't bought it yet I highly recommend it. 10 bucks and it goes to charity. It's a short read, but gives a ton of good information about venting. As far as return pipes, since you say this is a one pipe system you really shouldn't need venting on the return pipes. They are condensate returns and don't need steam in them. As far as how many vents you need on which pipes it is essentially a function of pipe length and diameter. You calculate how much air is inside the pipe then figure how fast you want to vent it and pick the vent based on that. It is all explained in the book I recommended. The one thing I will add is if you want to operate at extremely low pressure (below 1 ounce) you will have to increase venting beyond what is recommended in the book. The lower the pressure you try and operate at the "slower" the vent goes. Below 1 ounce isn't necessary just mentioning it for reference as sometimes this question comes up.
http://store.heatinghelp.com/product-p/300.htm

tcapron

Thanks to all and I'll purchase the ebook now!

Fred

tcapron said:

Thanks Fred, Abracadabra and KC!

I'm pretty sure I can add Gorton #1s and/or #2s on the supply side of the terminal radiators up on the top floors myself with a little help from my local plumbing supply.

If I do that, do you think I should still add Gorton #1s or #2s in the basement just before the mains coming out of the boiler meet the risers? Or, just start with venting the ends of the risers and see where that gets me? As I said, I think I can do the tops of the risers myself. Probably need a professional if I'm going to add something to the larger mains in the basement.

Last, I'm a little unclear about what to do with the return lines (per the photo I attached in the first post). Just replace what is there with Gorton #2? From what I have read on this site, I take it that I cannot over-vent the outbound mains but is that also true of the returns??

This has been incredibly helpful so thanks again.

If you put enough venting on top of those risers, you probably don't need to put vents on the mains in the basement near those risers. However, putting those vents down there will vent those sections of mains faster and keep some of your large vents out of the living areas of the building and probably much easier to maintain. With the vents in the basement, you can probably get by with 1 or 2 Gorton #2's on the end of each riser. With no vents in the basement, I'm betting you will need probably 4 Gorton #2's on a 3/4 inch antler.