venting risers?

jimmythegreek

I have a large commercial building with 40+ rads on 3 floors, 1 pipe steam.  I am going to add an antler setup to my mains with a few gorton #2's on each side.  after reading tons of info here i found 1 main vent on each of the main branches near the main ends that were painted shut and replaced w jacobus main vents.(all the local shop had)  Im trying to balance out the system, I still have rads that wont heat, mostly a couple top floor rads.  I was thinkin of adding a main vent to the top floor supply pipe with a T instead of a rad valve to help bring up steam faster.  Im waiting for 20 new vents I ordered to arrive to start balancing this system, but I have rads that have been repitched, re vented, vents removed, and still nothing.  The lower floors get heat though.  I was thinking of shutting off lower rads and crankin the heat to see if these particular upper rads will eventually heat up, which I have heard happens once in a blue moon when its cold or boiler gets a cold start and runs a while.  basically the rest of the riser gets hot or mostly hot on floors 2 and 3 but not floor 4.so this leads me towards extra venting for that riser branch right at the top, kinda treating it as a main.   thanx for any help and opinions u share w me.... 

Dave in QCA

Balancing.....

Your main vents should help a lot.  You can try turning off the lower radiators just to prove to yourself that the steam pipes are all connected.

After your new main vents are installed, see where you are then.  Riser vents should also help, but it really sounds like you have situation of your lower floor radiators be vented too fast.  What happens is the steam starts to enter these too fast, and the cool cast iron, once the steam hits it, becomes a condensor, and condensors on steam produce a vacuum and suck in all the steam they can get.  They hog the steam until fully heated, when it finally starts to make it to the radiators that have had to wait their turn.

Balancing is based on the premise, vent your mains FAST, and your radiators slow.  You may need vents on the risers, but I'd wait until you first replace your main vents and see where you are.

What kind of vents are on the radiators?  Are they all the same?

Rod

Riser Vents

Hi- I've attached a couple of drawings that might be of help to you.

- Rod

Steamhead

Here's another way to do it

which has the advantage of keeping the vent from getting kicked. 

nicholas bonham-carter

venting advice

don't waste any effort on changing the radiator vents, until you get plenty of main vents in place. i have 55 radiators, and 18 gorton #2's, as well as 6 hoffman 75's. you may need some radiator vents along the way, but don't waste any time or money on them now.

put a good low pressure gauge [gaugestore.com  0-15 ounces], and look at the back-pressure in the mains as the boiler is starting to make steam. a low back-pressure reading of 2 ounces will show you when you have enough vents on the mains to let the air out. any higher pressure indicates that you are paying your fuel company to force the air out. in your situation a vaporstat [0-16 ounces] will probably reduce your fuel cost by quite a bit.--nbc

jimmythegreek

very helpful

thank you very much for the pics and the schematic posted above.  Thats an excellent idea.  For a little more info on my story..... its a 1902 4 floor building w a basement making it actually 5.  Restaurant on first floor (ground level) and a 2nd, 3rd, and 4th floor consisting of a previous hotel w 60 rooms, now 39 studios w some bathrooms mixed in.  10 yrs ago the restaurant had a dedicated hydronic air/ac system put in and 6 huge rads removed and capped in basement at the ends of the branches.  Upon inspection no risers go up from these T offs, all the risers and rads upstairs are there and connected.  There has been ALOT of switching of rad sizes and vents over the years, few are original setups, all kinds of diff brand names of vents around.  The biggest problem is 3 of about 14 risers not heating top floor rads.  2 of these go into an old crawl space w no access and no insulation in basement on these particular risers so I suspect alot of this due to the cold underneath.  The main vents as previously posted were 1 on each of 2 main branches both painted shut dinosaurs.  I grabbed 2 jacobus main vents from local shop for the moment.  Gonna try 3 gorton #2s on antlers on each main to start, but I think I need way more on mains and on the risers too.  The mains are 4" cast iron and about 75 feet one way and 90 feet the other way.  1/2" insulation on the majority of the piping, looks like 1" on the first 10 feet off the boiler and header.  Its a weil mclain gas job, EG series about 420k btus on stamp.  Had a coal system originally, then a few oil jobs til gas came around.  Im gonna re pigtail it w a union and get a 0-3 guage, and start trying to vent this thing.  some of the rads dont heat well and if I pull off a vent it blows some air pressure almost anywhere in the building, and most of the vents are wet.  I got a few to work better changing the valves that were bad and repitching them.  Still have a ways to go.  This site is super helpful, you guys know your sheet.  thanx in advance.  I'll post my progress....

ChrisD

Changing valves may not be necessary

I like riser vents, and riser venting may make a difference, but throttling some of your rads would likely make a bigger difference.  If your vents are wet, this is a sign that they are running pretty fast, and they may be hogging the steam.



Once your mains are properly vented, you won't need huge vents on the risers; the goal is to vent the riser itself, not the whole system.  A fast radiator vent should be sufficient, and will be orders of magnitude cheaper because if you use a vent with a 1/8" tapping, you won't need to change the valves; you can just screw the vent directly into the pipe wall.



Where you have exposed risers, the easiest and cleanest installation is the one that Steamhead suggests: put the vent up near the ceiling one floor down from the top.  Where your risers are buried, you may have to place them at floor level.  The attached picture shows a Gorton-C angle vent on a 1/1/4" riser in a third floor apartment.  The stand-off looks kludgy, but is necessary for the vent to clear both the valve and the floor.

jimmythegreek

makes sense

I see what you guys are saying with the vents up high on the lower level.  I am a contractor by trade and have no prob drilling and tapping pipes myself.  A weird thing on one of the rads up on top floor is the riser gets hot all the way up the wall, when it goes into the joist bay(hidden) and then angles down a few feet in the bay to the rad, it wont get hot even w vent removed from rad.  I suspect the settling of building or along those lines is makin water stand in the horizontal supply to rad at top of the riser.  If I remove the rad and open valve ill get steam after a little while out of the valve, but never on the rad  or on other side of wall a foot away with an adjoining rad.  This puzzles me.  I have water in almost all my vents, I am making wet steam, and I just removed some insulation from boiler header piping to inspect and found the piping done nicely and the way weil mclain suggests in manual, BUT the outlets on this boiler is 3" on both top taps and they have bushing in them to 2" right at boiler tapping and again once it reaches the original header then back to 3" and then to 4" when it hits the main a few feet away.  I have read to full size the pipe right from boiler, so in the spring I will repipe this and even add a drop down to the header as in Gerrys pics of a beauty system.  Its alot of work and research to get this steam workin right!