Multifamily main venting off balance, how best to correct

josepha

I have a four floor multi-family property that I am trying to better balance a single pipe steam system.

BACKGROUND

• Boiler is operating a a low PSI (sub 1) .
  
• Controls are new and calibrated to the furthest radiator.
  
• Mains branch off in 3 directions from the boiler located in the front of the building in the basement 1) line of apartments directly above, 2) line in the front of building on the other side of the building, 2) to the back of the building (which further branches into 3 lines).
  
• All corners of the building get sufficiently hot, EXCEPT, radiators on the third and fourth floor in the line directly above the boiler serviced by two risers about 20ft from the boiler. If I raise the controls to compensate, the rest of the building is overheated.
  
• Far as I can tell radiators are setup properly with proper gorton radiator vents (#5 or #6 I think, maybe a #C or #D at the top of the riser in that line).
  

MAINS AND VENTING

• All mains are vented on the return, at the top of the pipe when it turns down back to the boiler. There are no vents on the hot side of the mains themselves.
  
• I did notice though that the problem area has the return vented some ~30+ft from the start of the riser (ie. right by the boiler) whereas the others turn down right at the start of the riser and thus have the vents close by (so not sure if that makes a difference).
  
• All these vents on the return appear to be similar, but gotta grab a ladder and inspect if can discern what each are (they are bullet shaped)
  

QUESTIONS

1. As I inspect the vents close up, what should I be looking for with regard to proper sized and operational vents (other than mains should get hot fast and in a balanced way). BTW: they are old.. best guess over 25yrs
   
2. Should the mains be vented on the hot side as opposed to the top of the return pipe? would adding one there help?
   
3. Would moving the vent on the problem side closer on the return where the riser starts up (or adding another one there) help?
   
4. There seem to be too many options listed on the board for types to use on the mains, so was inclined to use Gorton #1 or #2 as needed to remedy. Any reason I should instead look to something else?
   

Many Thanks!!

Steamhead

Those vents sound like Hoffman #4A- quite small. How long is each steam main and what pipe size?

Jamie Hall

That vent location on the return isn't bad (assuming it's a dry return), but it's almost certainly too small. If it's working at all...

josepha

The exterior diameter of the hot mains providing steam to the risers are about 4" and the returns are about 1-1/2"
1) problem main - 20 ft
2) other side front main - 45 ft
3) back main 65 ft straight back, at it's midpoint branches off to another run that is an additional 45 ft

The returns are a little longer because they travel down to the floor and make a few turns. For the problem main, the vent is about 25' away from the start of the return because it's the only on that goes back along the ceiling and then down to the floor (as opposed to down then over).

Where should vents be places to faster eliminate air? on the hot main or, on the start of the return? or just replace what is there with something larger?

Thanks

Jamie Hall

I see nothing wrong with the vent locations as they are. What I do see is that that problem main most likely isn't being vented at all. Try replacing all the existing main vents with either Big Mouth or Gorton #2s.

josepha

Thanks! gonna try replacing and see how goes and report back.