Air vent theory - could fast upper floor vents ever "assist" sub-optimal mains vents?

Jim_NY

The expertise and experience shared here is educationally addictive. . .
Have been trying to absorb air venting practice from forum posts, and was thought-experimenting about combinations when things aren't optimal:
- Say, single-pipe steam, with the boiler close to the middle of the basement, and smaller-than-ideal mains vents at the front and back of the old house.
- Say, on the top/2nd floor, there are fat pipes with (slower) radiator-type vents in the bathrooms, again at the front and back of the house.
So, curious if fast vents* were present on those 2nd floor fat pipes, could they in any significant way "assist" the basement mains vents in more quickly purging air from the system - or are they just too distant to matter?

*Looking at the Gill and Pajek chart, a "fast" 1/8" could be something like a Gorton or Maid O Mist C or D, or a Varivalve.

Jamie Hall

Remember that in one pipe steam, vents actually serve two purposes -- and they don't mix well. The main vents are there to allow air to get out of the pipes leading to the radiators. The radiator vents are there to regulate how fast air gets into the radiators.

So...

In partial answer to your question, main type vents on risers to second or higher floors, on the riser before the radiator runout, can and sometimes are used to assist in balancing when steam actually reaches the radiator. They are not usually needed in a two story structure, but on occasion they will be helpful -- and they won't hurt.

You still need a radiator vent suited to the size of the radiator and the space being heated to control the radiator, however.

That help?

Jim_NY

> That help?
@Jamie Hall comments always help.

Hmm. Guess was considering the mains in isolation in this thought experiment: would the mains fill with steam any faster with the presence of both types of vents at the terminus of the building - though one type of vent would be 20 feet higher.
Even in this scenario wouldn't want to mess with proper radiator venting/balance, so only mentioned the fat pipes - which I've always supposed are an informal, non-critical way to throw some radiant heat into a room without a radiator.

Jamie Hall

Probably wouldn't make much difference to the basement mains, unless they are undervented now -- in which case it would, of course. I've often said -- as you may have seen -- that overventing can't hurt anything (usually!). What is much less obvious is that it won't help, either, beyond "enough". Up to the location of the vent. But -- a riser serving more than one radiator is, in many ways, still a main, even though it is vertical. And so venting can speed up how fast steam gets up the riser.

I dare say the fat pipes are indeed an informal, cheap, and non-critical way to get some heat into a room. Very common, in fact. And, of course it works -- but one doesn't really think of them or control them as one would a radiator.

Jim_NY

Informative as always. Thanks.