VentingQuestion

gehring

I have a one pipe steam system. There are two mains that run to opposite sides of the building (and two dry returns that come back to the boiler). I have a Gorton #1 on my short main/return and just ordered a Gorton #2 for my long main/return. These vents are located back near the end of the dry returns before they drop back down to the boiler.

At various points along and at the outer reaches of each main (back in crawl spaces, etc.)are various capped off pipe stubs where radiators were removed or relocated to other positions in the rooms above by previous owners.

I was wondering if I could tap into some of those stubbed off pipes and add additional Gorton vents at those locations on the outer reaches of the mains. Would that help system performance or would it be irrelevant, overkill or even incorrect to do so?

The system otherwise works fine, but I was wondering if such additional venting (located at the far ends not back at the boiler at the end of the dry returns) would speed things up even more.

I await the opinion of the experts. Thanks.

gehring

Addendum


I forgot to add the 2nd part of my venting question...

I have noticed that a few minutes after the system shuts down after satisfying the thermostat the Gorton on the long main will open up and actually suck air back into the system. Is that normal?

Al Letellier

additional venting

The key to your question is the words "IT works fine otherwise". I see no need to add additional vents if the system operates normally, and in a crawl space, service and replacement would be a pain.....The vents will "suck in" some air as the system cools and tries to pull a vacuum...that's how the condensate gets back to the boiler.

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Steamhead

You want all your venting capacity

at the end of the main, or dry return in this case. This way each radiator will get steam at about the same time.

Are your steam mains and dry returns insulated? If not, this might cause the vacuum that opens those main vents.

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gehring

Yes. My mains and returns are insulated (just did so this past weekend)- which brought on a new issue. Whereas before (prior to insulation)all of the radiators seemed to heat at about the same speed, now several don't even begin to get warm until others are fully hot. Should I add quicker vents to those that remain cool? Why would the addition of insulation completely change these dynamics?

CK

Venting

Steamhead:

I am not so sure about your reply about venting only at the end of a main. I have a one pipe system (circa 1922) with a 2 1/2 inch, 96 foot continous main. When i bought the house i replaced the main vents (I believe they were originals for the long gone coal fired system). But the point is that there was a vent about midway on the main and another about 18 inches before the end of the main. I am almost certain it was installed like this. i replaced both with Gorton 2's figuring maybe they knew something i didn't. But it seems to me that a midway (helper?) vent would exhaust the air quicker from the main bringing heat more evenly to the radiators. Thoughts?

scrook_2

venting midway

A vent midway would help the main fill with steam up to the vent only then it would close, but if you moved that midway vent to the end, next to the original end vent, the vent would help vent to the midway point is was at untill the steam got there, then instead of closing it would stay open and continue to vent the air from the midpoint to the end until the steam reache the end at which time both would close. The major resistance to the air is going to be the vent itself, not the big pipe between the boiler and the vent, so put'm all at the end (or just before).

CK

Venting II

That makes sense to me. Now would 2 Gorton #2's at the end of the main be sufficient to vent this very long main?

scrook_2

Venting speeds

2.5" Sch 40 is 4.788 sq in internal cross section so 96 feet would be about 5500 cubic inches or 3.2 cu. ft.

If I recall, a Gorton #2 vents 5.5 CFM at 2 oz. pressure so it should vent it in about 35 seconds (give or take a bit), and a #1 vents ~1.4 CFM(?) at 2 oz. so would take about 2.5 minutes, yes?

Hoffman says on their site that a #75 vents about 0.75 CFM at 1/8 psi (2 oz.) -- slower than a Gorton #1 -- so that should be about 4.5 minutes.

Steamhead

On a long main like that

a pair of Gorton #2 vents should work perfectly. This is because a long main has more internal resistance than two shorter ones carrying the same load. The second vent compensates for this.

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gehring

I answered my own question ref. the two cold radiators by replacing their standard vents with Gorton #6's. Now they actually heat faster than the others (which is fine considering the rooms they are in). But now I got thinking, why not replace ALL of the vents and speed up ALL of the radiators (proportionally) with the various different fast and superfast Gorton's. Is there any reason not to get the steam to the radiators as quickly as possible? Would it be wrong to try to make all of the radiators super fast?

CK

venting thoughts

Steamhead: Are you saying that i should eliminate the midway and place both at the end?

Also, Just thinking about this. On something like this long main, if you sized for and installed 2 Gorton #2's at the end of the main, what if you added a 3rd Gorton #2 at the midway point? Wouldn't that increase the efficiency of the delivery? It seems to me that even after the midway vent closed, the 2 at the end, capable of venting the entire main, would still be available to vent. Don't mean to bother you guys, but just asking in "theory".

Unknown

good idea

if you vent too fast, water will spit from the vents because of velocity when everything is cold.

Then you just slow that one down and balance from there.

Noel

scrook_2

fast radiators

On a milder day wouldn't you 'overheat' the rad (heat it *all* the way across) and then overheat the room, vs w/ a slower vent the rad might heat only part way across before the t-stat was satisfied and stopped the steam.

OTOH a rad on a very tall/long riser might want a fast vent so the riser vented fast and the radiator *started* heating fast.