steam vents not venting

Bob W._3

In Dan's book, The Lost Art of Steam Heating, he gives examples of how some turn up the pressure to get heat, which works to a point, but causes other problems with the system. If you have adequate venting, like Steamhead says, you shouldn't need to run at that high a pressure. In fact, many vents, such as the adjustable Hoffman 1A, will slam shut and not open unless the steam pressure drops to 1.5 lbs. That is the "drop away" pressure that Steamhead talks about. You should vent the pee out of your mains, and experiment with different size vents on your covectors. Since you wanted to try adjustable vents, try Hoffman 1A's (they are an angle vent, not straight shank; if your convectors need straight shank vents you could use a nipple and a 90degree ell to mount an angle vent; I think Hoffman had an adjustable straight vent called the 2A). Also check your thermostat to make sure the anticipator setting is allowing a longer on time. Do a search on anticipator settings and you will find many threads on the issue. Its possible that you have a low setting which is allowing your boiler to short cycle. Good luck.

Jack Demczuk

I have a few convectors that get hot when the boiler fires but when the pressuretrol shuts the boiler off and the steam pressure drops towards the cut-in, the convectors get cold. I have tried new gorton steam vents and varivent, but the problem still persists. when i loosen the vent enough to let steam leak out, the convectors work great, but i am using too much make up water this way. just for the record, i think convectors suck. I think changing to radiators will solve my problem. any ideas?

Steamhead (in transit)

What pressure are you running?

Sounds to me like you're exceeding the "drop-away" pressure of your vents, thereby holding them closed except when the system has cooled down.

If your pressuretrol has been set as low as it will go, the pigtail underneath it may be clogged.

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Jack Demczuk

i am running 5psi with 3psi subtractive differential. my pressuretrol has the capability of running 15psi with a 6psi maximum subtractive differential. is there a benefit to running at the maximum differential? I have pressure gages to confirm that the pressuretrol is indeed operating propery.

Jack Demczuk

From my understanding, steam vents are supposed to get the air out, and when the hot steam reaches them they close. They only reopen when they cool down. Is this correct? One thing i don't understand is that when steam expands and reaches all the radiators and they get hot and the vent closes, why does it have to reopen? I mean as the steam collapses and the radiator gives off heat, wouldn't the collapsing steam automatically get replaced with fresh steam? I wish they made a vent that was adjustable so i can set the temperature that it opens on, that would solve my problem as well.

Steamhead (in transit)

The pressuretrol is operating

but you need to turn the settings down. Set the Main at 1.5 pounds and the Differential at 1 pound. This will stop the burner at 1.5 pounds and restart at 1/2 pound. Bet your vents start working then.

If you have trouble distributing steam thru the system at these lower pressures, you have a main-venting problem. If this happens, post it and we'll help you out.

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Steamhead (in transit)

They close on steam temperature

and are supposed to reopen when they cool. But excessive system pressure can hold them closed when they should reopen.

You're right about condensing steam pulling in fresh steam, that should keep the vents closed on temperature. But sometimes the vent cools faster than the radiator, opens, and closes again when it re-heats. That's normal.

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Ryan_10

QUOTE[I wish they made a vent that was adjustable so i can set the temperature that it opens on, that would solve my problem as well.]

They do, if you're willing to pony up the cash. I thought about it, then looked at the price tag, and forgot about it.

Jack Demczuk

i am really reluctant to do this. first off, at this low of a pressure setting the radiators don't get hot enough. I don't mean they don't work, but steam at 5psi is hotter than steam at 1.5psi. unfortunatly this house is old and contrary to how most homes of the period were build, the radiant area is undersized. quite simply the house doesn't get warm enough. i have tinkered with this system for quite some time. i read some of dans materials and ran at 1.5psi last year and the house wouldn't get warmer than 65. then i experimented and ran as high as 12psi. boy do those convectors get hot. also, right now when the boiler fires it stays on for two minutes and stays of for two minutes between cycles. when i ran it at 1.5psi, the unit was on and off every minute. i know that the higher the steam pressure the more oil i burn, but doesn't short cycling also consume more oil? See, this is the dilemma i face. honesty, i still think having radiators would be better than convectors. i saw these nice radiators that are designed to fit inside the wall like the convector and the are finned so that the air can go through them and out the existing convector grille. the radiators would stay hot longer between cooling and that would probably reduce the amount of short cycling even more. what do you think?

Jack Demczuk

who makes this? I am really curious to see and maybe implement. how expensive is expensive. i only have 10 convectors.

Steamhead (in transit)

I still think you have a venting problem

and you're building pressure to try to overcome it. In my experience a well-vented convector will pound out the heat at 8 ounces pressure. Jacking up the pressure is unheard of in residential steam heating. For me it's not an option.

Start with your steam mains- measure length and diameter of each, and tell us what vents they have. Also, what vents are you using on your convectors?

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Steamhead (in transit)

You mean the 1B

for straight-shank convector service. The 2A was an angle-pattern vacuum vent and is no longer nade.

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Bob W._3

Thanks Frank. Thats what I meant. It was Friday night.

Rodney Summers

It's just

a thermostic vent. Do a quick Google search and you should turn something up. Danfoss makes them, and so do a few others. About $80 to $100 each. For a discussion see

http://forums.invision.net/Thread.cfm?CFApp=2&Thread_ID=23165&mc=16