vacuum or non-vacuum air vents/vavles in low pressure steam 1 pipe system

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Old 01-16-12, 10:17 AM
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vacuum or non-vacuum air vents/vavles in low pressure steam 1 pipe system

I have a 1 pipe low pressure steam heating system, and I want to replace some of the air valves on the radiators. Original air valves are Hoffman No. 2 Vacuum. I have replaced a few with Hoffman Specialties No. 2-A - which are also vacuum valves.

I did so because years and years ago a great plumber who is no longer around told me to only replace the valves with vacuum valves to keep the system efficient.

Today, all I find available are non-vacuum valves - like Model1A PartNo.401422 Air Valve.

Has the practice changed and non-vacuum valves the way to go, or do I need to find vacuum valves - and where would I find them - goggle searches are not helping.

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Old 01-16-12, 04:56 PM
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I hope rbeck stops by... or FURD! c'mon in here!

I'd like to know the answer to this myself...

Wonder what the advantage might be to a 'vacuum type' ? What's the difference ?
 
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Old 01-17-12, 10:40 AM
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I'm here but I haven't a clue. Commercial doesn't use air vents on the individual radiators.
 
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Old 01-17-12, 05:42 PM
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I was afraid you were gonna say that Furd! c'mon steamheads! answer the question! pleeeze?
 
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Old 01-23-12, 06:26 PM
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I heard from a local company - said Hoffman do not make the A1 vacuum valve any more - on an A2 - non-vacuum - and only said that the A2 would be noisier - but not make any difference.

Than just doesn't sound like an answer - but unless I get something from someone else - don't know where to turn.
 
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Old 01-24-12, 01:14 AM
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After thinking about this for a few days I remembered something I read several decades ago. SOME steam systems used a vacuum pump at the boiler to return condensate to the boiler. These boilers could, under some circumstances, actually develop a vacuum inside during burner off periods, usually when the boiler was controlled by a time switch and went down overnight. I suspect that the vacuum-type valves were used with this obsolete system and that the non-vacuum type of air vent is not only suitable but preferred for your needs.
 
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