Radiator Vent Valves


Old 01-19-07, 05:56 PM
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Radiator Vent Valves

How do radiator vent valves work? How do these valves let you adjust the room temp... I bought a few Varivalve vents at the suggestion of HVAC-EMT ...I am not clear how these work...would like replace valves in all radiators...
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Old 01-20-07, 06:03 AM
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Do you have a steam system? I'm assuming so. The varivent controls how fast a radiator gets hot by how fast the vent allows the air in the radiator to escape. With a steam system, this is how areas are controlled. Steam cannot travel throughout the system unless it can displace the air.

The slide control on the vent increases or decreases the size of the hole where the air escapes. If you set it at a higher setting, the air gets out faster, and the radiator gets hot.

You should set the vents lower on the radiators that are getting hot fast, and higher on the ones that take longer. This will allow the problem areas to catch up to the other areas.

It may take some tinkering.

PS. Check out radiators that never seem to get hot by removing the air vent and starting the system & letting it run. If it still never heats up, the radiator may be plugged, or there may be a piping problem. Be careful, it could get hot REALLY fast.
Old 01-20-07, 06:22 AM
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Thumbs up Good description HVACGuy

The only thing you excluded is that there is a little needle valve inside them that closes when steam hits it. The heat from the steam causes the part inside to expand, closing the vent.
Old 01-20-07, 02:38 PM
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How does the air get into the radiators...one would assume that steam would push the air out of system and since the valves are unidirectional, air should not get back in?

Last edited by christy123; 01-20-07 at 02:59 PM.
Old 01-20-07, 08:07 PM
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Radiator vents

They are not uni-directional. Once the radiator starts to cool, the vents allow air into the system. If they did not, the system would go into a vacuum & the condensate would not return to the boiler.
Old 01-20-07, 08:14 PM
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Thanks I stand corrected. everything else make sense now
Old 01-02-09, 01:49 PM
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Question VariValve questions

If I may rejuvenate this older thread....I have a few questions about VariValves specifically for my 1913 Dutch Colonial home:

1) How long do they last? When do you know to replace them?

2) Can someone offer some guidance on balancing my house using the valves? I have four levels: unheated basement, 1st/2nd floor living space, unheated attic. Do I adjust the 2nd floor to heat faster (get hot sooner) than 1st floor or the opposite? The 2nd floor is always hotter than the 1st floor and drives us crazy.

If the questions are too broad and specifics are needed, please ask.

Old 01-02-09, 04:18 PM
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The radiator vents should be replaced about every 5 years although it never happens.
To balance the steam system you start with a good main line vent or maybe even multiple vents on the main steam line. Than adjust the radiator vents according to the radiator size. Faster radiator vents on larger and slower on smaller radiators. Than fine tune from there. I will repeat the most important vents are the main line vents.
Other vent questions can be answered here.
Steam FAQ

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