Conveting a radiator

Luv'nsteam

I'm searching for several steam rads to add to my system.  Many that I have found have what appears to be a Hoffman #3, located at the top of the rad.  Some have a plugged bung 2/3 of the way up for a standard air vent, others don't.  Can the #3 simply be removed and replaced with a standard air valve or does it have to be lowered for best operation?  I have not bought any yet, especially since I (well, mainly the momma) wants Victorian style radiators.  



Second question: after a full season of use with new boiler, main vents and new rad air vents, so I can get a base line of fuel consumption for a season, as well as, system operation with all upgrades & changes, I want to convert to vacuum system.  This will require the installation of the Hoffman #3 valves.  If I install these in place of the standard air valves that are 2/3 of the way up the radiator, will this negatively impact the use a vacuum with my radiators?  Anybody have experience with this conversion and results?



Thanks,



Mike

JStar

Air Vent Placement.

You want to use the tapping that is 1/2 to 2/3 the way up. You do this because the steam will rise to the top of the radiator first and work all the air down and out. If the vent was kept on top, the whole radiator would never get warm because the initial presence of steam would close it prematurely. 

Luv'nsteam

Air vent location

That makes sense.  Thank you Jstar.



Mike