Is there a step-by-step guide for converting Hoffman 76 to 75?

Mark_125

Hi Steam Wall,

Background:

I have one-pipe steam (non-vacuum) - last year I asked my heating guy to change my main vents and he put in Hoffman 76s. No worries I thought, the system will just break the vacuum from the rads.

This year I replaced my Hoffman 40s on the rads with Gorton valves (nine #6, two #5, one #4 and one #C. Now when the system breaks the vacuum it appears like it is coming from the radiator closest to the boiler and boy is it a loud wooshing sound for about 4-5 mins.

I've heard in passing that NBC and others have converted a Hoffman 76 to a 75 by 'removing a disc' and I was just wondering if there was a step-by-step guide to doing so.

Would it be difficult, is there real danger that I could break the valve?

TIA,

Mark

nicholas bonham-carter

conversion to #"75"

it is best to remove the vent from the riser first, and then locate the cap at the top where the air comes out. this cap will unscrew, revealing a disk underneath which is covering the exit hole. this disk, when shaken out of its place is the one-way vacuum valve. put the cap back on, reinstall the vent  and you're all done.--nbc

Mark_125

Propping disc open also works.....

Thanks Nick, I've realised now that I've taken a closer look that a thin piece of wire holding the disc off the top of the valve also works if you don't want to remove the vent from the main.

-Mark

nicholas bonham-carter

converting hoffman main vent

that of course will work, but may lessen the  outbound air flow somewhat.

remember as some great sage has said here, "air is the enemy, to be chased away, like a raccoon from the garbage cans!". you can never have too much mainline venting.--nbc