Hoffman #75 Steam Vent Issue

I have an old one pipe steam system with a Hoffman #75 vent at the end of the loop. My system actually works quite nice in general, I have tuned it up and balanced it over the years to much success. The issue that I just started having about 6 months ago is that my main vent is no longer closing and it requires a small 'smack' on the side in order for the plunger to completely seal the vent and close. The pin does rise into the orifice but it just doesn't seem to seal 100% and I get a nice solid steam jet until the boiler can finally overcome the vent release and get up to 3psi to cycle properly.
I thought that it was a scaling issue or something but then again, since the water is steam, there really shouldn't be any minerals in it to actually build up scale.
Any thoughts? I figured the vent would last more than 1 year? Should I take it off and soak it in lime-away for awhile? Also, the vent is perfectly vertical so it isn't a 'slanting' issue or anything.
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I have an old one pipe steam system with a Hoffman #75 vent at the end of the loop. My system actually works quite nice in general, I have tuned it up and balanced it over the years to much success. The issue that I just started having about 6 months ago is that my main vent is no longer closing and it requires a small 'smack' on the side in order for the plunger to completely seal the vent and close. The pin does rise into the orifice but it just doesn't seem to seal 100% and I get a nice solid steam jet until the boiler can finally overcome the vent release and get up to 3psi to cycle properly.
I thought that it was a scaling issue or something but then again, since the water is steam, there really shouldn't be any minerals in it to actually build up scale.
Any thoughts? I figured the vent would last more than 1 year? Should I take it off and soak it in lime-away for awhile? Also, the vent is perfectly vertical so it isn't a 'slanting' issue or anything.
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responding to http://www.homeownershub.com/hvac/Hoffman-75-Vent-Issues-27254-.htm avantiservices wrote: mhavoc wrote:

Change your gauge to an oz/kpa, turn down the press to around 8oz(try less if you can)***I know this does not SEEM to make sense but it works!*** then add a fine mesh stainless screen to the bottom of the air-vent OH YEA... you should be using a hoffman no.76 not a 75check the specs at: http://www.hoffmanspecialty.com/pdf/hs900/HS900-76.pdf Test this. I think your steam is picking up debris from the return water and carrying it to the vent. Lowering the pressure will save energy, run less, run safer, run quieter.
J.P. Avanti Services HVAC, Steam and closed loop Hydronic heating. In the service field for 25 years.
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3psi? Wow hehe Most residential boilers never even show any movement as you can heat a large home with less than 0.5 psi steam. You should stop tinkering with your boiler until you know how steam actually works. Bubba
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With my long run of stream pipe, if I set the boiler cutoff to .5 psi then the boiler ends up short cycling. Once the main vent closes (if it would close completely), my boiler can go from .1 psi up to 3 psi in about 30 seconds as it can pump out the steam volume. I found that a setting of 3 psi works well for me for boiler cutout in getting steam to my rads effeciently and evenly. When the steam starts up, my main line fills quick (at low psi) as the hoffman #75 is huge (ventwise)... my main line fills realtively evenly and then the steam goes out to the rads all at the same time as they all vent very slow compared to the #75. If I put my boiler cutout to lower than 3psi then when the #75 closes and the only venting options are the hoffman #1A's (7 in this case), the boiler can build up more than .5 psi fairly quickly and the shutdown before the steam fills the rads.
My copy of Ancient Art of Steam Heating is tattered... maybe you can send me a better copy? As a public service of course!! :-)
So... any thoughts on the #75 not closing?

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Yeah. You do know it is a quite simple device? It lifts and closes. If it doesnt, then it needs to be repaired/cleaned or replaced. As a company, Id replace it. As a tinkerer, you can mess with it till your fingers fall off if you like. Yes, I know its only a year old. Take it back in warranty (hahaha) or get a new one. Nothing is made like it used to be. Bubba
and NO, you CANT have my copy of the Ancient Art of Steam Heating by Dan Holohan

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