Welcome! Here are the website rules, as well as some tips for using this forum.
If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
I have a gas-fired two-pipe Webster system (100 yr old house). The system has crossover traps from the steam mains to the returns, and there is one main vent on the return (the original Webster Vent Trap). The vent trap has the small ball valve on top which is effectively a vaccuum vent, but there is no vaccuum pump nor any sign there ever was one in this system. I've read all the comments that say I should replace that ball valve with a standard vent. But I just don't understand any of the explanations on why I should do that.
This is my first winter in the house, and I noticed that someone else was thinking about the same thing because the previous owner left me with an unused new Hoffman #75 right next to the vaccuum vent- they can easily be interchanged. Since I have both, I've tried running the system with and without the vaccuum vent. When the system runs with the vaccuum vent, it hits a maximum pressure of about 1oz after the boiler fires for a very long time, and (not surprisingly) drops into vaccuum pretty quickly after the boiler turns off. The system seems to hold vaccuum for a pretty long time- on cold days the system is under almost continuous vaccuum except for when the boiler is firing.
When put on that Hoffman #75 (or I just take the vaccuum vent off and run with nothing) the system heats fine, but there is a lot more air hissing in and out of that vent. The boiler pressure gets a little higher late in the cycle, but I've never seen more than 3oz.
So is there any reason not to run this as a true vapor system (with the ball valve)? The way I figure it, with the vaccuum vent there is less air in the steam mains for the boiler to push out every time it fires up, and the steam should remain uncondensed in the pipes for longer as they cool down (since the pressure is low when the boiler shuts down).
I know that they designed this way for coal firing, but I don't see why the basic principle that low pressure is good would not also apply to gas or oil firing.
My question is, what exactly is the problem with running a gas fired steam boiler with a vaccuum vent? Is it going to cause me problems down the line, or somehow cost more in energy? Or should I do it?