vacuum and main vents

rmoore007ri

I have a one pipe steam system with two mains. The main venting is near the end of the dry returns. The system runs well at about .05 psi. Occassionally when the furnace shuts down on pressure (1.4 psi) I see a vacuum in the 0-3 psi gauge.



The mains are 33 feet and 13 feet of 2 inch pipe. The returns are 1 inch pipe. I have a pair of Gorton #1s on the 33 foot run and a Maid-O-the-Mist #1 in the 13 foot run (Yes i've built these out on antlers so I can add more after pay day) . . .



I seem to remember an article that said the Gortons were not opening (when the boiler shuts down) because they were remaining too hot for too long. And that was why I was seeing vacuum in the gauge. If that is true, just adding more vents seems unlikely to help. Commments please.

MDNLansing

Distance

You can try moving the vents further away from the main. They will cool a little faster that way. Having some vacuum shouldn't be a big deal though. You'll either have a vacuum from the condensing steam, or a pressure drop from the air rushing back in. Adding more vents will help, but only because your additional vents are moving further out the antler and they will cool faster. Float style vents might open faster as the reservoir will drain quickly after shutdown.

JStar

Vents

What's wrong with a vacuum? It won't last long anyway.

rmoore007ri

moving the vents

Thanks. Lengthening the antler seemed to help. As a homeowner who has recently switched to a 0-3 psi gauge I'm not used to seeing the system breathe. So I'm not certain of what I am looking at.

nicholas bonham-carter

What's wrong with a vacuum

Whistling vents are the only results of the vacuum you have. It probably is also an indicator that you are paying for extra fuel to push the air out of the system, so maybe another Gorton 2 on each dry return is in order.

Using your 0- 3 psi low-pressure gauge, you can see how effective the main venting is, the venting should take place at 2 ounces of back-pressure.--NBC