2 pipe steam, new boiler, revisited

Garret

Good question... i assumed it wasn't, since I could stop the boiler by dialing down the main setting on the vaporstat until I reached the pressure shown on the gauge.

But I'll check, just to be sure...

Garret

Greetings, gentlemen... you might remember me from a while back, when I got the advice of many here (Steamhead, Boilerpro, Christian Egli, Robert O'Connor, Patrick Linhardt, and many others) regarding my two-pipe vapor system.

http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=261364
http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=229995

It's now a year and a half later, and I have been poring over our gas bills, comparing the before and after figures, adjusting for HDD, etc. The bottom line is, we are saving just 10% on natural gas, compared to the 90 year old beast.

Last night, I spent an hour watching the boiler operate under normal conditions, and during a long, boosted call for heat.

A couple of things look puzzling to me:

1) Except when actively making steam, my boiler is under vacuum. The return side has an open pipe, but there is no vacuum breaker on the supply side that I can find. The highest vacuum I observed was -5”Hg.

2) I think the vaporstat we installed is bogus. I noticed when it was first installed that it mysteriously had a “pressuretrol” name plate on the front. My installer and I puzzled over that, but we decided it was just a factory mistake, given that everything else on the device indicates it is a Honeywell L408A-1132 vaporstat... The differential and main settings show oz/sq. inch, the honeywell model number is correct, etc.

Last night, with the vaporstat set at very low pressures (2 oz cut in, 5 oz cut out) the boiler reached 2psi during a long call for heat. I believe it would have gone higher had I let the test continue... as it hit 2psi, I dialed back the main setting until it finally shut off the boiler, at precisely “2 oz/sq.inch.”

So I believe I got a bum vaporstat, which is really a 2-16psi pressuretrol. And I think I've been operating my vapor system on 2-5psi. I should have noticed this earlier, but the house was warm, everything ran quietly, and we were busy with a newborn in the house... Here's the part where I bang my head against the desk.

I have a call in to my plumber to ask about the bum vaporstat... but what do you all think about the boiler going in to vacuum so much of the time? Good/bad? A symptom of running under high pressure?

Thanks as always for your guidance.

-Garret

Steamhead (in transit)

Are you sure

the pigtail under the Vaporstat is not plugged up?

"Steamhead"

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