Short Cycle / Vaporstat

Brad White

If you used to run the system at a higher pressure, that may have been enough to force venting ahead of the steam better than the low pressure will do now.

With lower pressure, the back-pressure from under-sized vents may cause you to reach pressure before the steam hits the vents and radiators. You have pressure, but I suspect it is air at the radiator end...

With lower pressure, your venting should be more generous to work at those lower pressures, ounces.

Hardly the last word, just one thing to look at.

What does your main and radiator venting look like now?

SusanB

Short Cycle / Vaporstat

We recently had a new boiler installed and it's short cycling, every 15-30 seconds. The vaporstat main is set at 2psi and differential is at 3kPa (8oz/in2). I know the differential is subtractive, but I don't know the correct setting so that it doesn't go off/on so quickly. Once the pressure hits 2psi, it cuts off, and as soon as the mercury float drops back, it kicks on - this is a matter of a few seconds. We also have a pressuretrol as backup which was doing the same thing (short cycle) before we installed the vapporstat. Suggestions?

SusanB

All new vents

All of the vents have been replaced on radiators and on the main in basement. Several of the radiator vents were clogged and it took forever for the steam to make it's way to those radiators furthest away(those were the clogged ones). We started out with the psi set at 1 on the vaporstat and it did the same thing, short cycle. I don't recall the pressure before replacement of the boiler. Right now, the whole thing seems to be acting up. Burner kicks on for a moment, then a whoosh sound and it shuts off. Could this be caused by the on/off so often.

SusanB

All new vents

All of the vents have been replaced on radiators and on the main in basement. Several of the radiator vents were clogged and it took forever for the steam to make it's way to those radiators furthest away(those were the clogged ones). We started out with the psi set at 1 on the vaporstat and it did the same thing, short cycle. I don't recall the pressure before replacement of the boiler. Right now, the whole thing seems to be acting up. Burner kicks on for a moment, then a whoosh sound and it shuts off. Could this be caused by the on/off so often.

Brad White

New is fine

but what type are they? Gorton's or other larger capacity or direct replacements of what was there?

It really gets down to "breathe-ability", the capacity to freely expel air ahead of steam at modest pressure.

If you have 2" mains of any consequence, these have about 2.3 cubic feet of volume per 100 feet of pipe. It may not sound like much but if you want to get that out of a hole that looks smaller than the point of a ballpoint pen, you can see how these can restrict.

gerry gill

you may need

to skim the boiler again.

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heatguy

ounces or psi

make sure your looking at psi and not ounces good luck