One-Pipe Steam Pressure

superMARKet

I've got a one-pipe system in a four-story Manhattan walk-up. For the most part, it's reliable, but I've got a couple of "quality" issues I'd like to take care of. There's some undesirable water hammer, the building is often too hot, and the firing cycle seems too long. I said, "hmm, sounds like someone played with the pressure."

There is a new 5psig gauge with a new pigtail on the boiler that never lifts off 0psig. The old gauge never moved either. The pressuretrol (which I don't trust anyway and am replacing) is set to 10psig cut-out and 5psig cut-in. Seems too high to me, but it was set long ago by the service tech. I dropped the cut-in as low as it would go, and the cut-out just a bit above, but it kept on firing. (But the needle never lifted, so maybe there really was no pressure and the pressuretrol did the right thing?) All of the vents are functioning properly.

I know that the system will operate at low pressure, but is it normal to not get any reading on the gauge? Of course, if the pressure is that low, it makes no sense for the pressuretrol to be set so high, and 5+5 seems wrong anyway. What's the right ballpark for the pressuretrol in this type of building? And will fixing the pressure rid me of at least some of my problems?

Hey, Dan, if you swing by, I'll buy all of your books! :)

Thanks,
Mark

Steamhead

Yes, that's normal

if you build pressure in a steam system, you're just storing the steam instead of moving it out to the radiators.

That Pressuretrol should be set as low as it will go. 0.5 cut-in, differential 1, which will make it cut out at 1-1/2 PSI and back in at 1/2 PSI.

Try to isolate the source of the banging, then look for places where water could collect and steam could come in contact with it.

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superMARKet

But with all of the vents closed and the burner still firing,

But with all of the vents closed and the burner still firing, shouldn't I be building some pressure? Especially if the pressuretrol doesn't interrupt the burner because it's broken or set too high (or both)?

If the thermostat makes an hour-long call for heat, I'm not expecting the burner to fire steadily for the entire hour, which is what it does now even with the pressuretrol set low. Which is wrong, my expectation or the controls?

Thanks for your help, Steamhead.

Mark

Steamhead

Could be

the firing rate is too low. Check it against the amount of radiation you have to be sure. If the system heats slowly, this may be one reason.

Or the inside of the boiler may need cleaning.......

Or, if you're also adding lots of feed water, there may be a leak somewhere.

Let us know how you make out!

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neilc1

are you

sure the pigtail isnt plugged... no gage , no pressuretrol op.... humm

superMARKet

Separate pigtails for the gauge and pressuretrol

and the gauge and its pigtail were replaced a few months ago. The pressuretrol looks like it's been through hell and its pigtail is probably clogged, but I'm changing them anyway.

Mark

superMARKet

Thanks for the tips

I believe the boiler is sized properly but I'll verify tomorrow. I've got an automatic feeder, but I doubt that there are any leaks, since tenants have a tendency to complain whenever there's a leak. By the same logic, I'm assuming that all of the vents I haven't inspected myself recently aren't stuck open, and probably none are stuck closed either (no heat causes my phone to ring almost as quickly as a leak does - I'm sure you know EXACTLY what I mean).

I appreciate all of the useful suggestions.

Mark

Gary Fereday

Sheekie leekie

If there was an above the water line crack in the boiler it would never get up pressure. Check the chimney for visable whit vapor when the fire is going especilay when cold outside. bigugh

Gary Fereday

Sheekie leekie

If there was an above the water line crack in the boiler it would never get up pressure. Check the chimney for visable whit vapor when the fire is going especilay when cold outside. bigugh

superMARKet

Fixed!

I found two marginally operating radiator vents and a main vent that wasn't fully closing. As soon as I replaced all three and let the burner fire for 20 minutes, I began building pressure. After adjusting the pressuretrol down to 2.5+1 (and fixing it - hopefully it'll keep working now), the boiler began cycling properly. All of the radiators get hot (they always did) but not too hot, and the water hammer seems to be gone. I discovered another leaky radiator today that will be replaced soon, but it seems like the worst of my problems are behind me.

Thanks again to everyone for the helpful tips!

Mark