System Pressure

Douglas Sanborn

I have replaced the thermostatic traps, changed the 0-15 lb gauge with a 0-5 lb gauge and set the pressure to cut in at .5 lb and out at 1.5 lbs but still cannot get the system to build any pressure. The boiler just runs untill the thermostate is satisfied. If I plug the main vent pipe with my hand while the boiler is on the gauge pressure will build so I am confident that the system doesn't have a leak.
How can I isolate the problem?

Al Letellier_9

pressure

A little confused.....if you have thermostatic traps, why the main vent?? If you have traps at the radiators, there is usually Traps at the ends of the mains. If you "plug" the vent with your hand, it's bad. It should shut off when steam hits it. Can you explain your system layout a little better. Where do the traps drain to? What is at the end of the main, and where does it go?

Douglas Sanborn

My system is a two pipe dunham system. The steam supply has at its end a drop to a wet return and a thermostatic trap which crosses over to the end of the dry return. There is one vent coming out of the air eliminator near the boiler. Each rad has its own thermostatic trap

Ken_40

What the pressure gage reads is interesting...

How much water you feed in is everything!

It is not uncommon for some systems to never make a pound of pressure; vapor systems a readible ounce. A well insulated home, little to no night setback and by today's standards "oversized" rads will work beautifully with zero visible pressure.

The question however is" "Is there a leak that is the cause, or not"?

This is not verified by pressure gages. It is verified by water feeding.

A good rule of thumb is this: In fall and spring-like weather, if you must add water more than once a month - beware. In the dead of winter, if more than once every two weeks, also beware.

This assumes many generalities. It also presumes the normal water line is in the center of the glass to begin with, and around 1" or slightly less -above the bottom of the gage glass when re-filling is needed.

What has your experience in this regard been?

Mark Hunt

Your system

was designed to work on ounces of pressure, not pounds.

The pressure-trol that comes on just about every boiler is useless IMO. Even your new pressure gauge will not read ounces.

The boiler IS making pressure, you just don't have anything that read that low. If there was NO pressure, you would not get steam to the radiators.

A vapor-stat is what you need to cycle the boiler on ounces of pressure.

Mark H

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Douglas Sanborn

My system is a two pipe dunham system. The steam supply has at its end a drop to a wet return and a thermostatic trap which crosses over to the end of the dry return. There is one vent coming out of the air eliminator near the boiler. Each rad has its own thermostatic trap