Trouble with boiler dumping gas out flu then back into comb. air

[Deleted User]

I have a customer with a mysterious gas leak. They are getting an intermitant gas smell in their house and I can't figure out why. They have a small hydro-therm direct vent boiler on the lower level of their house which I suspect is the cause of the problem. Someone has installed a regulator on the gas line going to the boiler,; why I don't know. In another house next door there is the same exact set up but no regulator. Could this regulator affect the firing cycle of the boiler? Maybe there is a problem with the gas valve?
I'm stumped. Any help would be greatly appreciated!

Unknown

regulator outside

If the regulator outside doesn't lock up tight after the unit shuts off, the pressure in the line can creep up until the unit fires and brings it back down to normal. If it doesn't fire right away, the outdoor regulator relief valve could lift. Somebody might have put the regulator on the indoor piping to limit this from effecting the inlet pressure to the unit. Check your gas pressures, before the appliance regulator, running and locked up. You will learn what those regulators are doing. If that regulator won't lock up, have it replaced. Noel

Dale

Gas smell

If this is a natural gas system get the gas company out, they'll look for it at no cost to the customer. It is not unusual for sealed direct vents to have a gas valve that leaks through enough to get an odor HW and other and other valve manufacturers will say with a straight face that the leakage is OK under ansi standards. If it is natural gas the gas company should see what the flow and lockup pressure is, the boiler only need about 5" wc to run, I have reduced leakage and smell by reducing the flow through the regulator outside from 8 to 5 inches. The othe post on the lockup pressure is a good one. The lockup for the utility regulator shouldn't be more than 1 to 1.5 inches WC above flow pressure, if it is the utility will fix the regulator. As to the extra regulator sometimes the gas company puts 2 pound gas to the house and a separate regulator is needed inside to get down to 7". Sometimes things get missed and a regulator is missing. I would get a manometer or magnehelic on the gas pressure and see what it is at lockup = no flow and at flow.

Unknown

gas leaks

I strongly suggest that you get a professional gas man to check this out. No one who is not a gas man should be adjusting a house regulator. The only regulator that a service tech should ever fool with is the one on the boiler or if built in to the gas valve. There should never be a smell of gas in the room or in the air. Something is wrong and needs a professional with a combustible gas indicator to test. There could also be a problem with the combustion on this boiler and possible even a reverse chimney. As for the regulator in the line before the boiler, on older boilers that did not have a regulator built into the valve the regulator was installed before the gas valve. However if the valve has a servo regulator built in that regulator before the gas valve should be removed. You can not have two (2) appliance regulators in series with one another. The typical gas pressure after the regulator should be 3.5" W.C. and ahead of the regulator 6" to 7" W.C.