Gas boiler question...

[sailor61]

OK so I know we're generally wood based on here but the energy source is not the problem or question. I've got a gas fired hydronic system that is in addition to my Woodstock Fireview, for various reason I've been running the boiler the last few days. Today I noticed water on the floor near the boiler...moved everything out of the way and, luckily, it's not a major problem. There is an intermittent flow/drip coming the relief valve.

Last fall I had a similar problem and replaced the relief valve since I assumed that was the issue. Didn't notice the problem after that but also did not run the boiler that much. On the basis of a new relief valve last fall and no other leaks the only point where I can see a potential problem is with the diaphragm expansion tank. If that had lost its pressure or the diaphragm wore out that could cause this problem, correct?

The relief opens and drops the system pressure, the autofill opens and brings it up to pressure. Then when the house calls for heat the boiler kicks on, the water in the system expands, if the diaphragm is shot or there is no head preassure in that tank then the relief valve opens to bleed off some pressure in the system. Does this scenario make sense? If so how do I tell if the diaphragm is gone or the tank simply needs some air added to it?

 

[eriesigtau]

sounds like the diaphragm tank to me. If that is broke, the water expands and has nowhere to go. pressure builds until the relief pops. they are pretty cheap to replace.

 

[sailor61]

checked the tank pressure and it came up at zero but I didn't get any water out of the valve so it doesn't appear the diaphragm is leaking. brought he tank pressure up to 12 pounds which seems to be where most of them need to be. Boiler has cycled a coupe times since then....so far the relief has not opened again.

 

[ewdudley]

May be relevant, maybe not, I have a tank that uses a tubeless-tire valve-stem, which developed a leak after a few years. After I pumped it up I could see a tiny leak at the base with soap bubbles. I dried it off and a few days later cleaned it up with brake cleaner and then worked a little Permatex into the seal, which seems to have cured it.

 

[BoilerMan]

What does your pressure gauge tell you in the various states of boiler temps/calls for heat.

The system pressure should be Zero, fill valve off, and then pump expansion tank to desired PSI.......then open fill valve, which should also be set to the same PSI as you pressureized tank.

This pressure is calculated based on total height of the system and total volume of water and temp change.

TS