Oil Furnace Water Relief Valve

A pressure relief valve rated at 30 psi., 535,000 btu/hour discharged no water the 1st 2005 heating season----Through 2006 it began to discharge small amounts of water. This heating season it could discharge 3 gallons in 2 days. I replaced the valve with one rated at 30psi 510,000 btu/hour... Can anyone comment on this replacement Re: the btu/hour figure. Because I do not know the relationship of the btu/hour rating on the valve

If the BTU per hour rating is greater than the firing rate of your burner, then it is big enough. It is about 3 times the firing rate of most household boiler so you are safe.

It is not unusual for boiler valves to leak if they are actuated after a few years.

You should look at the gauge on the boiler. If it gets to more than 25 psi you should be finding out why and fix it. You may have a bad expansion tank, or it could be waterlogged. Check the temperature gauge. Too high a temperature will cause excess pressure.

valve

You are treating the symptom, not the disease. You have to find out why it is discharging, not just change it because it is discharging. The only time the capacity of the valve is an issue is when you have a "run away" boiler that is out of control and will not turn off. And then you have an entirely different problem.

I also vote for a shot expansion tank. Another possibility is if it has an autofill valve - that may be adding water when it shouldn't, forcing the pressure up. Not as likely, but possible. If the boiler has an indirect WH, or a tankless coil, there could be a cross connection there, which would be similar to having a bad autofill valve, except for health reasons, the worst possibility. There are probably more, but I'd check the expansion tank first...if you knock on it, it should sound essentially hollow as it should be filled with air not water. There are more definitive tests, but that is quick and easy.

water relief valve

Thank you for the replies-----While I did replace the valve ---the solution was in the expansion tank.......WATER.........Got the water out-----At 170 deg water temp the pressure is less than 20 now