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Re: Hydronic Boiler relief valve problem?
Check the pressure guage. Typically the pressure in a water boiler should not be more than 20 psi. If you are approaching 30, the relief valve is doing it's job. I would replace or adjust the automatic water feed if the pressure is high. Always replace the boiler relief valve. Tap on the expansion tank, it should sound hollow. Replace it if it is full of water. If you have one of the old expansion tank that has no bladder in it, drain it.
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typically hydronic systems like that need to be bled, start with the highest radiator, the bleed valve have a little square head and you need to have a key that fits them, most supply HVAC houses have them sitting on the counter but you can ask them for one.
3 Bar = 43.5 PSI When you heat water it always expands increasing pressure.
In a closed vessel volume can increase by 2-3%. Either expansion tanks allow for this and PSI is maintain or without an expansion outlet the PSI will increase in proportion to heat supplied.
Is this a low temp hydronic boiler operating at or <140F, a hi temp hydronic boiler @ >180F or steam boiler?
Is the pressure in the boiler higher than the set pressure of the relief valve? If it is, there is a problem that the relief valve is trying to correct.
If not, did you try making the valve open?
Be careful, but step back, lift the lever and briefly let the relief valve discharge into a bucket of some sort, maybe you could put some old rags in it to keep from spraying out at you. If there is sediment in the valve this may flush it out.
possible problems not knowing age of unit the
control valve could be sticking open allowing gas to continue to flow until high limit is reached and shuts down valve another possible problem with the newer style back flow preventer being install by water companys the rapid heating and expansion of the water over pressures the water system causing releif valve to pop open and reclose most water heater manufacters are recommending instalation of an expansion tank to allow the growth in volume of water somewhere to go is valve constantly leaking or only during heating cycle if you could supply additional information does unit only leak when heating
or is steam expelled when releif valve opens
t-stat not opening gas valve sticking partially open
bad high limit bad pressure releif valve no expansion tank to allow for thermal expansion if steam is present and unit is boiling water inside replacement of water heater for safety concerns,would be reccomended if only water and pops couple of times water temp not over 140 degrees after most hot water has been used out of tank and is reheating most of capacity probably lack of expansion tank as the releif valve is the final safety device on a water heater is of great concern
the temp control gas valve or high limit are supposed to shut unit done long before the safety limit of releif valve is reached
you have air in the water lines try going to your water heater and lift the pressure relief vavle slow hold open have hot water valve on sink on let water run till water comes out pressure releif vavle make sure water heater is off and cool first
Hi, it appears you have a defected relief valve. you can try one solution. lift the handle on the relief valve and let some water out. sometimes that can flush out materials thats blocking the stem in the valve. if it's still leaking it must be replace.
If this doesn’t work for you please write back.Thanks,
So the boiler relief valve is leaking? What is the boiler pressure when the relief valve leaks? The relief valve will have a pressure rating on it. If the relief valve leaks when the pressure in the boiler is lower than the relief valve setting then its just a bad relief valve. If the relief valve is leaking when the boiler pressure gets above the relief valve pressure setting then the relief valve is doing its job and there is another problem. Several things can cause the boilers pressure to go higher than the relief valves setting. It could be a bad expansion tank or one that needs to be drained and re-charged. It could be a bad cold water fill valve that isn't shutting off and is over filling the system, rasing the pressure above the relief valve setting. If this boiler also does your domestic hot water, I have seen where the domestic hot waters heat exchanger has a hole in it and the domestic hot water is mixing with the boilers water and over pressuring the boiler.
your make up water pressure is greater than the safety relief pressure. The safety should be 30psi lift. the makup usually goes through a regulator called an automatic makeup valve. these valves operate infrequently on a closed system and get rusty. They stick. If yours is stuck open, then your makeup water pressure which is probably greater than 30psi is overpressuring your boiler.