I have a gas boiler and water baseboard heater ,The boiler would turn on for about 5min then turn off even though it has not reach the tempature on the thermostat I notice that the overflow valve leaks , my psi is at about 15 ,temperature on the boiler is about 80-85.I also can hear a small humming noise coming from the return pipe .what can this be...
If your system has and expansion tank it may have become water logged and hydrostaticly full. When the burner trys to heat the water in the boiler, the water has no place to expand, and.the pressure builds up and the pressure switch on the boiler turns off the boiler prematurely as if it was up to heat. Your relief valve is probably set for 30 lbs but has been building and relieving at each try for heat due to the hydrostatic pressure in your system, If your Expansion tank has a bladder, charge the bladder with a bit of air. If it is a tank only then Isolate the tank from the system with a hand valve, drain the tank to empty while opening a vent on it to let air into the tank.. Close of the drain and the vent and re-open the hand valve to the system. The system will flood water back into the tank but the air cushion will be captured in the top of the tank. Now when firing it will have a space of air to expand to. Hope this helps.
With gas injection, in case you would be not on time by way of a couple of minutes, positioned the transmission in park. if it is going to be longer than a couple of minutes, you could close the engine off. gas injected vehicles do no longer 'waste' gas once you shut an engine off and then initiate it returned up. The engine is heat and there is not any extra gas being dumped into the cylinders. in case you're waiting on the interstate for a wreck to get cleared, close the engine off. Any TIME an engine is sitting and idling, no longer moving, this is a waste of gas.
It could be the aquastat, the ignition module if it has one or the gas valve. The humming noise is probably the circulator pump running because your thermostat is calling for heat. Check for 24v at the gas valve. If you have no power there, whatever component is supposed to send power to it is messed up. If the relief valve leaks at 15 psi the relief valve is bad. They shouldn't open until 30 psi.
