Pilot lights, fan comes on, but burner doesn't switch on when set to CH, but it is OK on HW.
If both CH and HW are on, once HW has reached temperature, the burner goes out, and the pilot and fan come on again, but no burner.
Could there be a fault on the Gas Valve? It has three solenoids - one called Pilot, one called Main, and the other Hi Low, according to the Instruction Manual. Looking at the valve in situ, the Hi Low one seems to be associated with the burner pressure adjusting points (High(pressure) for HW, low(pressure) for CH). The pilot solenoid would seem to be working, and I presume the Main one is too, as the Pilot presumably wouldn't light without it.
I'm ignorant as to how exactly the Gas Valve functions in detail, and wonder just how the desired gas pressure is selected by the system. As the Electrical Functional Flow diagrams in the Instruction Manual show that the High Low solenoid is only live on Hot Water mode, I presume that when the solenoid is not activated, the gas valve would be left in CH mode ie low? This suggests that this part of the valve defaults to a low pressure ie CH, situation, and would therefore be expected to light. So something else is not activating, but what, or am I barking up the wrong tree?
So why won't the burner light on CH?
I would appreciate any informed comments and suggestions on how to solve this problem.
(Thanks for getting this far, and I hope this long post hasn't confused!)
If both CH and HW are on, once HW has reached temperature, the burner goes out, and the pilot and fan come on again, but no burner.
Could there be a fault on the Gas Valve? It has three solenoids - one called Pilot, one called Main, and the other Hi Low, according to the Instruction Manual. Looking at the valve in situ, the Hi Low one seems to be associated with the burner pressure adjusting points (High(pressure) for HW, low(pressure) for CH). The pilot solenoid would seem to be working, and I presume the Main one is too, as the Pilot presumably wouldn't light without it.
I'm ignorant as to how exactly the Gas Valve functions in detail, and wonder just how the desired gas pressure is selected by the system. As the Electrical Functional Flow diagrams in the Instruction Manual show that the High Low solenoid is only live on Hot Water mode, I presume that when the solenoid is not activated, the gas valve would be left in CH mode ie low? This suggests that this part of the valve defaults to a low pressure ie CH, situation, and would therefore be expected to light. So something else is not activating, but what, or am I barking up the wrong tree?
So why won't the burner light on CH?
I would appreciate any informed comments and suggestions on how to solve this problem.
(Thanks for getting this far, and I hope this long post hasn't confused!)