The wiring of a boiler is essential to its good running and long life. Boilers need wiring which serves as a power source, and also wiring for the boiler controls. This wiring is usually a combination of low and line voltages. Like the wiring in all electrical systems, boiler wires can sometimes stop working, overheat, or fail to carry current to the correct point. You may find that you have problems controlling the thermostat, or that the boiler will not come on when you have programmed it to. The wiring for gas-fired and oil-fired boiler systems in domestic areas are similar, so the basics will be serve for whichever kind of boiler you have.
Checking your Boiler Wiring
The first place to look if you have a problem with the wiring is within the power source. This usually originates with a 120-volt power pack, which is then passed into a transformer, which turns the current into a much lower voltage. Take the transformer, and check the connections to and from the box, and then look at the fuses. Remove each fuse, and use in a working appliance. If any of the fuses prove broken or troublesome, replace, and then test the boiler again. You should also check the power supply by connecting it to a different system. If the power pack itself is not working, you may need to call in an engineer and have the house electricity supply examined.
Checking the Controls
If the power supply and transformer are all working correctly, the next place to look is at the individual controls. The spill switch, which can be found on the draft hood, shuts off the gas to the burner if it senses gas spilling back into the hood. The power to the burner cannot be activated unless the switch is reset. If the spill switch activates repeatedly, this is a sign that there is a problem with your vent system which will need to be examined by a professional boiler engineer. Another problem with the chimney system may be in the damper switch, which can prevent boiler activation while the damper is closed. If your damper is completely open, check the circuitry of the switch, and examine any fuses it may have.
Other sources of power supply cut-off are the Low water temperature switch, and the low water cut-off. The latter will make the boiler shut off if there is only a little water in the coils, in order to prevent damage to the boiler. If your water is sufficient, check the wiring of the cut-off switch, and any fusing. The Low water temperature switch prevents the boiler from turning off if the temperature is not within a prescribed range, which you can set manually. First check that this manual setting is not too high, and then check wiring.
Check your entire system for obviously loose connections, or failed circuits, and examine any fuses which may have popped out on your main board (if you have an older boiler, you may not have a main control board, and will need to check the fuses of all your devices). If you still cannot find a problem, you may need to call in an engineer.