Alpha 1.012849 CB50 Air Pressure Switch
This Alpha Air Pressure Switch 1.012849 operates when it detects air flow created by the fan. It is connected to the fan via venturies via heat resistant differential pressure tubes.
The Alpha boiler will not go through its ignition mode until the this Air Pressure Switch has proven that the fan is running, by doing this the boiler can safely take any burnt products away from the boiler via the flue. If the fan was to jam or slow down this air pressure switch would electrically open circuit and turn off the boiler, this ensures that no carbon monoxide or other toxic gases can be present within the boiler if the fan as stopped running.
Most engineers change the heat resistant tubing that connects the fan to this air pressure switch because over time the tubing becomes brittle and can cause the boiler to fail. If you would like to purchase the tubing it can be viewed below and purchased below.
The term OEM stands for "Original Equipment Manufacturer" this part is an original part and was bought from the Original manufacturer of the part.
What does that really meanr a boiler manufacturer such as Wocester Bosch, Baxi, Glowworm etc.
Below is an example:
Gas Valves on most British Gas Boilers are made by Honeywell, Sit, White Rogers etc. This means that these manufacturers are the OEM for the Boiler Manufacturers, so as long as the original part is purchased (Honeywell, Sit, White Rogers) from the OEM it can be sold as an original OEM product.
OEM parts are also referred to as After Market Parts.