Zoomup:

Extractor fans are normally quite small loads, and the manufacturers often specify a 3 Amp fuse to protect the wiring to them. This can pose a problem, as the permanent live and the trigger switched live for the fan if it is a timer model, both need to be 3 Amp fused. Often fans are supplied from circuits protected by 6 Amp M.C.B.s such as lighting circuits. So a 3 Amp supply needs to be available for the fan and its associated lighting circuit, say in a bathroom or shower room. A switched or unswitched fused connection unit can do this. As the lighting and fan in the public w.c. are likely to be running at the same time, the full running load will be Ib. So depending upon the size of the installation one or two lighting circuits may be installed to give reliability. If modern L.E.D. panels are installed in the ceiling they are very efficient and use less electricity than old fashioned fluorescent lights. So, to determine the total current drawn you just add up the individual loads and calculate it from there. A circuit using suitable cable and a suitable protective circuit overcurrent protective device will be used according to the total design current. R.C.D. protection will be a good ideas as you can not rely upon members of the public always being sensible, and vandalism can occur.


 I hope that the wiring  above the ceiling is  suitably enclosed in containment and not just flapping about. All single insulated wires need to be enclosed in boxes/enclosures.


If the lights are meant to come on when somebody enters the room the P.I.R. relay will detect them. It will need a Live and Neutral supply at 240 Volts. It then has a load connected in this case  the lights. It may be set to stay on for a period of time, say 10 minutes. After 10 minutes the lights are automatically turner off.


The fan may or may not be connected to the same  lighting circuit. The fan may have a permanent Live to it, and just be triggered by the lights coming on, and then run for longer than say 10 minutes to really exhaust the foul air thoroughly. There are several ways of wiring extractor fans. Have a look at timer extractor fans online to see the wiring diagrams for them. The popular domestic ones are 100mm (4 inch) in diameter.



Z.

Zoomup:

Extractor fans are normally quite small loads, and the manufacturers often specify a 3 Amp fuse to protect the wiring to them. This can pose a problem, as the permanent live and the trigger switched live for the fan if it is a timer model, both need to be 3 Amp fused. Often fans are supplied from circuits protected by 6 Amp M.C.B.s such as lighting circuits. So a 3 Amp supply needs to be available for the fan and its associated lighting circuit, say in a bathroom or shower room. A switched or unswitched fused connection unit can do this. As the lighting and fan in the public w.c. are likely to be running at the same time, the full running load will be Ib. So depending upon the size of the installation one or two lighting circuits may be installed to give reliability. If modern L.E.D. panels are installed in the ceiling they are very efficient and use less electricity than old fashioned fluorescent lights. So, to determine the total current drawn you just add up the individual loads and calculate it from there. A circuit using suitable cable and a suitable protective circuit overcurrent protective device will be used according to the total design current. R.C.D. protection will be a good ideas as you can not rely upon members of the public always being sensible, and vandalism can occur.


 I hope that the wiring  above the ceiling is  suitably enclosed in containment and not just flapping about. All single insulated wires need to be enclosed in boxes/enclosures.


If the lights are meant to come on when somebody enters the room the P.I.R. relay will detect them. It will need a Live and Neutral supply at 240 Volts. It then has a load connected in this case  the lights. It may be set to stay on for a period of time, say 10 minutes. After 10 minutes the lights are automatically turner off.


The fan may or may not be connected to the same  lighting circuit. The fan may have a permanent Live to it, and just be triggered by the lights coming on, and then run for longer than say 10 minutes to really exhaust the foul air thoroughly. There are several ways of wiring extractor fans. Have a look at timer extractor fans online to see the wiring diagrams for them. The popular domestic ones are 100mm (4 inch) in diameter.



Z.