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I would like to have a double wall switch for the toilet where one switch (#1) turns on both the light and the fan while the second switch (#2) turns only the fan. Please note the light and the fan are separate devices operating at 220V.

So if I turn on the switch #1 both the light and the fan are turned on and the switch #2 has no function while the switch #1 is turned on.

If I turn on the switch #2 while the switch #1 is turned off, I was the fan to be turned on while the light is turned off.

I usually deal with DC circuits and in that case I could most probably just throw 1N400X diode between the light and the fan both of which would be connected in parallel to the source. However, I'm dealing with 220V AC here and I'm not quite sure how to make it work in this case.

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You can achieve this in several ways.

The most brain bending method :-) is to use two SPDT (2-way / changeover) switches.

This is a standard item, but this is a not too usual means of connection. Note that terminals should be sleeved with appropriate colours as electricians may at first be confused with the arrangement.

Connect thusly :

When both switches are "up" neither device is powered.

When SWA is down live is connected to the light AND also to the fan via SWB top contact.

When SWA is up and SWB is down live is connected to the fan via SWB lower.

When both switches are down the light is powered by SWA and the fan is powered by SWB.

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If only SPST switches are available then.

Use switches A & B - each SPST, and a SPST relay.

Switch A operates Fan.

Switch B operates Light and Relay. Relay operates fan.

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    By golly, this will pass Code! Except you actually need two SPDT switches. Those are readily available as 2-way switches (3-way in US). – Harper - Reinstate Monica Apr 11 at 16:00
  • Excellent solution. -- the two switches should not be tied together in the diagram, since they must be operated separately. – A. I. Breveleri Apr 12 at 4:19
  • @A.I.Breveleri Yes - the connection was due to the component I used in the dwg package. (Late at night :-) ). I've edited it and changed switch names. – Russell McMahon Apr 12 at 14:06
  • @Harper Yes - braino re switch type naming - edited. I've also separate the switch halves into two switches as is required. I've also restored the relay solution which somebody removed for some reason - usable when only SPST are available. || "Passes code" would ideally have sleeving on wires to switches I think - this would bend a few brains :-). I "made this up" on the spot but was still surprised that it was possible :-). – Russell McMahon Apr 12 at 14:09
  • Thanks, I'll give this a try tomorrow. – choxnox Apr 21 at 18:10

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