One way voltage

[Sidewinder]

Oh it’s doable, the issue being that it’s covered by specific requirements and laws.

 

[Andy™]

The logic of what you want to do is no different to the old bathroom without a window, but a fan and light...

Where customer wants to have single switch that can turn on both light & fan for when having a shower...

But another switch to turn on just the light for when only using the loo...

(in this case the light is equivalent to the dust extractor...

and the bathroom fan the equivalent to the saw..)

So if the light is wired via 2-way switch sort of arse about face..

Perm Supply to L1,

Lamp to Common

Switched supply from fan to L2...

So if the light is switched on its perm live via L1 and Common  (but NO feed to the fan).

if the light is switched off it will also become live if the fan switch is turned on.

e.g.  light switch will ONLY turn on light

Fan switch with turn on fan and also light even if light switch is turned off...

Done it for a bathroom with a double gang switch, one marked Light other marked Light+Fan…

Not sure if this concept is adaptable for this scenario though... especially 50m apart!

Guinness   But the logic is do-able.  

the most simple solution of all,  use a DP switch thatlly switch both. that way when the fan is on on its own, it wont affect the machine

seen similar on lights before. shared bathroom fan. use a DP switch so that either light switch will turn the fan on & their respective light, but not the other light. always fun once someone changes the DP switch to a SP because both sides were live and switching at the same time, they not cant figure out why the light randomly comes on...

 

[Sidewinder]

You can’t do that and comply Andy.

 

[Andy™]

You can’t do that and comply Andy.

of course not, and my example is only really used on domestic lights, but by the lack of response from the OP he might have already figured that out and has now bodged his contraption in this way

 

[binky]

How about a wireless switch for the fan with button at the saw? That way the controls aren't linked and if the emergency stop is activated at the fan, or machine shut down for maintenance, it won't have a secondary live supply. 

 

[Andy™]

How about a wireless switch for the fan with button at the saw? That way the controls aren't linked and if the emergency stop is activated at the fan, or machine shut down for maintenance, it won't have a secondary live supply. 

that would also allow the machine to run without the extraction system....

 

[ProDave]

Can I suggest the easy option.

MOVE either the saw, or the extractor, so they are next to each other.

 

[Andy™]

or employ 2x staff and a couple of radios. one to stand at each end and to shout commands to the other. suppose if your budget is low you would use a few bits of string instead of the radios

 

[Doc Hudson]

https://www.bing.com/images/search?q=tin+can+string+phone&id=54BCF7187D4BFB95484F1DD3F334BCAAC8A5FE7F&FORM=IQFRBA

Numerous options to suit budget and personal preferences.

Doc h.