fan overrun issue

[JohnW2]

Yes switch live has 230v to earth when on and 0v to earth when off. Timer works fine when testing so I don't think I've fried it.

As you've undoubtedly decided for yourself, this really makes no sense. If the L and S/L have the right voltages (relative to both N & E) at the right times, and you've tried connecting L and S/L to the fan 'both ways around', it really does make sense that it does not work 'as expected', whereas it does on the bench (when you presumably are supply exactly the same voltages to the same terminals.

I find it hard not to conclude that you must be 'missing something' - but goodness knows what! You haven't somehow managed to get the perm L and N connections to the fan swapped, have you (that would probably give the results you are observing)?

Kind Regards, John.

 

[studentspark]

I agree it must be something, and an error on my part would seem to be the logical answer, but I can't find my error.

Anyhow thanks for thinking about it.

 

[AndyPRK]

I guess you will have to get it back to the bench with a switch and light to test it again

 

[vibrobullit407]

I take it that you've tested between permanent live and neutral when the switch is off and your getting 230V?

 

[flameport]

Disconnect the wiring from the fan, and check the voltages on the wiring with the switch on and off.
If there is some problem with the supply, the fan itself will cause false readings.

 

[jeff the gasman]

Now let me see ..........................................
I'll come back to you on that one

 

[studentspark]

Just to update...

One of those odd jobs.

put it back on the wall and it all worked!

Everything the same!

The only thing I can think of is that the fan seems to reset itself after isolation, so when first started after power loss it switches straight on, and switches off when the light is switched off.
I guess its a mechanism to test it works when first installed.

If you then switch on at light switch a second time, you get the 120 second delay, and when off the over run.

Thing is I did keep switching it on and off a few times.

But I guess it was this reset thing

 

[333rocky333]

More likely the neutral wernt in properly
A good start would have been to verify the neutral by testing voltage L to N