Problem replacing pull chord switch in bathroom

[DaftPunk]

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

Certainly not a device for proving dead though.

 

[sparkwright]

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

I wouldn't say that.

 

[JohnW2]

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

... if there is no earth anywhere in the building (or any 'real earth' outside it!) and/or you don't have a long enough lead.

Kind Regards, John

 

[EFLImpudence]

Wasn't the 'advice' given on how to determine which is the switched live?

So, not really a polarity test and can be done with a continuity tester.

Therefore, I agree with Sparkright.

 

[JohnW2]

Wasn't the 'advice' given on how to determine which is the switched live? So, not really a polarity test and can be done with a continuity tester. Therefore, I agree with Sparkright.

I agree with sparkwright, too, but I don't think you can call a neon screwdriver a "continuity tester"!

BTW, I took DaftPunk's comment to be a general one in relation to what non-contact testers are useful for, not a comment about the OP's situation - but I may be wrong!

Kind Regards, John

 

[EFLImpudence]

I see now there is some confusion.

I was commenting on this:

It is a screw type yes, how do I find out which is the switch live mate? I have one of those little screw drivers that can test for current! Will this suffice?

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

Certainly not a device for proving dead though.

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

I wouldn't say that.

 

[JohnW2]

I see now there is some confusion.

Indeed

I was commenting on this:

It is a screw type yes, how do I find out which is the switch live mate? I have one of those little screw drivers that can test for current! Will this suffice?

Yes, I realise that, that far. However, rather than the other posts you go on to quote, the next relevant one in sequence was:

The screwdriver testers are not something that is considered as safe or reliable as a test instrument. A two pole voltage indicator would be more appropriate.

Good enough in this case just to give an indication which is the switched live though, wouldn't you say?

... and it was that comment of sparkwright's with which I was agreeing

Kind Regards, John

 

[PrenticeBoyofDerry]

Good enough in this case just to give an indication which is the switched live though, wouldn't you say?
Or not?

You may think and do so, I personally am against anything that uses me as part of the circuit and test characteristic of the instruments require the body to be uninsulated to earth and resistor failure/fault could be quite shocking! Life is too precious.

 

[ban-all-sheds]

Yes, it's pretty much the only way to determine polarity on a 2 wire AC supply.

You shouldn't have one - there's supposed to be a cpc.

 

[bernardgreen]

In the absence of suitable test equipment the supply and the switch cable can be identified using the lamp.

Power off at fuse box. connect lamp to one cable. power on

If lamp lights that cable is the Permanent Live and Neutral
If lamp doesn't light then that cable is not the supply and probably the cable from the switch. The black in the cable is probably the switched Live.

Power off and reconnect Neutral to the threaded tube of the lamp holder. Switched Live to the centre contact in the lamp holder.

 

[PrenticeBoyofDerry]

Could you determine the switch live and neutral, using this test? As that is the issue!

 

[bernardgreen]

Could you determine the switch live and neutral, using this test? As that is the issue!

There is a risk that the supply cable has reversed polarity ( black Live ) so this test cannot 100% ensure the correct polarity to the lamp holder.