What to check after wiring a new bathroom mirror/light

[m0wax]

I've just completed installing a new LED/Mist Free bathroom mirror.

Untitled

• m0wax
• 4 Aug 2014
• 1

Previously there was a mirror with light and shaver socket so I've not had to run any new wiring. However, I did have to connect the old (1mm 2-Core + Earth) wires to the black (transformer?) box in the new mirror. I've read in my DIY book that work like this should be check by an electrician afterwards? What would an electrician do here? Is it necessary? Can I do any checks myself or should I really just get a sparky in?

Any advice appreciated.

 

[PrenticeBoyofDerry]

There are a number of checks an electrician would make on a circuit to ensure the circuit was suitable for continued service.

I would for a replacement use the test required by a minor works certificate.
These would include the following:
*Confirming the type and existence of your earth arrangement.
*Method of fault protection
*Protective device type and cable size
*Adequate bonding
*R1+R2 readings (continuity of line/live and circuit protective circuit/earth)
*Insulation resistance of all circuit conductors
*Polarity
*Zs
*RCD

https://www.elecsa.co.uk/Documents/.../BS7671-Amd1-Minor-Works-Certificate-(1).aspx

These test would require the use of calibrated test equipment and a knowledge of how the the test should be performed and an understanding of the results given.

Normally I would not expect a DIYer to have the equipment or knowledge and in general they would not go to the expense of employing an electrician to do the tests. But some do consider the dangers of electricity and are wise enough to make sure things are safe.

 

[JohnW2]

...I would for a replacement use the test required by a minor works certificate. These would include the following: <list> These test would require the use of calibrated test equipment and a knowledge of how the the test should be performed and an understanding of the results given. ... Normally I would not expect a DIYer to have the equipment or knowledge and in general they would not go to the expense of employing an electrician to do the tests. But some do consider the dangers of electricity and are wise enough to make sure things are safe.

It's difficult, isn't it. No-one can argue with the theoretical desirability of all the tests you mentioned ("to ensure that the circuit was suitable for continued service"), but one also needs to keep everything in perspective.

What the OP has done has involved minimal work on the fixed wiring - merely swapping the connection from an old mirror light to a new one. That being the case, the results of the majority of the checks/tests you have mentioned would be no different after the work had been undertaken than before it was undertaken. In fact, of the things on your list, polarity and (conceivably) IR are about the only things which could have changed as the result of the work.

You could, of course, argue that all the other checks/tests are desirable ('to ensure that the circuit was suitable for continued service') but that would theoretically be equally true whenever one plugs a new appliance/equipment into an existing socket (or even replaces a dead lamp/bulb!)!

As I said, it's difficult, but I would think that many/most people in the OP's situation would feel it appropriate to exercise a degree of 'common sense' (even if you regard that as a 'calculated risk').

Kind Regards, John

 

[PrenticeBoyofDerry]

I think replacing lamps and inserting plugs are little different to actually handling the hardwired part of a system, but I do get your point.

It is possible that the circuit was fine prior to replacement but a fault introduced on replacement for any number of reasons. And it also possible that the circuit has become faulty during service or was never correctly installed originally.

As the location is within the bathroom, I think it is best to check things are safe.

As the OP did ask what an electrician would do, I imposed what I would consider the best solution to assure safety.
Some electricians maybe happy to do the minimal amount of work, for the maximum payout! So I cannot speak for all!

 

[JohnW2]

I think replacing lamps and inserting plugs are little different to actually handling the hardwired part of a system, but I do get your point.

Yes, I agree that there is a point. As I implied, as far as I can see "Confirming the type and existence of your earth arrangement, Method of fault protection, Protective device type and cable size, Adequate bonding, R1+R2, Zs and RCD" are really no more likely (give or take the 'vanishingly improbable'!) to have changed as a result of the OPs work than would have been the case following a lamp change or plugging in a new appliance.

It is possible that the circuit was fine prior to replacement but a fault introduced on replacement for any number of reasons. And it also possible that the circuit has become faulty during service or was never correctly installed originally.

Yes, all true. I suppose it depends upon the extent on which one wants to use the fact that work is being done as an 'excuse' to undertake 'a general check-up'. If you take your car to a garage to have its brake pads replaced, do you necessarily expect that the entirety of the braking system (hydraulics, ABS etc.) will be inspected and, where possible, tested?

Kind Regards, John

 

[PrenticeBoyofDerry]

If you take your car to a garage to have its brake pads replaced, do you necessarily expect that the entirety of the braking system (hydraulics, ABS etc.) will be inspected and, where possible, tested?

If my brake pipes were leaking or corroded, I would hope someone was diligent enough to spot this and make me aware.

 

[JohnW2]

If my brake pipes were leaking or corroded, I would hope someone was diligent enough to spot this and make me aware.

Sure, if they 'happened to notice' that (in the vicinity of the part of the vehicle on which they were working) during the course of doing the work, then one would hope that they would bring that to your attention.

However, that's very different from expecting them to do a full, formal, 'inspection and testing' of the entire braking system. Would you expect that, if you had only asked them to replace the brake pads?

Kind Regards, John

 

[PrenticeBoyofDerry]

I wouldn't be impressed if I got half a mile down the road and my vehicle failed to stop! What ever it takes to assure safety, is my motto!

 

[JohnW2]

I wouldn't be impressed if I got half a mile down the road and my vehicle failed to stop! What ever it takes to assure safety, is my motto!

That doesn't really answer my question - would you expect, and be prepared to pay for, a 'full, formal, systematic I&T of your entire braking system' when you just put your car in for replacement of its pads?

One would expect a competent garage to undertake a 'functional test' of the braking after replacing the pads (i.e. ensure that the brakes functioned satisfactorily when the pedal was depressed). However, that's analogous to switching on the mirror light and making sure that it comes on, and that nothing goes bang. Systematically inspecting the entire system for small hydraulic leaks, checking function of the ABS etc. etc. are a different matter, but probably broadly analogous to most of the things you've listed in relation to replacement of a mirror light.

Kind Regards, John

 

[PrenticeBoyofDerry]

I would accept the recommendations of my mechanic.