A Few Electrical Questions

[con1_uk]

Our lighting curcuit doesn't have an earth I belive this is the way things where done some time ago. When we first moved in 5 years ago we had an electrical report done and all it said really was we needed some earthing put on the bath.
Is this type of curcuit safe? Assuming im only going to fit the double insulated switched and fittings on. Is this some thing I can change in a few years?

The other question is I have one plug socket that is metal but it is earthed on the back box and the actual unit is this ok?

Last question is before part P I was well underway on my loft conversion to which I needed to fit 3 interlinked mains smoke alarms. I got the 3 Kiddie units and the correct wire with the extra white cable in I ran the cable to the correct points and fitted the alarms according to the manufacturers instructions. The only thing I didnt do is connect them up to the CU. I have a seperate RCD for the smoke alarms to be fitted to on their own. Is this something I could do? Bearing in mind I could have connected them all up before part P.

Thanks.

 

[andy]

smoke alarms must not be on an RCD, unless its a TT supply. as for part P, money comes before safety (even more in your case). or just ignore it like many other people.

if the lights dont have an earth it suggests the wiring is old and could need a re-wire. and what do you mean by bath? what exactly did the report say, and did the spark recommend a re-wire?

you must only fit class 2/double insulated if you dont have an earth, which you already understand.

what do you mean by 'is this something i can change in a few years?'

 

[Big_Spark]

Smoke, Burglar and any form of fire detection system should NEVER be controlled by an RCD or RCBO.

If you have a TT installation, then the main incomer must be an RCD, but this should be a time delayed 300 or 500mA Type S RCD. All power circuits then are protected by individual 30mA RCBO's or by use of a split load board where the power circuits have a seperate 30mA RCD as the main switch on that side.

As for the installation..I would urge a rewire.

The circuits are probably not UNSAFE, they almost certainly rely on the conduit the cables run in for the cpc required. The circuit will have complied with the regulations when originally re/wired..sometime in the 1970's probably. It is likely that you have BS3036 rewireable fuses as the overload protection, if this is not the case, and the protective devices have been upgraded to MCB's, then there is a disconnection time issue.

No disrespect, but as you have asked these questions, then your not knowledgable or experienced enough to test your installation and probably rewire it..that being the case I would urge you call in a Suitably qualified Electrician. Whether they are Part P registered is a matter for you to decide, but in my opinion, Part P registration is no guarantee of quality workmanship.

Before deciding on a rewire, I would get several quotes, and ask the comnaies, individuals if you could speak to some former clients to gauge their professionalism and quality of work...

 

[con1_uk]

It seems my upstairs lighting is missing the earths my downstairs one seems to have it I dont think the wiring is that bad as it would have show up on the report. I just want to make it as safe as possible if it needs it. The report didnt say we needed to rewire just a few jobs most of which we have had done.

I was told which switch to buy for the CU. I may be mixing it up a little. Which other types are there? If I have the correct one would you recommend me taking this on myself? I only have to connect the wires to the CU.

 

[andy]

itll have to be on a 6A MCB. wether or not it has to be RCD protected depends on earthing arrangments (TT, TNCS, TNS)

 

[pdcelec]

I only have to connect the wires to the CU.

........and test the insulation resistance, polarity, earth fault loop impedance, prospective short circuit current, voltage, current usage, tripping times, heat dispersal, safe routing, fire barriers etc

 

[andy]

I only have to connect the wires to the CU.

........and test the insulation resistance, polarity, earth fault loop impedance, prospective short circuit current, voltage, current usage, tripping times, heat dispersal, safe routing, fire barriers etc

R1+R2...

 

[JohnD]

The other question is I have one plug socket that is metal but it is earthed on the back box and the actual unit is this ok?

If you mean the ring is earthed only to the box, it is relying on the fixing screws to earth the plate to the backbox. It will probably work most of the time but is not correct. If will definitely not work if the screws are corroded, or are removed, or when the plate is taken off for any reason. The ring should earth to the socket, An alternative is to earth to the box and have a piece of G&Y sheatheed earth wire from the socket to the earth terminal in the box (which is more complicated)

 

[ban-all-sheds]

Won't all metalclad sockets have an integral connection from the earth terminal to the front plate?

 

[JohnD]

yes, but it seemed to me that he was relying on the fixing screws which I have been told is not good practice.


edited to say:

If he was only concerned about the front plate being earthed from the socket connections then I misunderstood.

 

[con1_uk]

Sorry I was so long posting back

I have found the MCB I was told to buy for the Mains wired smoke alarms

Its a Wylex B6 NSB06

Is this suitable for the wire (3 core and earth) and smoke alarms (kiddie) already fitted?


Thanks.

 

[con1_uk]

yes, but it seemed to me that he was relying on the fixing screws which I have been told is not good practice.


edited to say:

If he was only concerned about the front plate being earthed from the socket connections then I misunderstood.

To clear this one up both the socket and back box are earthed.

 

[ban-all-sheds]

Sorry I was so long posting back

I have found the MCB I was told to buy for the Mains wired smoke alarms

Its a Wylex B6 NSB06

Is this suitable for the wire (3 core and earth) and smoke alarms (kiddie) already fitted?

Yes. Where do you plan to connect the cores from the 3C+E cable?

 

[con1_uk]

I think we have already decided im not the one to do it.

BUT....

Live and Neutral go into the alarm and the white interconnects all the units.

The manual says the units MUST NOT BE EARTHED.

 

[con1_uk]

Any more advise please people? Been very helpfull so far.