Cable sizes

[echoes]

The shower will be between 9 and 10kw , customer has not yet bought it.

Forgive me for any presumption, but as someone charging for services and doing a building-controlled job such as a shower install, should you not know that a shower would require a higher rated switch than 20A?

 

[RMS]

Amongst other things how can you sign this off?

With a pen I assume.

 

[securespark]

Hi guys, is 1.5mm ok to use to take a spur off another socket to run a fridge on? And is a 20amp isolation switch suitable for an electric shower? Cheers in advance.

The shower will be between 9 and 10kw, customer has not yet bought it.

I cannot believe that you are asking whether an isolation switch rated at 20A is suitable for use with a 9-10kW shower, all the while proposing to charge someone for this work.

 

[echoes]

Beat ya to it!

Beat me also

 

[starspark]

Great minds think alike!!

RMS your a funny guy!!

 

[littleleaks]

I am actually a plumber, the house is my girlfriends and i am asking questions to make sure it is done right. I have a vague idea of what I am doing, been building for 30 years now ) but am always wary of electrics.

 

[littleleaks]

I cannot believe that you are asking whether an isolation switch rated at 20A is suitable for use with a 9-10kW shower, all the while proposing to charge someone for this work.

I`m not charging her : o) I just want to ensure I do it right, I`m a plumber and plasterer, she can`t afford a sparky so I am doing it very very carefully, hence the stupid questions.

 

[elrobbo82]

starspark

not good practice i would install an fcu. but in theory if you have a 5A socket outlet you are restricted to the load that can be attached. but there are no load sizes hence my very vague response.

But you couldn't put a 5A socket on a circuit protected at 32A anyway, so you'd deffo need a FCU.

AIUI ring circuits must be in >2.5mm cable and that includes unfused spurs. Except for MICC of course.

are you sure as i have not seen this in the regs. the 1.5mm would be protected due to the max of the connected load. also greater than 2.5 meaning that 2.5 would not be adequate?

 

[RMS]

AIUI ring circuits must be in >2.5mm cable and that includes unfused spurs. Except for MICC of course.

So your saying you cant use 2.5mm cable for ring final circuits.

 

[OwainDIYer]

AIUI ring circuits must be in >2.5mm cable and that includes unfused spurs. Except for MICC of course.

So your saying you cant use 2.5mm cable for ring final circuits.

By >2.5mm I mean greater-than-or-equal-to. ASCII does not have greater-than-or-equal-to sign.

 

[RF Lighting]

≥2.5mm²

 

[echoes]

I am actually a plumber, the house is my girlfriends and i am asking questions to make sure it is done right. I have a vague idea of what I am doing, been building for 30 years now ) but am always wary of electrics.

Very glad you have asked then. The socket spur is a trivial job, and to avoid doubt on installation methods, should be done in min. 2.5 mm² cable. However, the socket you intend to spur from must be on the ring, and not already a spur from a ring.

As for the shower install, there is much to consider: cable size, installation method, RCD protection, MCB rating, supplementary bonding may be required. It MUST be tested. Get it wrong and it could be lethal.

You must have a sparky mate or two after 30 years on the job who can help you out with this; rather than installing something which might appear to work one minute and kill you the next?

 

[ban-all-sheds]

but am always wary of electrics.

Stay that way.

If you've been a builder and plumber for 30 years you must by now know at least one reputable electrician.

Use him.

 

[littleleaks]

Have recently moved, all my sparkys are a long way away ) Is it better when taking a spur to use a fused box? ie cut the cable which is currently a spur install a fused box and then run the new spur from that? I seem to recall that being the way to do it. Regarding echoes saying it has to come off the ring, this would mean tearing down ever more ceilings ) If possible I would like to avoid that lol, Cheers again.

 

[Space cat]

Is it better when taking a spur to use a fused box? ie cut the cable which is currently a spur install a fused box and then run the new spur from that?

I'm afraid that doesn't help. An FCU that could take a 13 amp fuse is really no different from a single socket with a 13 amp fused plug in it. Remember this:

There is actually an inconsistency here because that size of cable is not rated at 32 amps. It's one of the few situations where fuses protect the cable lying upstream. (The other common one is the cable leading into your house from the street.) The assumption is that you can only draw a maximum of 26 amps from a double socket - and even this is unlikely to happen - so 20 amp rated cable is acceptable.

If you add an extra socket or FCU to an existing spur, you increase the total current that could be drawn from it and risk overloading the cable.