Confused.

[conny]

Overheard part of a conversation between two electrical contractors at work today.

They had been discussing jobs they had done in the past and one of them mentioned wiring up his brother in laws summer house. He was explaining to the other guy how he brought the supply in from the "fuse box" and fitted a 20amp mcb outside the house before connecting the swa. (No idea what size he used). The other guy asked him why he fitted it and he said to protect the cable run.

Second guy said he never bothered as if the cable got damaged it would take the main RCD out anyway before the mcb tripped.

I never heard the rest of the chat and was never involved but I am now confused as to who was right and why. Can anyone enlighten me please?

 

[EFLImpudence]

Not really enough details.

There are several ways of doing it depending on the situation but you don't really want swa to have an RCD at the source as a little fault in the summerhouse will cut off everything.
I don't know why you would fit an mcb outside the house (either main house or summer house) but you would need some protection for the swa somewhere.

 

[ban-all-sheds]

you would need some protection for the swa somewhere.

he brought the supply in from the "fuse box"

Overheard part of a conversation between two electrical contractors at work today.

That will be "contractors" in the sense of semi-skilled people who can follow instructions to put-this-wire-in-that-hole, rather than proper electricians, I expect.

 

[Lectrician]

What some "electricians" do is scary. Some is just laughable, some dangerous. It seems you don't need much to call yourself an electrician these days.

I have seen submains supplied from an RCD with no overcurrent protection because they think the current rating of the RCD is its "mcb" rating. I have seen failed two module RCBOs on caravan sites replaced with RCDs, meaning a 16amp socket is then protected by an 80amp fuse. Some people think if you install a 40amp submain, you need a 40amp incomer in your DB in place of the 100amp, and they struggle to find one. What you hear in the wholesalers can be scary.

 

[bernardgreen]

What you hear in the wholesalers can be scary

It is even more scary when you see the work these "electricians" (*) have done in people's homes.

(*) can't think of a suitable name for them.

 

[PBC_1966]

What you hear in the wholesalers can be scary.

The "advice" you can overhear in Lowe's, Home Depot (or B&Q et al) can be pretty scary too.

 

[conny]

Unfortunately that was about as much of the conversation I heard so can't give any more info.

They are installing a new fire alarm system and modifying parts of the existing one.

Thanks for the replies.

 

[john4703]

The "advice" you can overhear in Lowe's, Home Depot (or B&Q et al) can be pretty scary too.

I occasionally shop in B&Q and nearly always wander along the electrical isle to see what is on display (never to buy anything there). I worry about the questions I am asked by other customers, examples have included "Is this wire OK to supply my TV?" pointing to coax or on a different occasion "I don't want to spend that much" when I suggested 2.5mm T&E for a spur to a socket, is this any good? holding up a roll of bell wire!
I now say that I have no idea and they should ask a staff member. The general public should not be let loose with a AA battery let alone main voltages and currents.

 

[ban-all-sheds]

It is even more scary when you see the work these "electricians" (*) have done in people's homes.

(*) can't think of a suitable name for them.

I can think of lots.

But I'm not allowed to tell you what they are.