RCD protection on these tails and why 2 isolators?

[Electrics]

Hi all I have a few questions about that video.

1. I don't understand why there are two isolators on the tails between the meter and the CU. One is fused and one isn't, so what's the point in the one that isn't?

2. Why would this 'require RCD protection' like the guy in the video says? I thought we normally went supply -> meter -> main switch -> rcd protected board.

3. If this does actually need RCD protection where would it go? Between the fused main switch and the CU?

Thanks for helping me out with my newcomer questions.

 

[suffolkspark]

Hi all I have a few questions about that video.

1. I don't understand why there are two isolators on the tails between the meter and the CU. One is fused and one isn't, so what's the point in the one that isn't?

2. Why would this 'require RCD protection' like the guy in the video says? I thought we normally went supply -> meter -> main switch -> rcd protected board.

3. If this does actually need RCD protection where would it go? Between the fused main switch and the CU?

Thanks for helping me out with my newcomer questions.

The first isolator is fitted by the DNO the second one is to give the cable a fuse for fault protection if the board is over 3m away, the tails only need rcd protection if they're less than 50mm in the wall

 

[Dustydazzler]

Ah . Chris the plumber . Haven’t seen one of his vids in a while .

2 switches , presumably the Dno installed the first one and the builder fitted the second one to fuse down the the supply.

30 ma rcd protection is required if they are 50mm or less from the finished surface , this you simply can not ascertain from the video footage

Chris the plumber mentioned earthed metal containment which is another option but extremely rare in domestic work

 

[Dustydazzler]

On a side not , not really sure why he is moaning about the top of the isolater, yes strictly speaking the gap is greater than 1mm but it’s hardly an issue inside a locked meter cupboard.
there are millions of meters and isolater switches up and down the country just like it...

 

[Baddegg]

Steady @Dustydazzler...you keep questioning his methods and you’ll get another mention ?

 

[Electrics]

The first isolator is fitted by the DNO the second one is to give the cable a fuse for fault protection if the board is over 3m away, the tails only need rcd protection if they're less than 50mm in the wall

Ah right - howcomes the DNO, seeing as it's a newbuild so they knew where the CU was going to end up - didn't just put it straight into a mains fused isolator?

Just confuses me since (even though one is fused) we can isolate it from either one of those so the unfused one is literally pointless isn't it?

Or is it a case of 'we've put one in and done our job, you need to put in whatever you need after and that's your responsibility'?

 

[Dustydazzler]

Steady @Dustydazzler...you keep questioning his methods and you’ll get another mention ?

I’m counting on it ..

 

[Baddegg]

Ah right - howcomes the DNO, seeing as it's a newbuild so they knew where the CU was going to end up - didn't just put it straight into a mains fused isolator?

Just confuses me since (even though one is fused) we can isolate it from either one of those so the unfused one is literally pointless isn't it?

Or is it a case of 'we've put one in and done our job, you need to put in whatever you need after and that's your responsibility'?

I’d imagine the DNO had no idea where the units would be mounted finally, nor cared, they’ve supplied and protected they cables ?

 

[Electrics]

I’d imagine the DNO had no idea where the units would be mounted finally, nor cared, they’ve supplied and protected they cables ?

Ah ok so makes sense - they just said 'right our job is done' which meant the spark doing the job then had to put a fused breaker in?

I'm still a little confused as to why - aren't we 100a protected where the supply enters the building? This particular one goes through a meter then through an unfused isolator to then be put through another 100a (?) isolator?

What's the point in two lots of 100a fusing?

 

[Baddegg]

The bigger question is what rcd protection he puts in and where...or does he not offer any explanations?...i havnt the willpower for 30 mins of chris on a Sunday morning ?

 

[Dustydazzler]

Could be a 60 or 80 in the builders fused isolater

 

[7029 dave]

Ah right - howcomes the DNO, seeing as it's a newbuild so they knew where the CU was going to end up - didn't just put it straight into a mains fused isolator?

Just confuses me since (even though one is fused) we can isolate it from either one of those so the unfused one is literally pointless isn't it?

Or is it a case of 'we've put one in and done our job, you need to put in whatever you need after and that's your responsibility'?

The metering supplier because its a new build are not responsible for the final connections/testing etc, therefore an isolator is fitted as a demarcation point.

 

[Dustydazzler]

The bigger question is what rcd protection he puts in and where...or does he not offer any explanations?...i havnt the willpower for 30 mins of chris on a Sunday morning ?

https://www.ebay.co.uk/itm/Masterpl...274249&hash=item35f6bd3fba:g:N0cAAOSwFSxZ5h6U

 

[Lucien Nunes]

What's the point in two lots of 100a fusing?

The point is who owns the fuses. The DNO's cutout protects their network, service cable and meter, but is not to be relied on to protect the customer's equipment because it's not the customer's property and is not accessible to them. It is acceptable for it to protect up to 3m of tails as this represents a low risk. If the layout involves a longer run of cable that is part of the installation although before the CU, then the DNO can't take responsibility for the adequacy of their fuse as protection for the cable and the customer is required to provide their own.

 

[Electrics]

The point is who owns the fuses. The DNO's cutout protects their network, service cable and meter, but is not to be relied on to protect the customer's equipment because it's not the customer's property and is not accessible to them. It is acceptable for it to protect up to 3m of tails as this represents a low risk. If the layout involves a longer run of cable that is part of the installation although before the CU, then the DNO can't take responsibility for the adequacy of their fuse as protection for the cable and the customer is required to provide their own.

I see, good explanation thanks.

 

[ipf]

The bigger question is what rcd protection he puts in and where...or does he not offer any explanations?...i havnt the willpower for 30 mins of chris on a Sunday morning ?

What's special about Sunday mornings? ?