Rcd Upgrade

[Dug]

Iv been asked to upgrade a 12 way bored that's is feed off a 100a DP main switch, I'm looking to give the client a few price options. 

The bored is 11 years old and in good condition so what I'm wondering is if it is acceptable to just change the DP switch for a 100amp RCD?? 

The main income is also fittd with a 100amp single poll isolator after the meter. 

Cheer's.

 

[SPECIAL LOCATION]

What reg are you thinking of that requires a 100amp RCD?

thats one heck of a fault current before it trips???

 

[betty swollocks]

No it isn't, it is not acceptable to install a single rcd for a whole installation, as any fault on any circuit will lead to the whole installation being de-energised. Why are you being asked to upgrade the boArd? What are you trying to achieve? More details required for a complete answer Dug

 

[misssweden]

Please correct me if I'm wrong but doesn't RCD's operate on milliamps?

 

[Dug]

There is no RCD fitted at the moment and they were wanting a bored with RCD protection was basically looking for a cheep option than changing the whole bored to a 17th edition bored, as the bored in place its not that old.  

The reason I was thinking 100amp's was because the the main switch that it would be replacing is 100amp rated. 

 

[ProDave]

Well given you can get a fully loaded dual RCD board for £50, I can't see the poing faffing about trying to bodge something together. Just do a full CU swap and jobs a good un.

 

[Marvo]

Please correct me if I'm wrong but doesn't RCD's operate on milliamps?

RCD's operate in milliamps only if the fault current is flowing to earth. If it's a short circuit current (live-neutral) then it will operate somewhere above 100Amps if that is the current it's rated to carry.

I doubt there's anything in the regs against replacing the isolator with an RCD but it would be an annoyance for the customer if there was ever a low insulation fault. As Dave says, if it's only GBP50.00 for a fully populated board then it's kind of a no-brainer. 

 

[steptoe]

yer, and an RCD will cost over 20quid anyway.

 

[misssweden]

RCD's operate in milliamps only if the fault current is flowing to earth. If it's a short circuit current (live-neutral) then it will operate somewhere above 100Amps if that is the current it's rated to carry.

I doubt there's anything in the regs against replacing the isolator with an RCD but it would be an annoyance for the customer if there was ever a low insulation fault. As Dave says, if it's only GBP50.00 for a fully populated board then it's kind of a no-brainer. 

Thank you Marvo. A scoob for educating me However, I'm slightly confused now as my teachers at college keep telling me that RCD's only operate on earth fault currents. (Insert confused looking smiley here )

 

[Evans Electric]

RCD's operate in milliamps only if the fault current is flowing to earth. If it's a short circuit current (live-neutral) then it will operate somewhere above 100Amps if that is the current it's rated to carry.

I doubt there's anything in the regs against replacing the isolator with an RCD but it would be an annoyance for the customer if there was ever a low insulation fault. As Dave says, if it's only GBP50.00 for a fully populated board then it's kind of a no-brainer. 

Thank you Marvo. A scoob for educating me However, I'm slightly confused now as my teachers at college keep telling me that RCD's only operate on earth fault currents. (Insert confused looking smiley here )

They do , Miss Sweden , as far as I know .   There is no overload protection in an RCD .   The 100Amps refers to the current it will carry /switch on & off.

And the  best thing Dug can do is change the whole board to a dual RCD  . 

 

[Steve3948]

Off Load or On Load

 

[Marvo]

The phrase RCD's can be confusing, similar to RCCD, RCCB or ELCB, it's one of those 'catch-all' phrases for most devices that protect against earth leakage current. Some RCD's have no overload built-in so they would only operate to an earth fault. Some RCD's have overload protection as well so would operate to both earth and short circuit faults, they're often known as RCBO's or GFCI's. The terminology varies considerably depending on where in the world you are.

 

[betty swollocks]

RCD's operate in milliamps only if the fault current is flowing to earth. If it's a short circuit current (live-neutral) then it will operate somewhere above 100Amps if that is the current it's rated to carry.

I doubt there's anything in the regs against replacing the isolator with an RCD but it would be an annoyance for the customer if there was ever a low insulation fault. As Dave says, if it's only GBP50.00 for a fully populated board then it's kind of a no-brainer.

Regulation 314.1 & 2

Requires that every installation shall be divided into circuits as necessary to avoid danger and minimise inconvenience, in the event of a fault. Also reducing the possibility of unwanted RCD tripping, due to excessive protective conductor currents but not due to an Earth fault.Separate circuits may be required for parts of the installation, which need to be separately controlled in such a way that they are not affected by the failure of other circuits. The appropriate subdivision should take account of any danger arising from the failure of a single circuit eg. an RCD trip on a socket outlet causing the unwanted failure of a lighting circuit and its associated hazards.

 

[misssweden]

They do , Miss Sweden , as far as I know .   There is no overload protection in an RCD .   The 100Amps refers to the current it will carry /switch on & off. 

Cheers Deke I'm less confused now Sorry for hijacking your thread Dug.

 

[betty swollocks]

First steps then andy now deke....... She has no shame!

Just jealous....

 

[matt.leung]

just changed a CU today and had issues with the lighting circuit as the up stairs and down stairs two-way switching (hall and landing) observiously had a norrowed neutral... what a pain as i was using RCBO's...

 

[Marvo]

Regulation 314.1 & 2 Requires that every installation shall be divided into circuits as necessary to avoid danger and minimise inconvenience, in the event of a fault. Also reducing the possibility of unwanted RCD tripping, due to excessive protective conductor currents but not due to an Earth fault.Separate circuits may be required for parts of the installation, which need to be separately controlled in such a way that they are not affected by the failure of other circuits. The appropriate subdivision should take account of any danger arising from the failure of a single circuit eg. an RCD trip on a socket outlet causing the unwanted failure of a lighting circuit and its associated hazards.

Thanks for the reg Betty. So does that mean it's not allowed or just not recommended to use a single RCD as a main isolator?

 

[SPECIAL LOCATION]

Thanks for the reg Betty. So does that mean it's not allowed or just not recommended to use a single RCD as a main isolator?

A single RCD protected installation would not comply with the current regs...

But as for "allowed" thats the area of interpretation of Non Statutory guidance I believe??

The preferable regs solution is an individual RCD for every circuit..

i.e.  NO sharing of RCD's between circuits..

But its cost -vs- whats reasonably practicable issue..

Guinness

 

[batty]

just changed a CU today and had issues with the lighting circuit as the up stairs and down stairs two-way switching (hall and landing) observiously had a norrowed neutral... what a pain as i was using RCBO's...

So how did you get over the problem?

 

[matt.leung]

So how did you get over the problem?

i had to put both circuits onto the same RCBO. did the calculations to make sure the breaker could handle the load etc...

got to go bk in a couple of weeks to do some remedial work.....