RCD or MCB
- Thread starter ack351
- Start date
Sponsored Links
MCBs and RCDs are two different things, an MCB basically replaces your fuses. An RCD protects against earth leakage (i.e. if you get a shock). You will need RCD protection on socket circuits which can reasonably be expected to supply equipment outdoors. You can do this by having a split load board installed, or by having a normal board with RCBO (combined RCD and MCB) protection.
You want some of both... their purposes are quite different, an MCB does roughly the same job as a fuse, a RCD gives additional portection against electric shock, you can't use an RCD on its own to protect a circuit, also some circuits (sockets that may beused to power stuff outdoors is the main one) need to have rcd protection on, in addition its a good idea to rcd protect all sockets and showers and stuff in bathrooms.
The usual approach is a split load board, its a board that has an MCB for each circuit (as you would expect) but half of them are covered by an RCD and half arn't (you don't want lights on RCD)
The advantages are that its the cheapest way, the disadvantages are that if the RCD trips you loose a handful of circuits... and the more circuits you have on it... the more likely it is to nuisence trip
The alternative is a device called an RCBO, its an RCD and MCB in a package the same size as an MCB (well a tad bigger), you would have a straight forward board with a main switch, and MCBs for circuits that you don't want RCD on, and RCBO for circuits that you do.
The disadvantage of this is that RCBOs usually cost about £40 each
The usual approach is a split load board, its a board that has an MCB for each circuit (as you would expect) but half of them are covered by an RCD and half arn't (you don't want lights on RCD)
The advantages are that its the cheapest way, the disadvantages are that if the RCD trips you loose a handful of circuits... and the more circuits you have on it... the more likely it is to nuisence trip
The alternative is a device called an RCBO, its an RCD and MCB in a package the same size as an MCB (well a tad bigger), you would have a straight forward board with a main switch, and MCBs for circuits that you don't want RCD on, and RCBO for circuits that you do.
The disadvantage of this is that RCBOs usually cost about £40 each
Sponsored Links
rob884 said:
Not on earth leakage, but they will trip out on large currents to earth as much as they would large currents to neutral or to the moon, or whereever, which is why ELFI is an inportant concept
What they wont do is trip out on the milliamps of leakage through a living person etc...
They will trip on fault current wether it be a live to neutral or a live to earth fault, the current they take to trip for a type B to trip at 0.1seconds is 5 x the rating of the MCB, i.e. if it is a 6A MCB it will take 30A.
It only takes somewhere in the region of 40mA-250mA to cause death, this is why RCDs are used.
It only takes somewhere in the region of 40mA-250mA to cause death, this is why RCDs are used.
john D must have missed this one because he hasnt mentioned RCBO's yet!
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
