Domestic CU Change

[Power Ball]

When doing a CU Change in a domestic house I uaually put everything on to both RCD's ? is there anything you would not cover by RCD say maybe smokes or intruder alarm ?

What do you do .....

Chas

 

[a1spark]

RCDs required for...

Cables buried less than 50mm , without mechanical protection [ usually all in domestic]

Socket outlets [ with certain allowed exception [Labelled freezer etc}

All circuits in Bathroom / shower room.

and any circuits where Earth fault loop impedance max values cant be met [ Fault protection]

- Use Main switch C.U with RCBOs or High integrity C.U [RCDs & RCBOs} if worried about preservation of essential services etc.

a1spark.

 

[PC Electrics]

Everything on RCDs or RCBOs or a combination thereof. Unless you can be certain a circuit can be non-RCD'd, best default to it being RCD'd - can't be wrong then.

For modest houses with 4 to 8 circuits and no seperate smokes I usually use a dual RCD board. If there's a seperate smokes (or lights smokes combo) circuit or a sub main out to a garage I'll use a hi int board. Rarely use all RCBO in domestic.

Every installation has to be asessed on its own merits though.

 

[jackfrosty]

whats the different between a high integrity and dual rcd board?

 

[Manator]

High integrity boards have two, three or four ways that can be used as seperate means of isolation. This can be via rccbo's or mcb's providing they conform to the 17th edition wiring regulations.

Fire alarm and intruder alarms would be the most used in this case, but it can be for any circuit with any special limitations or special requirements, like walk in fridges and freezer for example, or specialist computer equipment that would cause more harm if closed by a nuisance trip from a circuit protected by a multiple circuit RCD.

 

[Evans Electric]

They have a third BB with a couple of ways on it , do what you want with them , RCBOs or MCB .

I'm considering puttting smoke detectors on their own circuit ,from an MCB on the assumption that the cables are in the floor /ceiling void .

 

[sanny]

i never put smoke alarms on a seperate circuit reason being if the breaker goes no one notices they are off wont be long till the batteries go flat! Atleast if they are doubled up with a lighting circuit theres more chance of the breaker being put back on!

 

[a1spark]

Same here sanny .

a1spark.

 

[Andy™]

and here. not many people would leave the lighting circuit not working if there was a fault. smoke alarm circuit, 'fix it later'

 

[initforthemoney]

High integrity boards have two, three or four ways that can be used as seperate means of isolation.

Not strictly correct.

 

[wozz]

whats the different between a high integrity and dual rcd board?

when it comes to MK boards nothing, you can set them up how u want, the most important thing is a 3rd neutral busbar rather than linked neutrals as most of the others have.

 

[Manator]

Not strictly correct.

Again nonsencical in implication, its true or false, right or wrong.

If there is another definition of integrity then please explain how it is not strictly true. As I stated the normal circuits seperated from dual RCD protection are fire alarms, intruder alarms and other services where nuisance tripping would or could be harmfull to the effect of the circuit to operate. The circuits could be protected via RCCBO's or MCB's providing the circuit design permits this.

 

[SPECIAL LOCATION]

i never put smoke alarms on a seperate circuit reason being if the breaker goes no one notices they are off wont be long till the batteries go flat! Atleast if they are doubled up with a lighting circuit theres more chance of the breaker being put back on!

I do question this Logic ?:|

Why would a breaker go at random on a very low power smoke detector circuit?

Most mains / Batt alarms I fit give a bleep every minute if the mains is off, this soon annoys the customer into doing something..

What if the mains is off your lighting circuit during the daytime?

(and the sumer months.. long days.. lights not on much!?)

oh yes we are back then to the Alarm itself chirping to warn the customer.

Lithium 7 year battery life anyone...

only need a 7 year power cut and they are shot!!!

Not exactly quite so water tight not to use a dedicated circuit I think?

 

[initforthemoney]

Again nonsencical in implication, its true or false, right or wrong.If there is another definition of integrity then please explain how it is not strictly true. As I stated the normal circuits seperated from dual RCD protection are fire alarms, intruder alarms and other services where nuisance tripping would or could be harmfull to the effect of the circuit to operate. The circuits could be protected via RCCBO's or MCB's providing the circuit design permits this.

There isnt really any such thing as a "high integrity" CU. All they are is just a split load RCD CU, but for some reason, they had this "type" given to them in the early days of the 17th edition.

High integrity, refers to an earthing arrangement.

 

[Manator]

Yes that is true High integrity earthing has been an electrical term for some time.

However adaptation of the word integrity includes consumer units that offer seperate spaces for individual circuits to be connected without interference from another circuit.

We can only define the word and its implication by common use of the terms, otherwise we will all end up calling them by different names and getting more confused as to what we actually want or need.