more bonding!!!!

[ashm]

hello and thanks to all that reply,

I'm afraid its another bonding question!!!!

currently:

The water and gas are bonded direct to the MET (within 600mm)
All the pipes at the combi boiler are bonded together, but not to the MET or any other circuit
The boiler is about 1 metre from the bathroom
All circuits in the bathroom are RCD protected.

my question is this: under 17th addition is there any requirement for further bonding (not sure but seem to remember an earlier post about supplementary or equipmental)?

Cheers

 

[Lectrician]

No nonsence reply....

NO.

 

[ashm]

like no-nonsense!!! cheers

 

[GaryMo]

You say all circuits in the bathroom are are RCD protected? The rating of the RCD must not exceed 30mA and must trip within 40mS at 5 x its rated current.

 

[Spark123]

Also, any extraneous conductive parts in the location must be effectively connected back to the MET, can be tested by measurement.

 

[ashm]

You say all circuits in the bathroom are are RCD protected? The rating of the RCD must not exceed 30mA and must trip within 40mS at 5 x its rated current.

how is the 30mA calculated? it currently has the upstairs lights/fan (6A MCB)and shower (32A MCB) I'm not sure until i check next time i'm there but i think it has the kitchen sockets on it aswell.

are all RCD's 30mA?

Also, any extraneous conductive parts in the location must be effectively connected back to the MET, can be tested by measurement.

such as copper pipes? all my pipes are boxed in or in a vanity unit except for a flexible connector for the toilet. Are any of the above classed as extraneous?

 

[GaryMo]

how is the 30mA calculated? it currently has the upstairs lights/fan (6A MCB)and shower (32A MCB) I'm not sure until i check next time i'm there but i think it has the kitchen sockets on it aswell.

are all RCD's 30mA?

It's not calculated as such, it's specified by BS7671 that additional protection by RCD's is required which shall be 30mA.

Have a look at your RCD, it may say 30mA or even 0.03A.

Not all RCD's are 30mA, they come with numerous ratings.

 

[Spark123]

such as copper pipes? all my pipes are boxed in or in a vanity unit except for a flexible connector for the toilet. Are any of the above classed as extraneous?

As the taps will be accessable they will be extraneous in a copper pipe installation, even if the pipework isn't accessable.

 

[ashm]

As the taps will be accessable they will be extraneous in a copper pipe installation, even if the pipework isn't accessable.

Okay but if the extraneous pipe work is sufficiently (tested via measurement) bonded to the MET ,via pipework and boiler bonding, no further bonding is required - is that correct?

If so is this testing beyond the scope of i DIYer?

It's not calculated as such, it's specified by BS7671 that additional protection by RCD's is required which shall be 30mA.

How do you no how much can go on a RCD? obviously the circuits are operating far in excess of 30mA so where does the milli amps come from?

thanks for the replies

 

[JohnD]

30mA is the difference in current flowing down the Live and down the Neutral.

Obviously if it working properly the current should be the same down both wires

however if you have put your finger on the live, and some of the current is running through your body, then the current in the live conductor will be greater than that running through the neutral conductor.

E.g. for a lamp, there might be 1Amp for the lamp, and 1 amp running through you. So the live conductor would be carrying 2Amps, and the neutral conductor would be carrying 1Amp.

the RCD detects if this leakage is 30mA or greater, and if it is, it cuts the power. The bigger the leakage current, the faster it cuts it (within limits).

30mA is calculated as a current that will not kill you. The speed of cutting the circuit is also so fast that it will be cut in less than a heartbeat, so the time of shock is too short to kill you. Some RCDs are manufactured with a time delay so that they do not trip immediately. this means that they do not cut the current fast enough to be sure it will not kill you. The delay is regardless of current flow.,

RCD rating has nothing to do with the fuse or MCB rating of the circuit.

Okay but if the extraneous pipe work is sufficiently (tested via measurement) bonded to the MET ,via pipework and boiler bonding, no further bonding is required - is that correct?

No. Read the article on Supplementary Bonding in Bathrooms again.


If you are relying on RCDs, you must RCD the lighting, immersion heater, central heating pump, shaver socket, electric shower, shower pump - whatever goes into the bathroom. Few people have RCDs on their lighting circuits.

 

[ashm]

thanks for the the explanation, i now understand the 30mA but how does this relate to how many circuits you can have connected to it? this reply may be confussing me?

You say all circuits in the bathroom are are RCD protected? The rating of the RCD must not exceed 30mA and must trip within 40mS at 5 x its rated current.

will read up more on the bathroom bonding.

cheers

 

[GaryMo]

All circuits in the bath/shower room have to be RCD protected.
The RCD must be rated at a maximum of 30mA.
The RCD requires testing with a specific meter. Its operating time must not exceed 40ms when subjected to a test of 5 times its rated current.

 

[ashm]

got it, cheers!

 

[JohnD]

by "rated current" he means the 30mA

(other RCDs are 100mA, 300mA, 500mA etc, so the "rated current" depends on what sort of RCD it is)

Depending on what sort of consumer unit you have, there may be one RCD for all the circuits (bad practice) one RCD for several circuits (better) or two RCDs, each for several circuits (modern acceptable practice) or one RCD (RCBO) for each circuit (best, but most expensive)

It is particularly undesirable for all the lights to go out when e.g. the kettle boils over and trips the RCD, because being unexpectedly plunged into darkness can cause accidents.

It is inconvenient and undesirable if you can't use the cooker because the immersion heater is cracked.

This is why the fewer circuit you have on a single RCD, the better.

edited: too slow!