Earthing Cable

[Mr.Fixit]

i am installing a dishwasher and i need to know if i need to earth the mains cold water 15mm pipe which is coming through a TEE compression underneath the sink and it is already earthed there. Would i need it to be earth by the dishwasher as well? Also do i need to earth it (if i need to) with 4mm earth cable only or a 2.5mm earth cable would do? Do i also need to earth the dishwasher itself as well, dishwasher to the 15mm copper pipe??? Please Help....

 

[Jaymack]

There is no additional bonding required; but check that there is a main earth bond, to the water and gas, main incomng service pipes to the main earthing terminal at the consumer unit.

Jaymack

 

[JohnD]

Earthing of the kitchen pipes used to be considered necessary in the old days when I was a lad, but is not required now by the electrical rules. You have probably seen this kitchen bonding from when it used to be the practice, or in a non-current book.

However, as Jaymack says, you do need the incoming gas and water mains earthed (with 10mm direct to the consumer unit or main earthing terminal) where they enter your property, and in many cases this in in the kitchen.

Aditionally, the Corgi people say that all the pipes (water and gas) have to be bonded together and to earth at the boiler, so you can do this with your 4mm while you're at it; but this is a gas, not an electrical, rule. In my kichen, this means the boiler and cold water taps (next to each other) are all bonded, so I've chosen to bond the hot tap too so there should be no risk of a voltage difference. Modern electricians tell me it is not necessary.

If your water pipes are in copper, with soldered joints as is most usual, you only need to bond each pipe once as the copper pipe is a good conductor.

Bathrooms are different and need extra.

 

[Jaymack]

However, as Jaymack says, you do need the incoming gas and water mains earthed (with 10mm direct to the consumer unit or main earthing terminal) where they enter your property, and in many cases this in in the kitchen.

For the record, the size of the main equipotential bonding conductor is dependent on the size of the supplier's main fuse, 10 sqmm is ok for 60 to 80 A but 16 sqmm is reguired for 100A.

Aditionally, the Corgi people say that all the pipes (water and gas) have to be bonded together and to earth at the boiler, so you can do this with your 4mm while you're at it; but this is a gas, not an electrical, rule. In my kichen, this means the boiler and cold water taps (next to each other) are all bonded, so I've chosen to bond the hot tap too so there should be no risk of a voltage difference. Modern electricians tell me it is not necessary.

Modern electricians? There is up to date; and not so up to date electricians, IMO, the latter should not be giving advice.
There is no requirement for supplementary equipotential bonding in kitchens to the IEE regulations: BS 7671.

Jaymack

1. There's them who know,
2. There's them who don't know
3. There's them who don't know: - they don't know.

1 and 2 are OK but 3 is fatal.

 

[securespark]

Earthing of the kitchen pipes used to be considered necessary in the old days...

Blinkin' 'eck, lad! Now I've 'eard it all!

So the 15th (1981-1992) is the old days, then?

 

[JohnD]

"There is up to date; and not so up to date electricians, IMO, the latter should not be giving advice."

My mouth is shut.

 

[securespark]

For the record, the size of the main equipotential bonding conductor is dependent on the size of the supplier's main fuse, 10 sqmm is ok for 60 to 80 A but 16 sqmm is reguired for 100A.

Can you reference this?

I cannot back this statement up....

 

[Jaymack]

For the record, the size of the main equipotential bonding conductor is dependent on the size of the supplier's main fuse, 10 sqmm is ok for 60 to 80 A but 16 sqmm is reguired for 100A.

Can you reference this?

I cannot back this statement up....

OSG Page 24: - 4.2 "For 100A TN installations, the main earthing conductor csa needs to be 16 sqmm and that of the main bonding conductors 10sqmm where the size of the supply neutral conductor is not more than 35 sqmm" etc. and OSG Page 161 Table 10A for 50 sqmm supply neutral conductor.

Jaymack

 

[RF Lighting]

You are getting confused with main earthing and main bonding conductors. Two different things.

 

[the_jinj]

I would say 10mm as well - table 54H (from memory) in the regs has the spec
- unless you were supplied with a larger main earth I guess then it would be nearest half that size - 16mm is standard min in domestic(?)

 

[Spark123]

If the supply is PME (TN-CS) the main equipotential bonding conductors are sized relating to the size of the neutral conductor of the supply, the DNO should be consulted as may have additional requirements which can over-rule this.

 

[securespark]

Yeah, that's how I recall it. </=35mm2, then 10mm2, or 16mm2 for up to 50mm2.

I nearly always fit 10mm2, however, some DNO's ask for 16mm2, mostly on PME supplies.

 

[JohnD]

When the dust settles, what size earthing cables do the up-to-date electricians say is required for the gas and water mains bonding in a house?

 

[Spark123]

There is no single answer to this, it depends on the supply type, size and DNO requirements .

 

[JohnD]

two typical cases then - 80A supplier's fuse, PME, 16mm tails; and 100A, PME, 25mm; in the absence of special requirements?