Cottage supplied by 16mm SWA 300+ yards! Trying to resolve a high Ze reading

[RobertLow]

You can consult the supplier but as to what you can do about it, very little. I assume this is a TN-S supply where the suggested Ze should not exceed 0.80 but this is not an absolute requirement.

I should correct myself, it is a 32A mcb with an 80A type A rcd fitted at the c/u. Also the box in the field where the 16mm SWA originates appears to show the system as TNCS as SSE have the earth coming out of their service head.

 

[RobertLow]

The maximum permitted Zs for any final circuit with a 30ma 61009 or 61008 device at its origin is 1667 ohms, so the Zs on your ring circuit is satisfactory on a 32a rcbo.

Hi, isn't the 1667 ohms reading only for Type S RCD's? in page 70 of the regs i see that value in a table. regarding S type?

 

[westward10]

I should correct myself, it is a 32A mcb with an 80A type A rcd fitted at the c/u. Also the box in the field where the 16mm SWA originates appears to show the system as TNCS as SSE have the earth coming out of their service head.

Fault protection is still provided by the RCD.
If it is TN-C-S then the armour of that cable is inadequate to support main protective bonding.

 

[RobertLow]

Fault protection is still provided by the RCD.
If it is TN-C-S then the armour of that cable is inadequate to support main protective bonding.

Perhaps i should suggest to the farmer an earth spike should be installed at the meter box beside the two cottages in order to provide an adequate earthing arrangement?
This is where the SWA terminates into the box 300 yards away. Don't you think that the cable size is massively underrated for the distance?

 

[westward10]

It is certainly undersized by some way but they are not necessarily working to the requirements like us. I would question it and see their response.

 

[RobertLow]

It is certainly undersized by some way but they are not necessarily working to the requirements like us. I would question it and see their response.

This cable was not run by the electricity supplier. It was run by a previous electrician who did work on the farm and this cable was reconnected into the new mains box when the supplier brought in new overheads. So unfortunately it isn't them who are to blame, but some old retired spark somewhere around here!

 

[westward10]

Got you. That cable is certainly undersized with regard to volt drop which isn't necessarily a concern with an EICR unless it is giving issues but the armour is, personally I Code 2 these instances as it is inadequate to support main protective bonding.

 

[Flanders]

Agree with westwood That SWA need terminating correctly. I would give a code 2 for that. I would also code 2 those exposed single insulated cores of the SWA . To fix the HI zs though you would have to down rate the main fuses, fit a main upfront 300ma RCD at the DNOs supply box Or run in a new cable.

 

[Greenarmy]

The two supplies are also sharing the same neutral .

 

[mainline]

Hi, isn't the 1667 ohms reading only for Type S RCD's? in page 70 of the regs i see that value in a table. regarding S type?

type S rcd = time delay
The 1667 ohm is the maximum earth loop for a 30ma rcd