Stange fault on new installation

[yellowvanman]

Next up part (b) for every circuit. Other than at the origin........

What reg are you refering to?

537.2.1.1 says that every circuit shall be capable of being isolated (DP in the case of TT) but no where does it say each circuit needs to be individually isolated - see the 2nd part of 537.2.1. (the part I quoted above)

 

[Simlec]

What reg are you refering to?

537.2.1.1 says that every circuit shall be capable of being isolated (DP in the case of TT) but no where does it say each circuit needs to be individually isolated - see the 2nd part of 537.2.1. (the part I quoted above)

For easy reading OSG green page 45, OSG yellow should be the same page (i use the crap online thing) section 5

 

[Deleted member 26818]

What it is saying, is that if a circuit requires isolating separately from any other circuits, then the device used must be double pole in TT installations.
What it is not saying, is that every circuit must have a method of isolating it separately from other circuits.

 

[yellowvanman]

For easy reading OSG green page 45, OSG yellow should be the same page (i use the crap online thing) section 5

I believe that relates to 'circuits that may have to be isolated without interrupting the supply to other circuits' generally in domestic scenarios I can't think of reason for this.

 

[Simlec]

What it is saying, is that if a circuit (or group) requires isolating separately from any other circuits (circuit or group), then the device used must be double pole in TT installations.
What it is not saying, is that every circuit must have a method of isolating it separately from other circuits.(not sure i understand this as an isolation device in a TT system would disconnect all live conductors)

I believe that relates to 'circuits that may have to be isolated without interrupting the supply to other circuits' generally in domestic scenarios I can't think of reason for this.

Where does it say anything about the type of premises ?

 

[Simlec]

I believe that relates to 'circuits that may have to be isolated without interrupting the supply to other circuits' generally in domestic scenarios I can't think of reason for this.

I believe you are referring to 314

 

[Deleted member 26818]

All installations should have a double pole Main switch to provide isolation.
There is no requirement to provide isolation for individual or groups of circuit/s, just a requirement that where it is provided that it be double pole in TT installations.

 

[Simlec]

All installations should have a double pole Main switch to provide isolation.
There is no requirement to provide isolation for individual or groups of circuit/s, just a requirement that where it is provided that it be double pole in TT installations.

That will be reg 314

 

[Deleted member 26818]

Yes 314.1, your point being?

 

[Simlec]

You do know the installation is a TT yes?
so the OP has divided his installation up (as 314) into to, sub mains A & sub mains B.
Sub main A is a circuit and sub main B is also a circuit.
So to isolate say, sub main B you would lock of the RCBO feeding sub main B BUT table 53.4 says all devices used for isolation must disconnect all live conductors which the single pole RCBO the op has will not.

 

[Deleted member 26818]

Are you stating that there is no Main switch, just the RCBOs?
If that is the case then yes double pole RCBOs should have been used.
Where do you get the information about the lack of a Main switch from?

 

[Simlec]

Are you stating that there is no Main switch, just the RCBOs?
If that is the case then yes double pole RCBOs should have been used.
Where do you get the information about the lack of a Main switch from?

there is a main switch.
For a TT system are you saying that when you work on a circuit or group that you always isolate the main switch?

 

[Deleted member 26818]

What would you do when working on a circuit in a TT installation, where the CU is populated with re-wireable fuses, cartridge fuses or MCBs?
How would you provide double pole isolation with re-wireable fuses?

 

[Simlec]

Not sure where you are going with the old stuff, but most older TT installations have double pole rcd's or more than one CU. The problem is the op has designed/upgraded this install with single pole devices where they should be double pole. The whole design is a dogs dinner but he should be putting that part to current standards at least. As to his tripping problems it looks like he may have to run a third sub main/ circuit to divide up the parts with the kitchen appliances to reduse the earth leakage on the current 30mA units.

 

[Deleted member 26818]

Not sure where you are going with the old stuff, but most older TT installations have double pole rcd's or more than one CU. I'm trying to go to the place where you understand that the requirement for double pole isolation does not equate to a requirement for double pole protective devices.
The problem is the op has designed/upgraded this install with single pole devices where they should be double pole.
Again there is no requirement for double pole protective devices.
The whole design is a dogs dinner but he should be putting that part to current standards at least.
Yes there are problems with the installation, but as far as I am aware it complies with the requirements of BS7671!
As to his tripping problems it looks like he may have to run a third sub main/ circuit to divide up the parts with the kitchen appliances to reduse the earth leakage on the current 30mA units.

The OP may well have to run in a third sub main, though I would advocate replacing the upfront RCBOs with 100mA s type RCDs if possible and the use of RCBOs in the CUs.