B
Big_Spark
Conduit (Metal) can be used as a cpc so long as the following criteria are met.
1: The integrity of the conduit can be confirmed throughout the installation and that all exposed and extraneous conductive parts of the installation are connected to the conduit by means acceptable to BS7671:2004
2: The cross sectional area of the conduit meets the requirements for a cpc as defined in BS7671:2004
3: The use of the conduit as a cpc has been designed into the installation and that the disconnection times for protective devices on the given circuits complies with BS7671:2004
4: All reasonable care has been taken to ensure that the conduit, and thus the integrity of the cpc, cannot be disconnected accidentally, thus leaving the circuit in a dangerous state.
Personally I would always recommend that a seperate cpc be installed into these circuits for peace of mind. Steel conduit, especially Black enamel, deteriorates over the years, it's oxide content increases, thus increasing the resistance of the conduit, and this can have dramatic effects on the ability of the conduit to perform it's cpc tasks when the time comes. The installation may be at an age that might means you simply need to pull in a new cpc, however if the installation is in excess of 20 years old, it might be easier to bite the bullet and get it rewired, as it is in conduit it is a relatively easy and mess free task.
1: The integrity of the conduit can be confirmed throughout the installation and that all exposed and extraneous conductive parts of the installation are connected to the conduit by means acceptable to BS7671:2004
2: The cross sectional area of the conduit meets the requirements for a cpc as defined in BS7671:2004
3: The use of the conduit as a cpc has been designed into the installation and that the disconnection times for protective devices on the given circuits complies with BS7671:2004
4: All reasonable care has been taken to ensure that the conduit, and thus the integrity of the cpc, cannot be disconnected accidentally, thus leaving the circuit in a dangerous state.
Personally I would always recommend that a seperate cpc be installed into these circuits for peace of mind. Steel conduit, especially Black enamel, deteriorates over the years, it's oxide content increases, thus increasing the resistance of the conduit, and this can have dramatic effects on the ability of the conduit to perform it's cpc tasks when the time comes. The installation may be at an age that might means you simply need to pull in a new cpc, however if the installation is in excess of 20 years old, it might be easier to bite the bullet and get it rewired, as it is in conduit it is a relatively easy and mess free task.
