I am a project manager, constructing new waste water treatment works, for a water company. The contractor building the new works has provided a program which has 4 months between part 1 (dead testing) and part 2 (live testing) of the NICIEC certification. In between these dates, the contractor will test and commission of the plant and equipment e.g. pumps, actuated valves, instrumentation, screens etc.
Would it be correct to say, this does not comply with the wiring regulations ?
davezawadi (David Stone):
Hi Derek
There is probably quite a lot that is out of the scope of BS7671. The equipment to be powered is classed as “appliances”, and the wiring between them (eg. a VFD and Motor) is something of a grey area for a number of complex reasons. Whilst BS7671 may cover some of the control wiring, this depends on design features that BS7671 may not cover.
This procedure is very much the Main Contractors problem, you may like to ensure that he is aware of it by asking for details of the overseeing design Engineer and commissioning Engineer, and even a method statement as to how he/they is going to carry out their responsibilities. This will undoubtedly lead to a lot of “snag shifting” and you may well be blamed for raising difficulties that are not your responsibility! Such is life, but the legal responsibility for the process (Under CDM) is the Main Contractor. If anything goes wrong it is his problem. Whilst we have many discussions here about “possible” bad outcomes of many things, this is generally just a reflection of general awareness of H&S and the responsibilities of contractors.
For complex installations BS7671 offers general principles, it is impossible to cover all possibilities. Your principle live test is Earth Loop Impedance testing, but if you have RCD protection everywhere (which is unlikely to be at “additional protection” levels for your type of installation) this may well be relatively easy. It becomes difficult once a VFD is in the final circuit, and the need to have the equipment operating normally. Getting the whole control system into the correct state may be very difficult.
You will see from this that the statement you would like is not possible from anyone, even the IET! You could show interest with the main contractor, but I suggest you need a good reason for that interest, and why you think it may not be done correctly, for your own protection. Such could be for procedures for maintenance and periodic test in the future, that may not have been considered at the design stage.
Regards
David CEng etc.
Hi David, thanks for the detailed reply.
In my case, I have a main incoming feeder supplying one large control panel, which in turn feeds about 30 seperate circuits. So the main feeder comes into the control panel, through an MCB, on to busbars which act as the source for the other circuits. One of these is for a pump motor circuit which is quite straight forward. A TPN drop is taken from the busbar common section and fed into a seperate section for the pump motor circuit in question. This section starts with a fuseswitch, followed by a electronic overload and contactor. The contactor tails are connected onto the field terminals in the control panel.
There are 3 seperate cables, which leave the control panel to control, monitor and supply power to the pump. These 3 cables are about 60m in length and run to an above ground local control station. All 3 cables are terminated here. However, the pumps are installed below ground directly beneath the local control station. The pumps are ordered with 10m of cabling for power and monitoring. These 2 cables are brought from below ground level and terminated in the local control station.
As the control panel has seperate regulations to comply with, I suspect it is out of the scope of the wiring regulations, even though it contains all of the protection equipment ?
I would guess the pump with 10m of cabling must also fulfill certain criteria, meaning it is out of the scope of the regulations ?
Leaving the 3 interconnecting cables between the large control panel and local control station to be inspected and tested ?
Regards, Derek
davezawadi (David Stone):
Hi Derek
There is probably quite a lot that is out of the scope of BS7671. The equipment to be powered is classed as “appliances”, and the wiring between them (eg. a VFD and Motor) is something of a grey area for a number of complex reasons. Whilst BS7671 may cover some of the control wiring, this depends on design features that BS7671 may not cover.
This procedure is very much the Main Contractors problem, you may like to ensure that he is aware of it by asking for details of the overseeing design Engineer and commissioning Engineer, and even a method statement as to how he/they is going to carry out their responsibilities. This will undoubtedly lead to a lot of “snag shifting” and you may well be blamed for raising difficulties that are not your responsibility! Such is life, but the legal responsibility for the process (Under CDM) is the Main Contractor. If anything goes wrong it is his problem. Whilst we have many discussions here about “possible” bad outcomes of many things, this is generally just a reflection of general awareness of H&S and the responsibilities of contractors.
For complex installations BS7671 offers general principles, it is impossible to cover all possibilities. Your principle live test is Earth Loop Impedance testing, but if you have RCD protection everywhere (which is unlikely to be at “additional protection” levels for your type of installation) this may well be relatively easy. It becomes difficult once a VFD is in the final circuit, and the need to have the equipment operating normally. Getting the whole control system into the correct state may be very difficult.
You will see from this that the statement you would like is not possible from anyone, even the IET! You could show interest with the main contractor, but I suggest you need a good reason for that interest, and why you think it may not be done correctly, for your own protection. Such could be for procedures for maintenance and periodic test in the future, that may not have been considered at the design stage.
Regards
David CEng etc.
Hi David, thanks for the detailed reply.
In my case, I have a main incoming feeder supplying one large control panel, which in turn feeds about 30 seperate circuits. So the main feeder comes into the control panel, through an MCB, on to busbars which act as the source for the other circuits. One of these is for a pump motor circuit which is quite straight forward. A TPN drop is taken from the busbar common section and fed into a seperate section for the pump motor circuit in question. This section starts with a fuseswitch, followed by a electronic overload and contactor. The contactor tails are connected onto the field terminals in the control panel.
There are 3 seperate cables, which leave the control panel to control, monitor and supply power to the pump. These 3 cables are about 60m in length and run to an above ground local control station. All 3 cables are terminated here. However, the pumps are installed below ground directly beneath the local control station. The pumps are ordered with 10m of cabling for power and monitoring. These 2 cables are brought from below ground level and terminated in the local control station.
As the control panel has seperate regulations to comply with, I suspect it is out of the scope of the wiring regulations, even though it contains all of the protection equipment ?
I would guess the pump with 10m of cabling must also fulfill certain criteria, meaning it is out of the scope of the regulations ?
Leaving the 3 interconnecting cables between the large control panel and local control station to be inspected and tested ?
Regards, Derek
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