C2 coding

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Jc1996

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Hi I’m not from a domestic background but trying to relate periodic to industrial maintenance as far as potentially dangerous codes are issued I.e poor Zs values that don’t comply. If we come across this on day to day maintenance activities PPM etc should we switch of there and then and if we don’t isn’t this negligence and we can be prosecuted? 

 
Just my opinions:

I would say that in all circumstances, industrial or domestic, it would be a risk assessment, (in it's true sense, not a box ticking exercise).

If, in your technical judgement, there is an immediate threat to life or health then the power should be isolated immediately, more or less regardless of cost or consequences.

If the danger is judged less severe, such as marginal non-compliance with regulations, deterioratiing  condition of installation, etc, then you should highlight it for urgent attention. 

And yes, if you are negligent in carrying out your responsibilities you can be prosecuted under H&SaW act. 

I think you, as an operator, would have to be very negligent though. Action would be more likely against your supervisors or managers for failing to have adequate supervision or training in place.

 
Just turning things off can be dangerous in it's own right. We have never had the right to isolate a supply, unlike gas, when inspecting an electrical system. We inform the customer of any faults found and advise as to repair. However, if there was a clear and present danger to life, I would switch off the cct and  talk to the customer immediately. 

When assessing the Zs are you using the full value of 80% figure you tend to find in the On-site guide? 

 
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Just turning things off can be dangerous in it's own right. We have never had the right to isolate a supply, unlike gas, when inspecting an electrical system. We inform the customer of any faults found and advise as to repair. However, if there was a clear and present danger to life, I would switch off the cct and  talk to the customer immediately. 

When assessing the Zs are you using the full value of 80% figure you tend to find in the On-site guide? 
Yes on-site guide values. The motor is fed from a 100a bs88-2 and the zs I was getting was 0.48 ohms. I was told in writing by a supervisor to keep it running in writing but had a think about this and though if it came down to law surely me switching on a faulty circuit is negligent? 

 
on sie guide ony gives 80% values, the true figures are in BS7671.

Is this a new or exisitng cct? If it's an old cct that has been running for years without causng issues, then imho, you are over worrying, but you have done the right thing in reporting your findings to your supervisor. If it's a new cct, then it's clearly unacceptable, but again the final decision lies with your suoervisor. 

You have , in writing, enough to cover your arse in legal terms - make sure you keep a copy.

 
Yeah it’s an old install but had to reconnect a motor so then I was thinking due to being the last person working on the circuit am I then liable due to the bad readings and should I be reenergising? 

 
What are the R1+R2 values?

and are they proportionate to the length & CSA of the supply cable?

Have you compared how much of a difference are you to the actual Max Permissible in BS7671? 

If the difference is not massively off the expected values..  

Could be a poor joint somewhere..

Could be down to poor connections between your test meter & the circuit you are testing..

Could be dirty contacts on a switch / isolator somewhen along the circuit..

On old existing circuits its not uncommon to take a reading that initially appears outside of its expected values..

sometimes a bit of further investigation can give a different perspective..

 
What is the purpose of the motor and is it actually covered by the scope of BS7671.

 
If you consider this problem to be equivalent to a PIR C2 code, I am not convinced there would be any requirement to disconnect the circuit. A C1 immediate danger would be a different consideration, but a C2 is only potentially dangerous. Even though urgent remedial attention is recommended for a C2, it is not actually dangerous at the time of testing/inspection.  

Doc H.   

 
What are the R1+R2 values?

and are they proportionate to the length & CSA of the supply cable?

Have you compared how much of a difference are you to the actual Max Permissible in BS7671? 

If the difference is not massively off the expected values..  

Could be a poor joint somewhere..

Could be down to poor connections between your test meter & the circuit you are testing..

Could be dirty contacts on a switch / isolator somewhen along the circuit..

On old existing circuits its not uncommon to take a reading that initially appears outside of its expected values..

sometimes a bit of further investigation can give a different perspective..
Yeah I’ve tested the ZDB and the outgoing side of the cable to the local isolator (r1+R2) this is not included the possibility the contractor adding a few ohms due to being old and these 2 values exceed the on-site guide values by 0.15ohms I believe. 

What is the purpose of the motor and is it actually covered by the scope of BS7671.
That is a very good point I know machinery is only covered up to the machine feeder or something like that but this is a motor fed from a star delta starter 

If you consider this problem to be equivalent to a PIR C2 code, I am not convinced there would be any requirement to disconnect the circuit. A C1 immediate danger would be a different consideration, but a C2 is only potentially dangerous. Even though urgent remedial attention is recommended for a C2, it is not actually dangerous at the time of testing/inspection.  

Doc H.   
Yes that’s what I was thinking but probably overthinking if anything did go wrong who would be to blame. 

 
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