Safe Isolation and switching!

[leighman]

Hello

I had problem at work on a Caravan/camp site where I installed a distribution box for the caravans parked on the site. The same circuit on the Camp site had the need for a replacement of a length of cable between a single phase isolator and a junction box (because it was incorrectly sized.) So I went on to safely isolate the installation and perform the necessarie work: I then switched on the distribution circuit isolator. The Current using equipment had not been disconnected or isolated from the DB during the time that I performed the works. The only means of isolation had been the 100A main single phase breaker.
I was then told that allegedly the act of not disconnecting the current using equipment before replying the current via the Main isolator had caused the switching current to Damage the current using equipment

Just wanted to know how Electricians on this Forum would react to this situation and what regulation you could quote from to either prove or disprove a stance you may have on this issue??

 

[truckster]

Re: Safe Isolation and switching

Possible but sounds iffy to me. Was there a notice to this effect at the point of isolation? What would happen if the breaker went out on overload or short circuit?

 

[leighman]

Re: Safe Isolation and switching

Thank you for your reply truckster


No! - There was no 'Notice to this effect' at the point of isolation (what effect are you talking about truckster??). If the breaker went out on overload (which it did not! ) then presumably this would offer some protection to current using equipment. Please note I have now added to my post and included my proposed detailed note to the contractor overseeing the site. Please read it and tell me what you think!!



Reference: Complaint by Customer/s that a routine isolating procedure allegedly caused current using equipment malfunction and /or damage.

Although it is advisable by some electricians and possibly some manufactures recommendations to follow the Switching on procedure:

1. and firstly disconnect current using appliances and/or equipment at the point of utilisation - i.e at the MCB that feeds the final circuits...
2... and then secondly switching on any isolators on the distribution circuit forming part of that circuit.

-Please Note the above procedure is NOT a non-Statuary regulationary requirement (and indeed neither is it a regulation!) and does NOT form part of the Statuary Health and safty at work Act 1974.
It is excepted by me that it could possibly pose an increased potential for higher starting currents to and the customer by not following the above procedure and so in light of the alleged highlighted incident (referenced above) that was brought to my attention the above procedure will be adhered to in future.

Unfortunately for the customer in this circumstance it was a case of a routine procedure of switching on an isolator that allegedly caused a higher than usual switching current that allegedly caused damage to the customers current using equipment.

I installed the Consumer unit box feeding the final circuits and replaced a short length of cable between an isolator and a Junction box that formed part of the circuit for the customers in question

I did NOT install the isolator and other eqiupment on the circuit being used by the customers in question.

I installed part of the circuit in question in the standard and correct way by adhering to the required regulations BS7671 and correctly sizing of the cable and any associated mcb's and then inspecting.

I ( the installer ) cannot be held liable if the current using equipment used by the customer has not been conceived for tolerant enough use for potential switching currents.

The alleged incident was caused by allegedly: a random occurrence of an unusually high switching current and NOT by a fault on the circuit.

Any Grievances by the customer in My opinion should be directed at the manufactures of the equipment and appliances being used by the customer and or/the manufactures of equipment forming part of the distribution circuit.
I did not design or specify the current using equipment and distribution circuit and/or equipment, I merely and correctly checked that the distribution circuit and equipment conformed to current British Standards and was installed and inspected/tested according to the current regulations.

As previously mentioned in my opinion I cannot therefore be held liable for the particular damages sort by the customer/s in question for this incident.

 

[leighman]

Re: Safe Isolation and switching

I guess you mean: A notice to the effect that you should follow a certain switching on procedure should be situated at or near the point of isolation.

 

[Spazz]

So they booked the work with you - to change a DB.
You isolate the supply as expected - did you tell them you needed to isolate the supply - if so what was their reply?
Whilst isolating the supply you cause damage to the equipment using that supply.

This can go 1 of 3 ways
1. they are liable as you must work dead in all occasions unless there is a very good reason to work live and they knew you where isolating it
2. you blown the equipment whilst doing an Insulation Test - your liable as you didn't ensure you unplugged it
3. you didn't tell them and presumed they knew that you where disconnecting the supply - you again are liable - check the BGB - there is a reg in there about safe isolating - I don't have the book on me at the moment sorry, or I would look it up.

I hope you have insurance!

Good Luck!

 

[telectrix]

sounds like they're trying it on.

 

[telectrix]

Re: Safe Isolation and switching

-Please Note the above procedure is NOT a non-Statuary regulationary requirement (and indeed neither is it a regulation!) and does NOT form part of the Statuary Health and safty at work Act 1974.

should read "NOT a statutory requirement" etc.

 

[Guest123]

***Threads Merged***

 

[leighman]

So they booked the work with you - to change a DB.
You isolate the supply as expected - did you tell them you needed to isolate the supply - if so what was their reply?
Whilst isolating the supply you cause damage to the equipment using that supply.

This can go 1 of 3 ways
1. they are liable as you must work dead in all occasions unless there is a very good reason to work live and they knew you where isolating it
2. you blown the equipment whilst doing an Insulation Test - your liable as you didn't ensure you unplugged it
3. you didn't tell them and presumed they knew that you where disconnecting the supply - you again are liable - check the BGB - there is a reg in there about safe isolating - I don't have the book on me at the moment sorry, or I would look it up.

Thank you for your reply
After reading your reply I would say: Yes, I did tell them exactly what I was isolating. and they gave me permission. The problem was not allegedly caused by isolating but rather the switching back on of the supply
I did not run an insulation test on the circuit whilst the current consuming equipment was connected - because I know of the dangers that this would cause. i.e 500v applied.

The following is a more detailed exchange on this subject I have just had regarding this incident, please read and tell me what you think if you like. After it could happen to any one of us Electricians so best to be fore warned. Thanks

[h=2]

Re: Safe Isolation and switching[/h]

Thank you for your reply truckster


No! - There was no 'Notice to this effect' at the point of isolation (what effect are you talking about truckster??). If the breaker went out on overload (which it did not! ) then presumably this would offer some protection to current using equipment. Please note I have now added to my post and included my proposed detailed note to the contractor overseeing the site. Please read it and tell me what you think!!



Reference: Complaint by Customer/s that a routine isolating procedure allegedly caused current using equipment malfunction and /or damage.

Although it is advisable by some electricians and possibly some manufactures recommendations to follow the Switching on procedure:

1. and firstly disconnect current using appliances and/or equipment at the point of utilisation - i.e at the MCB thatfeeds the final circuits...
2... and then secondly switching on any isolators on the distribution circuit forming part of that circuit.

-Please Note the above procedure is NOT a non-Statuary regulationary requirement (and indeed neither is it a regulation!) and does NOT form part of the Statuary Health and safty at work Act 1974.
It is excepted by me that it could possibly pose an increased potential for higher starting currents to and the customer by not following the above procedure and so in light of the alleged highlighted incident (referenced above) that was brought to my attention the above procedure will be adhered to in future.

Unfortunately for the customer in this circumstance it was a case of a routine procedure of switching on an isolator that allegedly caused a higher than usual switching current that allegedly caused damage to the customers current using equipment.

I installed the Consumer unit box feeding the final circuits and replaced a short length of cable between an isolator and a Junction box that formed part of the circuit for the customers in question

I did NOT install the isolator and other eqiupment on the circuit being used by the customers in question.

I installed part of the circuit in question in the standard and correct way by adhering to the required regulations BS7671 and correctly sizing of the cable and any associated mcb's and then inspecting.

I ( the installer ) cannot be held liable if the current using equipment used by the customer has not been conceived for tolerant enough use for potential switching currents.

The alleged incident was caused by allegedly: a random occurrence of an unusually high switching current and NOT by a fault on the circuit.

Any Grievances by the customer in My opinion should be directed at the manufactures of the equipment and appliances being used by the customer and or/the manufactures of equipment forming part of the distribution circuit.
I did not design or specify the current using equipment and distribution circuit and/or equipment, I merely and correctly checked that the distribution circuit and equipment conformed to current British Standards and was installed and inspected/tested according to the current regulations.

As previously mentioned in my opinion I cannot therefore be held liable for the particular damages sort by the customer/s in question for this incident.

[h=2]

Re: Safe Isolation and switching[/h]

I guess you mean: A notice to the effect that you should follow a certain switching on procedure should be situated at or near the point of isolation.​

​

 

[mechelec]

I have had electronic equipment (telemetry) that has been switched off at its own isolator, fail when reenergised. There is no possible other way to isolate it. This equipment had been in service for some time and i can only assume a component failed due to a combination of age and inrush to the circuit.

 

[leighman]

Thank you for your reply Mr Owen

Please read further up or down this post(which ever it may be), I have published a more detailed proposed email to the contractor overseeing the site... and feel free to comment if you.
like.

This situation could happen to any one of us Electricians so it is perhaps useful to pre-warn our selves!

regarding your answer:

Yes I told them I was going to isolate and then switch on the circuit.
I did not not do any tests on the circuit with current using equipment connected - because am aware of what damage 500v insulation test can do to current using equipment

 

[leighman]

Interesting yes, but whom is at fault?? - the person who caused the current or the equipment for not protecting it's self adequately?

 

[parker56]

So how & what did you test before switching back on?

 

[UKMeterman]

What is the item they allege has been damaged?

 

[leighman]

12v equipment was allegedly damaged

 

[leighman]

I inspected the circuit and then switched it back on. I then switched it back off to test it. I now realize I should of tested the circuit before switching it back on. But even Not testing before switching back on would not of caused current using equipment to fail and the tests themselves could not of highlighted the potential to do so.

 

[leighman]

Let me clarify what I just said: I think I confused the reply: I completed the installation and then switched it back on before testing it - which was wrong!

I then isolated the final circuits again so that I could perform the necessary tests.

 

[parker56]

Sorry leighman, could you give us more details of the tests you carried out.

 

[UKMeterman]

Ok,
So how do they suggest that your testing on the 240V AC side caused a problem on the LOAD side of their power supply? I presume you were testing at 500V DC with a standard megger or MFT?