Panel isolators with mechanical interlocks

[paul_c]

Hello chaps, i'm hoping that someone can help me out with a question i have about panel isolators.

Is it UK legislation that an electrical enclosure should have a mechanical interlock on a door mounted isolator (if fitted) to prevent the door being opened with the power still switch on? If this is legislation then could someone please let me know where i would find it in writing so i can quote it to a supplier. Or is it just guidance?

Thanks in advance for any help!

Paul

 

[Notsosmart]

Hi Paul,

I don't think that interlocking is mandatory, more good practice you can get defeatable isolator handles (ie Square D)

You could quote Regulation 14 of the EAW act:

"Regulation 14 – Work on or near Live Conductors
Status – Absolute
No person shall be engaged in any work on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless:
It is unreasonable in all the circumstances for it to be dead and
It is reasonable in all the circumstances for him to be at work on or near it while it is live and
Suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury. "

 

[Griffin]

See if this document helps.

Rgds

G

 

[Notsosmart]

Alternatively this HSE guide specifically mentions interlocks (item 14 on page 6)

 

[Darkwood]

As far as im aware if you require a tool to access the electrics or key then it dosnt require interlock but if there is no local means of isolation and the supply goes straight in then it does as local means of isolation is required for maintenance and safety. If the interlock is used as local means of isolation then the permanent live incomming needs checking to make sure is shielded and warning signs affixed, also i normally fix an 'isolate elsewhere before opening' to the outside lid.

 

[paul_c]

thanks for the info so far, all very usful tips!

Darkwood, yes the panel does require a tool to gain access....my concern is that even for a competent person it would be advisable to be forced to switch the power off before opening the door. Of course switching the power back on once the door is open for testing etc would then be a deliberate act rather than forgetting the power is on at all!

Personally i would aways build a panel with a mech isolator, but these panels are imported (within the EU) and i would like to be able to easliey justify to the manufacturer that mechanically interlocked isolators are the way forward!

 

[Darkwood]

With respect using a tool or key means anyone with said tool or key should be competent enough to know what they are doing and such keys or tools should be kept safe with factory maintenance only having access, regardless if you use an interlock you still need a industrial cabinet key to gain access and leaving these around for general use would be for the company to monitor not us, and say you had an interlock, turned it off then opened it - their is still dangerous supply voltage coming into the control panel so it there just for a competent person to isolate not for an imcompetent person to be safer.
As i said before the panel only needs an interlock for isolation purposes for maintenance and not for the unqualified running the machine to have safe access, i see nothing wrong with no interlock if there is an isolator on nearby wall as this does more or less the same job without leaving a dangerous incoming voltage to the panel.

p.s. Using a key or tool to gain access is a deliberate act thus to do so you should be competent in electrical to start with.