Electrical Safety in Stainless Steel Enclosures*
Stainless steel enclosures, in fact, any metal enclosure, have several safety, environmental, and practical advantages over enclosures made from other materials, such as glass-reinforced plastic (GRP).
We’ll touch upon barrier protection, electrical design and other protective measures that you can take to ensure electrical safety in stainless steel enclosures.
Barrier Protection
The main safety role of an electrical enclosure (or feeder pillar) is as a barrier to prevent someone on the outside from touching what is on the inside of the cabinet (maintaining IP3x as a bare minimum, see more on Ingress Protection).
If an external electrical enclosure is damaged then this protective barrier is compromised. The much higher impact strength of a stainless steel enclosure, as opposed to one made from GRP, obviously makes this much more secure.
Electrical Design
What to Check On-Site
With respect to electrical safety, there are two main scenarios to check on-site when installing a metal external enclosure and that might need addressing in the electrical design if encountered.
Firstly, is there a possibility of a live conductor coming loose inside and making contact with the body of the cabinet?
Secondly, is the cabinet bonded to a TT earth system (they typically are) and also within touching distance of an item of street furniture (or any other conductive item) that is connected to a PME earth system (i.e. one with a combined neutral and earth)?
Protective Measures
These are some of the measures that our customers take to mitigate these risks, comply with the IET Wiring Regulations (BS7671 in the UK) and create the safest installations using our stainless steel enclosures:
Potential internal fault
- The cabinet and all its conductive parts (e.g. the door) need to be connected to the equipotential earth bonding terminal.
- Include an RCD on the ‘upstream’ side of the distribution board.
- Extra shielding before the RCD. For example, running cables through plastic trunking, using double-insulated tails etc.
Potential for simultaneous contact between a PME system and the cabinet on a TT earth
- Move the cabinet to at least ~2 metres (beyond arm’s reach) away from any conductive parts that are connected to a PME earth.
- Put an insulating barrier between the cabinet and the other item. For example, plastic wraps for sign or lighting poles or even a fence.
Incorporating these features into your electrical design, with a stainless steel cabinet will give you a compliant and safe installation with the added safety of increased security of the enclosure.
Then the safety benefits can be combined with environmental benefits that come with choosing to manufacture stainless steel feeder pillars.
Did you know that 85% of stainless steel is recycled, whereas on the other hand, if you opted for GRP feeder pillars, virtually 0% of GRP is recycled. (Glass reinforced plastic, also known as fiberglass, is a composite material).
As well as a very long service life (highly corrosion and UV resistant).
And, finally, stainless steel enclosures just look a lot smarter than other external enclosures.
Have a browse through our RB Cabinets or see all of our ranges of stainless steel enclosures. Contact us for more information on all Ritherdon stainless steel enclosures.
*NB. This post is only intended to highlight certain aspects of electrical safety with external enclosures and is of limited scope. It is imperative that you discuss/check the points raised and any proposed electrical installation with an electrician/electrical engineer with suitable and up to date qualifications.
References:
Stainless consortium publishes life cycle report – Recycling Today
Fibreglass Recycling | Glass Reinforced Plastic (GRP) Recycling (businesswaste.co.uk)
