Q4 of 5 - How do you know when to use plastic or metal support and do I need to use plugs to fix the fixings?

Not every support for a cable would need to be made of something metallic, the idea behind the Regulation 521.10.202 is to prevent the electrical system prematurely collapsing, one way to achieve this is to install metal supports throughout. As always the regulations are open to interpretation and do not give a definitive answer as to what is expected, the point being that it isn’t necessary for all supports to be made of something metallic (unless required by other standards) as long as manufacturers’ instructions are followed.  

The need for plugs isn’t always necessary dependent on the fixing being used. If the question is can they be used to satisfy the regulations around premature collapse, then yes they can.  The construction of the material they are housed in would need to reach a significant temperature before the point of failure.

For more information, check out our SGTV episode on Cable Management Systems at https://youtu.be/9qdwKzCJm6Q