Can someone please clarify these queries ina commercial unit?

[toroid19]

I Have just removed the wiring from a 900 sq ft unit with a 900 sq ft mezzanine and I now have a fresh start. ( I had my doubts about the pvc insualtion tape holding it together!)

Could someone please clarify the following points:

1. As I understand it RCDs are not mandatory in a commercial application. However I intend to install 2 Redring instant water heaters each rated at 2.5kW. I was planning to supply each unit with 2.5mm2 T & E  protected by a 16A mcb with the heater connected to a 13A rcd fused spur since I am concerned about water and the manufacturer supplies these with a 13A plug. Am I also right in thinking that the pipe work should be earth bonded throughout.

2. Have I interpreted the tables correctly that 2.5mm2 T & E inside trunking (plastic) is derated to 21A current carrying capacity and therefore if used in a ring main then a 20A mcb is the most appropriate choice?

I am trying to make sure that I get this roughed in correctly beforew I get it tested and inspected. Many thanks

 

[Essex1]

Welcome,

It may be a little easier to give you advice if you told us what your current qualifications and experiences in electrical installation is. 

 

[Andy™]

very vague questions, and somewhat basic for someone who should be competent? as above, what qualifications / experience do you have?

 

[toroid19]

I have been an electrical transformer designer for 20 years. I have rewired all of the houses I have lived in in both the UK and Canada and I have had them all successfully inspected over a 30 year period. I have a bachelors degree a Masters degree and a doctorate.  I have not looked at an installation for at least a decade so I am rusty so before I go blundering about I thought I might get another opinion since the worl has moved on.

 

[Andy™]

yes, the world has moved on, you might have plenty qualifications, but you do not appear competent to be doing this. maybe go do a 17th ed course to get upto date on current regs before doing the job? there are a lot of things changed in 10 years, too many to try and tell you on here. do you have a copy of the current regs?

commercial may need RCD's, its moving more towards risk assessment based, so you may need a good reason not to. bonding still needs done, although the requirements of that havent really changed

 

[Essex1]

Ok well generally speaking all sockets up to 20A must have RCD protection. 32A if likely to feed outside portable equipment. This is detailed in 411.3.3. 

Your cable design is calculated taking many things into account so you have given no where near enough info to give you sound advice. 

As Andy says a 17th edition update course is a must. Industrial installations if done wrong would leave the business owner in all sorts of legal problems if someone was to get hurt of a fire were to start due to poor workmanship.