12-02-2015, 10:22 AM
With a TT system all circuits must be RCD protected. The CU I illustrated is typical of current domestic practice. It's the cheapest way of meeting 17th ed. The better way is a simple main switch with an RCBO for each circuit. The only downside is expense.
Not sure what to say about the damp conditions. I assume there's no water falling directly on the CU so IP rating isn't very important. The problem is damp atmosphere hence corrosion and tracking. A plastic bodied CU will be better under these conditions. I would certainly stand it off the wall by 0.5" or so. Some bits of plastic conduit would do for that. What I'm really worried about is how the MCBs etc will fare under damp conditions. Might be worth an enquiry to MK. My preferred solution would be to put just a main switch (or even a junction box) in the cellar and the CU in a dry location. A tiny bulb or small resistor, perhaps 2 or 3 watts dissipation, inside the CU would be an unconventional solution to damp. I don't know if it's a good idea.
Ancient paper insulated cable is actually very reliable unless it's been physically damaged. I've seen jointers working on stuff that's well over 50 years old and inside it looks as good as new.
Not sure what to say about the damp conditions. I assume there's no water falling directly on the CU so IP rating isn't very important. The problem is damp atmosphere hence corrosion and tracking. A plastic bodied CU will be better under these conditions. I would certainly stand it off the wall by 0.5" or so. Some bits of plastic conduit would do for that. What I'm really worried about is how the MCBs etc will fare under damp conditions. Might be worth an enquiry to MK. My preferred solution would be to put just a main switch (or even a junction box) in the cellar and the CU in a dry location. A tiny bulb or small resistor, perhaps 2 or 3 watts dissipation, inside the CU would be an unconventional solution to damp. I don't know if it's a good idea.
Ancient paper insulated cable is actually very reliable unless it's been physically damaged. I've seen jointers working on stuff that's well over 50 years old and inside it looks as good as new.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
