Napit Codebreakers #14

Napit Codebreakers #14

Need help with cracking those EICR codes? The technical team at NAPIT, with the help of the 18th Edition Codebreakers publication, answer your latest coding queries. Click on the photos for a closer look!

NEIL WOODMAN: I found this shocker on an EICR. The shower was wired int othe ring main MCB, the cooker and hob wired directly to the CU, the hob live extended with a piece of melted 1MM2 cable – plus, there was no earth sleeving etc.

Most of us will have seen this on an EICR at some point, it’s either client DIY or very inexperienced labour. The list is excessive for this one, so I’ll try and break it down by different issues. I’ll also assume it’s a sub-board as there appears to be no meter tails or lighting circuits present.

1. Shower circuit connected to the Ring Final Circuit (RFC) OCPD. Separate final circuits should be connected to separate ways in a CU/DB. This can be mildly abused for radial socket circuits, lighting circuits, and lighting circuits supplying a smoke alarm, or a hob and oven. It is to prevent the energizing of a circuit that it is required, for some reason, to be isolated. Showers fed from the same MCB as a RFC show a poor understanding of BS 7671. It’s likely that the shower exceeds 7kW, so the shared 32A MCB and combined RFC loading is likely to exhibit unwanted tripping in times of high load and usage. Other than the aforementioned requirement for circuits being on their own way in a CU/DB, we need to make a judgement call as to whether this would attract a C2 or a C3. Although not an ideal design, the potential for danger may be low. The cable containment of the shower cable and absence of an RCD are also a problem. Without knowing the Earthing and bonding (Main and Supplementary) requirements, it’s hard to call if the RCD warrants a C2 or C3, so I’ll assume all bonding is in place and there is no RCD protection from the main CU, which offers up a C3.

2. The cooker and hob appear to be fed from the same 40A MCB on the right of the picture, which isn’t a crime in itself and depends on loading requirements of the equipment to say if it is underrated. The 1mm2 extension of the cable is strange though, as it appears there is enough slack cable to reach the MCB. It may be that the MCB doesn’t have the capacity for both the oven and hob conductors, which isn’t something I can say from just a picture. The 1mm2 cable is definitely underrated though, with signs of thermal damage. Cable containment of the oven supply is also an issue.

Where Neil has stated the oven is wired directly to the CU, I‘m assuming he means that there is no cooker connection unit and/or cooker connection plate, and the supply cable exits the wall and is connected directly to the oven. Although not best practice and poor workmanship, the lack of a cooker isolation switch isn’t technically required, as the MCB and main switch both offer isolation when needed (reference Table 537.4). The lack of a cooker connection plate is not a Regulation issue, provided when not connected to an oven or hob, the cable is adequately terminated and supported, but does have limitations on maintenance, if the cable becomes damaged too close to the wall to be repaired or replaced.

There are mixed equipment types, but they appear to show no signs of thermal damage. The socket-outlet circuit appears to have no RCD protection; if the sockets are supplying equipment outside, this would be a C2, otherwise a C3. If the inspector has good reason to suspect sockets-outlets are being used to supply equipment outside, but they’re not at the time of the EICR (if an electric mower, strimmer, or pressure cleaner, etc., are stored nearby and obviously being used at some point, for example) it is more than acceptable to give a C2 code for no RCD. I’m assuming this isn’t a commercial/industrial scenario, where RCD protection for individually marked socket-outlets may be omitted, with the presence of a Risk Assessment in accordance with 411.3.3.

JUSTIN NEEDHAM: This one would have given Mr Rat a toothache! Thoughts of the new regulations for AFDDS spring to mind.

The threat from vermin damage of any kind is always a problem, which can be exasperated for installations in either rural locations or where access for vermin is unavoidable. In circumstances such as these,where damage can be expected, careful choice of the wiring system to limit or deter vermin should always be determined. Where damage has been found, especially in extreme cases such as this one, the potential for fire can be high, as well as increasing danger due to access to live parts. The use of metal/plastic conduit systems, trunking and armoured cables are all useful in protecting against vermin, but not always practicable, especially in domestic scenarios. After repairs are carried out, the installation of AFDDs could disconnect the circuit before any future damage could initiate a fire risk. AFDDs, however, won’t remove the vermin, so a call to a reputable pest controller would also be a good idea for the client.

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