The £1300 AFDD consumer unit

I will look into those two BS/IEC later, once I have got them. As you say the results will be mighty interesting (again)!

Unlike I am not a fence sitter like Graham I have objected the DPC to the mandating of AFDDs leaving them for the designer and client to decide if they accept the recommendation for them to be fitted. I did this because of the high cost and at best the doubtful benefits as I have not seen any fire statistics where the cause of the fires relates to continuous arc faults. I believe that a properly constructed installation with RCD protection with T&E cables does not need AFDD protection as any arcing or carbonisation of the cable will be detected by a 30mA RCD long before an AFDD. The same for cables in steel conduit, SWA, FP200 type cables. Also I have objected on the grounds that people with limited financial means needing a consumer unit change for safety reasons may be able to scrape together the £300 to £400 but not £2000 so mandating of AFDDs will adversely impact on public safety. I would prefer to see the banning of PVC cables and the mandating of XLPE cables.


If I believed that AFDDs had even a minimal increase in fire safety I would fit them in my own house regardless of cost. I have no plans to install AFDDs. 


As for SPDs I am pro installation. I have submitted a DPC suggestion to say move the requirement for Type 1 SPDs in Part 5 where they are required for buildings with an LPS to Part 4 so all the requirements for SPDs can be found in one place. The mandate them for preservation of life and where safety services are installed. For all other installations they should be a "shall" unless the owner of the installation states they do not want them and they accept the risks to damage to equipment and any consequential losses. Then delete all the references to risk assessment and the Flash Density map as the cause confusion with the difficulty in obtaining accurate information to put in to the calculation. The cost of SPDs have come down and they are being fitted as standard my consumer unit manufacturers so they are cheap insurance. 


I have a Type 2 SPD on the tails of my own installation as you can see on the Wylex thread. I also had already protected all my IT kit on my desk with a decent SPD protected extension lead with a SPD for the phone line that plugs in and out of the unit. I did this after a thunder storm that screwed my modem along with 2 others in my road. I found this out after heading to PC world on a Saturday morning and stopping at a neighbors house who is an electrical engineer if he wanted anything whilst I was there, he said  yes that is the third one after last night, I just thought it was my cheap kit did not even think it was weather related.  Overhead line with no evidence of a direct strike but probably an induced voltage on the line. Now and again I have had my Fluke PQA when on charge. Looking at the oscilloscope screen live I can see that the supply waveform looks nothing like a smooth sign wave, flat top, fast spikes, short duration gaps etc. 


We will have to wait for AMD 2 to be published to see what goes in to the new book post the DPC process?

I'm with John on the AFFD thing. The SPDs? I'm not so sure.

Here is a poser for those concerned about insurance companies - Say a SPD equipped installation is submitted to repeated surges of high magnitude in rapid succession such as a heavy storm during the night, the 1st strike 'blows' the SPD and is followed by successive strikes within seconds.

Damage is caused to consumer electronics as a consequence.

Who is responsible for paying out? AND - How can it be proved that the SPD actually saved the kit 1st time round but was unable to do so afterwards due to the nature of it's one-shot activation?

Interesting question regards the insurance company.


My take on it, is:

• without the SPD fitted, the insurance company could say that the cost of damage clearly shows that SPDs should have been fitted in accordance with BS 7671. Since they weren't, perhaps no payout, or a letter saying "We'll pay out this time, but not next time if no SPDs fitted."

• with SPDs fitted, the get-out isn't there. I guess the insurance company wouldn't want to get tangled up with the SPD manufacturer, so they just pay out? At least the owner of the installation can say they have all reasonable precautions in place to help prevent the event?

I've had a few such occurrences, where SPDs (or other precautions) were in place, and damage was caused by switching events or similar during large construction contracts causing damage to equipment - these paid out. I've also been involved in another case of switching events during supply cut-over caused extensive damage to remote terminal unit electronics, no SPDs (or other precautions) fitted, and it was declared the design specification was inadequate - no pay-out.