What is going on with SPD's and A3

[Mark1969]

We were all told that SPD's were mandatory under A3 from September last year and even sat through the webinar spelling it out. I work an area with lots of overhead lines, I ran out of the Type 1's I bulk buy online and could not find any local wholesalers who stocked them (type 2 yes but no type 1). It seemed strange that it is now mandatory to fit them but you can't buy them at the wholesalers.

Fast forward a few weeks and I am sitting in an Aico fire alarm training session and I raise this point afterwards with the trainer. His response was that no one stocks the expensive Type 1's because they aren't mandatory, they realised that making it mandatory was a stupid idea and they pulled that amendment.

So what is going on? Did they pull the amendment? Is the amendment still in force but being largely ignored? What's going on with this...

 

[Mark1969]

I don't know why you think you can't fit smoke alarms without an SPD.
I don't want to cause you to faint but I have added smoke alarms to VIR lighting circuits and lighting circuits with no CPC. In the former case the house was a fire waiting to happen and I felt the family waking up was more important than anything else.

That would be the new 443.4.1 See above post for how Napit instructed us to interpret it.

 

[pc1966]

The OP is right that the original requirements basically made an SPD mandatory for mains alarm systems, which might have been a sound engineering decision but of course caused a serious issue for most practical situations so they dropped the (ii) section of it in May 2023. You can get the BS 7671:2018+A2:2022 Corrigendum (May 2023) from here for free as a PDF document:

Updates to 18th Edition - BS7671- IET Wiring Regulations

Keep checking our updates page for urgent technical changes or editorial corrections.

tinyurl.com

 

[pc1966]

As well as that, the AM2 dropped the risk assessment for SPD which was introduced in the original 18th, again made practical sense as nobody will know the cable routing feeding a given site in many cases, but personally I would still advise folks to have SPD fitted if they have overhead lines feeding the site due to the greater risk of induced energy and the amount of valuable electronics folks have, even if they don't realise it (such as LED lights, most white goods having electronic controls and always-on, boilers with electronic controls, TV/PC/broadband, etc)

In such cases type 1 are a better choice as they can cope with more energy, but as you say they are not commonly stocked as the majority of installations do not have a Lightning Protection System, not do they have overhead lines feeding them. Yes, in the countryside they do, but that is small compared to the number in town and cities nearby.

Also type 1 are not cheap, both due to less demand and due to the much bigger devices needed to cope (typically 10x the energy in the 10/350us pulse compared to the 8/20us pulse). We got some directly from here:

Mains Products - Kingsmill Industries

MAINS SPDs TO BS:EN 62305 Device selection information where External Lightning Protection is installed SPD PRODUCT SELECTOR Interactive...

kingsmillindustries.com

Early on they only had the double-module type 1+2 at vast expense, but they also now offer single-module ones and slightly less painful prices. An advantage of the double-width ones are the two terminals that makes Kelvin style connections easy and effective.

Even a type 2 SPD are better than nothing, but chances are they would fail after one high energy event and of course nobody ever monitors them, just as nobody ever checks their RCD (other then EICR time, and not even at that sometimes...)

 

[pc1966]

Also what I like about those devices, such as this model for single-phase TT (or TN) supplies:

Type 1+2 Lightning Current and Surge Arrester (KM1+2-12.5-1+1 SC) - Kingsmill Industries

System: 1 Phase TT/2 Pole Nominal Voltage: 230V AC

kingsmillindustries.com

Is they are suitable for use with a 160A supply fuse so no added MCB and they can be put in a small DIN box before the CU so no issues of busbar compatibility. However, the single module terminals won't take 2*25mm for Kelvin style connections so for a DIN box you need to be looking at some other means of connecting to the post-isolator switch tails.

 

[Risteard]

That would be the new 443.4.1 See above either post for how Napit instructed us to interpret it.

They're not infallible. If this was since the Corrigendum then I would suggest that whoever started it is simply incorrect, regardless of which body he represented. Also Type 1 SPDs are only really relevant where there is an LPS, and would still need to cascade down to Type 2 etc.

 

[timhoward]

That would be the new 443.4.1 See above post for how Napit instructed us to interpret it.

ah but that bit was dropped in a subsequent update. @pc1966 beat me to it - see above.

They rambled on for a bit but made it clear we had no choice but to fit SPD's even in single dwellings

Napit can say whatever they like (I'm a member too btw) but the regs are clear that with the exceptions in the first part of 433.3.1, the owner of an installation can still essentially opt out if they want to. Napit advice at the A2 Expo in Manchester was to get a signed declaration from the owner in such circumstances.

The last page of appendix 16 makes interesting reading, suggesting that more prominence is given to voltage limiting characteristics of an SPD rather than the energy it can withstand. I take that to mean that a Type 2 will still protect equipment if there's a direct lightning strike outside, but may be useless afterwards.
It occurs to me that one could replace a few type 2 modules before the price of a type 1 has been reached.

Of course, if I fit any new CU I fit surge protection. Where possible I add and SPD if adding a new circuit but I won't die on my sword over it. A reality of domestic sparking is that we have to be pragmatic when extending or altering existing installations and decide where we draw the line. At the end of the day, the regs are not statutory (I'll get my coat)

 

[Mark1969]

My apologies for the slow reply. I wasn't being rude, family matters overtook me and I am only just getting back to business as normal.

Well, my question was answered. Thanks for the info and taking the time to link the Corrigendum.