Surge protection devices without overcurrent protection

Hi,

I don't think Regulation 524.4.5 exists in the latest version of BS 7671, unless I'm mistaken?

As per the datasheet below it looks like the SPD relies on upstream fuse protection (<=100A gG required).

Kind regards, 

Interesting. thank you for finding that.  It does say that, and it says its a Gg so  That must be the incomer?  So, I wonder if that regulation for 'overcurrent with respect to short-circuit currents is being met?  It does still exist in the brown book. And, I might stick my neck out and question as much as 100A protection in terms of disconnecting the device.

I'm sure the manufacturer wouldn't have done anything untoward, but I'm designing for a TPN thatched residence right now and I must turn every stone.

Zs

Bh said:

I don't think Regulation 524.4.5 exists in the latest version of BS 7671, unless I'm mistaken?

No, but 534.4.5 does.

Apologies, my typo.

Zs said:

Any views? Where do we stand with that then, in terms of compliance as installers?

I would seek written confirmation from the manufacturers that the device is compliant.

As an aside, like other SPDs, this one has a red/green flag, but what use is that to anybody when it is hidden under an opaque cover?

Their website states product description states 'with No MCB required'. 

As I understand it, such devices are meant to have in-built overcurrent protection (if only a blob of solder type "fuse" which when opens also releases a spring lever that triggers the red 'replace' flag) - the upstream gG fuse is only needed for backup protection (like making M6 MCBs good for 16kA).

   - Andy.

There certainly are designs with what is in effect an combination indicating fuse and thermal trip in series internally, and even versions where the indicator actuates a contact that can sound an alarm. 

~Does the little circuit in the side indicate anything of use ?
I'd expect and hope that the 100A fuse is not normally the thing that pops - if it was, that would be very awkward in many  situations.
Perhaps on a supply with a massive PSSC and an unlucky dead short failure of the MOV - but mostly MOVs fail by leaking more and more and then becoming unpleasantly hot - hence the thermal trip aspect to the internal fuse - the blob of low melting point solder alluded to above.
Of course the main objection is none of this, but rather that it appears to be pink ! 
Mike

Personally I would return it back to FuseBox and explain the reason.  Get a replacement from Navitas which has SPD type 2 with MCB and job done.  

The main issue here is the responsibility is with the designer and not really the installer.  Now in some smaller companies that may well be one and the same person.  Thus in that scenario they will normally rely in what the Manufacturer states HOWEVER and there is always an However or Caveat.  Some manufacturers are being lead by their marketing and sales department and the regulations and product specifications are somewhat slower to catchup.  A prime example of this would be battery storage and inverters in UK lofts.  Previously seen as OK by the marketing and sales department but when engineers start to discuss the issue and apply their engineer judgment then the industry is told that placement in the loft in unwise or a complete no-go.  There electrical industry I’m the UK is constantly evolving and thus so will the rules.

Back to the subject at hand.  Does the SPD really need an MCB?  In my opinion yes.  Some reason (not all reasons) listed below
 - MCB allows for safe isolation when the SPD needs replacing
 - MCB provides overcurrent protection for the SPD
 - MCB will be your fall back when the SPD fails due to fault or it gets to the end of it’s life cycle

For the real lowdown I would recommend "Kirsty at SPD".  Kirsty Johnson, Technical Sales Director at Surge Protection Devices (SPD), a company specialising in surge protection products. She has put out a lot of information on the internet and well worth at least 15 mins or anyone time.

Her linkedin profile is below

linkedin.com/in/kirsty-johnson-5a07ab71

Additional reference is one of the many Navitas videos by Will Winter

https://youtu.be/94tJ-lpo6rY?si=ydL0wgGmSCiObWPs

As others have said in the past.

Trust BUT verify

Back to the subject at hand.  Does the SPD really need an MCB?  In my opinion yes.  Some reason (not all reasons) listed below
 - MCB allows for safe isolation when the SPD needs replacing
 - MCB provides overcurrent protection for the SPD
 - MCB will be your fall back when the SPD fails due to fault or it gets to the end of it’s life cycle

On the other hand the MCB may "nuisance trip" - given the purpose of an SPD is to momentarily short-out L/N/PE - a simple thermal only device may be more reliable in that respect. Safe isolation can be done by other devices (a DP isolator might be somewhat better than a single pole MCB) and as long as there's overload protection built-in to the SPD aren't the other two points covered?

what about these? shop4electrical.co.uk/.../6693-wylex-rec2spd-18th-edition-standalone-rec-unit-with-100a-switch-disconnector-isolator-type-2-surge-protection-device-in-insulated-enclosure-5013601107127

    - Andy.

Would the SPD type 2 overload protection still work when the SPD reaches the end of it's lifecycle?

Would the SPD type 2 overload protection still work when the SPD fails due to fault?