UK SPD OR NO SPD?

[Thrashman]

Hi everyone ,

Only my second post and hoping to get some information on installing an SPD Type II incorporated within a new consumer unit upgrade I will be doing next week.

With the new 18th edition regs I’ve been generally installing RCBO consumer units with integral SPD as standard .

The house I’m about to work on has 2 consumer units, The one that is going to be upgraded that has no RCD protection ( bathroom lighting and new sockets being installed ) hence new board ,
Both consumer units are supplied via meter tails split at Henley block,

Now the newly installed board DB1 that supplies the kitchen sockets and an induction hob and oven, already has and Incorporated type 2SPD installed,

This may sound like a stupid question, but will Installing a secondary SPD TYPE 2 incorporated within the consumer unit DB2 I intend to upgrade be beneficial as their is already one installed within DB1?

If so, then great I’ll go ahead and install one as usual, if not, then will install a mains switch consumer unit loaded with RCBO’s with no SPD?

All opinions and comments are appreciated and thanks in advance.

 

[happysteve]

My understanding is the SPDs protect downstream devices and installations.

So having a type 2 SPD in DB1 will not protect anything in DB2 (or anything supplied from DB2).

If you want/need to provide surge protection for DB2, then carry on as you were and fit a board with one in.

 

[Pete999]

Hi everyone ,

Only my second post and hoping to get some information on installing an SPD Type II incorporated within a new consumer unit upgrade I will be doing next week.

With the new 18th edition regs I’ve been generally installing RCBO consumer units with integral SPD as standard .

The house I’m about to work on has 2 consumer units, The one that is going to be upgraded that has no RCD protection ( bathroom lighting and new sockets being installed ) hence new board ,
Both consumer units are supplied via meter tails split at Henley block,

Now the newly installed board DB1 that supplies the kitchen sockets and an induction hob and oven, already has and Incorporated type 2SPD installed,

This may sound like a stupid question, but will Installing a secondary SPD TYPE 2 incorporated within the consumer unit DB2 I intend to upgrade be beneficial as their is already one installed within DB1?

If so, then great I’ll go ahead and install one as usual, if not, then will install a mains switch consumer unit loaded with RCBO’s with no SPD?

All opinions and comments are appreciated and thanks in advance.

Is the Garage CU fed from the House CU?

 

[happysteve]

Is the Garage CU fed from the House CU?

No Pete:

"Both consumer units are supplied via meter tails split at Henley block,"
Source URL: UK - SPD OR NO SPD? - https://www.electriciansforums.net/threads/spd-or-no-spd.184541/#post-1615350

 

[SparkyChick]

It's not as straightforward as it first appears and this is my very limited understanding.

Most SPDs are purely passive devices consisting of MOVs. When you install one, it will effectively be connected across the line and neutral of the incoming supply and as such will provide a limited amount of protection to anything connected to that supply.

However, it's ability to do so is governed largely by the length of the cables, so if they are relatively short and within the SPD manufacturers guidance it may provide adequate protection, but if they are too long they may not.

You should perhaps refer to the manufacturers data sheet and see what it says, but I wouldn't necessarily be installing a second SPD in the scenario you have.

 

[Pete999]

No Pete:

"Both consumer units are supplied via meter tails split at Henley block,"
Source URL: UK - SPD OR NO SPD? - https://www.electriciansforums.net/threads/spd-or-no-spd.184541/#post-1615350

Missed that dooh, !

 

[happysteve]

Missed that dooh, !

It's easily done!

 

[Pete999]

It's easily done!

Especially if you have just woken up from a Nap on the sofa! We used to fit up front SPDs (FURZE made them they had their own enclosure) and needed to be fused see the cable CSA reccomended in the OSG

 

[Strima]

If you can fit an SPD close the the Henley blocks, this would cover the whole installation. Some manufacturers don't require over-current protection for their SPDs.

 

[Mike Johnson]

My understanding is that SPD's supply a path to earth with the least resistance compared to the installation, if that is correct, do you have a main CPC in DB2? As said above installing an SPD at the Henley block would cover the whole installation.

The only SPD's I'v seen that do not need OCPD are the units with one built in?

 

[Strima]

The only SPD's I'v seen that do not need OCPD are the units with one built in?

Some manufacturers are happy if the suppliers fuse is blow a certain rating that no OCPD is required.

Last Wylex SPD I looked at if the fuse was <100 amps then no protection required.

 

[Mike Johnson]

Just had a look at the Wylex range on page 26 here: https://www.wylexreasons.co.uk/Content/pdf/Wylex DCP catalogue Feb 2018.pdf and can't find anything different to any other SPD, can you provide a link.

 

[Strima]

Just had a look at the Wylex range on page 26 here: https://www.wylexreasons.co.uk/Content/pdf/Wylex DCP catalogue Feb 2018.pdf and can't find anything different to any other SPD, can you provide a link.

Bottom of page 2 TN-S system: https://www.tlc-direct.co.uk/Technical/DataSheets/Wylex/REC2SPD_combined.pdf

 

[Mike Johnson]

Seems to require a back up fuse to both types of installation? 80A for V wiring and 100A for Stub wiring or am I reading it wrong? (Yes I was)

Ah Ha the diagram below seems to indicate that if F1 is below 125A F2 is not needed, very obscure way of denoting it though.

 

[Strima]

Seems to require a back up fuse to both types of installation? 80A for V wiring and 100A for Stub wiring or am I reading it wrong? (Yes I was)

Ah Ha the diagram below seems to indicate that if F1 is below 125A F2 is not needed, very obscure way of denoting it though.

I had to read it a few times but that's how I see it. Makes sense as you need the SPD as close to the incomer as possible with the shortest possible leads, an OCPD would be another weak link in the chain.

 

[Mike Johnson]

In truth, I am a bit sceptical about SPD's, especially if you are hit multiple times, which has happened on more than one occasion to our place, even though we have SPD's in place, I still unplug everything when a storm hits and when we leave the place for any period of time.

 

[Strima]

One SPD covering the whole installation won't protect sensitive equipment.

Type 1 for atmospheric i.e lightning
Type 2 for supply surges
Type 3 for sensitive equipment

Types 1 & 2 to protect the fixed installation, Type 3 to protect equipment.

An SPD won't stop a surge but reduces it's impact to more manageable levels. So Type 1/2 at source then Type 3 at socket-outlets.

 

[Mike Johnson]

All true, that's why I unplug everything when a storm is brewing, the coming of a storm is usually indicated by the TV Satellite picture pixelating, time to turn it off and unplug open a bottle, go to the window and watch the show, one hit a few years ago and was close enough that it unlocked my car and turned on the dashboard and lights.

 

[pc1966]

All true, that's why I unplug everything when a storm is brewing, the coming of a storm is usually indicated by the TV Satellite picture pixelating, time to turn it off and unplug open a bottle, go to the window and watch the show, one hit a few years ago and was close enough that it unlocked my car and turned on the dashboard and lights.

TV pixelating is down to the heavy rain droplets as that has a big effect on signal strength (for satellite TV, terrestrial broadcast in UHF is hard to impact that way) and thus picture quality.

Depending on where you are that means either very wet, or lighting AND very wet...
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The real issue is inductance, as for a short lighting pulse that will be a far higher impedance then the resistance we know and love/hate for AC power!

The IET says max distance for SPD wiring is 1m, but recommands less than 0.5m. So probably if the length from the Henley block (or whatever) to the SPD inside the CU with them fitted including internal CU wire lengths is below 0.5m you are fine.

If you are in an area of high risk, say you have overhead feeder cables, etc, then you ought to have a Type 1 SPD first then anyway as they can cope with a lot more energy than the Type 2 used for your typical board.

As already mentioned, most have a maximum protection fuse/breaker limit. For many SPD it is around the 100A-160A region so the DNO fuse is usually sufficient. Some it is less and you will see a dedicated 32A (or similar) MCB just for the SPD.

Some have the option for "V wiring" (Kelvin connection) where there are two terminals for each phase and neutral connection so you route the power "through" the SPD to minimise series wiring inductance. For that there may be an additional current limit based on the size of the internal conductor path as it may not be up for more than 80A/100A or whatever, even if the SPD can cope with a 160A supply fuse for absolute worst-case fault conditions.

 

[Mike Johnson]

Yes commonly called Rain Fade, the size of the main board being a four zone vertical unit it's very difficult to get the SPD wiring below 500mm, the dedicated MCB for the SPD is 20A, underground feeder cables, have we not had the conversation before?