Type 1 SPD at Mains Intake Advice Please on a TNCS

[John-]

Hi

Have done some additions to an existing multibuilding non domestic site. I noticed no SPD on the mains intake side, they are in a reasonably high lightning strike area. So suggested they should have one. Did some research and was going to use the Hagar SPA4501 along with the metal IU4 enclosure.

But in order to follow the guidance it has to be fitted as close to the mains intake as possible. And i am a bit concerned about the only protection for a metal enclosure, in the mains cupboard, being the DNOs 100A fuses.

The installation consists of the three fuses in the head then the earth and Nutural coming out in 25mm, into a 4 pole rotary, plastic 100A Isolator. Then the tales come out of the load side of the isolator in single insulated, fine stranded 25mm that leads off in Copex to the Sub Mains Dis boards a few feet away.

Was thinking i could install another set of 25mm tales in the load side of the Isolator, then install the SPD directedly below the isolator. So only protection for it / cables is the DNO fuses.

Seeing as the IU4 is metal, was wondering if to install the metal housing within a separate plastic enclosure to prevent a access to touch without a tool?

The cupboard is not locked. It is a small lean to building with large doors, it only contains the meter and the distribution equipment for the site. So a meter reader, IMHO, could be at risk if the case had short. I realise that any short so close should blow the fuse quickly enough, not like a TT situation. So am I being too cautions?

Hypothetically if this was a TT i guess it would have to be installed after the Main RCD?

Thnaks

JOhn

 

[Rockingit]

is this a 3ph intake into a 3ph system or 3 x singles? Slightly confused.

Either way, my gut tells me you may be overthinking this.... if the board/s are only 'a few feet away' then fit what's appropriate at that point. If there's no other CPD in between the intake and that first board then the DNO's fuses are doing that job regardless of any other devices you install.

 

[John-]

it is 3 phase.

 

[Rockingit]

So it's INTAKE > 100A ISO > 25mm Tri-rate > First DB?

 

[John-]

yep

 

[Rockingit]

If so.... swap out the 100A ISO for an enclosure for the SPD which has an incoming insolator. Same-ish footprint.

 

[John-]

@Rockingit not sure what you mean. Why would i remove the Isolator? It serves the purpose of allowing us to work on the Dis boards in the mains room? I should have also mentioned that the Isolator feeds two boards, one for general kit, and the other board via a changeover switch for essential services fed via on site generator. In the event of power fail, they manually switch the three position switch to generator that isolates the mains from the 2nd dis board, and introduces the feed from the generator - then they start the generator.

With respect to the SPD I'm just wondering if i need to install a plastic enclosure with the metal one in. I 'think' i am being too cautions?

John

 

[Rockingit]

@Rockingit not sure what you mean. Why would i remove the Isolator? It serves the purpose of allowing us to work on the Dis boards in the mains room? I should have also mentioned that the Isolator feeds two boards, one for general kit, and the other board via a changeover switch for essential services fed via on site generator. In the event of power fail, they manually switch the three position switch to generator that isolates the mains from the 2nd dis board, and introduces the feed from the generator - then they start the generator.

With respect to the SPD I'm just wondering if i need to install a plastic enclosure with the metal one in. I 'think' i am being too cautions?

John

You'd still have your isolator. HOWEVER...... with this new information, my guess is that you actually need the SPD downstream of the dual supply?

 

[John-]

Suppression (Type 1) needs to be close to the mains supply, to protect the site from external influences.
Re reading what you wrote earlier: -

"If so.... swap out the 100A ISO for an enclosure for the SPD which has an incoming insolator. Same-ish footprint."

Do you mean provide an SPD and Isolator, in the same enclosure?

 

[Rockingit]

Do you mean provide an SPD and Isolator, in the same enclosure?

Yes.

 

[pc1966]

I would put the SPD in a metal DIN enclosure. If something goes wrong / big strike they might get very hot (though they have solder links to disconnect in that case).

If you can run the cables (25mm tri-rated?) from isolator to DIN box to board then use the sort with the double connections so they have practically no additional inductance. This is the sort I have used (TN-S style):

Type 1+2 Lightning Current and Surge Arrester (KM1+2-25-4+0 SC) - Kingsmill Industries

System: Three Phase TN-S & TN-C-S/4 Pole Nominal Voltage: 230V AC

kingsmillindustries.com

They also do one more like the common sore with different N-E protection for TT systems:

Type 1+2 Lightning Current and Surge Arrester (KM1+2-25-3+1 SC) - Kingsmill Industries

System: Three Phase TT/TN-S/4 Pole Nominal Voltage: 230V AC

kingsmillindustries.com

They are OK with 125A supply fuses for "V wiring" (Kelvin 4-ware style), not requiring any additional protection.

 

[John-]

Thanks @pc1966 I already have the antisurge device. Will look at ours next time. I was going to just spur off the isolator, hence the lugs so the isolator would have three sets of cables coming out - two to the loads and one set to the SPD. If there was any doubt about the terminals in the isolator taking the three sets of lugs, i was going to use Henley blocks and use insulated and sheathed tri rated cable - or just tales. I need to go back to site and check the options.

 

[pc1966]

OK!

Just to add if you had space for the likes of the Hager JK116EA3 (assuming it has to meet amendment 3, I used the glazed one for industrial site) you could put in a 50A D-curve MCB for the SPD if worried about the DNO fuses (or want a quick means of isolation for IR testing) and you could also put in some linked DIN terminals to allow 4 connections for each of L1-3 & N:

• power in
• SPD MCB feed
• board #1
• board #2

All with minimum distance and inductance to the SPD.

The likes of these terminals allow 35mm cable to be attached and are rated at 125A, but I have not checked if they clear the DIN box (can do later):

1SNK516010R0000 | Entrelec Grey ZS35 Feed Through Terminal Block, 35mm², ATEX, 1 kV ac | RS Components

uk.rs-online.com

These are the jumper bars to link an adjacent pair of terminals together:

1SNK916302R0000 | Entrelec JB16 Jumper Bar for Terminal Block | RS Components

uk.rs-online.com

You get them up to 10-way but not from RS, think I got mine from these folks:

Entrelec 1SNK916310R0000 JB16-10 10 POLE JUMPER BAR | Kempston Controls

Entrelec 1SNK916310R0000 JB16-10 10 POLE JUMPER BAR part of DIN Rail Terminal Blocks and Accessories, distributed by Kempston Controls. Shipping to 240+ countries worldwide.

www.kempstoncontrols.co.uk

 

[telectrix]

as it is non-domestic, you don't need to use a metal enclosure. use plastic.