Why are the two poles of the Hager SPD rated differently

spud1 · Jan 28, 2019

So I was installing a new split load Hager DB (with the integral SPD) and noticed that the SPD cartridges connected across the neutral and line poles of the SPD were rated differently. Is there a reason for these different ratings?

Spud

Pete999 · Jan 29, 2019

spud1 said:
So I was installing a new split load Hager DB (with the integral SPD) and noticed that the SPD cartridges connected across the neutral and line poles of the SPD were rated differently. Is there a reason for these different ratings?

Spud

Any chance of a piccy of the SPD rating plate, when you say different ratings, ratings as in what, volts amps etc?

spud1 · Jan 29, 2019

Pete999 said:
Any chance of a piccy of the SPD rating plate, when you say different ratings, ratings as in what, volts amps etc?

[ElectriciansForums.net] Why are the two poles of the Hager SPD rated differently

Deleted member 26818 · Jan 29, 2019

The neutral being connected to earth, is more likely to suffer from surges caused by lightning strikes.

spud1 · Jan 29, 2019

spinlondon said:
The neutral being connected to earth, is more likely to suffer from surges caused by lightning strikes.

gotcha. That makes sense. Cheers

Carl S · Jan 29, 2019

The ones I’ve had dealings with had three values, operating voltage, let through voltage and kA handling. They were for industrial installations.

westward10 · Jan 29, 2019

Have you retrofitted that or did it come with the board?

spud1 · Jan 29, 2019

westward10 said:
Have you retrofitted that or did it come with the board?

It came with the board but looks retrofitted right ?

MJPD29 · Jan 29, 2019

Never fit hager but they look like a right mess out of the box! Would make your good work look bad

Deleted member 26818 · Jan 29, 2019

I’m a bit surprised that the isolator was not already connected.

spud1 · Jan 29, 2019

spinlondon said:
I’m a bit surprised that the isolator was not already connected.

It was! The crimped 6mm tailing connecting the main switch to the SPD is HAGERS!

Ian1981 · Jan 29, 2019

Are the SPD’s fused or at least the line internally,or direct from the isolator where fault protection is then through the dno fuse?

Deleted member 26818 · Jan 29, 2019

spud1 said:
It was! The crimped 6mm tailing connecting the main switch to the SPD is HAGERS!

Is that the main switch?
So if the main switch is off, there’s no surge protection.

spud1 · Jan 29, 2019

Ian1981 said:
Are the SPD’s fused or at least the line internally,or direct from the isolator where fault protection is then through the dno fuse?

The DNO fuse is the only upstream OCPD, nothing within the board. I think the current ratings of the cartridges and base must take this into account and I guess the board has been tested and the 6mm tails are deemed as suitable for current carrying capacity for the nano seconds that the SPD is in closed circuit. These are all assumptions you understand!!

spud1 · Jan 29, 2019

spinlondon said:
The neutral being connected to earth, is more likely to suffer from surges caused by lightning strikes.

Been thinking on this one. Presumably you mean its more likely to suffer than the line in a PME installation where the multiple earth's at the poles are more susceptible to indirect strikes? But at the SPD in the consumer unit of the TNCS installation the neutral and earth are at the same potential so how does the SPD dump voltage from the neutral to the earth if they're are essentially the same conductor at the same potential ?