Curious - Hager CU and SPD

[LeeJC]

Afternoon All,

Purely a curiosity question this but -
Hager and most other CU manufacturers in the past had a secondary protection device (MCB) upstream of the SPD.
The RCBO board I've bought now takes directly from the 100A incomer and their literature states no upstream protection is required.

Does anyone know what changed from a design perspective to enable this change?

Like I say just curious around what technology has now been integrated into the SPD (if any) that's allowed the removal of this upstream protection.

Cheers
Lee

 

[Risteard]

I don't recall Hager every having a protective device upstream in most instances.

 

[EFLImpudence]

Nor any other manufacturer.
Are you confusing a simple isolator near the meter.

Also, how could a device upstream of the CU be a secondary protection device?
Also, SPDs are only a recent requirement.

 

[LeeJC]

Residential SPD board

ready to go residential SPDF boards support need for best practice

hager.com

​

No secondary upstream protection devices required​

In the past, surge protection devices required an MCB or fuses in the consumer unit to provide backup protection using one of the outgoing ways. Our solution removes this requirement, freeing up space in the consumer unit.

 

[SUNRAY]

Residential SPD board

ready to go residential SPDF boards support need for best practice

hager.com

​

No secondary upstream protection devices required​

In the past, surge protection devices required an MCB or fuses in the consumer unit to provide backup protection using one of the outgoing ways. Our solution removes this requirement, freeing up space in the consumer unit.

So it still takes up 2 units of space.

 

[securespark]

 

[securespark]

There are many manufacturers who supply an MCB to fit with their SPDs.

 

[ericmark]

Fuse box use to have no MCB with the SPD now they do, it was the early versions that were direct.

 

[ebee]

I thought it tother way round Eric. The early ones I saw said must be used with an MCB and often supplied one as part of the kit. Later models by some manufacturers stated you could use them directly without a MCB. I might have viewed them in reverse history order though but I am not aware of it

 

[EFLImpudence]

I am puzzled.

If an SPD requires an MCB, does that mean that a separate SPD is needed for every circuit.

 

[ebee]

nope. an MCB fed from the CU Mainswitch then to the SPD will ensure all other MCB circuits in the Consumer unit are protected unless the SPD circuit MCB is tripped methinks

 

[SUNRAY]

I am puzzled.

If an SPD requires an MCB, does that mean that a separate SPD is needed for every circuit.

Thank heavens for that, at last someone else is having the same thoughts as me.

I see absolutely no point in in providing a MCB to supply a SPD.

 

[SUNRAY]

nope. an MCB fed from the CU Mainswitch then to the SPD will ensure all other MCB circuits in the Consumer unit are protected unless the SPD circuit MCB is tripped methinks

I doubt the silly arrangement will protect very much. The impedance of the wiring will render the SPD almost useless against impulses.

 

[ebee]

Well, very near adjacent circuits in the CU perhaps, as you get away from the CU depending upon the wavelength then you need another apparently say a DB feeding a DB feeding a DB situation you would need one in each DB is the way I understand it

 

[EFLImpudence]

nope. an MCB fed from the CU Mainswitch then to the SPD will ensure all other MCB circuits in the Consumer unit are protected unless the SPD circuit MCB is tripped methinks

...but, the one pictured comes with a 32A MCB; how can that cover multiple circuits?