Fitting off spd

[Tom swann]

If you have 2 c/u s in a property and they want a spd do you need to put he in front off both ?

 

[littlespark]

No. You can add an enclosure with an SPD to cover both

 

[Tom swann]

No. You can add an enclosure with an SPD to cover both

Ok how does that work. ? As I’ve put one in another fuseboard for his air con he’s had fitted

 

[littlespark]

The spd needs a live neutral and earth, normally connected after the mainswitch in a Cu, but there’s no reason it can’t be connected before.

you’ve already put one in? Then it’ll protect both if both main switches are on

 

[pc1966]

The main issue with SPD is the cable length.

What they are trying to stop are surges in the microsecond range and as a result all of the power is spread up in to the 100kHz+ region and so cable inductance dominates over resistance in almost all cases.

So if you have the SPD on the CU such that the cable length from supply L tap point to SPD and back to N tap point & E to MET is less than 1m (but ideally less than 0.5m) the SPD will protect loads off both CU.

 

[ChrisElectrical88]

Single phase or 3 phase?
[automerge]1601235786[/automerge]

The spd needs a live neutral and earth, normally connected after the mainswitch in a Cu, but there’s no reason it can’t be connected before.

you’ve already put one in? Then it’ll protect both if both main switches are on

As @pc1966 says there is a length of you need to be under for it to be fully effective.