Moving CU away from service head. SPD at the fused switch or CU?

[ojchurch]

I'm moving my CU away from the service head. About 8m in 25mm2 SWA. Do I need to put an SPD T2 at the 100a fused switch I'm installing or can I get away with just having one at the new CU location? I'm struggling to find options for the service head location. They a lot more expensive and the box is bigger, smaller would work better for me. Also, most DBs now come with SPDs included. Any advice appreciated.

 

[mainline]

I'm moving my CU away from the service head. About 8m in 25mm2 SWA. Do I need to put an SPD T2 at the 100a fused switch I'm installing or can I get away with just having one at the new CU location? I'm struggling to find options for the service head location. They a lot more expensive and the box is bigger, smaller would work better for me. Also, most DBs now come with SPDs included. Any advice appreciated.

What is the earthing system ?
Why 2 core swa ?

Edit: I thought it said 2 core.

 

[James]

What is the earthing system ?
Why 2 core swa ?

op has not specified 2 core but it may well be suitable, so why not?

 

[littlespark]

maybe not 2 core swa…. I think it’s “25mm squared”

The common practice is “at source” so I’d say at the fuse end… The SPD is there to protect the installation which will include the SWA you’re putting in.

However, an SPD at the CU would be better than no SPD at all… so whatever’s easiest.

A lot of houses have the fuse and meter outside, with a CU inside… in that situation, youre not permitted to put an SPD, or anything else, in the meter box.

 

[ojchurch]

op has not specified 2 core but it may well be suitable, so why not?

I'll be using 3c 25mm2 SWA (yes that's squared, should be superscript )

 

[ojchurch]

maybe not 2 core swa…. I think it’s “25mm squared”

The common practice is “at source” so I’d say at the fuse end… The SPD is there to protect the installation which will include the SWA you’re putting in.

However, an SPD at the CU would be better than no SPD at all… so whatever’s easiest.

A lot of houses have the fuse and meter outside, with a CU inside… in that situation, youre not permitted to put an SPD, or anything else, in the meter box.

That's helpful as the long term plan is to get the DNO to move the head and I'll be planning ahead to move my switch fused disconnector next to it when we get a porch built. Atm it's above the door as you walk in and isn't very pretty.

 

[westward10]

A tip for anyone using a phone or tablet to produce mm² and not mm2 hold your finger on the 2 after mm and you should be able to do it through the options.

 

[westward10]

mm¹²³⁴⁵⁶⁷⁸⁹⁰

 

[Tom256]

Is the incoming supply overhead lines?

When you say 'about 8 mtrs' how accurate is that word 'about'

 

[ojchurch]

A tip for anyone using a phone or tablet to produce mm² and not mm2 hold your finger on the 2 after mm and you should be able to do it through the options.

I forgot about that! ²²²

 

[ojchurch]

Is the incoming supply overhead lines?

When you say 'about 8 mtrs' how accurate is that word 'about'

It's TNS with a Ze of 0.14 at the existing CU next to the service head

 

[ojchurch]

It's TNS with a Ze of 0.14 at the existing CU next to the service head

And just under 8m

 

[ojchurch]

It's TNS with a Ze of 0.14 at the existing CU next to the service head

Should be less than 0.03 added with the additional cable to the new CU

 

[Tom256]

Should be less than 0.03 added with the additional cable to the new CU

My comments were not in relation to the loop readings following the CU replacement.

 

[Teddy Lop]

I'm moving my CU away from the service head. About 8m in 25mm2 SWA. Do I need to put an SPD T2 at the 100a fused switch I'm installing or can I get away with just having one at the new CU location? I'm struggling to find options for the service head location. They a lot more expensive and the box is bigger, smaller would work better for me. Also, most DBs now come with SPDs included. Any advice appreciated.

I keep them in the CU

A failed device is more likely to be observed in this case Mr inspector.

 

[mainline]

I keep them in the CU

A failed device is more likely to be observed in this case Mr inspector.

I agree no benefit in having it at the Db.