4mm Radial Circuit using Wago 5-way?

arrkaye · Sep 6, 2024

Hi,

Is it okay to wire a radial circuit like this? All 4mm apart from the fused spur to light. No length >3m except the initial CU -> Wago. Cable will be running through 25mm MDPE piping below floor (open air). Use is for a garden office. TV/Computer/Monitors.

Fleeting · Sep 6, 2024

4.0 will not be rated at 32A if contained in MDPE.
Why MDPE?
That is an odd way to do it for a new circuit incorporate as few joints as possible.

arrkaye · Sep 6, 2024

Thanks, so that needs to be a 20A MCB. Presumably that will be sufficient for those sockets/load?

Fleeting · Sep 6, 2024

Are you notifying Building Control over this new circuit.

Murdoch · Sep 6, 2024

Rather unorthodox - who is signing this off?

As this is for a garden office, my advice would be to get professional help - for the electrics

binky · Sep 6, 2024

nothing wrong with it in principle, just not how most would do things.

SJD · Sep 6, 2024

If you are just powering IT equipment & similar, then 20A ought to be easily sufficient. But will you need heating in the winter & Aircon in the summer? If not now, perhaps when you realise it is too cold or too hot in the office? If so, I'd check for sure what the loading might be, before deciding on the circuit rating, though 20A might still be enough.

As mentioned, assuming this is a domestic property, notification to Building Control ought to be done, which is usually a lot easier & cheaper if done by a scheme (NICEIC, NAPIT) member.

Andy™ · Sep 6, 2024

arrkaye said:
Hi,

Is it okay to wire a radial circuit like this? All 4mm apart from the fused spur to light. No length >3m except the initial CU -> Wago. Cable will be running through 25mm MDPE piping below floor (open air). Use is for a garden office. TV/Computer/Monitors.

View attachment 17035

by MDPE i hope you don't mean blue / yellow since you wouldnt expect a cable in a gas/water pipe. not done cable calc but 4mm may be undersized too

many wago's are also only rated to 20a

SPECIAL LOCATION · Sep 6, 2024

Andy™ said:
many wago's are also only rated to 20a

Wago's greater than 20A are easily available.

SPECIAL LOCATION · Sep 6, 2024

arrkaye said:
Hi,

Is it okay to wire a radial circuit like this? All 4mm apart from the fused spur to light. No length >3m except the initial CU -> Wago. Cable will be running through 25mm MDPE piping below floor (open air). Use is for a garden office. TV/Computer/Monitors.

View attachment 17035

Is this RCD supplying other MCBs? if yes, its poor design in my opinion.
Is the RCD a type 'A'? if no, then is needs changing to a type 'A'
Dedicated RCBO much better solution.

arrkaye · Sep 7, 2024

SJD said:
If you are just powering IT equipment & similar, then 20A ought to be easily sufficient. But will you need heating in the winter & Aircon in the summer? If not now, perhaps when you realise it is too cold or too hot in the office? If so, I'd check for sure what the loading might be, before deciding on the circuit rating, though 20A might still be enough.

As mentioned, assuming this is a domestic property, notification to Building Control ought to be done, which is usually a lot easier & cheaper if done by a scheme (NICEIC, NAPIT) member.

Thanks. There's underfloor heating (wet) and the AC is fed from the condenser which is on a separate 6mm feed (professionally installed).

arrkaye · Sep 7, 2024

Thanks all. The Wagos are the ones rated for 4mm cable to 32A. The MDPE is just to shield the cable from the elements and rodents, running in open air under the joists.

binky · Sep 7, 2024

arrkaye said:
Thanks all. The Wagos are the ones rated for 4mm cable to 32A. The MDPE is just to shield the cable from the elements and rodents, running in open air under the joists.

What cable are you planning on using for the run back to the house?

I would run swa from house to shed off MCB not sharing a rcd. Install a mini board in shed and treat each cable run as separate circuits from RCBOs in mini board. You also need to consider earthing arrangements, if you main fuse has axsticjer saying PME supply, you should not be exporting the earth from the house, and install an earth rod in the shed making it a TT system

Murdoch · Sep 7, 2024

arrkaye said:
Thanks all. The Wagos are the ones rated for 4mm cable to 32A. The MDPE is just to shield the cable from the elements and rodents, running in open air under the joists.

Still not convinced that your sketch makes any sense - too complicated by far and no internal lights?

arrkaye · Sep 7, 2024

Murdoch said:
Still not convinced that your sketch makes any sense - too complicated by far and no internal lights?

That's right. I'm going to use light strips (hue) that plug into the wall.

arrkaye · Sep 7, 2024

binky said:
What cable are you planning on using for the run back to the house?

I would run swa from house to shed off MCB not sharing a rcd. Install a mini board in shed and treat each cable run as separate circuits from RCBOs in mini board. You also need to consider earthing arrangements, if you main fuse has axsticjer saying PME supply, you should not be exporting the earth from the house, and install an earth rod in the shed making it a TT system

Apologies, I missed a detail there. The 4mm feed is already laid and the office is actually attached to the house - it's a side extension/annex.

Fleeting · Sep 7, 2024

There is no requirement to make it TT.

arrkaye · Sep 7, 2024

Andy™ said:
by MDPE i hope you don't mean blue / yellow since you wouldnt expect a cable in a gas/water pipe. not done cable calc but 4mm may be undersized too

many wago's are also only rated to 20a

Agreed. It is the blue stuff I have leftover, but I'm marking it up across the length with green tape and labelling it across the short length.

Fleeting · Sep 7, 2024

This is being notified to Building Control?

Andy™ · Sep 7, 2024

arrkaye said:
Agreed. It is the blue stuff I have leftover, but I'm marking it up across the length with green tape and labelling it across the short length.

so you agree that its wrong, but you're doing it anyway because its spare...

4mm Radial Circuit using Wago 5-way?

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