Cable sizing question

tom1ie

Hi all,

I just want to check my maths with the sage amongst you:

Ive a new extension with a ring circuit wired in 2.5 T+E.

I want to take a feed off one of the sockets and into a fused spur.

From the fused spur I want to go through the wall into an outside IP66 rated double socket.

Off this socket I also want to run an SWA that will feed approx 10 lights and a 4KW infrared heater. The run is about 15m long.

So the 4KW heater will draw 16.66A at 240v

The lights are about 10W each so 100W which draws about half an Amp so 17A all in.

The rating for 2.5 PVC insulated cable is 30A so I should be well within design constraints having 2.5 SWA off a 20A fused spur?

The only thing I’m thinking is if I had the heater and all the lights on and then someone plugged in another heater or a heavy load it would blow the fused spur but sure that’s what it’s for really isnt it!

Can anyone see any issues with this?

2011

That Is too much for a single circuit.

I would put the heater on its own circuit for starters. Note this device draws 17 A as we use 230 V not 240 V in the ROI.

I would also be best to have the lighting on its own circuit .

Also the maximum fuse rating for a spur outlet is 13 A.

I could go on but I’m afraid that I will only encourage you to proceed with this work. I suggest get a professional electrician in. No offense intended but I think you are proposing wouldn’t align with best practice and suggests that this work is beyond your abilities

tom1ie

https://www.boards.ie/discussion/comment/121657727#Comment_121657727

Thanks for the input 2011.

I will look into getting an electrician but just so I know for myself, could I use a 20A DP switch instead in this scenario?

Or are you saying to take a feed off the ring to one 13A fused spur and go out to the outside socket, then feed the heater off that.

Take another feed off the extension lighting circuit to a switch and go out to the lighting circuit outside.

Keep them separate.

Also just so I know, if the heater draws 17A and the max size fused spur is 13A, what can be used as protection? A 20A DP switch or something?

RetroEncabulator

What you’re proposing there isn’t in line with regs and it also isn’t safe.

The ring circuit methodology is predicated on everything connected to the ring being locally fused at 13amp absolute max, either in the plug top fuse or in an equivalent fixed connection unit. It’s not intended for anything other than IS411 / BS1363 sockets that only accept fused plugs.

4kW loads cannot be connected to a socket circuit and lighting shouldn’t be connected to one either.

You need to get an electrician to install this correctly. Also bear in mind that in Irish law, not just the regs, it’s illegal to carry out DIY work that involves adding new circuits to the distribution panel (consumer unit / “fusebox”).

I wouldn’t advise it both from a legal and an insurance point of view.

tom1ie

https://www.boards.ie/discussion/comment/121657905#Comment_121657905

Ok so if i got an electrician to wire an outside plug off the ring circuit and had the following 2kw infrared heater plugged into the outside socket (forget about the lights off that circuit) it would be ok?

https://outdoorliving.ie/gemini-heatwave-ipx5-heater-2000-watt?gad_source=1&gclid=Cj0KCQiAwbitBhDIARIsABfFYII-XMLuQ4SHA3sTZ_UA5J-nT9GwVrmujHOarDomKRbK_b-_R1hyrmUaAl4vEALw_wcB

2011

https://www.boards.ie/discussion/comment/121658105#Comment_121658105

No, that would not be a satisfactory solution.

You definitely need a REC (Registered Electrical Contractor). I think we need to close it at that before someone gets hurt or worse.