Fit flush mounted double socket to 25mm mdf panel.

[Martin Trickett]

I'm a newcomer. Only a DIYer but I have done a lot of general household wiring in the past. My daughter wants an extra double plug socket flush fitted to one side of a 25mm mdf panel. I can access the other side of the panel and run an external spur cable from an existing socket. I would like to fit the extra socket by hollowing out the panel behind it sufficiently to accomodate the "workings and connections" and to allow me to flush fit it. The panel is thick enough for this to be possible without completely penetrating through the panel (apart from a single hole for the spur cable). This seems a logical way to achieve the required result, and I have tried it out successfully on a piece of scrap 25mm timber. But is it acceptable practice, or are there unforeseen (to me) hazards?
Fingers crossed I've explained what I mean!
Any advice gratefully received. Thank you.

 

[littlespark]

The socket must have a back box fitted.

Just cut a hole right through the board, metal boxes usually have fixing holes on the sides.

 

[brianmoooore]

If the metal box doesn't have holes in the right place on the sides, it's nothing a 4.5mm drill bit won't cure.
Note that you cannot extend from an existing socket without establishing the type of circuit it is.
If it's a radial circuit (16A or 20A MCB usually), then it's normally OK, but if the existing socket is a spur off of a RFC (usually 32A MCB, and likely to be only one cable at the socket), then the wiring cannot be extended as you propose.

 

[Martin Trickett]

The socket must have a back box fitted.

Just cut a hole right through the board, metal boxes usually have fixing holes on the sides.

Littlespark, thank you very much for your reply. I knew I would miss out important information! The other side of the panel has a fridge almost touching it, which means a back box would contact it. This is why I was hoping hollowing the wall would work. I have always used back boxes in walls in the past but I have not faced this particular situation before. Do you know why hollowing the wall won't work, apart from it not being normal practice? Sorry for the late response, your reply arrived in the early hours (I live in New Zealand). Thank you again, Martin

 

[littlespark]

OK... I didnt realise you were not in UK... so our regulations will be no doubt different.

However, I have actually done work in New Zealand, and if i recall, there was back boxes used.. .but these were in a partition wall with a hollow void between two skins of plasterboard.

Would it be possible to use a surface mounted box in your instance?

 

[Martin Trickett]

The socket must have a back box fitted.

Just cut a hole right through the board, metal boxes usually have fixing holes on the sides.

Hi again littlespark. A further bit of info for you. I have a shallow surface mounting box, plastic like most boxes (surface or recessed) are in NZ. Surface mounting was my first thought when trying to please my daughter. It was rejected on aesthetic grounds! It's approx 15mm deep. I could fairly easily recess this in to the panel without effecting the other side. Would this fulfill the need to have the socket mounted in a back box? Thank you again, Martin

 

[Martin Trickett]

If the metal box doesn't have holes in the right place on the sides, it's nothing a 4.5mm drill bit won't cure.
Note that you cannot extend from an existing socket without establishing the type of circuit it is.
If it's a radial circuit (16A or 20A MCB usually), then it's normally OK, but if the existing socket is a spur off of a RFC (usually 32A MCB, and likely to be only one cable at the socket), then the wiring cannot be extended as you propose.

Thank you Brian for your reply. I have replied to littlespark giving further info and asking whether a surface mounting box, recessed, would fulfill the requirement he mentioned.
I will check out the circuit. As far as I know here in NZ ring mains are not used domestically, only radial circuits. That's certainly the case in my own house. I will also hope to find more than one cable attached to socket I hope to spur from.
Many thanks, Martin

 

[timhoward]

I'm not familiar with the depths of standard accessory boxes in NZ. Nor am I familiar with wiring regulations that apply there.
But in general you can't just bury a socket without a box in wood or composite board, any spark from a loose connection could start a fire!
If a surface box with a depth of 15mm can in fact accommodate the socket, then routing out and burying the box seems a reasonable solution to me.
I'm also thinking that if a 15mm surface box exists there are probably other boxes with similar depth that are designed to be buried in walls?

 

[Martin Trickett]

OK... I didnt realise you were not in UK... so our regulations will be no doubt different.

However, I have actually done work in New Zealand, and if i recall, there was back boxes used.. .but these were in a partition wall with a hollow void between two skins of plasterboard.

Would it be possible to use a surface mounted box in your instance?

Hi Littlespark, thank you for your further info. I'm delighted you've spent time, and worked, in NZ; I hope you enjoyed being here. You are right, back boxes are used and the vast majority of NZ domestic walls are as you describe. I suggested a surface box to my daughter. She rejected it as unappealing! Tim Howard has suggested I might be able to find a "normal", but slimmer, box which could be buried in the panel. I'm going to try and find one. Kind Regards, Martin

 

[Martin Trickett]

I'm not familiar with the depths of standard accessory boxes in NZ. Nor am I familiar with wiring regulations that apply there.
But in general you can't just bury a socket without a box in wood or composite board, any spark from a loose connection could start a fire!
If a surface box with a depth of 15mm can in fact accommodate the socket, then routing out and burying the box seems a reasonable solution to me.
I'm also thinking that if a 15mm surface box exists there are probably other boxes with similar depth that are designed to be buried in walls?

Hi Tim, many thanks for your reply. All that you say makes sense. And I particularly like your thinking in your last sentence. I'll try to find such a box as you describe. Thank you again, kind regards, Martin

 

[littlespark]

My brother in law lives in Nelson, South Island, and we were there 5 weeks over xmas 2017…. So while I was there, he wanted a few sockets changed to double outlets.

I remember the cable was like UK twin and earth, the distribution board was outside, and there was only one size of back box….
The plugtop flexes were at 45 degrees to the vertical, so if you had a double outlet one above the other, they didn’t get in the way of each other.

 

[Martin Trickett]

My brother in law lives in Nelson, South Island, and we were there 5 weeks over xmas 2017…. So while I was there, he wanted a few sockets changed to double outlets.

I remember the cable was like UK twin and earth, the distribution board was outside, and there was only one size of back box….
The plugtop flexes were at 45 degrees to the vertical, so if you had a double outlet one above the other, they didn’t get in the way of each other.

Small world! I live just outside Mapua, which is about 25kms from Nelson; been here for the last 19 years. You may well have visited Mapua while you were over here.
As you say there appears to be only one size of back box, I've had no luck finding a shallow one so far. Not the end of the world.
Thank you for all your advice. Kind Regards, Martin