UK Can you have 3 13 amp fcus in series on its own radial 16amp with each supplying single socket

[popeyedwazza]

Hi everyone. Im new here...

I need advice on wether it is safe and okay to have 3 × 13amp fcus on its own radial with each having single socket to supply a....

1st) fcu at 13amp-fridge/freezer

2nd) fcu at 13amp-washer/dryer combo

3rd) fcu at 13amp-Dishwasher

They will be protected by 4mm solid core twin and earth cable

Any help appreciated

Thanks in advance!

 

[mainline]

Hi everyone. Im new here...

I need advice on wether it is safe and okay to have 3 × 13amp fcus on its own radial with each having single socket to supply a....

1st) fcu at 13amp-fridge/freezer

2nd) fcu at 13amp-washer/dryer combo

3rd) fcu at 13amp-Dishwasher

They will be protected by 4mm solid core twin and earth cable

Any help appreciated

Thanks in advance!

You don't actually need fcus just 20 amp switches.
Also, the 4 mm depending on installation method etc could be a 32 amp.

 

[popeyedwazza]

You don't actually need fcus just 20 amp switches.
Also, the 4 mm depending on installation method etc could be a 32 amp.

That sounds much better. Didnt think of it like that. I was trying to be over cautious when hadnt needed. Do you think 16amp is too low. I thought 16-20amp was for radial and 32-40amp for ring

 

[popeyedwazza]

You don't actually need fcus just 20 amp switches.
Also, the 4 mm depending on installation method etc could be a 32 amp.

Also as they are built in i need the sockets behind the appliance aswel as an issolator to turn of when not needed/fault inspection ect. That was my reason for fcu so each had isolator?

 

[timhoward]

As above, the FCU's are not required, and in any case it's likely the 16amp MCB would trip before a 13A fuse.
It's hard to summarise installation methods and cable ratings.
One can say that with 4mm cable as long as you aren't stuffing it inside a wall and then surrounding it with insulation you will be ok on a 20 amp MCB.
(A 32 amp MCB is only ok if the cable is clipped directly to a wall for it's entire length, and not inside a stud wall or above a ceiling)

 

[timhoward]

Also as they are built in i need the sockets behind the appliance aswel as an issolator to turn of when not needed/fault inspection ect. That was my reason for fcu so each had isolator?

You can instead use a 20 amp double pole switch.
Something like this:

British General 900 Series 20A 1-Gang DP Control Switch White - Screwfix

Order online at Screwfix.com. Robust, square-edged profile. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[popeyedwazza]

As above, the FCU's are not required, and in any case it's likely the 16amp MCB would trip before a 13A fuse.
It's hard to summarise installation methods and cable ratings.
One can say that with 4mm cable as long as you aren't stuffing it inside a wall and then surrounding it with insulation you will be on a 20 amp MCB.
(A 32 amp MCB is only ok if the cable is clipped directly to a wall for it's entire length, and not inside a stud wall or above a ceiling)

Cable would be in some areas behind tiles and clipped in a cupboard

 

[popeyedwazza]

You can instead use a 20 amp double pole switch.
Something like this:

British General 900 Series 20A 1-Gang DP Control Switch White - Screwfix

Order online at Screwfix.com. Robust, square-edged profile. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Thats excellent. I shall indeed. Thanks

 

[mainline]

Cable would be in some areas behind tiles and clipped in a cupboard

You could always use 6 mm on a 32.

 

[westward10]

You could always use 6 mm on a 32.

How do you propose they terminate 2 × 6.0 into the terminals.

 

[mainline]

How do you propose they terminate 2 × 6.0 into the terminals.

A 6 and a 4 would probably squeeze in.

 

[westward10]

A 6 and a 4 would probably squeeze in.

Most 20A DP switches suggest 2.5×3, 4.0×2 or 6.0×1. Suggesting they could squeeze in is hardly professional advice.

 

[mainline]

Most 20A DP switches suggest 2.5×3, 4.0×2 or 6.0×1. Suggesting they could squeeze is hardly professional advice.

The Mk range of 20A DP switches designed for the connection of refrigerators, water heaters, central heating boilers and other fixed appliances.

 Terminal Capacity  Supply Terminal  2x 6mm2 stranded
 2 x 4mm2
 3 x 2.5mm2  Load Terminals  2x 6mm2 stranded
 (1x 6mm2 on earth terminal)
 2 x 4mm2


Or could he could fit 32amp DP switches

https://buildings.honeywell.com/us/en/products/by-category/electrical-and-wiring/wiring-devices/switches/double-pole-switches/k5105-dp-switch

 

[timhoward]

I'd have a look at the specific power consumption of the appliances you are after. A washer dryer could draw 10 amps on it's own. I wouldn't design for a 16 amp circuit breaker if it were me.

You've basically got a choice between going belt and braces, or getting someone in to advise you on appropriate circuit design taking into consideration the complete cable route and relevant derating factors.

As @mainline said it could be done with a 32 amp circuit breaker, 6 sq mm cable and careful choice of isolators but it would be a fair old fight that I'd avoid if I possibly could.
If I wanted a 32 amp circuit, at the risk of starting WW3, the easiest way that is suitable for the majority of installation methods featuring easy to handle 2.5 sq mm cable would be a very small ring final circuit. When all is said and done it's only one extra connection at the last isolator and a 2nd cable back the CU.

Other options may be suitable and possible but more knowledge of circuit design is required to choose and use them.

 

[popeyedwazza]

Also now after ordering the cables twice. All my diy/electrical outlets only sell 4mm2 twin and earth in stranded 7 cores solid copper. Do they sell anywhere online 4mm2 twin and earth with solid cores, or are they all stranded cores? Sorry if miss worded it!

 

[pc1966]

I would expect 20A is enough as the fridge-freezer only takes significant power for short busts, and the two others combined are unlikely to be more than 20A, certainly not for long periods. In that case you can use 2.5mm cable and it is a lot easier to work with.

You would not want to work with 4mm single-strand anyway! The stranding makes it much easier to bend and less likely to fatigue crack as a result.

 

[popeyedwazza]

I would expect 20A is enough as the fridge-freezer only takes significant power for short busts, and the two others combined are unlikely to be more than 20A, certainly not for long periods. In that case you can use 2.5mm cable and it is a lot easier to work with.

You would not want to work with 4mm single-strand anyway! The stranding makes it much easier to bend and less likely to fatigue crack as a result.

But would 4mm twin and earth stranded copper cores cable be ok if i chose that. As an upgrade so it will be there if needed for future more power hungry appliances?

 

[pc1966]

But would 4mm twin and earth stranded copper cores cable be ok if i chose that. As an upgrade so it will be there if needed for future more power hungry appliances?

Yes, 4mm is good as you can do 25A in virtually all cases, and if not covered in thermal insulation, etc, then 32A.

Main issue is making sure that switches are rated to accept 2*4mm cables and you have back-boxes deep enough that it all fits without too much strain.

 

[popeyedwazza]

Yes, 4mm is good as you can do 25A in virtually all cases, and if not covered in thermal insulation, etc, then 32A.

Main issue is making sure that switches are rated to accept 2*4mm cables and you have back-boxes deep enough that it all fits without too much strain.

Yes. We recently upgraded to the trendiswitches. They account for bigger diameter cable and multi cable also. Back boxes will be 40+ mm as this will just be its own radial for them only. And 3 cables in 2 of them. It will be all tested and certified. Just saves money end of day trying to do the bits myself. Very knowledgeable and good headed but very misunderstandings when it comes to cable needs in these modern times. But i appreciate all your expert help and knowledge. Thanks guys and girls!

 

[pc1966]

I just looked at the 20A Trendi Switch data sheet here:

https://files.ekmcdn.com/557fdc/resources/other/art-whs1.pdf

Terminal (Live) Diameter: 5mm; Capacity: 6 x 2.5mm²

Jesus wept, 6 wires in one terminal!

 

[popeyedwazza]

I just looked at the 20A Trendi Switch data sheet here:

https://files.ekmcdn.com/557fdc/resources/other/art-whs1.pdf

Terminal (Live) Diameter: 5mm; Capacity: 6 x 2.5mm²

Jesus wept, 6 wires in one

Extreme stuff, just like old mk but better!

 

[nicebutdim]

I just looked at the 20A Trendi Switch data sheet here:

https://files.ekmcdn.com/557fdc/resources/other/art-whs1.pdf

Terminal (Live) Diameter: 5mm; Capacity: 6 x 2.5mm²

Jesus wept, 6 wires in one terminal!

One thing making terminals big enough to accommodate six cables, but I reckon only one spark in twenty might manage to securely terminate six.

 

[pc1966]

One thing making terminals big enough to accommodate six cables, but I reckon only one spark in twenty might manage to securely terminate six.

What they might mean is it can take 2*6mm or 3*4mm, as similar CSA to 6*2.5mm, but to actually propose that as a use-case is bonkers!