Discuss Fused Spur with 16A MCB, advice needed in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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monkfish457

Hi Guys,
My first post so please bear with me.

I'm not a domestic electrician but am capable of carrying out most work myself. This has led to my parents requesting that I carry out a 'small project' for them and involves installing a couple of additional double plugs in their conservatory. As the conservatory was built after the main house it has its own foundations and has no access underfloor. It also had solid brick exterior walls.

The current electrics involves a 16Amp MCB on a Wylex MCU with a fused spur to the conservatory. This goes from the MCU up the wall to the attic and reappears at a double plug in the conservatory (about 10m). It then runs from that double plug to another on the same side. It also runs underfloor to another double plug on the other side of the conservatory.The cabling appears to be white (low smoke) 1.5mm T&E.

My parents would like to put another two double sockets in series, with a couple of metres between each, in addition to the single double already on the other side of the conservatory. Sorry I can't post a diagram as its my first post. I would liked to have run another separate ring but as I can't identify where the cable goes between the attic and the conservatory this option is out.

This leaves an additional two plugs on the original fused spur as the best option but I'm concerned that 5 doubles may be too much current drain for a single T&E. The likely loading would be a TV, Video, table light, two electric recliners, a electric storage heater (13a plug, not sure of the specs) and the hoover occasionally. Would I be able to install the two additional plugs legally? I would cut a slot in the original wall in the cement between two rows of bricks to recess the cabling. Is there a minimum depth for this?

I would be grateful for any advice or suggestions.

Best Regards,

Stu
 
Hi Guys,
My first post so please bear with me.

I'm not a domestic electrician but am capable of carrying out most work myself. This has led to my parents requesting that I carry out a 'small project' for them and involves installing a couple of additional double plugs in their conservatory. As the conservatory was built after the main house it has its own foundations and has no access underfloor. It also had solid brick exterior walls.

The current electrics involves a 16Amp MCB on a Wylex MCU with a fused spur to the conservatory. What size cable is that Stu?

This goes from the MCU up the wall to the attic and reappears at a double plug in the conservatory (about 10m). It then runs from that double plug to another on the same side. It also runs underfloor to another double plug on the other side of the conservatory.The cabling appears to be white (low smoke) 1.5mm T&E. Stu when you say the cable goes up the wall into the attic and then down into the first conservatory socket, is that cable protected by the Fused spur?

My parents would like to put another two double sockets in series, with a couple of metres between each, in addition to the single double already on the other side of the conservatory. Sorry I can't post a diagram as its my first post. I would liked to have run another separate ring but as I can't identify where the cable goes between the attic and the conservatory this option is out. If these 3 sockets are as I suspect protected by a 13amp fuse in the fused unit then having the 1,5mm cable (T+E most likely) is no problem

This leaves an additional two plugs on the original fused spur as the best option but I'm concerned that 5 doubles may be too much current drain for a single T&E. The likely loading would be a TV, Video, table light, two electric recliners, a electric storage heater (13a plug, not sure of the specs) and the hoover occasionally. Would I be able to install the two additional plugs legally? I would cut a slot in the original wall in the cement between two rows of bricks to recess the cabling. Is there a minimum depth for this? Your biggest draw out of that lot is that heater, you need to find out what size it is, if it's a 3KW then you may need to redesign your circuit. If it's less say a 2KW then there is nothing stopping you supplying all 5 sockets from the original fused unit

I would be grateful for any advice or suggestions.

Best Regards,

Stu

I've tried to give you some answers that in all honesty would be the easiest thing to do for you
 
Well that cable can carry 17.5A from what I remember...could be wrong. So the MCB should trip before the cable gets too much current to handle, I'm always too safe though and would up it 2.5, as for the plugs I'm unsure on the depth thing as I'm a Maintenance Engineer but I do know there's no limit to how many sockets you can have on a Main but there are other factors such as floorspace. You should do your calculations for worst case scenario and if the current on that main will exceed the 16A then you will have to up the breaker accordingly. However I will say that I'm unsure on whether you can bring sockets off a fused spur, and also unsure on whether that's what you're proposing haha.

Some links you may find useful:
Elecsa - Current Carrying Capacity of Cables
View attachment 17th Corrigenda July 2008.pdf
My attempt at help :yes:
 
Last edited by a moderator:
Thx for the replies. Malcom, I hope these are suitable answers:-

1) What size cable is that Stu? The cabling appears to be white (low smoke) 1.5mm T&E. I can't tell you any more than that.

2) Stu when you say the cable goes up the wall into the attic and then down into the first conservatory socket, is that cable protected by the Fused spur? The cable goes into a Wylex MCU, 2 banks of 6 MCB's. The conservatory plug sockets MCB is a Wylex 16A plugin type MCB, with no other outlets. I can't post a link but if you google 'wylex 16a mcb' in images it is the type with a blue gang and B16 on it. (12th image with MEM Supplies above it)


3) If these 3 sockets are as I suspect protected by a 13amp fuse in the fused unit then having the 1,5mm cable (T+E most likely) is no problem. The spur is on a normal 16A MCB. I assume this is OK for a low power spur. I guess I could replace it with a RCD or RCBO but don't really want to if I don't need to.

4) Your biggest draw out of that lot is that heater, you need to find out what size it is, if it's a 3KW then you may need to redesign your circuit. If it's less say a 2KW then there is nothing stopping you supplying all 5 sockets from the original fused unit. The heater is a Fischer 2.5Kw stove and is meant to be low power (runs off a 13A domestic plug). The rest of the things in the conservatory draw a very small amount of current and would likely not be used in combination, if at all.

5) If I use 1.5mm T&E for the additional plugs, is there a recommended depth the cable needs to be recessed into the wall before cementing it into the current brickwork?

Thx for the info and links Gage, it may help in my final decision.

Best Regards,

Stu
 
if its a 13amp fuse spur feeding the original sockets in 1.5 t&e you can add as many sockets as you like . if you overload the fuse will pop . bad design but perfectly ok
 
Well I don't know all the answers but;
The MAX depth horizontally in a wall is 1/6th of the thickness. Buried cables require mechanical protection unless they are in "safe" zones and they require RCD protection anyway.

Hope that's helpful
Laurie


5) If I use 1.5mm T&E for the additional plugs, is there a recommended depth the cable needs to be recessed into the wall before cementing it into the current brickwork?

Thx for the info and links Gage, it may help in my final decision.

Best Regards,

Stu[/QUOTE]
 
have you considered the possibility of cabling outside in pvc conduit and drilling through at each new socket?
 


5) If I use 1.5mm T&E for the additional plugs, is there a recommended depth the cable needs to be recessed into the wall before cementing it into the current brickwork?

Don't cement directly over the cable, as the pvc sheath can be compromised. Plaster is permissible, render isn't.
 

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