Hi all, just joined, starting my Nvq soon. Was wondering if I'm correct in assuming the cooker can be on a 6mm conductor on a 30amp RCD and the hood can be on 1.5mm if it's a spur?
- Thread starter Electromob
- Start date
Not sure cooker power i was asked to fit cable on a first fix, I done his shower cable and said it should be ok for cooker too.
M
malcolmsanford
Hi and welcome to the forum hope it will help you.
As your just starting then in most applications, and let's say it's a 6mm^ Twin + Earth cable it will be ok on a 32 amp protection device., but if it was in insulation exceeding 100mm thickness it would only take 27 amps, this is a rating factor you use when your designing a circuit, and you will be taught this.
Same as the use of RCD, RCB.RCBO, though you said 30 amp RCD you will find that it will either be in domestic situations a 63/80amp 30mA RCD with a 32 amp MCB or a 32 amp RCBO which is RCD/MCB combined, but again this will become clearer as you go along.
It is not normal to spur off of the cooker circuit to feed another aplliance ie a hood, as most manufacters advise a dedicated circuit for larger cooking appliances, the new modern under 3kw cookers can be treated differently but again let's not run before you can walk. A normal way to wire a hood would be to spur of the socket outlet circuit. So normally you would come of the socket in 2.5mm into a switched spur unit and then 1.5 or 1.00 to the hood, using a 3amp fuse in the switch spur
As your just starting then in most applications, and let's say it's a 6mm^ Twin + Earth cable it will be ok on a 32 amp protection device., but if it was in insulation exceeding 100mm thickness it would only take 27 amps, this is a rating factor you use when your designing a circuit, and you will be taught this.
Same as the use of RCD, RCB.RCBO, though you said 30 amp RCD you will find that it will either be in domestic situations a 63/80amp 30mA RCD with a 32 amp MCB or a 32 amp RCBO which is RCD/MCB combined, but again this will become clearer as you go along.
It is not normal to spur off of the cooker circuit to feed another aplliance ie a hood, as most manufacters advise a dedicated circuit for larger cooking appliances, the new modern under 3kw cookers can be treated differently but again let's not run before you can walk. A normal way to wire a hood would be to spur of the socket outlet circuit. So normally you would come of the socket in 2.5mm into a switched spur unit and then 1.5 or 1.00 to the hood, using a 3amp fuse in the switch spur
M
malcolmsanford
Sorry son who as asked you to do this, a friend, a relative or a sparks your working with. If it is a sparks then I hope he is guiding you as he should be, your not really ready to start taking decisions like this are you?
take easy on yourself, not sure as i left all my books on train and they goneeeeeeeeeeeeeeeeeeeeeeeee.. put il take your word for it. can you tell me if im wrong.. i was told last week you can come off busbar in any cable as long as fused within 3m , that lets us get away without using bigger cables if no ie room
M
malcolmsanford
You can as you say reduce the size of the cable CSA in many situations as long as you adhere to regulation as above. Part of that reg is the 3 metre distance you quoted, but another part the (i) (ii) is just as important, coming of a 300amp bus bar with a bit of 1,5mm will IMO be a fire risk in the advent of a fault I would not want to do it, perhaps others might.
S
SimpleSimon
As Malcolm has stated alot of the older less efficient cookers you shouldn't really take a spur off for a hood because it's so close to the maximum cable capacity load.
However we are starting to see some gas/elecrtric combined cookers that don't draw as much current and possibly than you could take a cooker hood supply off it.
But that you would have to find out for yourself, find out the power outage of the appliance, use the formula to convert to Amps and compare the total load with the maximum cable current carrying capacity dependent on the installation method. Simple when you know how
However we are starting to see some gas/elecrtric combined cookers that don't draw as much current and possibly than you could take a cooker hood supply off it.
But that you would have to find out for yourself, find out the power outage of the appliance, use the formula to convert to Amps and compare the total load with the maximum cable current carrying capacity dependent on the installation method. Simple when you know how
S
SimpleSimon
Think Malcolm wouldn't mind me saying that what's he's saying I=p/u is that it could be done given the relevant info and correct calculations but given that the question was asked by someone learning it's more benifical to them to understand basic concepts before we start on circuit capacity and designing circuits. As Malcolm said, you have to walk before you can run.
P
Paul.M
Now now boys calm down.
Ipu, yes you can connect a lower csa cable from a busbar up to 3m but this is mainly industrial and not for a cooker hood. If the hood was within 3m of the busbar you would still have to use a FCU to protect the 1.5mm cable. If you did it this way you would not be able to use normal T&E as per the regs Malcolm has stated. Don't confuse industrial and domestic applications of the regs.
The spurring off a busbar is used for installing a new c/u or isolation switch for a particular appliance using the correct thermal protect for the cable, normal t&e would not do. In the event of a fault the 1.5 would without a doubt catch fire or explode at 300A witch is against the regs that Malcolm said.
So ipu is right on one thing but wrong in so many other ways. Back to the OP yes you can spur it off long as the flc calcs have been done and you have a FCU protecting the cable. Don't spur it from the busbar.
Ipu, yes you can connect a lower csa cable from a busbar up to 3m but this is mainly industrial and not for a cooker hood. If the hood was within 3m of the busbar you would still have to use a FCU to protect the 1.5mm cable. If you did it this way you would not be able to use normal T&E as per the regs Malcolm has stated. Don't confuse industrial and domestic applications of the regs.
The spurring off a busbar is used for installing a new c/u or isolation switch for a particular appliance using the correct thermal protect for the cable, normal t&e would not do. In the event of a fault the 1.5 would without a doubt catch fire or explode at 300A witch is against the regs that Malcolm said.
So ipu is right on one thing but wrong in so many other ways. Back to the OP yes you can spur it off long as the flc calcs have been done and you have a FCU protecting the cable. Don't spur it from the busbar.
S
SMB
Well.....
As long as your 'sticker' says.....
"I want to learn".....and......"I will listen" Then im on your side.
P
Paul.M
Ipu, well done for trying to learn as much as possible in a short length of time, just slow it down a bit mate. It won't be long before we can take the stabilizers off your bike
.
S
SMB
Under fault conditions, 1.5 mm cable, connected directly to a 300amp bus-bar wouldnt go 'bang'.....well, it might go 'bang' but it would definately burn, and so would everything combustible around it.
aye.
Melt.
Last edited by a moderator:
P
Paul.M
Please mate let's not go backwards, as before yes but its done in industrial installations.
Another thing ipu is that people come to this forum for help and advice and if anyone looks at what you have written will think its ok to connect any size cable to a busbar in a house and end up setting it on fire or frying themselves. It's good to ask or debate what we don't understand but better to give a full answer so there is no misinterpretation and everyone is safe.
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