in after a cowboy, cooker nearly burnt the house down!

[ExArmy]

I have just been to look at a job where i was asked to install a cooker as the previous one had nearly burned the house down apparently. when i took the cooker out there was a large burnt patch (300m accross), loads of charcoal, almost got through 1/2" ply below . when i pulled out the heat resistant flex i couldn't see where it had been plugged into, but it's likely it was plugged into the ring. it is a 3200W cooker from argos, the customer had got an argos technician out and apparently the cookers fine and it was down to the installation. customer reckons it was sat ontop of the connections and it was bodged up, I did try asking the customer to clarify how the cooker was connected up, but couldn't get much out of her! theres a 2.5 T&E running below the worktop behind the cupboards, not connected to anything but still live? but couldn't find where it came from as all the cupboards are full to the brim!

it's only a small house, 2 up 2 down, it's TT, got a 100mA RCD upfront and a 8 way 3036 board with 3 circuits (ring, lights and shower). ZE is 5-6ish ohms. would it be ok to spur it off the ring to a fused spur above the worktop, and then down to the cooker? an just put it on a minor works?
I'm not entirely sure what the line is about working on a circuit without 30ma RCD protection, do i need to add an RCD first or not?

also, the voltage is 250V at this house, 3200W at 250V is 12.8, so it i put a 13A fuse in the FCU then it will be alright? i seem to remember something from college saying all calculations to be worked out at 230V, in which case the current will be 13.9A and it will be more than the fuse rating. probably never blow, but what should i do here?

 

[steveberry11]

230 volts is just the baseline for design calcs where supply details arent known.
If you know the actual voltage , in this case 250v , then use that value.

230 volts should always be used what happens when the the DNO changes the transformer trappings of carry out switching in the area.

Stick with 230v

 

[1shortcircuit]

"cables installed on the surface do not specifically require RCD protection, however, RCD protection may be required for other reasons, for example, for the fault protection, where the earth fault loop impedance is such that the disconnection time for an overcurrent device cannot be met"

Simple test and compare to max Zs for the protective device

 

[ExArmy]

230 volts should always be used what happens when the the DNO changes the transformer trappings of carry out switching in the area.

Stick with 230v

well they have been talking about it for a while, i suppose it might happen one day...

 

[edward cooper]

i know he has not done job yet. As i have treated it as fixed equipment then I would put it on its own circuit and then because i have done this it will require rcd protection. i do how ever think my post is pretty clear.

 

[spark 68]

is there something that says fixed equipment over 2KW has to be on a dedicated radial? it's just that i wouldn't know how to justify that to the customer, it's only 3.2KW, almost the same as a kettle!

and regarding surface mounting to avoid having to fit RCD, ihave just come accross Reg 411.5:

"cables installed on the surface do not specifically require RCD protection, however, RCD protection may be required for other reasons, for example, for the fault protection, where the earth fault loop impedance is such that the disconnection time for an overcurrent device cannot be met"

Point 1) is in App. 15 in the BGB and is a recommendation.

Point 2) would your 100mA RCD upfront not satisfy the disconnection time for the Zs (you don't say if it is TD or not), although that in itself contravenes Reg 314.

 

[Guest55]

230 volts should always be used what happens when the the DNO changes the transformer trappings of carry out switching in the area.

Stick with 230v

Thats not the guidance given in the IEE electricians design guide when making a detailed assessment.
But im too busy getting drunk to argue it out lol.
;-)

 

[edward cooper]

i was not stating i would not fit rcd i was just quoting what some one else stated. i believe that it needs rcd protecting. If you fit a 3.2kw cooker on the ring without 30ma rcd protection i think your a fool. Dont forget this is a TT system.

a kettle is not fixed equipment and there is no comparison to be made between a kettle that is on for 3 minutes and a cooker that maybe on for three or four hours possibly a lot longer

 

[ExArmy]

Simple test and compare to max Zs for the protective device

it's about 6ohms at the socket next to the cooker which i would spur off, so on a 3036 it would almost certainly not disconnect within 0.4 seconds. if that is the limit for TT? i must admit i've not done an awful lot with TT. yet

 

[sedgy34]

Either put cable in trunking and install a rcd spur if your that concerned

 

[edward cooper]

TT ExArmy disconnection is 0.2sec

 

[spark 68]

Ex Army,

Welcome to my world,

Where the client says it is only a little job....

When you get there, there is no main bonding, no RCD, no spare ways in the CU (usually a 3036 4 way board) and/or no CPC on the lighting circuit, and they want class I (from B&Q)lights fitting, and on it goes...

The upshot of this is a bloke down the pub does it anyway, lol

 

[edward cooper]

Very true Spark 68.

Its amazing how many different answers you get to the simplist questions too.

 

[Guest55]

If you fit a 3.2kw cooker on the ring without 30ma rcd protection i think your a fool. Why ? whats so dangerous about a cooker ?


Dont forget this is a TT system. Yes , and it has a upfront 100mA rcd , so what ?

a kettle is not fixed equipment and there is no comparison to be made between a kettle that is on for 3 minutes and a cooker that maybe on for three or four hours possibly a lot longer That true , no arguement there , but youre talking about the de-rating of a ring mains capacity , has no connection the issue of rcds.

............................

 

[edward cooper]

Nothings dangerous with the cooker especially apart from the fact that its made from metal and if fault occurs its only a 30ma rcd or lower that protects life.

socket outlet circuits on a TT system must be protected by a residual current device with an operating current of 30 mA and as he wants to spur off the existing it needs rcd protection.

I dont want to argue im just saying that i would not fit this cooker without a 30ma RCD regardless of what obsure regulation you can find.i would also fit it on its own radial. i might be going over the top in your eyes but at least when i leave i know its safe

 

[ExArmy]

Ex Army,

Welcome to my world,

Where the client says it is only a little job....

When you get there, there is no main bonding, no RCD, no spare ways in the CU (usually a 3036 4 way board) and/or no CPC on the lighting circuit, and they want class I (from B&Q)lights fitting, and on it goes...

The upshot of this is a bloke down the pub does it anyway, lol

yep, i really can't be bothered with this one either. i'm back there at 9 in the morning, still havent decided what to do. i said this evening i'll have to RCD protect anything i fit which would mean changing the board, so i said i'd have to carry out an EICR first before i could price for the work, which is going to be ALOT as the board is the opposite side of the house to the stop cock and the gas meter and theres no bonding. and the house is a tip, and dirty.