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.

 

[Strima]

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.

Didn't know you'd been round here, should have stayed for a brew...

 

[Guest55]

No bonding ??
lol , then youre not going to be doing any work till that sorted.
if i was you i'd just price mself out of the job , sounds a whole load of hassle unless the customer is gonna pay for all the extras.

 

[ExArmy]

so if i was to fit a new board, i'd have to fit a 100mA time delayed RDC main switch? also i would fit bonding, and what about the main earth to the erath spike? it's 10mm at the minute, dissapears into the wall and i can't see where it goes. how do i go about fettling this upto the 17th edition, and how do I test it?

 

[1shortcircuit]

No bonding ??
lol , then youre not going to be doing any work till that sorted.
if i was you i'd just price mself out of the job , sounds a whole load of hassle unless the customer is gonna pay for all the extras.

Have you weighed the client up yet? Judging a book by it's cover is never good (and sometimes it goes wrong) but is there money in it for you? Are they likely to go for it OR are could this be a factor as to how they ended up with a shoddy job done in the first place?

If in doubt price yourself out of it and walk away:thumbsup

 

[ExArmy]

No bonding ??
lol , then youre not going to be doing any work till that sorted.
if i was you i'd just price mself out of the job , sounds a whole load of hassle unless the customer is gonna pay for all the extras.

yeah thats looking like the option i'm leaning towards, i'll do the EICR and then whack in a sky high price...

 

[spark 68]

so if i was to fit a new board, i'd have to fit a 100mA time delayed RDC main switch? also i would fit bonding, and what about the main earth to the erath spike? it's 10mm at the minute, dissapears into the wall and i can't see where it goes. how do i go about fettling this upto the 17th edition, and how do I test it?

No need to fit a 100mA TD upfront, provided the CU you replace it with is Class II (plastic) and at least a Dual RCD split load, see OSG p16 Fig 2.1(iii).

 

[ExArmy]

Have you weighed the client up yet? Judging a book by it's cover is never good (and sometimes it goes wrong) but is there money in it for you? Are they likely to go for it OR are could this be a factor as to how they ended up with a shoddy job done in the first place?

If in doubt price yourself out of it and walk away:thumbsup

yes, the person paying for the work is the landlord, who owns several properties, and the people who bodged the cooker have worked on his houses for years and never had any problems before (nothing short of a miracle from some of the wiring i saw today) i'll get some pics on my periodic tomorrow

 

[Guest55]

so if i was to fit a new board, i'd have to fit a 100mA time delayed RDC main switch? Yes

also i would fit bonding, Yes
and what about the main earth to the erath spike? it's 10mm at the minute, Needs to be 16mm
dissapears into the wall and i can't see where it goes. You need to find and check the rods condition , but it sounds like its giving good readings from your earlier posts.

how do i go about fettling this upto the 17th edition, and how do I test it? Use earth loop test from CU main switch terminals and earth rod conductor.

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

 

[1shortcircuit]

so if i was to fit a new board, i'd have to fit a 100mA time delayed RDC main switch? Yes

I disagree, if fitting a new board then all circuits will be protected with 30mA protection so the 100mA could be binned and an isolator fitted in it's position or tails sent straight into the board.

 

[spark 68]

Why does he have to fit a 100mA TD upfront RCD Biff ?, if he replaces the CU with a plastic Dual RCD one there is no reg that says you must fit an additional Upfront TD 100mA RCD.

I Know some sparks have their own preference on this, as I would consider it in certain circumstances, but on such a small domestic install I wouldn't bother.

Likewise on the earthing conductor, so long as the cable isn't buried he could use 6mm, in fact if it was mechanically protected it is possible to use 2.5mm on a domestic TT (not that you would).

 

[Guest55]

I disagree

And just as i thought we might be getting near the end of this long journey lol.

 

[1shortcircuit]

And just as i thought we might be getting near the end of this long journey lol.

Hey it's only stating I disagree I'm not trying to start an argument over it lol

Perhaps I have typed before engaging brain but I do not come across many TT installations so perhaps you know something I do not? If so I would be more than happy for someone to enlighten me and I will stand correct. We've got 6 minutes for me to learn something new today:thumbsup

Make that 5

 

[Guest55]

Why does he have to fit a 100mA TD upfront RCD Biff ?, if he replaces the CU with a plastic Dual RCD one there is no reg that says you must fit an additional Upfront TD 100mA RCD.

I Know some sparks have their own preference on this, as I would consider it in certain circumstances, but on such a small domestic install I wouldn't bother.

Likewise on the earthing conductor, so long as the cable isn't buried he could use 6mm, in fact if it was mechanically protected it is possible to use 2.5mm on a domestic TT (not that you would).

I stand corrected with the point of not needing 100mA if dual 30mA ( im blaming it on the liquor lol )
However if he cant prove the rod earth conductor is mechanically protected when buried ( and i bet its not ) then 16mm is required.

 

[Guest55]

But youre right , i'd be happy to use the 10mm if its giving good readings , i cant be arsed digging up the drive for a new rod install either

 

[Des 56]

i said this evening i'll have to RCD protect anything i fit which would mean changing the board,

​

Stand alone Rcd
It will certainly make you more competitive than John from the Pub,that's comparing to the proposed all singing and dancing 17th compliant and possibly un necessary new board