Moving Cooker & Oven to the opposite side of the kitchen

[diy888seeker]

Hi I am thinking of moving my cooker and oven to the opposite side of the kitchen. My questions are:

1. I am confident that I can do the job myself (tho Im not an electrician) Can I just extend the wire and connect them in a junction box? Of course I will move the isolator near the new location as well. Is this notifiable?

2. Now the route, can I just use the back of the Base carcass like the existing ring, but is therefore passing under the sink? If not legal/advisable my next option (I was trying to avoid) is to dig under the floor as prefer not to touch the floor above

Thanks in advance

 

[ericmark]

In a new system with RCD protection likely no problem but you must remember it's not as simple as putting in more wire. There are two problems which are related volt drop and earth loop impedance.

With an induction hob I would worry about volt drop as don't know how they will handle low volts but simple elements although will not work as well not really any danger or damage if volt drop too high.

With RCD protection ELI is unlikely to be a problem but without it is very important as if too high the automatic disconnection in the event of a fault may not work.

So information given is not enough to give proper answer.

 

[diy888seeker]

Thanks for that quick reply Ericmark,

I think I have MCB just for additional info. Am I required to have it changed to an RCD?

My cooker is induction, would the possible voltage drop be caused by the splice in the junction box?

Are you saying if I have my MCB replaced to an RCD by an electrician, I can safely do my DIY cooker wiring?

How about my second question on the route of the wire?

 

[ericmark]

I do not know the tolerance for volts on your induction mine says 220 - 240V but I think that is nominal volts so just use the standard 5% volt drop so in real terms if the ELI passes so will the volt drop.

All cable hidden in a wall needs to be special or RCD protected but surface cables don't need RCD protection however with no RCD protection the earth loop impedance is important. For a B32 MCB the max value is 1.44 ohms.

I know many DIY people don't follow regulations and as long as it works they don't worry but you have asked what you should do and I have answered clearly you can break the rules and take a chance and do no testing and 9 times out of 10 it will be OK.

But there is a reason why electricians pay out £750 for test gear and if you want to cut corners then you have to accept that there may be errors.

Being honest if I did not have test gear I would still DIY but I have done it for long enough to judge when near limits and when no problem. How long will the run be once moved?

 

[JohnW2]

With RCD protection ELI is unlikely to be a problem but without it is very important as if too high the automatic disconnection in the event of a fault may not work.

Are you suggesting that it's acceptable (or, at least, 'good practice') to (in a TN installation) rely upon an RCD to provide satisfactory disconnections times because the Zs is too high for an OPD to achieve that?

Kind Regards, John

 

[ericmark]

I see no difference between a TT system relying on a RCD to a TN system relying on a RCD but admit one should strive to keep within the impedance figures however where a RCD is fitted it will be the line - neutral impedance which has to be within the limits for MCB not the line - earth impedance the impedance needs to be measured to insure the RCD will trip but with the B32 example 1.44 ohms is only really needed for the line - neutral.

However trying to explain to a DIY guy what the ELI is would be hard enough without explaining about PFC or the relationship between them.

 

[EFLImpudence]

I see no difference between a TT system relying on a RCD to a TN system relying on a RCD

Only because, with TT, there may be no choice unlike TN when it is allowed, with permitted installation method, not to have an RCD.

but admit one should strive to keep within the impedance figures however where a RCD is fitted it will be the line - neutral impedance which has to be within the limits for MCB not the line - earth impedance

More than strive, surely.

the impedance needs to be measured to insure the RCD will trip

It would be some circuit to exceed 1666Ω

but with the B32 example 1.44 ohms is only really needed for the line - neutral.

Even that, assuming 6mm², would have to be over 137 metres (or 80% of, 109)

However trying to explain to a DIY guy what the ELI is would be hard enough without explaining about PFC or the relationship between them.

That may be true but I am sure that saying "Is the cable less than 109 metres long?" would probably be understood.


I do agree about the testing but if that were the criterion then we may as well switch off.
So, ensuring the posters do not live in palaces, domestic installations rarely exceed the maximum allowed values of VD or EFLI.

The only way my cooker circuit could exceed any of these values would be if the kitchen were in another house several doors away.

 

[JohnW2]

I see no difference between a TT system relying on a RCD to a TN system relying on a RCD but admit one should strive to keep within the impedance figures however where a RCD is fitted it will be the line - neutral impedance which has to be within the limits for MCB not the line - earth impedance the impedance needs to be measured to insure the RCD will trip but with the B32 example 1.44 ohms is only really needed for the line - neutral.

I can understand that view. However, although the regs do talk about using an RCD to achieve disconnection times when that cannot be achieved with an OPD, I have always assumed that they were not simply talking about situations in which one could not be bothered to install a cable of adequate size - otherwise they might just as well explicitly allow an RCD to be the protection against L-E faults on a 'blanket' basis.

In any event, as you imply, R1+R2 is not that much greater than R1+Rn (i.e. the CPC/earth conductor does not have that much higher a resistance/impedance than the neutral one) - so, in practice, there's a pretty small window in which an OPD would give adequate protection for L-N faults but not for L-E ones.

Kind Regards, John

 

[diy888seeker]

Im assuming this is still a healthy discussion as I am a bit lost here.

If I would install a single rcd...(maybe similar with link below?)
....At the end of the original wire and before the start of the new cable... I will be okay?

http://www.diy.com/nav/fix/electric...d-30mA-32-and-6A-Mcbs-12808574?skuId=13319280

Come on guys give it to me in simple words. Im starting to think its more complicated than originally thought.

 

[flyingsparks]

To the OP: extending the circuit will be ok. You can run behind the carcasses if you want, not best practice but ok. Try and clip it to the wall if possible.
RCD protection is required if the cable is buried in the wall, or if you have a cooker switch with a socket on it.

To the rest of the posters: at my old employers my qualifying supervisor asked the niceic inspector if the max zs values couldn't be met, for example with a high rated c or d type breaker, could a RCD be used to compensate, and he said yes. I assume right up to 1666 for 30mA or 500 for 100mA.

 

[EFLImpudence]

Never assume those in charge know what they are doing.

 

[flyingsparks]

Never assume those in charge know what they are doing.

Eh? This is a DIY forum, and I have given him answers to his questions.

 

[Iggifer]

I think that was directed at the NICEIC guy

 

[ericmark]

the impedance needs to be measured to insure the RCD will trip

It would be some circuit to exceed 1666Ω

411.5.3 TABLE 41.5 NOTE 2:* The resistance of the installation earth electrode should be as low as practicable. A value exceeding 200 ohms may not be stable. Refer to Regulation 542.2.2. So 200Ω is the limit.

but with the B32 example 1.44 ohms is only really needed for the line - neutral.

Even that, assuming 6mm², would have to be over 137 metres (or 80% of, 109)

For a TN system there is 0.8 ohm or 0.35 ohm allowed for incomer depending on type so 87.5 meters max loop impedance to reach 1.44Ω but volt drop would limit it to 49 meters for 6mm² for 4mm² down to 32.5 meters sounds a lot but by time one runs cable up and down walls and L shape around beams easy to exceed.

However trying to explain to a DIY guy what the ELI is would be hard enough without explaining about PFC or the relationship between them.

That may be true but I am sure that saying "Is the cable less than 109 metres long?" would probably be understood.


I do agree about the testing but if that were the criterion then we may as well switch off.
So, ensuring the posters do not live in palaces, domestic installations rarely exceed the maximum allowed values of VD or EFLI.

The only way my cooker circuit could exceed any of these values would be if the kitchen were in another house several doors away.

I have been surprised at results when testing although often found something wrong was the reason for bad results rather than simple too much cable. From the ex-immersion heater feed extended to tapped off ring and even ex-shower cable so cooker feed went to top of house and back down again I have and I am sure every one else has had the odd time when the meter alerted us to something strange and we looked further and found a fault.

I did say "Being honest if I did not have test gear I would still DIY" but we have no idea of size of house. "flyingsparks" has likely given best answer to original question.

Question is:-
1) If the guy does the work then puts the house up for sale will an electrician doing an EICR list anything he has done as a fault attracting a code?
2) Will anything he has done likely damage the equipment he is using?

I honestly do not know if under voltage can damage an induction hob? Neither do I know how much under voltage it would require if it did. Likely with a 220 to 240 volt on label it will stand the maximum volt drop so still work OK at 203 volts (220v - 3% - 5%) rather than our limit of 212 volt (230v - 3% - 5%) but this is a pure guess.

When UK voltage dropped from 240 to 230 in real terms we saw little or no change but solar panels and grid-tie inverters now mean to stop them cutting out the voltage often needs to be dropped so now even dead of night with no off peak used as gas is in the area voltage 236 at my house but few years back was always over 240 must remember to look at Christmas eve when all cookers are doing the turkeys.

 

[ericmark]

Im assuming this is still a healthy discussion as I am a bit lost here.

If I would install a single rcd...(maybe similar with link below?)
....At the end of the original wire and before the start of the new cable... I will be okay?

http://www.diy.com/nav/fix/electric...d-30mA-32-and-6A-Mcbs-12808574?skuId=13319280

Come on guys give it to me in simple words. Im starting to think its more complicated than originally thought.

A RCBO

and a small enclosure

£22 + £8 is smaller and will do same job. To be honest if it were mine I would not bother I would use a simple cooker connection unit

and just extend from that. If you want RCD protection I would likely put it next to the consumer unit not in kitchen.

Sorry I went a bit OTT as others have pointed out I was having a blond moment.