Electric Hob question again.

[Spikenaylor]

Hi there

just been to look at a job,
client has existing gas hob fitted, wants to change to Inductiuon hob.

Cooker switch is already fitted,
two 6mm cables run from switch behind the plaster out behind the cooker unit and into a double socket where the oven and gas hob are currently plugged in.

CU is an old wired fuse board 3 ways 5A lights, 30A ring, 30A cooker.

Option 1 is to remove one of the 6mm cables and use the other to power the new hob and remove the double socket and get the client to plug in an extension to nearby socket for the oven unit.

Option 2 is to fit new 17th CU then do option 1 and extend ring for oven unit.

Option 3 is to fit 2 way RCD CU just for the cooker circuit, extend cooker cable at cu end to fit new cu, splitting the tails and upgrading tails and bonding as required.

Option 4 walk away.

Option 1 Can't do due to lack of RCD, due to cables being <50mm embedded.

Option 2 is too costly for the client.

Option 3 ends up being costly for the client.

Option 4 looks good, they just upgrade their gas hob.

How is like for like(ish) hob replacement covered in regs? ( due to lack of RCD)

anyone got any other options I have missed

 

[chrish_1977]

Firstly, calculate the loading required for the induction hob, would be surprised if you still end up with the original 6mm cable, chances are you will need to put a new cable in, then just put it on a stand alone rcd. Other than that tell the customer no they can't have an induction hob

 

[Octopus]

If you are changing an oven to a hob thats not a change to the circuit is it?

 

[Spikenaylor]

Murdoch - no they want to change a Gas Hob to an Electric Hob.

Chris-1977 - The Hob in question show a Max. absorbed power (kW) : 7200

I assume that means 7.200KW and not 7200KW

anyway calcs show 7200/230 = 31.304A

diverstity = 19A (no socket on circuit)

cable capacity Reference Method A (cable only in plaster then in floor space clipped to joists no insulation then down cavity to cu (don't know what insulation is in that bit)) anyway 32A

so border line capacity for full on hob operation, but diversity says it is ok,

Murdoch - I wouldnt, but could go with the ' there was an electric hob fitted govn'r so like for like swap'

Chris-1977 - I suspect fitting 10mm cable dhasing the wall , pulling up floor boards, fitting new 2 way RCD CU for new circuit will be too much cost and hasle.

 

[Octopus]

Murdoch - no they want to change a Gas Hob to an Electric Hob.

Chris-1977 - The Hob in question show a Max. absorbed power (kW) : 7200

I assume that means 7.200KW and not 7200KW

anyway calcs show 7200/230 = 31.304A

diverstity = 19A (no socket on circuit)

cable capacity Reference Method A (cable only in plaster then in floor space clipped to joists no insulation then down cavity to cu (don't know what insulation is in that bit)) anyway 32A

so border line capacity for full on hob operation, but diversity says it is ok,

Murdoch - I wouldnt, but could go with the ' there was an electric hob fitted govn'r so like for like swap'

Chris-1977 - I suspect fitting 10mm cable dhasing the wall , pulling up floor boards, fitting new 2 way RCD CU for new circuit will be too much cost and hasle.

Why not, if you test the circuit and its ok then a MWC would be OK.

Bonding? Rcd's?

 

[Spikenaylor]

Why not, if you test the circuit and its ok then a MWC would be OK.

Bonding? Rcd's?

Thats why, there isn't any

 

[Engineer54]

Firstly, calculate the loading required for the induction hob, would be surprised if you still end up with the original 6mm cable, chances are you will need to put a new cable in, then just put it on a stand alone rcd. Other than that tell the customer no they can't have an induction hob

Whys that then??

Also if this is an older house, the chances are that the 6mm stated, is in fact a 7/044 T&E, which will carry more current than a 6mm cable!! lol!!

 

[Octopus]

Thats why, there isn't any

Why do you need to add a RCD to an existing cable for a hob?

 

[Spikenaylor]

So it is perfectly ok due to the wiring being there already to fit a like for like hob without RCD protection as long as all tests carry out fine with the mwc stating lack of RCD protection and client informed as recommendation to think about cu upgrade, as long as client agrees that at some point past, an electric hob was fitted, then changed to gas, now to be changed back to electric, just thinking about covering myself.