Wiring up an oven.

[nick78]

I know various aspects of this subject have been covered many times before but I have been left confused by the installation instructions received with my new built-in single oven.
Here's its specs quoted directly from the install leaflet:
Model: Logik LBPCKX10
voltage:230-240V
Power: 3200-3500W
Current: 13-14A [don't know how that was calculated as 3500W/230V is 15.2A but that's what it says]
etc .

And here's the install instruction paragraph:
"An approved suitable cable must be connected from the Consumer Unit (main fuse box)and be protected by its
own 30amp fuse or Micro Circuit Breaker (MCB).
The electrician must provide a fused double-pole isolation switch, which disconnects both the line (live) and
neutral conductors, with a contact separation of at least 3 mm incorporated into the fixed wiring. The fused
switch should be fitted to the kitchen wall, and must be placed in an easy accessible position in accordance
with IEE regulations. Connect the fused switch to a junction box which should be fitted on the wall. The ovens
power supply cable can then be connected. Connect one end to the junction box and connect the other end
to the ovens power connection box which is located at the back of the oven. Remove the cover of the power
connection box and install the cable, in accordance with the connection diagram....etc"



My take on this is that as I don't currently have a cooker circuit I should fit a new cooker radial using 6mm^2 cable running to a DP switch above the (worktop as described above) then running to a hard-wirable cooker connection unit below the worktop from where the oven would be connected.
What I don't understand is:
1/ why does the instructions stipulate a 30A fuse/MCB be used when the current drawn should not be above 16A (3500W/230V=15.2A)
2/ What sort of DP fused switch should be used- as fas as I can see the majority of DP fused switches are 13A which wouldn't do for this.
3/ Assuming I can find a DP fused switch somewhere (any suggestions?) and since the rating has not been specified, I'd fit a 16A fuse in this- is this appropriate?
4/ If I can't find a DP fused switch would installing a 16A fuse/MCB at the consumer unit and simply using a 20A or 45A DP unfused switch be just as safe? Is there any advantage in either other than future-proofing possible oven upgrades later.


Any help and suggestions would be greatly appreciated.

Thanks, Nick78

PS a pdf of the install instructions can be found here if they're of any use:
http://www.buyspares.co.uk/images/m...anual lbpckx10_oven_vestel_ib_final110420.pdf

 

[securespark]

I would fit as large a cable as you can to allow for future expansion - you may want to fit a large double oven, range or hob.

But yes, I think you should protect the cable with a 16A breaker for your oven.

And I would fit a 30A min. DP switch within 2m of the oven.

However, you are best talking to the manufacturer to see how best to proceed as a fused switch is only rated to 13A.

Give them a ring.

 

[EFLImpudence]

You are correct in your suggestions.
The instructions do not really make sense.

Having said that, if you are having to run a new cable, you may as well do as is suggested in case you want a larger appliance in the future.

I take it you have a gas hob, do you?


Assuming no derating factor because of thermal insulation -

CU > 30A fuse or 32A mcb >> 6mm² cable >> 45A cooker switch >> 6mm ² cable >> cooker outlet plate >> 4mm² cable >> oven

Or
CU > 15A fuse or 16A mcb >> 6mm² cable >> 45A cooker switch >> 6mm ² cable >> cooker outlet plate >> 2.5mm² cable >> oven

 

[flameport]

It's only 3200w because of the silly function where the top oven element can be on at the same time as the grill. Without that, it would be well under 13A and could be plugged in.

What I would probably do - 16A MCB, 2.5mm T&E, 20A switch on the wall and a flex outlet behind the oven. 2.5mm flex from plate to oven.

 

[nick78]

Thank you for all your replies to my post and suggestions, really appreciated.

EFLImpudence- you are correct, the hob is gas.

For info the instructions suggest the connection between the wall connection and oven should only be 1.5mm^2. The current draw really can't be that high.

Nick78

 

[PrenticeBoyofDerry]

1/ why does the instructions stipulate a 30A fuse/MCB be used when the current drawn should not be above 16A (3500W/230V=15.2A)

Sounds like a little bit of nonsense by the MI, as you would get away with a 16A or 20A protective device. But if you had the addition of a socket outlet on cooker control unit it would be wise to have a higher rated protective device and as 25A devices are rare to most fuse boards/CU, then you could well be looking at 30/32A.

2/ What sort of DP fused switch should be used- as fas as I can see the majority of DP fused switches are 13A which wouldn't do for this.

You can buy DP Isolators rated at 20A and the standard cooker control switch will be rated at 45A-50A, these are very common.

3/ Assuming I can find a DP fused switch somewhere (any suggestions?) and since the rating has not been specified, I'd fit a 16A fuse in this- is this appropriate?

cooker control switches
DP 20A Isolator switches

4/ If I can't find a DP fused switch would installing a 16A fuse/MCB at the consumer unit and simply using a 20A or 45A DP unfused switch be just as safe? Is there any advantage in either other than future-proofing possible oven upgrades later.

Providing the rating of the isolator is more than the protective device rating, it will be safe.
And indeed it is worth at least upgrading the cable sizes, whether that becomes future proof only the future will tell.
In standard domestic installation when offer diversity to the circuit it is possible and allowed, to have a 15kW rated cooking appliance on a 4.00mm t&e cable. But I would at least go down the route of using 6.00mm t&e and if the distance is not too great and finances allow, you could go for 10mm t&e, might cost about £1.30 more per linear metre.

 

[EFLImpudence]

For info the instructions suggest the connection between the wall connection and oven should only be 1.5mm^2.

Not really should but yes

1.5mm² could be used.

1.5mm² would be sufficient with 15A fuse/16A mcb.