I intend to replace a built in single oven with a double oven.
The single oven is connected with 6mm T&E but does not have a local isolator. I will terminate the existing cable in a 45A cooker switch. How do I then connect the new double oven to the cooker switch? I don't know if the oven comes with a flex or not. Should there be a separate cooker outlet at the back of the oven housing to connect the oven to.
Thanks
You get a bit of suitable cable or flex and connect it.
Probably not but you'll find out. You'd normally use a bit of the same cable.
Yes. You'll need a separate cooker outlet plate which you locate on a wall box behind the cooker. It includes a cable clamp but the cable goes right through a conduit or chasing to the switch.
If the switch is right next to the unit and is on a surface mounting patress then you may be able to cut a slot in the edge of the unit and take the cable directly into the switch.
This "double oven" - is the "doubleness" simply in its internal layout, with just one cable to feed it? If so, wiring either the supplied flex (if it comes with such) or a length of 2.5mm T&E into the new 45A cooker switch is "probably" OK. The exact "probably" depends on the details of the cooker rating - what its peak current draw is, whether you're in fact likely to run at or close to that max for extended periods, and the length of that shorter piece of thinner cable. The calculation you need to perform is (a) whether the flex or thinner cable can carry the max load the double oven can create (with possible correction for higher ambient temperature if the feed cable/flex will be tucked up behind the oven housing where it'll be warmer than room temp), (b) whether the protective device on the cooker circuit (tell us what it is - a 32A Type B MCB?) will protect the thinner cable in the event of a short, and (c) whether the oven's installation instructions call for a lower-amperage protective device than your existing 6mmsq circuit has (though if you've only the one oven, you could change the MCB to a 16A one if that's what it says it wants).
If you want to avoid such calculations-and-considerations, connecting up with 6mmsq throughout is "clearly" OK, since that's what the existing circuit is designed in - provided the oven doesn't require lower-rated protection; as is putting in a fused connection unit (FCU) to transition between the 32A-MCB-protected 6mmsq to a supplied flex - now the 13A fuse in the FCU protects the flex; as is running a length of 2.5mmsq from the new cooker switch to a 13A socket (unswitched, to avoid mysterious loss of power!) in the back of or just next to the oven installation hole, if your oven comes with a moulded-on plug you'd rather not chop off - here the lower-rated 2.5mmsq cable is protected against overload by the Nature Of The Load (if fitted with a 13A plug, your oven clearly isn't designed to pull more than 13A) and against short circuit ("fault current" if we're using Regs-speak) by both the plugtop fuse and the MCB in the CU.
HTH - Stefek
Run from the isolator (within 2mtrs of appliance) to a cooker connection point behind cooker, connect new cooker to this point when it arrives it will not come with flex.
Peter
"nicoll" wrote | I intend to replace a built in single oven with a double oven. | The single oven is connected with 6mm T&E but does not have a | local isolator. I will terminate the existing cable in a 45A | cooker switch. How do I then connect the new double oven to the | cooker switch? I don't know if the oven comes with a flex or | not. Should there be a separate cooker outlet at the back of | the oven housing to connect the oven to.
From the cooker switch you continue in 6mm fixed wiring to the back of (or beside) the oven, where you use a cooker connection unit to make the final connection to the oven, either using the oven's integral flex/cable or another piece of 6mm.
Cooker connection unit (note these have a cable clamp for the flying lead, they are not just ordinary junction boxes)
Owain
If it requires more than a 13 amp feed, it's normal to wire from the switch to the cooker in the same cable as the 'main' feed - there are terminals in the back for connection.
Typically single oven/grills take 13A can be fed from a socket nearby in the cupboard below.
Double ovens/grills will typically require a 20A supply. This will be in
2.5T&E with a 20A MCB or you might use your existing arrangements for a freestanding cooker with 30,32 or 45 A and 4,6 or 10T&E wiring. In all these cases you run the wire to double pole switch within 2m of the appliance and then either to a connection outlet or a leave enough slack behind the oven to connect when you install the appliance.Thanks for answers.
We haven't selected the double oven yet so I don't know the rating.
Is there any particular type of flex (rather than cable) I should use between the oven and the connection unit?
4.0mm 3183TQ Butyl Flex Heat Resistant EPR Insulated and CSP Sheathed Temperature range: to 85°C Current Rating: 35 Amps
Peter
Premature, then, to select the cable/flex until you have at least a rough idea of the oven's current requirements. As noted, you won't go wrong using 6mmsq, but if the oven comes with a built-in and not-readily-replaceable flex you'll have wasted your time getting in the length of 6mmsq. Is there any great rush in this kitchen job?
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