Morning all,
I’m hoping one of the electricians around here may be able to help me with this one…
I’ve got a built-in Siemens eye-level double oven to connect to an existing circuit. The oven is rated 5.5kW @ 230V, i.e. 23.9A. They do not specify a fuse size or a cable size.
My existing circuit is run from a 32A RCBO, via 10mm t+e to a 45A Cooker Control Unit with socket, and on to a 45A Cooker Connection Unit.
As I understand it, the typical diversity rules for a ‘cooker’ consider a typical appliance with 4 hotplates, and oven and a grill. Am I correct that this cannot really be applied to a double oven, as the characteristics of that are more like a single fixed load?
If I am correct not to apply diversity, then the existing 32A breaker would appear to be the correct choice, and the cable/controls more than adequate.
The problem I have is with the flex to connect the oven to the connection unit. The manufacturer’s instructions insist on H05VV-F flexible cable or a higher rating, so that rules out ordinary t+e for me. I have got some of this flex in 4mm form (H05VV-F 3G4), and as far as I can tell, this is rated at 32A in Table 4F3A, but I would imagine that the ambient temperature at the back of an oven could be expected to be over 30 degrees, therefore derating the flex.
I am concerned that while 4mm would still be adequate for the designed load of the oven even if derated for 40 degrees (26A), it may not be adequately protected from overload by a 32A breaker. This brings me to another point – can I consider the oven to be a fixed load that does not require overload protection at the origin, and therefore use the 4mm flex provided that it is adequately protected from fault currents?
An alternative I have is to use H07RN-F flex in 6mm, would that be a better option? The problem with this is that it will be a very tight squeeze in the Cooker Connection Unit due to the overall diameter of it as a round cable.
In either case, I will of course be fitting bootlace ferrules to the flex before I fit it to the cooker connection unit, and the terminals in the oven itself appear to be suited to flex.
Thanks in advance for your help with this.
Dave
I’m hoping one of the electricians around here may be able to help me with this one…
I’ve got a built-in Siemens eye-level double oven to connect to an existing circuit. The oven is rated 5.5kW @ 230V, i.e. 23.9A. They do not specify a fuse size or a cable size.
My existing circuit is run from a 32A RCBO, via 10mm t+e to a 45A Cooker Control Unit with socket, and on to a 45A Cooker Connection Unit.
As I understand it, the typical diversity rules for a ‘cooker’ consider a typical appliance with 4 hotplates, and oven and a grill. Am I correct that this cannot really be applied to a double oven, as the characteristics of that are more like a single fixed load?
If I am correct not to apply diversity, then the existing 32A breaker would appear to be the correct choice, and the cable/controls more than adequate.
The problem I have is with the flex to connect the oven to the connection unit. The manufacturer’s instructions insist on H05VV-F flexible cable or a higher rating, so that rules out ordinary t+e for me. I have got some of this flex in 4mm form (H05VV-F 3G4), and as far as I can tell, this is rated at 32A in Table 4F3A, but I would imagine that the ambient temperature at the back of an oven could be expected to be over 30 degrees, therefore derating the flex.
I am concerned that while 4mm would still be adequate for the designed load of the oven even if derated for 40 degrees (26A), it may not be adequately protected from overload by a 32A breaker. This brings me to another point – can I consider the oven to be a fixed load that does not require overload protection at the origin, and therefore use the 4mm flex provided that it is adequately protected from fault currents?
An alternative I have is to use H07RN-F flex in 6mm, would that be a better option? The problem with this is that it will be a very tight squeeze in the Cooker Connection Unit due to the overall diameter of it as a round cable.
In either case, I will of course be fitting bootlace ferrules to the flex before I fit it to the cooker connection unit, and the terminals in the oven itself appear to be suited to flex.
Thanks in advance for your help with this.
Dave