5.3 kw double oven on a 20 amp fuse with 2.5 cable

[telectrix]

ok, so 30% of the 23 amps is 6.9 amps


so 16.9 amps as you said in your earlier post right

NO. 10A + 30% of remainder (13A, not23A)

 

[ebow72]

there is a hob but its on a seperate 6mm

Might be a stupid idea and I don't know the rating of the hob, but is there enough slack of the 6mm, to swap over to the cooker and vica versa...
I am still learning so please don't make me brew up

 

[GLENNSPARK]

it might be a start to look at app. A starting page (109) in the osg (green)....table A1....

 

[WPD Lad]

Might be a stupid idea and I don't know the rating of the hob, but is there enough slack of the 6mm, to swap over to the cooker and vica versa...
I am still learning so please don't make me brew up

Hobs are normally rated higher than ovens, something in the order of 7kw

 

[WPD Lad]

If its in a conduit surely it's easy enough to swap out for 4 or 6mm

 

[TaffyDuck]

Diversity on a cooker works fine until Xmas day when they trip out. personally I think regs are out of date on this one. Take a 10 kW electric range cooker. 10kW/230V= 43 amps. 10 amps plus 30% remaining load (approx 9.9amps) =19.9 amps so 2.5mm twin and earth on a 20 amp, dont think so. "At the installers discretion" is a term we ought to use more. On top of that you`ve got an appliance that draws for long periods of time allowing heat to build up in the circuit. Its not like a kettle that runs for a couple of minutes at a time. 6 or 4mm on this OP specs every time for me,

 

[Dave 85]

Bung it on the 2.5 on a 20A breaker with 20A DP iso. You're happy, regs are satisifed and client doesn't feel shafted and may actually call you again. I really don't understand this attitude of 'charge the client for an unnecesary job just to punish them for changing their mind.' Repeat business is good no?

 

[GLENNSPARK]

Diversity on a cooker works fine until Xmas day when they trip out. personally I think regs are out of date on this one. Take a 10 kW electric range cooker. 10kW/230V= 43 amps. 10 amps plus 30% remaining load (approx 9.9amps) =19.9 amps so 2.5mm twin and earth on a 20 amp, dont think so. "At the installers discretion" is a term we ought to use more.

well on such a load then...yes....it would be up to the designer as to the right action to take here.....short of treating it as a commercial load...100% of the first load....80% of the second and 60% of remaining appliances....

 

[ample current]

so what does the fl mean in the OSG (red one page 97)?? and i quote "10A +30% of fl of connected cooking appliances.........."

 

[GLENNSPARK]

full load...

 

[TaffyDuck]

well on such a load then...yes....it would be up to the designer as to the right action to take here.....short of treating it as a commercial load...100% of the first load....80% of the second and 60% of remaining appliances....

Well I was taught to build in redundancy and that diversity was to do with total demand not individual circuits but I may be wrong there.. May be considered old fashioned by some but Ive lost count of the times Ive come across burnt out 2.5mm on an oven. Whatever the regs say the buck stops with the installer, hoping the client doesnt cook much is daft in my book. I have always used 4 or 6 on an oven, might be over engineered in some peoples eyes but its a better quality job

 

[WPD Lad]

The 2.5 hasn't been de rated at all, we're assuming it'll have the full ccc, if it's in a conduit I'd stick a larger cable in

 

[ample current]

full load...

So why is it 30% of the remainder and not 30% full load
it says 10A + 30% fl not remainder :dizzy2: or am i missing something????? or just being a bit dim.

 

[TaffyDuck]

So why is it 30% of the remainder and not 30% full load
it says 10A + 30% fl not remainder :dizzy2: or am i missing something????? or just being a bit dim.

OSG page 110 10amps + 30% of remainder

 

[GLENNSPARK]

diversity becomes a problem when people start adding all connected loads together and then applying diversity....doesn`t work as the overcurrent device and associated cabling will be woefully undersized/underrated.....but as has been said before....the "regs" as we see it...that is BS7671 and anything seconded to it.....OSG GN3 etc are but guidance notes after all and as such are open to question as regards issues like this.....of course it is wiser to go over rather than under in terms of protective devices and cable/s and theres the issue of futureproofing as well....but how far do you take it?....Diversity is there for us to utilise ...given the guidance laid out in BS7671....its just a case of how and where....like you wouldn`t apply diversity to such a thing as an instantainious water heater would you.....as someone who posted on this forum about 3 weeks ago was going to do.....until advised not to of course....

 

[ample current]

OSG page 110 10amps + 30% of remainder

I take it thats the green one.

 

[GLENNSPARK]

if you look it is refering to 10A +30% fl in which it means you take the full load and apply the first 10A then 30% of whats left......

 

[Gordon]

The diversity applies to a cooker incorporating oven, rings, grill and assumes that they won't all be drawing full power in one go. likelihood
is that a double oven will draw full current at some time. Better to upgrade cable accordingly.

 

[TaffyDuck]

Table A1 is concerning diversity on individual circuits and states 10amps + 30% of remainder. Table A2 is diversity of a whole system and states 10amps +30% Full load in excess of 10a

 

[GLENNSPARK]

The diversity applies to a cooker incorporating oven, rings, grill and assumes that they won't all be drawing full power in one go. likelihood
is that a double oven will draw full current at some time. Better to upgrade cable accordingly.

yet again....looking at the appliance first...or if the appliance isn`t on site at the time of design....then gathering info (make model) etc from the client and doing a bit of research on it.....find out the KW rating etc...so as to calculate/design accordingly....isn`t that the difference between installers and electricians.......