DUAL APPLIANCE OUTLET PLATE

[Ira Jag]

Hi everyone,

I have read few posts about dual appliance outlet and wonder now if it can be used in my case. I have 32a 6mm cable to 45a switch supplying 6200w hob. Current oven is 2,4kw 13a plug. It will be replaced with 7,4kw induction hob and 3,6kw oven. Can hob circuit be used for both appliances connected to dual outlet plate and using same 45a switch? We were told by an electrician 6mm cable will be ok for both appliances, but when we had a quote for new kitchen they builder told us he would not connect both appliances to one 6mm cable and we heed to add new circuit. In our case it has to run outside around house and we would like to avoid it if possible.

Any advice is appreciated

 

[telectrix]

what you have to bear in mind is diversity. with cooking appliances yo won't usually have all elements on at the same time, and they cycle on annd off with the thermostats, so a cooker /hob rated at say 11kW total rated power ( 48A) will have an average current of only approx. half of that (24A).

 

[Ira Jag]

what you have to bear in mind is diversity. with cooking appliances yo won't usually have all elements on at the same time, and they cycle on annd off with the thermostats, so a cooker /hob rated at say 11kW total rated power ( 48A) will have an average current of only approx. half of that (24A).

11kW was total 7,4 hob and 3,6 oven and it what I said to the builder that that both appliances will not be run on full, but he said it would be dangerous and illegal. I want everything to be done according regs in case I have to sell or rent house in the future.

 

[telectrix]

not to worry. as i said, both oven and hob will be fine on a 32A MCB, 6.0mm cable (if cable is not smothered in insulation) . this application of diversity has been in use for 60+ years and found to be compliant. only reason to install separate circuits for oven and hob would be to isolate either if faulty and still have use of the other.

 

[Strima]

but he said it would be dangerous and illegal.

As previously stated, let him worry about slopping bricks together and let the electrician deal with the electrics. TBH if a builder that I had employed started coming out with comments like that he would be looking for business elsewhere.

 

[telectrix]

the only illegal thing here is a builder sticking his snout into something about which he knows bugger all (and probably due a nice backhander from his tame sparks odd job man to install an uneccessary circuit).

 

[Ira Jag]

not to worry. as i said, both oven and hob will be fine on a 32A MCB, 6.0mm cable (if cable is not smothered in insulation) . this application of diversity has been in use for 60+ years and found to be compliant. only reason to install separate circuits for oven and hob would be to isolate either if faulty and still have use of the other.

(if cable is not smothered in insulation) - we have vaulted ceilings so cables runs between roof and 100mm celotex and in the walls between terminal bricks and plasterboards without conduits. Roof can get hot in the summer, but there is a air gap between roof and celotex to prevent condensation.

 

[telectrix]

cables warm up in use. this is normal. as long as the heat can dissipate, there's no problem. covering cables in insulation reduces their current capacity, the derating factor dependent on how thick the insulation over the cables is.e.g. 6mm cable with no insulation is rated at 47A continuous. derating due to insulation can be as much as 40%. a reasonable air gap around the cable is recommended where cable is heavily loaded.

 

[Ira Jag]

cables warm up in use. this is normal. as long as the heat can dissipate, there's no problem. covering cables in insulation reduces their current capacity, the derating factor dependent on how thick the insulation over the cables is.e.g. 6mm cable with no insulation is rated at 47A continuous. derating due to insulation can be as much as 40%. a reasonable air gap around the cable is recommended where cable is heavily loaded.

Because of vaulted ceilings our cable runs in air gaps between insulation and roof, I don’t know building regs for air gap in roof but I believe it minimum 50mm or more. Maybe it is not same as no insulation, but there is good air gap.

 

[telectrix]

50mmair gap is good enough to maintain a current capacity close to max. maybe a 10% - 15% reduction.