Why 2 hob ratings per ring

[JohnS888]

Hi all.

Could someone clarify why there is two hob power ratings on AEG IKB64301FB Electric Induction Hob - Black - https://www.currys.co.uk/gbuk/household-appliances/cooking/hobs/aeg-ikb64301fb-electric-induction-hob-black-10186499-pdt.html

Also what would be the total wattage. Hoping this might go on same 6mm circuit with 3.2kw oven

 

[Simon47]

If you look at the manufacturer's instruction manual found at Induction Hob 60 cm - IKB64301XB | AEG - https://www.aeg.co.uk/kitchen/cooking/hobs/induction-hob/ikb64301fb/ you'll see that the smaller value is the normal capacity, and the higher value is the short term boost ability.

 

[JohnS888]

If you look at the manufacturer's instruction manual found at Induction Hob 60 cm - IKB64301XB | AEG - https://www.aeg.co.uk/kitchen/cooking/hobs/induction-hob/ikb64301fb/ you'll see that the smaller value is the normal capacity, and the higher value is the short term boost ability.

Thank you Simon

 

[snowhead]

From the link above it shows total load rating as 7350w, which does not include the boost, presumably as it's only short term and you're unlikely to boost all 4 zones at the same time

 

[JohnS888]

From the link above it shows total load rating as 7350w, which does not include the boost, presumably as it's only short term and you're unlikely to boost all 4 zones at the same time

Thanks Snowhead. Out of curiosity if you had a 3.2kw oven and 6.4kw hob would you have any issue with putting both on a 6mm? Have checked diversity equation in onsite guide and this seems to suggest would be ok but I am surprised at how much allowance this gives as all hobs and oven could potentially be on full power at the same time

 

[telectrix]

Thanks Snowhead. Out of curiosity if you had a 3.2kw oven and 6.4kw hob would you have any issue with putting both on a 6mm? Have checked diversity equation in onsite guide and this seems to suggest would be ok but I am surprised at how much allowance this gives as all hobs and oven could potentially be on full power at the same time

they could all be switchred on, but the stats. will cycle them on/off at different times.

 

[JohnS888]

they could all be switchred on, but the stats. will cycle them on/off at different times.

Thanks Telectrix. So your comfortable using the diversity calcs out of onsite guide? Still pretty new in with doing my own works. Have another job coming up and hob and oven would be combined 11KW. Would probably be easier to put them both on a 6mm but other option is the oven tapped of ring. What do you generally do?

 

[pc1966]

Thanks Telectrix. So your comfortable using the diversity calcs out of onsite guide? Still pretty new in with doing my own works. Have another job coming up and hob and oven would be combined 11KW. Would probably be easier to put them both on a 6mm but other option is the oven tapped of ring. What do you generally do?

Putting large loads on the ring is not a good idea!

If you are reaching the limit for already present radial circuit then options such as replacing with heavier wire or running a 2nd circuit are obvious better choices. 11kW => 48A for domestic use comes in at around 10 + 0.3*(48-10) = 22A for diversity, hence a 32A circuit would usually be considered OK and, length dependant, that might be fine for 6mm.

But if the planned use is not domestic, say commercial kitchen, or someone who acts like a professional chef doing parties at home, you might want to revise that up a little. Perhaps to a 40A circuit (or even 50A if worst-case is you expectation, but few dishes would stand every ring and oven on max thermostatic setting for any length of times).

 

[JohnS888]

Putting large loads on the ring is not a good idea!

If you are reaching the limit for already present radial circuit then options such as replacing with heavier wire or running a 2nd circuit are obvious better choices. 11kW => 48A for domestic use comes in at around 10 + 0.3*(48-10) = 22A for diversity, hence a 32A circuit would usually be considered OK and, length dependant, that might be fine for 6mm.

But if the planned use is not domestic, say commercial kitchen, or someone who acts like a professional chef doing parties at home, you might want to revise that up a little. Perhaps to a 40A circuit (or even 50A if worst-case is you expectation, but few dishes would stand every ring and oven on max thermostatic setting for any length of times).

Thanks PC for great explanation. Good to have my diversity calc confirmed also. Have already ordered 40amp for this so will go with this.

 

[pc1966]

Thanks PC for great explanation. Good to have my diversity calc confirmed also. Have already ordered 40amp for this so will go with this.

Hopefully checking that the cable is 40A rated, not just the MCB
[automerge]1589494168[/automerge]
Just to add: cable route and what it implies for thermal insulation / hot zones / grouping factors have all to be considered, but you would have to look at the specific site for those.

Trying to work out where the cable went in an existing installation to try and judge those can be a challenge!

 

[JohnS888]

Hopefully checking that the cable is 40A rated, not just the MCB
[automerge]1589494168[/automerge]
Just to add: cable route and what it implies for thermal insulation / hot zones / grouping factors have all to be considered, but you would have to look at the specific site for those.

Trying to work out where the cable went in an existing installation to try and judge those can be a challenge!

It is a 6mm and is just running through under floor joists ?

 

[telectrix]

It is a 6mm and is just running through under floor joists ?

then it's ref.method C and 6mm is rated at 47A. so you are OK with a 40A MCB. having said that, a 32A MCB is not likely to trip .even in a swicth on surge, as MCBs will take 1.45 x rating for some time.

 

[westward10]

It is not Method C as it is not clipped direct to a wall it is within a building void which makes Method B rating the cable at 38A.

 

[telectrix]

It is not Method C as it is not clipped direct to a wall it is within a building void which makes Method B rating the cable at 38A.

where does that come from? B is in conduit or trunking. if it's between floors with no insulation, that part is in free air.

 

[westward10]

where does that come from? B is in conduit or trunking. if it's between floors with no insulation, that part is in free air.

See Table 4A2 Number 40. Method C does not define a cable within a void.

 

[telectrix]

See Table 4A2 Number 40. Method C does not define a cable within a void.

from 4A2 no.40. ref. B applies when V < 20d, V being the height of the void, and d being the diameter of the cable. between floors, V > 20d. (unless its a very shallow void, in a house it's generally 300mm (ish))