Oven & Hob - Again!

[MikeBa]

First post on forum, so go easy on me please!.

I am looking to add a hob to an existing installation – details as follows:-
Existing oven 3 kW – adding 7 kW hob
1998 build
32A MCB type B feeding 6.0mm t&e radial circuit about 10m length clipped to wall, behind plasterboard connecting to 45A DP isolator with 13A plug – above work top – closed to oven/ hob area.
From DP isolator 2 x 4.0mm t&e to under worktop – one to 13A unswitched socket supplying the (present) gas hob ignition – the other to 45A cooker connection unit.
From the CCU a 2.5mm t&e to oven.

With diversity the proposed addition works – (3000W + 7000W)/ 230V – 43.5A
First 10A + 30% remaining + 5A for socket = (43.5A-10A) x .3 + 10A + 5 A = 25A < 32 A

My concern is that the 2 x 4.0mm from DP isolator and 2.5mm2 from CCU are being protected by a 32A MCB – not to regs and one of the 4.0mm.t&e would not be tight to supply the 7 kW hob.

To correct this I propose linking the 2 x 4.0mm t&e into a twin Cooker Connection Unit (discussed on this forum) and connecting the oven and hob into this. Probably replacing the 2.5mm2 t&e to the oven with 6.0mm2. This will place at least 6.0mm2 to the complete circuit and allow the diversity calc to be valid all the way to the CCU.

The hob requires a flexible high temp (90 deg) cable that I am trying to source (various threads on this forum relating to the rarity).

Thanks in advance for the help!.

 

[EFLImpudence]

First post on forum, so go easy on me please!.

I am looking to add a hob to an existing installation – details as follows:-
Existing oven 3 kW – adding 7 kW hob
1998 build
32A MCB type B feeding 6.0mm t&e radial circuit about 10m length clipped to wall, behind plasterboard connecting to 45A DP isolator with 13A plug – above work top – closed to oven/ hob area.
From DP isolator 2 x 4.0mm t&e to under worktop – one to 13A unswitched socket supplying the (present) gas hob ignition – the other to 45A cooker connection unit.
From the CCU a 2.5mm t&e to oven.

With diversity the proposed addition works – (3000W + 7000W)/ 230V – 43.5A
First 10A + 30% remaining + 5A for socket = (43.5A-10A) x .3 + 10A + 5 A = 25A < 32 A

OK so far

My concern is that the 2 x 4.0mm from DP isolator and 2.5mm2 from CCU are being protected by a 32A MCB – not to regs

OK apart from the 2.5mm².

and one of the 4.0mm.t&e would not be tight to supply the 7 kW hob.

What does tight mean?

To correct this I propose linking the 2 x 4.0mm t&e into a twin Cooker Connection Unit (discussed on this forum) and connecting the oven and hob into this. Probably replacing the 2.5mm2 t&e to the oven with 6.0mm2.

4mm² will do. Alright for 37A

This will place at least 6.0mm2 to the complete circuit and allow the diversity calc to be valid all the way to the CCU.

4mm². will do.

 

[MikeBa]

Thanks a lot for the quick and understandable reply EFLImpudence!!.

Considering the 2.5mm between the oven and Cooker Connection Unit - my other thought is to place a FCU in this - this would give the cable its own protection.

 

[EFLImpudence]

Considering the 2.5mm between the oven and Cooker Connection Unit - my other thought is to place a FCU in this - this would give the cable its own protection.

Yes, that would be good.

 

[MikeBa]

Thanks again EFLImpudence!!!!!!

 

[Taylortwocities]

Thanks again EFLImpudence!!!!!!

Hit him with the

Untitled

• Taylortwocities
• 9 Sep 2009
• 34

button.
He likes that.