Cable sizing for a stove.

[@SamboLindoh]

Hi All,

Kindly see the 3 attached document, what are your thought?

[AndyD]

They tell you what cable is suitable although my personal preference would be H07RNF which is the uprated neoprene version. I don't see any reason not to follow their recommended size.

[Leecatt]

They tell you what cable is suitable although my personal preference would be H07RNF which is the uprated neoprene version. I don't see any reason not to follow their recommended size.

As long as the cable is protected correctly with a 20 amp circuit breaker and not the recommended 25amp

[@SamboLindoh]

They tell you what cable is suitable although my personal preference would be H07RNF which is the uprated neoprene version. I don't see any reason not to follow their recommended size.

Hi AndyD, thank you for the reply. Did you view the PDF document attached together with these 2 pictures? I would like to hear your response and view on my question and analysis respectively.

[@SamboLindoh]

As long as the cable is protected correctly with a 20 amp circuit breaker and not the recommended 25amp

Hi Leecatt,

Thank you for your input on the subject matter. I assume your response is based on the burners alone, the burners when they are all operated to maximum at the same time they can draw a maximum current of 25 A. In your recommendation you recommend a 2,5mm2 Cable and a 20A C/B wouldn't this breaker trip when all the burners are turned on to maximum?

[Leecatt]

Hi Leecatt,

Thank you for your input on the subject matter. I assume your response is based on the burners alone, the burners when they are all operated to maximum at the same time they can draw a maximum current of 25 A. In your recommendation you recommend a 2,5mm2 Cable and a 20A C/B wouldn't this breaker trip when all the burners are turned on to maximum?

I am not taking the load into account at all.
My concern is simply for the amperage in the cable. Protecting a 2.5mm cable with a 25 amp circuit breaker is incorrect. The maximum rating in the cable is 23 amps, therefore the recommendation to use a 20 amp circuit breaker to protect it.

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[AndyD]

These types of trailing cables are fine stranded conductors plus the CPC is the same CSA as the line conductors and the insulation has a higher temperature rating than standard PVC so they carry a relatively higher current rating than PVC installation cables with solid conductors like flat twin. 2.5mm 3-core H07 for example is usually rated at 25Amps. Data sheet attached below, see page 4.

I'd personally follow the manufacturers recommendations regarding cable size and overcurrent protection.

h07rn-f-bs-en-50525-2-21-flexible-rubber-cable.pdf

[AndyD]

The load of the stove is limited to 3.4 kw (about 15A depending on the actual voltage) at any given time. There will be a mechanism inside the stove to prevent all the elements running simultaneously.

[@SamboLindoh]

I am not taking the load into account at all.
My concern is simply for the amperage in the cable. Protecting a 2.5mm cable with a 25 amp circuit breaker is incorrect. The maximum rating in the cable is 23 amps, therefore the recommendation to use a 20 amp circuit breaker to protect it.

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Hi Leecatt,

In my opinion I wouldn't say using a 25A circuit breaker for a 2.5mm2 cable is incorrect. The maximum protection rating for a 2.5mm2 is indeed 25A. The maximum amount of current that a cable can handle depends on various factors such as the method of installation (Pg 89), the length of the cable, the type of cable (i.e single core,multicore, PVC, armoured, unarmoured, copper,aluminum, etc) see. table 6.2(a), table 6.3(a) and table 6.4(a)....SANS 10142-1

Please see the attached pdf document and go through the analysis of the scenario there, I would appreciate your comment on the analysis there.

[Leecatt]

You are correct the max rating depends upon the installation method.
According to your diagram the cable is a 2.5mm twin core and earth and is to be installed into conduit on a wall.
This means I have to refer to table 6.2(a), installation method 2.
The maximum current is limited to 24 amps.
In my world this requires a 20 amp circuit breaker for protection not a a 25 amp.




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[Leecatt]

Using this same procedure the max amperage for a 6mm cable is 41 amps.

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[Leecatt]

I've been looking at the wrong table. Using table 6.3(a) the max current for the 2.5mm cable is 23 amps using installation method 2. Same solution though, needs to be protected by a 20 amp cb.


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[Leecatt]

The maximum for 6mm is 3 8 amps unless you surface mount the cable

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[@SamboLindoh]

You are correct the max rating depends upon the installation method.
According to your diagram the cable is a 2.5mm twin core and earth and is to be installed into conduit on a wall.
This means I have to refer to table 6.2(a), installation method 2.
The maximum current is limited to 24 amps.
In my world this requires a 20 amp circuit breaker for protection not a a 25 amp.




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In this case you are 100% correct in selecting the 20A breaker. I thought you were saying it is incorrect (under any conditions) to use a breaker that is more than 20A on a 2.5mm2 cable, because in other methods a 25A C/B can then be used to protect a 2.5mm2 cable.

[@SamboLindoh]

Let me clarify my problem here:

I've got burners and an oven.
Burners rated current=25A
Oven rated current= 15A
Total rated current=40A

I wanna use 1 cable (Multicore PVC Insulated cable, unarmoured, one two-core cable, single phase) to supply power to both the oven and the burners.

Lenght of cable from DB to isolator is 6meters and from the isolator to the burners and oven is less than a meter

Installation method to be used is Method 2.

When I select a cable for this installation I find that a suitable cable for this combined load is a 10mm2 protected by a 45A C/B. Now, i've never seen a 10 mm2 used for a stove before. Am I right with this cable size for a stove? Am I right in using the combined maximum rated current (40A) in sizing this cable? Where am I missing it?