Oct 27, 2020
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If you're a qualified, trainee, or retired electrician - Which country is it that your work will be / is / was aimed at?
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Hi,
I'm sorting out an off grid installation and I've been provided with 25mm cable labelled "Hi=Flex 25mm CE made in EU" to connect the batteries to an inverter. Looking them up they appear to be rated at between 140A and 170A depending on which website you go to.

Now the batteries will be providing 24V to a 3kW inverter, so the cables only need to carry 125A, so there is going to be a 125A inline fuse. If these cables are rated correctly everything should be good.

I've only been able to find one document which implies these cables are to BS6862 and has it's own data table. Question is are they to BS7671 or am I going to have to list these in the paperwork as a departure ?
 
Last edited:
I assume you have H07RN cable. It complies with BS7671
 
I assume you have H07RN cable. It complies with BS7671
This is the dilemma I've got. If I go with the cables listed in BS7671 I'd have to go up to 35mm. On further research these cables are specifically designed for 100V or less applications where high current is present, and need high flexibility and a high probability of being used outdoors temporarily or environments where there is a high probability of prolonged vibration (ie Cars, Caravans etc)
 
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Why not call a cable manufacturer for their recommendations & BS standards? Or go with the 35mm cable as BS 7671 assuming they will fit the terminations on the inverter. If put down as a departure then you are almost saying the cable you fitted was not really suitable for purpose. Is the installation indoors/outdoor or both?
 
Tri-rated cable is easy to use and generally available by the meter, for example:

Bear in mind some auto cables are short-term rated (e.g. for jump leads) and others like tri-rated have assumed working temperatures as high as 110C which is unsustainable for many accessories, so look at the BS 7671 table for the method and, say, 70C PVC when looking to size the CSA needed. I would be thinking 35mm here.

Finally voltage drop - it will seriously bite you are ELV and may impact on the behaviour of the inverter, if not on the overall power efficiency under load. If the cables are of any non-trivial length you might be in for a very large cable.
 
Also generally battery cables are in free air from battery to chassis or to starter motor solenoid, a bit like meter tails, so they need significant de-rating if clipped to a surface or enclosed in any sort of trunking or conduit.
 
I've been provided with 25mm cable labelled "Hi=Flex 25mm CE made in EU" to connect the batteries to an inverter. Looking them up they appear to be rated at between 140A and 170A depending on which website you go to.

Now the batteries will be providing 24V to a 3kW inverter, so the cables only need to carry 125A, so there is going to be a 125A inline fuse. If these cables are rated correctly everything should be good.

I've only been able to find one document which implies these cables are to BS6862 and has it's own data table. Question is are they to BS7671 or am I going to have to list these in the paperwork as a departure ?
 

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If you're a qualified, trainee, or retired electrician - Which country is it that your work will be / is / was aimed at?
United Kingdom
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Practising Electrician (Qualified - Domestic or Commercial etc)

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Hi-Flex Cable CE Made in EU ?
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