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AC cable question


viceroy
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I'm in the process of moving my Inverters, and want to relook at the AC cables I have.

 

Currently I have 8mm solid core copper cable (I hope that's the correct teminology)

Looks like the image below.

single-core-pvc-coated-8mm-copper-wire.j

 

The cable is perfectly suitable, but an utter pain in the ass to manipulate, and is bulky considering I have 2 inverters with inputs and outputs, which means man-handling 12 cables.

 

Are there other options available locally which are suitable for my needs?

I'd prefer something more flexible, and ideally with all three cables housed in the same sheath.

 

Please let me know whats available locally and where I can purchase.

Much appreciated.

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I'm in the process of moving my Inverters, and want to relook at the AC cables I have.

 

Currently I have 8mm solid core copper cable (I hope that's the correct teminology)

Looks like the image below.

single-core-pvc-coated-8mm-copper-wire.j

 

The cable is perfectly suitable, but an utter pain in the ass to manipulate, and is bulky considering I have 2 inverters with inputs and outputs, which means man-handling 12 cables.

 

Are there other options available locally which are suitable for my needs?

I'd prefer something more flexible, and ideally with all three cables housed in the same sheath.

 

Please let me know whats available locally and where I can purchase.

Much appreciated.

First of all, 8mm diameter ?

That's about 50mm2 or 1swg cable

Cable sizes are 6mm2 then 10mm2 then 16mm2

What are the inverter ratings ?.

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If you are in JHB try Lite Glo electrical wholesalers. Ask for panel flex wire, it's much more flexible as it has loads of tiny copper strands.

You do get multiple core panel flex wire, just not sure what the largest size they have is?

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Maximum size of Cabtyre cable is 4mm2 (32A)

Trailing cable is available in large sizes, not sure about the colour coding of 3 core, it may be for 3 phase and not have a yellow/green conductor.

Note that: loads of thin copper strands are difficult to get into the din rail terminals.

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First of all, 8mm diameter ?

That's about 50mm2 or 1swg cable

Cable sizes are 6mm2 then 10mm2 then 16mm2

What are the inverter ratings ?.

Aah, yeah, sorry, that's about 8mm with the insulation.

It's the same gauge as what comes from Eskom, so I think 16mm2.

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Are you using this cable to connect the batteries?

 

That isn't really the type of cable to use with batteries...

 

I highly recommend you use this cable for your batteries:

http://www.aberdare.co.za/sites/default/aberdare_cables/files/brochures/649/jpg/large/page-16.jpg

 

For your AC side: (NOT batteries)

General purpose wire: http://www.aberdare.co.za/sites/default/aberdare_cables/files/brochures/649/jpg/large/page-4.jpg

Surfix: http://www.aberdare.co.za/sites/default/aberdare_cables/files/brochures/649/jpg/large/page-10.jpg

Flat twin & earth: http://www.aberdare.co.za/sites/default/aberdare_cables/files/brochures/649/jpg/large/page-11.jpg

 

General purpose must run in a plastic or metal conduit.

Surfix and Flat twin & earth do not and can also be embedded in plaster (according to regulations)

 

Example:

4kW Axpert is rated at 8kW surge.

Battery side: Assuming 80% efficiency which is a good estimate, you are looking at 100amps at full load and 200 amps surge. (eg. Must use at least 50mm cable)

AC side: 17 amps full load, 34 amps surge. (eg must use at least 4mm)

 

What kind of inverter specifically?

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This is AC side. I would never dream of using this on the battery side.

The Surfix cable looks like it would fit my needs, but you say 34 amps surge. Surely then the 6mm is required?

as an aside, since you mentioned it, my battery side is fused at 100 amps. As discussed in another thread, if my system was pulling over 100 amps, I'd be worried, thus I would rather a fuse go than allow that much current into the inverters.

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8 hours ago, viceroy said:

This is AC side. I would never dream of using this on the battery side.

The Surfix cable looks like it would fit my needs, but you say 34 amps surge. Surely then the 6mm is required?

 

4mm wire is rated for ±30amps continuous load. A surge of 34 amps is perfectly fine. For an Axpert 4kW, in fact, I would put a 20amp circuit breaker on the output side.

Circuit breakers only break after continuous output of quite a bit higher than their rated output (eg. 24 amps or whatever). They also break on instantaneous output of something like double their rated output.

The reason for this is because the cable can actually be loaded for a short amount of time at much higher load.

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57 minutes ago, superdiy said:

Usually only the cable between the street connection and the house...

To this end, the 16mm2 solid core cable I want to replace is the cable from the street connection > Inverters > house.

Is the 4mm surfix suitable for the entire trip?

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Should that not be the municipalities issue to handle from the street to the house?

I really do not see why the inverter needs a 16mm2 cable from Eskom or from inverter to the house. For that purpose there are breakers to protect the smaller cable just in case.

If you are worried, consult an knowledgeable electrician on the matter, for my mind says your wiring in the house can run all that is on in the house with the geyser / stove / oven / microwave all being on at the same time. And I do not see 16mm2 cable for that, bar from the street to the DB board.

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Where the cable from street enters the propery it is in a box with a 60A breaker.

From that breaker it would normally go into the house to the DB board.

I intercept it here to the inverters, and then from the inverters to the house DB.

I've just phoned the local cable supply company and they only have the 6mm in stock, so that's what I'll get.

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13 minutes ago, viceroy said:

Where the cable from street enters the propery it is in a box with a 60A breaker.

From that breaker it would normally go into the house to the DB board.

I intercept it here to the inverters, and then from the inverters to the house DB.

I've just phoned the local cable supply company and they only have the 6mm in stock, so that's what I'll get.

You've mentioned inverters - I assume you have a few in parallel supplying the whole house?  It is all about losses and voltage drops here, not about breakers protecting the cable. What length of cable are you looking at? The longer the cable the thicker it should be, but I won't even consider using 6mm2 if you are supplying power to everything in your house over that cable. If it is a short piece of cable, say 1m or less, I would maybe use 10mm2

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37 minutes ago, superdiy said:

You've mentioned inverters - I assume you have a few in parallel supplying the whole house?  It is all about losses and voltage drops here, not about breakers protecting the cable. What length of cable are you looking at? The longer the cable the thicker it should be, but I won't even consider using 6mm2 if you are supplying power to everything in your house over that cable. If it is a short piece of cable, say 1m or less, I would maybe use 10mm2

Agreed, I have runs of between 7-9 meters from my main DB to and from my inverter and the same for the combiner box and use 16mm2 and use this to have basically no voltage drop

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9 hours ago, viceroy said:

Where the cable from street enters the propery it is in a box with a 60A breaker.

From that breaker it would normally go into the house to the DB board.

I intercept it here to the inverters, and then from the inverters to the house DB.

I've just phoned the local cable supply company and they only have the 6mm in stock, so that's what I'll get.

I can't imagine a cable supply company not having larger cable, they must have quoted you on Surfix cable which only goes up to 6mm2.

6mm2 is rated up to 40A, you will have to double up if determined to use 6mm2.

The length of the cable and load is not the only criteria, the size of cable must also match the circuit breaker capacity i.e. 60A.

As a matter of interest, the short circuit current (KA rating) of circuit breakers is also important especially if near a substation.

Edited by Eugene
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