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Hello there guys,

I have a Axpert Standard 5 Kva 48V. I am a qualified electrician, but this is my first time installing a inverter. There is no solar panels, so it will be used solely as a back up, for load shedding. Please may I get some advise as to the correct way of installing. I wish to have all essential circuits in a separate D.B. I will be using 200ah Gel Batteries. Does someone perhaps have a wiring diagram and a list of components needed and  cable sizes  ect? What size DC cable would be required for the batteries 35mm Permaweld? Is it necessary to install a change over switch and pilot lamp on the DB? 

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Posted (edited)
1 hour ago, David27 said:

What size DC cable would be required for the batteries 35mm Permaweld?

35mm^2 is suffiient for 5kVA at 48V (5000/50 ~= 100A), but do watch out for voltage drop on a longer run, which should ideally by 1% or therebouts. Battery cables must be fused with a DC-rated fuses. If you use breakers on the DC runs, they must be DC-rated for the voltage you intend to switch.

1 hour ago, David27 said:

Is it necessary to install a change over switch and pilot lamp on the DB? 

Many places (certainly Cape Town) want to see that changeover switch. It's more of a bypass switch than a changeover. I believe the pilot lamp is required where there is an alternate power supply. I am not an electrician, so this is kinda your area 🙂

Edit: And crimp the lugs onto the cables using a proper crimper, not a vice or some other means 🙂

 

Edited by plonkster

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Hi Plonkster, Thank you for your reply, yes this does answer my questions. Is it necessary to install fuses on both Positive and Negative battery cables? On the 48V would a 80A fuse be suitable?

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The Change over switch (Bypass Switch), I find it to be a inconvenience, as when there is a power outage, one would have to manually go switch over from Grid to Inverter??? If not at home there will be no power?

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With regards to the battery lugs, Yes, most definitely will crimp on the lugs with a hydraulic crimper. The cable are less then a Metre from batteries to Inverter, Thanks all the same.

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1 hour ago, David27 said:

The Change over switch (Bypass Switch), I find it to be a inconvenience, as when there is a power outage, one would have to manually go switch over from Grid to Inverter??? If not at home there will be no power?

I think the point of the changeover is to use it as a bypass so in the event that the inverter is faulty, you can bypass the inverter and connect your loads directly to grid. The inverter has an automatic changeover when the grid fails.

BTW. Im just starting out as well. Bought a sunsynk 5kw inverter and trying to figure out the correct wiring for a diy install.

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2 hours ago, David27 said:

Hi Plonkster, Thank you for your reply, yes this does answer my questions. Is it necessary to install fuses on both Positive and Negative battery cables? On the 48V would a 80A fuse be suitable?

I think it is required on both cables. You get battery disconnect switches with fuses as a single unit. In terms of rating. 5kw / 48V (worst case) = 104A so 80A is not really sufficient in this case. But the fuse should be matched to the cable size, similar to a circuit breaker. 

Regarding your 25mm cable, you could run 2 in parallel (2 positive, 2 negative)  to increase the current carrying capability as long as both are identical lengths. 

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Posted (edited)

You just need one fuse for the battery cable. 

The fuse is used to protect your cable. So if your cable is rated for 130A you need a fuse that is 'n bit smaller than that. The fuse will burn out saving the cable and disconnecting the battery. If you have 2 fuses one will burn out first leaving the other one useless. Now do buy a second fuse as a backup when you need to replace it...

For solar panel cables it will be better to fuse both cables as here there might be lightning strikes doing their part and they don't follow any normal rules :) 

Edited by Louisvdw

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13 hours ago, David27 said:

Is it necessary to install fuses on both Positive and Negative battery cables?

It depends. You would fuse both if there is the risk of an earth fault on both cables, eg think about a car, there is no need to fuse negative because the entire body is bonded to the negative, so any earth fault causes a high current to flow and pops the fuse on the positive side... but for applications where the body isn't bonded in that manner, you would have to fuse both sides.

If you put the fuse close to the battery and it is not in some metal enclosure, then you only fuse the positive side.

13 hours ago, David27 said:

On the 48V would a 80A fuse be suitable?

Probably too small. The fuse can be much larger than the 5kVA of the inverter, but must be sufficient to protect the cable from burning up. The fuse is there to protect the cable, not the inverter. The inverter is supposed to protect itself by switching off on overload. To prevent nuisance blowing of the fuse you'd make the fuse even larger than the 5kVA, I'd say go for 160A. That's sufficient to protect a 35mm^2 cable and provides oodles of current for a 5kVA.

11 hours ago, Vassen said:

I think the point of the changeover is to use it as a bypass so in the event that the inverter is faulty, you can bypass the inverter and connect your loads directly to grid. The inverter has an automatic changeover when the grid fails.

What he said ^^^ 🙂 The changeover switches your essential loads from being connected to the output of the inverter, or directly to the grid. When it is connected to the output of the inverter, the transfer switch in the inverter still works as it normally does and you still get automatic failover.

But the powers that be does want to see that changeover. Remember the guy who puts the stamp on the paper is not an electrical engineer, he just follows the rules. He wants to see an interlocking changeover between the two sources (even if the one that will be used 90% of the time is elsewhere, inside the inverter 🙂 ). This changeover switch is a godsend in any case. The last thing you want is a faulty inverter AND an unhappy wife. You want to throw that changeover and get her off your back... so you can diagnose the inverter in peace 🙂

 

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Hey guys, Thank you so much for the invaluable advise. I will most definitely install the Change over switch, also for reasons of my not causing a domestic feud....WaaaHaha.

Much appreciated guys, I have already started the installation  just awaiting the battery stand to be completed, 4 x 200AH Gel Batteries weight 240 kg's. I will post photos after completion. 

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