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Want to add solar panels to axpert 5k inverter


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Hi guys, I have had an axpert mks inverter for a few years running as a load shedding battery backup.

I now want to add some solar panels to the mix. I am thinking of getting some Canadian solar 410w panels and connecting them 4p x 2s, from what I understand this is safe as it is under the 145v voc?

The inverter is about 20 meters from where the panels will be mounted. what size cable do I need? looking at all the kits offered there are no included fuses for the parallel strings, are these recommended? They also include a 4 pole DC disconnector, does this mean that 2 parallel strings should be connected with y connectors, if that is the case how are they combined to connect to the axpert?

 

Thanks guys

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7 hours ago, John said:

Hi guys, I have had an axpert mks inverter for a few years running as a load shedding battery backup.

I now want to add some solar panels to the mix. I am thinking of getting some Canadian solar 410w panels and connecting them 4p x 2s, from what I understand this is safe as it is under the 145v voc?

The inverter is about 20 meters from where the panels will be mounted. what size cable do I need? looking at all the kits offered there are no included fuses for the parallel strings, are these recommended? They also include a 4 pole DC disconnector, does this mean that 2 parallel strings should be connected with y connectors, if that is the case how are they combined to connect to the axpert?

 

Thanks guys

Hi John, easiest way is to connect with a combiner box, this will already have the parallel connections in as well as fuses for every string. They also include a DC breaker. I attach a photo of my setup. This combiner box is for 4 strings.

6mm Solar cable will be sufficient

 

IMG-6314.jpg

Edited by PhilFM
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3 hours ago, Thee Mister EX said:

If i may ask, why use a combiner instead of Y connectors

Been asking myself the same question. I have used Y connectors and they work fine. If worried about over current, then you can protect the wires with inline fuse. 

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I am not 100% sure but from my understanding it is now a legal requirement to have a DC breaker (and fireman's switch) installed on a PV array over a certain (small size).

There is also a limit (legally) from what I understand as to how many strings can be connected via Y connectors before you need a combiner box. Then fuses and surge protectors are always a good idea to protect your investments.

Personally, I have 12 panels configured in 2S6P... 2 parallel pairs are joined via Y connectors and I bring 3 strings down to a combiner box which contains fuses per string, a master DC breaker and surge protector.

You can buy them off the shelf, have them made or make them yourself if you have the crimpers and time. I personally made it myself and have just completed the same for my parents. Not too cheap but significantly cheaper than purchasing off the shelf

 

To answer the cable question... From panels to combiner box 6mm will be perfect. From combiner box, if you are planning any expansion in the future, go 10mm.   6mm is good for 53A which would be more than perfect for your current setup but if you want to go 2S5P you would be at the absolute MAX of the cable which is never a good idea. Having said that, 10mm is A LOT more expensive than 6mm, so only use it for the combiner to inverter

Edited by Jay-Dee
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Thanks for the help guys!

In the end I made 2 strings of 2s2p. so two panels in series and then 2 pairs in parallel connected with y connectors. This made 2 banks of 80v 20 amps that I ran with 2 pairs of 6 mm wire to a combiner box from AC/DC ( very over priced, but nice unit that they had in stock). 

I am still confused regarding the y connector issue.

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On 2020/10/16 at 7:14 PM, Jay-Dee said:

6mm is good for 53A

This is a very misleading statement, no (unless you meant 6mm and not 6mm2 cable)? It all depends on the distance. OP said his distance is 20m, so 40m with negative, at which 6mm2 cable will not be sufficient to provide even close to 53A. Please school me if I am missing the bus here. 

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@profa I think we are both getting a little muddled here..

17 minutes ago, profa said:

(unless you meant 6mm and not 6mm2 cable)

I did say 6mm but should have said 6mm2. I left out the "2"'s  by accident... If it is was a 6mm cable in diameter, it would have a cross section measuring 28mm2 and that would be a hard solar cable to find.

 

20 minutes ago, profa said:

This is a very misleading statement ....  .... will not be sufficient to provide even close to 53A. Please school me if I am missing the bus here. 

Perhaps, I am the one missing the bus and need some schooling.. Most online retails spec to up to 70A for 6mm2 cable, Have a look at Metric Cables who are very well known... http://www.metriccables.co.za/flexible-solar-cable/ They spec to 54A on 6mm... So my 53A is more conservative. Yes, over 20m there will be a loss of voltage but the realistic cost of running the thickness cable to avoid those losses would be astronomical.

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3 hours ago, John said:

... connected with y connectors. This made 2 banks of 80v 20 amps that I ran with 2 pairs of 6 mm wire to a combiner box

How are you using Y connectors AND a combiner box? They both parallel strings, so you can't use both.

Each string of 2 panels has a positive and negative lead (a pair) that goes to the combiner box. Where are you wiring the Y connector?

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I used the y connectors to parallel 2 pairs.

Rather than taking 8 6mm2 (4 negative and 4 positive)wires to the combiner box I now take 4(2 negative and 2 positive).

The combiner box then takes those 4 wires and combines them into one 10mm2 cable to the inverter.

Is this ok? 

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