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1620w worth of panels producing a maximum of 1000w.


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I guess that’s why places like this are so important where people offer advice based on own experience without actually having any vested interest in what you buy. 

1. Correct 2. Correct Additional items, check to ensure that you have an inline fuses close to panels as well

So it seems it has to do with the inefficiency of a PWM inverter. Tested yesterday, by connecting 3 panels only (out of the total of 6). Put at least 1500w of load on the system, and the 3 panels prod

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31 minutes ago, profa said:

One last quick question, the cable length from the panels to the inverter is about 15m give or take. The cable used according to the invoice, was 6mm DC cable. Would that affect the amount of amps coming through to the inverter? I have felt the cable before as it comes into the fuse, and it is warmish. Not hot by any means, but definitely warm to the touch so that it is noticable. 

I’m no expert in this this but yes it does affect the current as well as the voltage to an extent. 
 

However, more importantly is that this becomes a hazard. Cables should not get warm to the touch under normal operation. 
 

googling some calculators, for a 32v system, operating at 40A (which is less than the 6x9A), over 15m with a 5% loss, you will require around 20mm2 of cable. 
 

Do you just have 1 cable coming from the panels to the inverter?

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1 hour ago, Vassen said:

I’m no expert in this this but yes it does affect the current as well as the voltage to an extent. 
 

However, more importantly is that this becomes a hazard. Cables should not get warm to the touch under normal operation. 
 

googling some calculators, for a 32v system, operating at 40A (which is less than the 6x9A), over 15m with a 5% loss, you will require around 20mm2 of cable. 
 

Do you just have 1 cable coming from the panels to the inverter?

So im busy chatting to the installer, he used 74m of cable from panels to inverter. 37m positive (going through fuse) and 37m negative going straight to inverter. 74m total. 

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So......i just did a very unscientific measurement from where i know the panels are on the roof and took huge (1m estimate) steps from within the house where the panels are, to the garage where the inverter is. counted 17 steps. now wondering how the hell that could remotely even get close to 37m worth of cable 🤔🤔

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6 mm² cable is about as thick as PV cable gets. But is it really 6 mm²? It should be printed on the side of the cable.

6 mm² cable should be good for nearly 40 A. Same as 6 mm² AC cable, neglecting skin effect, and the fact that any voltage drop has 9x the effect at 26 V (compared with 230 V).

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24 minutes ago, Coulomb said:

6 mm² cable is about as thick as PV cable gets. But is it really 6 mm²? It should be printed on the side of the cable.

6 mm² cable should be good for nearly 40 A. Same as 6 mm² AC cable, neglecting skin effect, and the fact that any voltage drop has 9x the effect at 26 V (compared with 230 V).

I went and checked and removed some covers but dont see any writing on the cables from the panels. However, on the battery cables to the inverter it says 25.00mm2. And those cables look to me like 4 gauge car sound cable thickness which I know pretty well. The cables from the solar panels look to me like 8 gauge car sound cable or about half as thick as the battery cables. Does this help?

 

Also, according to the inverter, the panels are happily producing between 28-30v now at about half load (500w being drawn from house and to charge batteries). At full load (well when I draw more than they can produce) they produce about +-28v but obviously not near the amps they should be producing (38-39 instead of 46-47).   

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13 minutes ago, Chloe said:

It sounds like your "installer" used the wrong tipes of cable we would normally recommend 6mm solar cable and 70mm battery cable that's tipictly the size of your car's battery cable if you want to compare.

If 6mm is equivalent to about 8 gauge car sound cable, then installer did in fact use that. Also the battery cable is about 4 gauge thick, while i think my car battery cable is about 0/1 gauge.

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15 minutes ago, profa said:

If 6mm is equivalent to about 8 gauge car sound cable, then installer did in fact use that. Also the battery cable is about 4 gauge thick, while i think my car battery cable is about 0/1 gauge.

Did a quick check online and it seem your solar cable should be ok but there's still the question about them feeling warm??? But your battery cable is incorrect for the batteries you are using it should be the same size as in your car.

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17 minutes ago, Chloe said:

Did a quick check online and it seem your solar cable should be ok but there's still the question about them feeling warm??? But your battery cable is incorrect for the batteries you are using it should be the same size as in your car.

Could you share the calculations (voltage, amps, distance) you used to determine that the solar cable is OK?

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14 minutes ago, Chloe said:

Did a quick check online and it seem your solar cable should be ok but there's still the question about them feeling warm??? But your battery cable is incorrect for the batteries you are using it should be the same size as in your car.

With a 3000w inverter at 24V, the max amps should be 125A. That translates to 35mm cable as far as I know. 
 

You can however use any size cable you want to as long as you have a fuse on the cable that is rated for the max current carrying capability of the cable. 

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1 minute ago, Vassen said:

With a 3000w inverter at 24V, the max amps should be 125A. That translates to 35mm cable as far as I know. 
 

You can however use any size cable you want to as long as you have a fuse on the cable that is rated for the max current carrying capability of the cable. 

35mm is battery cable correct?

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1 minute ago, Vassen said:

With a 3000w inverter at 24V, the max amps should be 125A. That translates to 35mm cable as far as I know. 
 

You can however use any size cable you want to as long as you have a fuse on the cable that is rated for the max current carrying capability of the cable. 

That's why I said it should be at least 35mm.

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5 minutes ago, profa said:

Could you share the calculations (voltage, amps, distance) you used to determine that the solar cable is OK?

I used a simple online calculater which converts gauge to mm to mm2. You don't have 20 panels so 4 mm2 solar cable should have been fine for your set-up. Unless you are refuring to this type of cable.

IMG-20201015-WA0006.jpg

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14 minutes ago, Chloe said:

You don't have 20 panels

Remember, he said he’s got 6 panels in parallel and each rated 8.7A at max power. So that’s 52A theoretical max. 
 

I can’t really find a proper site that specifies the max rating of dc cable. Different sites have different values. 😇

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8 minutes ago, Vassen said:

Remember, he said he’s got 6 panels in parallel and each rated 8.7A at max power. So that’s 52A theoretical max. 
 

I can’t really find a proper site that specifies the max rating of dc cable. Different sites have different values. 😇

Chart in this thread is blurry but is what you want, no? 

Here

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30 minutes ago, Chloe said:

I used a simple online calculater which converts gauge to mm to mm2. You don't have 20 panels so 4 mm2 solar cable should have been fine for your set-up. Unless you are refuring to this type of cable.

IMG-20201015-WA0006.jpg

I think we are talking past each other here. 

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3 minutes ago, Chloe said:

Ok missed that one 😉 then 6mm would be under rated as well thats only 54amp. That leaves him with 10mm solar cable rated at 75amp.

That means all his cabling is incorrect.

I would rather go with 2x 6mm2 cables. Probably cheaper, more common and easier to work with than 10mm2. 

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