Extra panels

mezza56 · Senior Member

Extra panels

T1 Terry · Guru

You will have a total of 3 x 80w = 240w plus 2 x 150w = 300w, a total of 540w. 80% of 540w = 432w divided by 12v = 36 amps. My advice would be to extend all the solar cables to the point you want to go through the roof to run the cables to the controller. Extend the cables using 6mm auto cable (4.35mmsq) At the point you plan to go through the roof, mount a junction box big enough for 2 x 7 wire neutral links to fit inside, (minus the plastic covers) that has a waterproof lid over this spot and glue it down using Selleys Armourflex. Put a plastic 2 ltr milk bottle full of water on top on it and let it sit for 24 hrs.

Once the Armourflex has gone off, cut a hole through the centre and down through the roof with a hole saw, large enough to fit a piece of 25mm flexible conduit and glue this into place. You could save some time by cutting the hole through the box and roof before gluing the box down, just make sure it isn't going to rain before the glue goes off.

Get a gland nut large enough for the 5 lots of 2 core 6mm auto cable to pass through, then cut a hole in the side of the junction box so the wiring can enter but be sealed to keep the water out using the gland nut and a bit of the Armourflex squeezed in between the cables.

Measure the distance from the hole in the box to where you will mount your fuse or NoArk circuit breaker (40 amp) Don't try and cheapen out on this bit with some other sort of circuit breaker, you want it to work properly the first time and not either melt or continually false trip due to heat. Now measure from where the circuit breaker goes to the solar input of the controller. Now measure from the controller to the fuse and on to the battery. The total of all these lengths is the length of 6 B&S (13.5mm sq min) you need to buy, plus a bit just to be sure.

Feed the 6 B&S cable up through the hole in the roof/junction box, take the plastic cover off the neutral links and wire the 6 B&S cables to the neutral blocks, one for the negative and one for the positive. Now cut the cables to length and connect into the fuse or double pole NoArk DC circuit breaker. Next, strip back the cables from the solar panels, all the negative cables to one block and all the positive cables to the other block.

Fit the lid to the box and seal the 4 screw holes with a dab of Armourflex to keep the water out.

The rest of the wiring is fairly straight forward, turn the solar circuit breaker on last. Why a 40 amp circuit breaker? This is to protect the smallest cable in the circuit, the 4mm cables coming from the solar panels, a double pole DC circuit breaker so you can turn the solar off if needed and the contacts won't arc because it was designed for DC and not for AC current.

T1 Terry

mezza56 · Senior Member

Thxs for the info Terry , I've got anderson plugs on each panel , connected to twin 6mm cable going direct to the terminal blocks in the junction box as suggested , 8 mm cable going down to the controller and 8mm down to the batteries . Where can I get a DC cb from ? I was under the impression that the Victron controller had some sort of internal protection could handle the amps if it did exceed the 50amps ( have added 3 x 150watt panels so its going to be up around 47 amps )What is the CB actually protecting ? The system is not connected as yet wanting to make sure its all ok b4 I connect all up .

Jaahn · Guru

Hi mezza56 smile

Just a couple of comments. Terry has given you some good practical pointers. I would just point out that there is a lot of confusion about cable size in Australia, so be sure you understand the difference between 6mm auto cable and 6BS. Some seller may try to lead you astray. If you look at the actual area of the copper wire in square mm for any cables you get you will be better advised and it is always available, and you will not be lead astray.

You can buy circuit breaker at Jaycar, an electrical supplier or on line. The CB is to protect the cables in case of a short or damaged insulation etc. The Victron looks after itself as you said. hmm

Jaahn

-- Edited by Jaahn on Wednesday 8th of May 2019 09:00:49 PM

mezza56 · Senior Member

Thxs Jaahn , I got the cable from Home of 12v and on the invoice it says BNS cable , do they have a specific CB for 8mm size cable . or is it a multi size connection

T1 Terry · Guru

We use Noark double pole because they are designed for DC voltage and don't suffer thermal creep like the units from JayCar etc that derate as they get hotter causing false tripping. www.tro-pacific.com/pages/search-results-page We use the 40 amp units because that is the max current the 4mm solar cabling supplied with the panels and the 6mm auto cable (4.35mmsq) can handle without melting the outer insulation. As you can see, they are not overly expensive and protect the system from a short circuit while also giving you a method of easily turning off the solar if required.

T1 Terry

mezza56 · Senior Member

Thxs Terry, I ordered a 50amp dc two pole non polarised noark from Tro pac yesterday , were adding 3 x 150watt panels on now and it all adds up to over 45 amps including the old panels So I thought 40 wouldnt work. I found a discussion paper online re the correct wiring of both polarised and non polarised cb , are lot are fitted incorrectly so the magnet doesnt drag the arc into the extinguishing chamber , very interesting . Maybe I should put inline fuses on each incoming panel As an additional protection .?

-- Edited by mezza56 on Saturday 11th of May 2019 01:50:49 PM

T1 Terry · Guru

mezza56 wrote:
Thxs Terry, I ordered a 50amp dc two pole non polarised noark from Tro pac yesterday , were adding 3 x 150watt panels on now and it all adds up to over 45 amps including the old panels So I thought 40 wouldnt work. I found a discussion paper online re the correct wiring of both polarised and non polarised cb , are lot are fitted incorrectly so the magnet doesnt drag the arc into the extinguishing chamber , very interesting . Maybe I should put inline fuses on each incoming panel As an additional protection .?

-- Edited by mezza56 on Saturday 11th of May 2019 01:50:49 PM

Fuses have a wider rupture range than a double pole circuit breaker designed to carry DC current. The 50 amp rating puts the trip value very close to the max current rating of the 4mm sq solar cabling, a short at the solar panel terminal box would put the full reverse current through those 4mm cables until the circuit breaker tripped as well as the full output form the solar array.

It is one of those "out there" scenarios, but after having one install suffer a ****atoo attack resulting shorted wiring, I'm extra careful not to have any part of the system exposed to a higher current than the max capability of the wiring insulation and make sure none of the wiring has a negative and positive conductor running side by side exposed to possible ****y attack. I also always double check the solar panel wiring to ensure they haven't used 2.5mm sq cable in place of the standard 4mm sq cable, they both look identical by the outside diameter, but the cable is marked along its length as to the size of the internal conductor. If there is no marking on the cable, replace it, you have no idea what the conductor size or the thermal insulation rating of the outer skin. 6mm auto cable is 4.35mmsq and rated at 50 amps.

T1 Terry