Solar PV - Cable Size ?

championc · 04-06-2019 8:30am #1

Hi all,

What cable size would be needed for 6 x 300w 24v Panels (2 strings of 3) - total 1.8kw ? Panels will have about a 20m run from the panels to the Batteries and Inverter so I want to minimise losses on the cable

rolion · 04-06-2019 10:14am

Welcome and enjoy the install.

Where do you get the panels from ?
Did they gave you any advice in relation to cabling ?
How do you link the panels,in series and or in parallel ?

Low voltage,small cable. High Amps,big cable.
For a typical install,a 6mmsq cable for PV installs does the job.
Make sure is for DC PV installs and not indoors electrical cabling.

Effects · 04-06-2019 1:21pm

rolion wrote: »

Make sure is for DC PV installs and not indoors electrical cabling.

Isn't SWA fine to use for DC? Based on advice from a PV supplier in Finglas.

championc · 04-06-2019 4:01pm

rolion wrote: »

Welcome and enjoy the install.

Where do you get the panels from ?
Did they gave you any advice in relation to cabling ?
How do you link the panels,in series and or in parallel ?

Low voltage,small cable. High Amps,big cable.
For a typical install,a 6mmsq cable for PV installs does the job.
Make sure is for DC PV installs and not indoors electrical cabling.

The plan is to get the panels from Italy. There are two suppliers that I was looking at online. I haven't asked about cabling to them. The plan is for 3 in Series in 2 Parallel strings. Possibly just worth getting the cable (and connectors) from the Panel suppliers too.

Would 10mm2 cable be excessive / waste of money ?

rolion · 04-06-2019 4:19pm

championc wrote: »

The plan is to get the panels from Italy. There are two suppliers that I was looking at online. I haven't asked about cabling to them. The plan is for 3 in Series in 2 Parallel strings. Possibly just worth getting the cable (and connectors) from the Panel suppliers too.

Would 10mm2 cable be excessive / waste of money ?

Panels from Italy are very cost effective ( i hate expression "cheap" ).

However,the financial savings made for 6 panels will be offset / killed by the transport and insurance. I paid e500. The delivery company will not allow you to open the panels on the pallet to check integrity of the shipment. ONLY after you signed the received docket and then if any issues, you take it with supplier,with delivery and again,a big ****ty loop.

What makes you think or desire to buy from so far ?
I will say UK is more cost appropiate to make sense for 6 panels.

10mmsq is ok but safer as you can go series and parallel.

Good luck and share the pain,please.

championc · 04-06-2019 10:00pm

Attached is my planned installation. I've already got the Charge Controller, the Batteries and the Inverter. I've built an frame with Unistrut for the Batteries, and I've all the racking kit for the panels for the roof. I've still to get all of the electrical breakers

Gumbo · 04-06-2019 10:09pm

championc wrote: »

Attached is my planned installation. I've already got the Charge Controller, the Batteries and the Inverter. I've built an frame with Unistrut for the Batteries, and I've all the racking kit for the panels for the roof. I've still to get all of the electrical breakers

You look dangerously close to being over your Planning Exemption array.
Nothing wrong with that, but just so you know for our own info, should it be reported.

Gumbo · 04-06-2019 10:47pm

championc wrote: »

Ah crap, never knew such a thing existed. Will look into it now thanks

12 Sq. M or 50% of the total roof space, whatever comes first.
There's a limit to the height to which they can project off the roof also, and a minimum distance to boundaries. 200mm comes to mind from memory.

unkel · 04-06-2019 11:10pm

Off grid system? Any reason for going off grid? Presuming the house does have a grid connection?

Also why the 24V panels, how much do they cost you shipped to Ireland and what wp rating have they what length and width are they? You'd have thought 36V panels sourced locally would have been far cheaper? What batteries are you using and how much did they set you back?

championc · 05-06-2019 11:07am

It's grid-tied, not off-grid

The panel's I've looked at are 1m x 1.6m. Who would you recommend for local supply ? The charge controller can take up to 150v / 40a so maybe 36v might just squeeze in. I wasn't aware of 36v panels tbh.

I got the batteries for free in work. They are about 3 years old

unkel · 05-06-2019 11:40am

Any link to a spec sheet for those panels? How much they costing you shipped?

championc · 05-06-2019 12:02pm

Here's one of the panels - https://www.solarenergypoint.it/shop/hf-energy-hf300ka-modulo-fotovoltaico-monocristallino-300w-24v

38 for first item and 22 per item after that

unkel · 05-06-2019 1:18pm

That's a terrible deal. The panel is expensive, it is brutally inefficient (15.9%) and then they are looking for €148 + VAT for shipping 6 of them?

I'm not sure if we are allowed post links to Irish suppliers, if not apologies to the mods - you can remove. But here is a cheaper panel that you can collect for free (6 or 7 panels fitted in my medium sized hatchback car) in Dublin that has a very high efficiency of 19.05%

Linky

championc · 05-06-2019 1:29pm

Fantastic. The whole "project" will be much cheaper thanks to that. My wife has a C-Max although if that was still a problem, I can just use my 318 with the roof down - lol !!!

unkel · 05-06-2019 1:35pm

I take my consulting fee in some free batteries if you have any spare

championc · 05-06-2019 5:40pm

Question - is a DFS mandatory ? So with the Panels typically going on the roof, would the DFS typically go in the attic ?

With my installation, the Charge Controller, the Batteries and the Grid-Tied Inverter are all being installed in my concrete shed. So I was going to bring the cables from the roof straight down the side of the house and so, I was not planning on bringing the cables anywhere near the attic. I have a manual mechanical circular DC disconnect switch for the Shed end of the cables coming from the panels

listermint · 06-06-2019 6:10am

championc wrote: »

Fantastic. The whole "project" will be much cheaper thanks to that. My wife has a C-Max although if that was still a problem, I can just use my 318 with the roof down - lol !!!

Go car rent vans now. Hourly

n97 mini · 06-06-2019 10:21am

@championc, what's your inverter?

(Your charge controller is the Victron one in the picture?)

championc · 06-06-2019 11:12am

I was originally going for the Victron until I found a similar spec'd (150/40) unit online via the UK and bought it instead. So I bought an eSmart 3 Series MPPT Controller - https://www.ebay.co.uk/itm/183232710071

As for the Inverter, it's a SunG GTIL2, from China - Grid-Tied with Limiter preventing Grid Feedback - https://www.ebay.co.uk/itm/192191478133

There's a pretty decent Facebook group for the Inverter where people help others with issues, and share problems and experiences - https://www.facebook.com/groups/1532777123642307/ You'll also see this Inverter feature in a number of YouTube videos.

n97 mini · 06-06-2019 8:39pm

Question. You're putting your inverter in the shed at the back of your house, but the wired clamp needs to go on your mains feed in your meter box, which is probably at the front of the house. How will you deal with that?

Charlie-Bravo · 07-06-2019 3:26pm

This is a hijack.

Just wondering what cable would be needed to come from an inverter in the attic, down to the consumer trip switch board? Going to doing some pre-cabling in advance of installing a system which will be around 3kW.

Solar PV - Cable Size ?

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