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Introduction and advice needed on small Off Grid System


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So to introduce myself, I’ve been registered on this forum since 2018, but this is my first post! I’ve been an avid reader of the posts around going solar (who in SA isn’t!!) for a while but since I have built a cottage in a reserve with no electricity whatsoever (the closest Eskom line is 5km away!), its now time to take the step. As an absolute neophyte in solar, I will welcome as much comment and advice as possible. My first foray into solar is quite modest, but even such a small system comes with not insignificant costs!!

I recently had a stay in the Tankwa Karoo National Park, and was very impressed by the system they had installed in the cottages. Since the size and usage requirements so closely mirrored my own it seemed to be ideal for my own needs. The Tankwa cottage had a standard fridge, ceiling fans, LED lighting, microwave and pool pump all running off an Victron Easysolar Inverter 24V/1600W/50 with 3 PV panels (unknown size) and unknown battery storage.

So when I saw a new Easysolar 24V/1600W/50 on sale for R14K the impulse buy was almost inevitable! Having now read a little more around this inverter I realise that there are some limitations, but in the greater scheme of things I am happy with the purchase and confident given the reputation of the brand.

 

My approx power usage of 220W will include the following:

Fridge (120W)

Celling fan (75W)

Lighting (40W)

It gets hot behind Picketberg so I expect the fridge to run 24/7!

 

My anticipated Solar setup will include and cost the following (The reserve limits PV panels to a max of 4m2 so quite constrained):

 

Victron Easysolar 24V/1600W/50 (R14 000) (Already purchased)

2 X Oliter 200ah 12 Gel batteries (R4 500 each)

Victron Battery Balancer (R1200)

2 X Canadian Solar HiKu CS3W-405 405W Super Power Solar Panel (R2 700 each)

Mounting clamps and channels (R1 500)

6mm Cabling and Lugs (12m from PVs to inverter) (R400)

DC Breaker 63A dipole (R850)

KETO Battery Disconnector and 125A fuse link (R1500)

 

TOTAL R33 850

I haven't put the suppliers from which I got the costs and most were online, but if any seem high I would appreciate some pointers to alternatives.

I am suggesting the highest wattage panels available due to the 4m2 restriction. As a push I will add a third panel (The Easysolar can manage 1400W PVs) and risk the wrath of the reserve rules! They will be mounted on a flat section of the roof, also due to rules. The panels are rated Voc 47.4V but the Victron calculator advises that it will exceed the MPPT max of 100V in temperatures below 10C so they will be in parallel not series (not sure what the relative merits are of this?). The PVs are quite expensive and I could save some cash using Chinese manufactured 330W panels but not sure if this is sensible. My main concern is that there is sufficient battery storage for the fridge in overcast weather, say 2 days running.

I’m also not sure if I need all the breakers and disconnectors as this may be incorporated in the EasySolar unit, but there we are.

I would really welcome advice, criticism, pitfalls as I am new to this and learning as I go along!

 

 

 

 

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1 hour ago, Gremlin said:

insults

OK... your mother dresses you funny!

On 2020/02/28 at 2:27 PM, Gremlin said:

So when I saw a new Easysolar 24V/1600W/50 on sale for R14K the impulse buy was almost inevitable! Having now read a little more around this inverter I realise that there are some limitations, but in the greater scheme of things I am happy with the purchase and confident given the reputation of the brand.

The 1600VA model is actually a nice little beast. It has some limitations as you say, running a Microwave oven for example is not an option. That was the one thing I missed most when I still had a 1600VA model, before I upgraded to a 3kva.

On 2020/02/28 at 2:27 PM, Gremlin said:

The panels are rated Voc 47.4V

That is at 25°C. The Victron calculator is quite correct in telling you to watch out. Ideally you should put them in series and use one of the 150V MPPTs, but parallel is fine too, just remember to size the cabling for at least 20 amps.

On 2020/02/28 at 2:27 PM, Gremlin said:

using Chinese manufactured 330W panels

All panels are chinese manufactured, even "Canadian" solar 🙂 The 330W modules are quite cheap at the moment due to manufacturing volumes, it will take a while still before the large >400W modules come down in price.

On 2020/02/28 at 2:27 PM, Gremlin said:

I’m also not sure if I need all the breakers and disconnectors as this may be incorporated in the EasySolar unit, but there we are.

Nope, as far as I know there's no DC disconnect in the EasySolar. But the 1600VA model does have a built-in 125A fuse if I recall. The KETO disconnect is a nice addition though and I would keep it.

On the AC side, I cannot remember if the built-in little DB has an RCD, so make sure you have that. In later models Victron actually dropped the breakers because in some countries it wasn't up to code anyway. In South Africa I believe you'll be fine.

Edit: Just to be clear, an RCD is a residual current device... an earth leakage breaker in other words 🙂

Edited by plonkster
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Hi Plonkster - Here I was all dressed funny waiting for advice!

Thanks I really appreciate the input. When starting out you can read as much as you like (understanding about 50% of what you read) but nothing is more reassuring when you get the advice of someone who has real knowledge and experience.

Regarding PV cable size, I have used a couple of online calculators and they seem to spit out 4mm2 for 20A. I was always going to use 6mm2 multi-stranded cable so I assume I will be ok?

Thanks for the advise on the KETO and I will retain this.

The EasySolar does have an earth leakage but earthing (which I have been advised to do) is a whole can of worms in itself!!! In town one would just use the grid supply earth. The area where my cottage is, is well off the beaten track and so getting an electrician out to install one problematic. Putting in an earth spike in rocky ground almost impossible and where the hell does one get a copper grid to bury 1 meter below ground!!!? And that the soil is bone dry does not help....... All sent to try me!

 

Thanks again for the advice!

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2 hours ago, Gremlin said:

Regarding PV cable size, I have used a couple of online calculators and they seem to spit out 4mm2 for 20A. I was always going to use 6mm2 multi-stranded cable so I assume I will be ok?

Definitely go with the 6mm^2 cable. Even that will be a little warm to the touch 🙂

2 hours ago, Gremlin said:

Putting in an earth spike

Yeah, you're supposed to put in spikes until the earth loop impedance is low enough. I'm not an electrician, but this is what I understand: It should be low enough that a fault current of double the main breaker size will flow when there is a fault.

So your 1600VA inverter has a 16A transfer switch (and can peak at maybe 13A for a second), so you will probably have a main breaker of 15A or maybe even 10A. So you want an earth impedance that will let 20A flow, and 230/20 ~= 10Ω.

You need an earth loop impedance tester though, and those are not cheap. Will have to bribe, steal or borrow 🙂

 

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