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Got the sign-off from CoCT about a month ago, so my DIY solar project is finally done and dusted. Thanks to everyone on the forum that provided advice - I probably would have stuffed it up if it wasn't for you.

The whole project took about three months of evenings and weekends to finish, and was a welcome distraction from the current state of the world.

 

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4 strings of 4 Canadian Solar 400Wp poly panels in series, facing NNE.

 

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Another string of 4 Canadian Solar 400Wp panels in series, facing WNW.

All five strings are paralleled together for a combined 8kWp.

 

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This is my main DB. CoCT installed a new split prepaid meter. According to the technician that installed it it has built-in reverse power blocking. I have tested it to see what it does when I try to feed in power in to the grid, and it charges me in both directions. That is perfectly fine in my opinion - much preferable to it tripping when there is momentary feed-in.

Grid power is measured by an ET112. There is a breaker that connects the main DB to the solar installation in the scullery:

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Top-left is the AC DB. Top-right is the DC combiner box. Bottom left is the Multiplus II 5kVA inverter, and bottom middle the SmartSolar 250/100 MPPT. The SmartSolar was initially running a bit hot for my liking, so I mounted it on a 6mm thick aluminium plate which brought down peak temperatures from 82C to 65C. Bottom-right is the Victron Cerbo. The battery cabinet on the floor contains 5 PylonTech US2000 batteries for a total nominal capacity of 12kWh. I've set it to 80% DoD:

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Close-up of the DC buses.

 

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Close-up of the AC DB, with and without cover.

 

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Close-up of the DC combiner box, with and without cover.

The geyser and oven, as well as the swimming pool DB are connected to the main DB, so those are unpowered when there is loadshedding. The AC DB in the scullery is connected to the output of the Multiplus, so all the essential loads stay powered when grid power goes down.

 

Edited by PierreJ
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4 hours ago, WeNotGood said:

Agree, very nice install, also like the additional "heatsink" idea on the SmartSolar 250/100 MPPT.

Thanks! Both the SmartSolar and Multiplus run quite hot under full load - which is pretty much from 10am up to about 3pm every day. I worry about longevity of the electronics. I am considering removing 3.2kWp of the panels from the SmartSolar and connecting them to an AC-coupled Fronius Primo, which will also reduce the load on the Multiplus during the day. It's an additional R25k+ outlay though, which is hard to jump over.

 

4 hours ago, WeNotGood said:

Perhaps a silly question, but why the two DC fuse boxes used  with 5 kVA inverter?

I have 5 PylonTech batteries so I needed to use two pairs of their cables. I couldn't find a 4 pole disconnect, so I decided to use 2 x three pole disconnects which will also allow me to add a third pair of battery cables in future if I add more batteries. There are 125A fuses in there to protect the cables in case something catastrophic goes wrong (like a short between + and -).

The PylonTechs do have on/off switches so a separate disconnect is perhaps not critical, but I feel more comfortable having a physical disconnect that I can pull to immediately isolate the batteries from the rest of the system.

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@PierreJ I was also very worried about the high temps on both of my smart solar MPPT's so I have installed 120mm 2000 RPM PC fans on both MPPT's as well as my PylonTech battery bank.

This holds the MPPT's temps below 40 degrees while at maximum output all while the 12v DC power supply only draws 20W AC running eight 120mm PC fans. Cheap and efficient.

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18 minutes ago, SolarNoob said:

@PierreJ I was also very worried about the high temps on both of my smart solar MPPT's so I have installed 120mm 2000 RPM PC fans on both MPPT's as well as my PylonTech battery bank.

This holds the MPPT's temps below 40 degrees while at maximum output all while the 12v DC power supply only draws 20W AC running eight 120mm PC fans. Cheap and efficient.

I reckon I might follow your lead and do something similar. While the heatsink has improved the situation with my SmartSolar (Interestingly I've never seen it throttle, even when it hit 82C), the Multiplus drops down to 3.7kW during the heat of the day. The outside case gets uncomfortably hot, so I can only imagine how hot it must be inside. I also get high temperature warnings in the VRM console from time to time.

I can hear the fan inside it running at full tilt but I don't feel more than a very gentle draught at the bottom air vent. Is this normal? The temperature inside the scullery is about 3C above ambient, so short of installing an air conditioner I can't do much to improve it. (It is open to the rest of the house so it is not like all the heat gets trapped there.)

Perhaps I should experiment with positioning a desk fan so it blows across both the Multiplus and SmartSolar. If that works well a permanent fan installation like yours is probably the way to go.

It's a pity Victron don't yet have a Multiplus or Quattro that can sustain more than 4kW that is also approved by CoCT. The 5kVA Multiplus is slightly undersized for my needs, and I don't have enough space to install two in parallel.

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