Victron DIY Install

[PierreJ]

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.

 

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

 

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

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

 

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:

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:

 

 

Close-up of the DC buses.

 

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

 

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 December 20, 2020 by PierreJ

[Gerrie]

Well done very neat installation.

[Tariq]

Very well done, congrats

[Yellow Measure]

Very neat install, congratulations!

[Gandalf]

Very nice. So neat and attractive looking. I love your clever use of a DIY  heatsink. 

[WeNotGood]

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

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

[WeNotGood]

Should perhaps be more specific, the two DC fuse boxes connected to the batteries?

[Jay-Dee]

Very Very Nice installation... Great thinking on the heatsink!  Well Done!

[PierreJ]

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.

[PierreJ]

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.

[DanieT]

Very nice and professionally done.

[LeeMun]

Very neat

[David27]

I am extremely impressed with such a neat installation, Very Professional. Great Job. Well done Pierre...!!!

[David27]

Hi Pierre, I am keen on installing a system, using The Victron Multiplus II and 2x Pylontech 2.4 Batteries, just for load shedding purposes, for some LED lights about 12x 5W and some plugs, for 2x Aircon, Wifi, T,V, and 2x Laptops, 1X Smart Fridge.

Would you be so kind so as to enlighten me exactly all the equipment I would require for the Installation. Such as Essential and non essential DB's, Surge protection, Main breaker size, etc..? Would I require a change over switch..?

AC and DC Isolators, DC Cable size, etc.

I would appreciate it very much. Thank you.

[PierreJ]

Hi David,

1 hour ago, David27 said:

Hi Pierre, I am keen on installing a system, using The Victron Multiplus II and 2x Pylontech 2.4 Batteries, just for load shedding purposes, for some LED lights about 12x 5W and some plugs, for 2x Aircon, Wifi, T,V, and 2x Laptops, 1X Smart Fridge.

I think you may have to sacrifice the air conditioners with only two batteries. If you insist on running the air conditioners during loadshedding then you would likely need to get a 5kVA Multi, in which case the recommended minimum number of Pylontech batteries is 4:

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

 

Quote

Would you be so kind so as to enlighten me exactly all the equipment I would require for the Installation. Such as Essential and non essential DB's, Surge protection, Main breaker size, etc..? Would I require a change over switch..?

AC and DC Isolators, DC Cable size, etc.

You're going to have to purchase a GX Device, like a Cerbo, in order to communicate with the battery BMS. If you want to update the firmware of the Multi you will also need the MK3-USB cable: https://www.victronenergy.com/accessories/interface-mk3-usb. The Ve.Bus and battery communication cables use normal CAT5 cable, and you can make them up yourself - the pinouts are available on the Victron website.

The breaker in your main DB is there to protect the cable, so the thickness of the cable will dictate the breaker: 30A for 4mm^2, 40A for 6mm^2, 50A for 10mm^2. The 5kVA Multi can pass through a maximum of 50A, so there is little point in going over 10mm^2. With the loads you listed above, 4mm^2 should be fine.

Victron recommends 70mm^2 for the battery cables (good for 200A), however the cables that come with the Pylontech batteries are only 25mm^2 (120A). If you're not ever going to be using more than 4 batteries, and the batteries will be right next to the inverter then you can perhaps save some money and use 35mm^2 battery cable instead. The fuses in the DC isolator should match the cables, so 125A fuses would be appropriate.

I don't know whether a changeover switch is a legal requirement, but it is certainly a good idea - if something goes wrong with your inverter setup you want to be able to use grid power while the issue is being addressed. While on the topic of legality: The Multiplus is a grid-tied inverter, so if you fall under City of Cape Town you technically have to apply for approval to install it.

Surge protection is always a good idea, especially if you live in an area where an indirect lightning strike is a possibility. (Nothing will save the inverter from a direct strike.)

There are photos in the original post of my essential loads DB. The layout is fairly standard, so if you copy that you should pass an electrical CoC inspection. Note the power indicator light at the bottom right, which is (as I understand the regulations) a requirement for a DB powered from multiple sources.

 

Edited January 19, 2021 by PierreJ

[branderplank]

On 2020/12/21 at 8:54 PM, PierreJ said:

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 -).

 

I have read the manuals and could not see such instructions. Is it a function of cable thickness and amps that you had to do this? Or is there some guidance on this matter?

 

Thanks

 

[PierreJ]

16 minutes ago, branderplank said:

Is it a function of cable thickness and amps that you had to do this?

Correct. The PylonTech cables are 25mm^2, rated at 120A. The recommended maximum charge and discharge current per US2000 battery is 25A, so if you have more than 4 in parallel and you're using them at the recommended maximum currents then you should use two pairs of their cables.

Edited January 20, 2021 by PierreJ

[HennieW]

Hi PierreJ

One thing you need to take cognizance of is during autumn and spring when it is cold, with occasional clouds, with bright sunshine hitting the cold PV panels when the clouds part, you get a huge spike in the current delivered to the MPPT controller(s). I have had more than doubble the rated PV current delivered for a couple of seconds during these times.

The point is your cables from the combiner box to the MPPT controller need to handle this spike. I have had my combiner box main 50A trip during such conditions.

Just a heads up. Nice installation.

[PierreJ]

Hi Hennie,

27 minutes ago, HennieW said:

The point is your cables from the combiner box to the MPPT controller need to handle this spike. I have had my combiner box main 50A trip during such conditions.

I've currently got 16mm^2 cable and a 63A breaker between the combiner and MPPT. I have five strings so the maximum rated current is 5 x 11A = 55A. So far (touch wood) it hasn't tripped.

The MPPT is rated at 70A input current, and given that I have space for another string on the roof, I was considering adding a 6th string... now I'm not sure that is a good idea anymore.

Thanks for the warning.

[Moffat]

Sweet and very neat installation Pierre, in your estimation and research would you rate this a better system than an equivalent 5kW Sunsynk?

[PierreJ]

14 hours ago, Moffat said:

Sweet and very neat installation

Thanks!

 

14 hours ago, Moffat said:

Pierre, in your estimation and research would you rate this a better system than an equivalent 5kW Sunsynk?

The big issue I had when I designed my system is that I absolutely wanted more than 3.5kWp on the roof, yet had to stay under the City of Cape Town's 15A current limit. The Victron Multiplus is one of very few grid-tied inverters that allows you to limit the current flow between it and the grid connection, without crippling its output at the same time. Victron also has a good reputation for reliability, and if you add a GX Device it is exceptionally feature rich. As a DIYer my installation experience was very pleasant, and everything just worked out of the box. If you do hit a snag (one of my Pylontech batteries developed an issue some time after install), Victron tech support is top notch.

The Victron system is very modular, which is mostly a plus, but if you add up the cost of all the components it can be quite expensive. Although the sticker on the Multiplus II says 5kVA, it is really a 4kW inverter if you look at the spec sheet. Those are the two negatives for me, but overall I am very happy with my purchase.

I don't know much about the SunSynk other than what I've read on these forums. It certainly looks like great bang for the buck, but I don't think there's enough evidence yet to draw a conclusion on reliability.

[Moffat]

On 2021/01/22 at 8:18 AM, PierreJ said:

Thanks!

 

The big issue I had when I designed my system is that I absolutely wanted more than 3.5kWp on the roof, yet had to stay under the City of Cape Town's 15A current limit. The Victron Multiplus is one of very few grid-tied inverters that allows you to limit the current flow between it and the grid connection, without crippling its output at the same time. Victron also has a good reputation for reliability, and if you add a GX Device it is exceptionally feature rich. As a DIYer my installation experience was very pleasant, and everything just worked out of the box. If you do hit a snag (one of my Pylontech batteries developed an issue some time after install), Victron tech support is top notch.

The Victron system is very modular, which is mostly a plus, but if you add up the cost of all the components it can be quite expensive. Although the sticker on the Multiplus II says 5kVA, it is really a 4kW inverter if you look at the spec sheet. Those are the two negatives for me, but overall I am very happy with my purchase.

I don't know much about the SunSynk other than what I've read on these forums. It certainly looks like great bang for the buck, but I don't think there's enough evidence yet to draw a conclusion on reliability.

I'm hearing raving reviews about it (the Sunsynk), but you are right in terms of long-term reliability, support and expertise by installers seems to be quite fledgling.

[David27]

On 2021/01/19 at 8:02 PM, PierreJ said:

Hi David,

I think you may have to sacrifice the air conditioners with only two batteries. If you insist on running the air conditioners during loadshedding then you would likely need to get a 5kVA Multi, in which case the recommended minimum number of Pylontech batteries is 4:

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

 

You're going to have to purchase a GX Device, like a Cerbo, in order to communicate with the battery BMS. If you want to update the firmware of the Multi you will also need the MK3-USB cable: https://www.victronenergy.com/accessories/interface-mk3-usb. The Ve.Bus and battery communication cables use normal CAT5 cable, and you can make them up yourself - the pinouts are available on the Victron website.

The breaker in your main DB is there to protect the cable, so the thickness of the cable will dictate the breaker: 30A for 4mm^2, 40A for 6mm^2, 50A for 10mm^2. The 5kVA Multi can pass through a maximum of 50A, so there is little point in going over 10mm^2. With the loads you listed above, 4mm^2 should be fine.

Victron recommends 70mm^2 for the battery cables (good for 200A), however the cables that come with the Pylontech batteries are only 25mm^2 (120A). If you're not ever going to be using more than 4 batteries, and the batteries will be right next to the inverter then you can perhaps save some money and use 35mm^2 battery cable instead. The fuses in the DC isolator should match the cables, so 125A fuses would be appropriate.

I don't know whether a changeover switch is a legal requirement, but it is certainly a good idea - if something goes wrong with your inverter setup you want to be able to use grid power while the issue is being addressed. While on the topic of legality: The Multiplus is a grid-tied inverter, so if you fall under City of Cape Town you technically have to apply for approval to install it.

Surge protection is always a good idea, especially if you live in an area where an indirect lightning strike is a possibility. (Nothing will save the inverter from a direct strike.)

There are photos in the original post of my essential loads DB. The layout is fairly standard, so if you copy that you should pass an electrical CoC inspection. Note the power indicator light at the bottom right, which is (as I understand the regulations) a requirement for a DB powered from multiple sources.

 

Hi Pierre, Thank you so much for your most valuable information. If we do not use  the A/C's on the essential board, would the 2x 2.4 Pylontech batteries be sufficient..?.

[David27]

On 2021/01/19 at 8:02 PM, PierreJ said:

I think you may have to sacrifice the air conditioners with only two batteries. If you insist on running the air conditioners during loadshedding then you would likely need to get a 5kVA Multi, in which case the recommended minimum number of Pylontech batteries is 4:

I am planing on using the Multiplus ii 5Kva 48V , is this the one you are refering to (5kVA Multi...?) So then I will need 4x Pylontech batteries..?.

If I sacrifice the A/C's, then the 2 batteries will be suitable.??

[PierreJ]

1 hour ago, David27 said:

I am planing on using the Multiplus ii 5Kva 48V , is this the one you are refering to (5kVA Multi...?) So then I will need 4x Pylontech batteries..?.

Yes. According to Victron, you need a minimum of 4 x Pylontech batteries with a Multiplus II 5kVA. It's not only about the total energy storage, but also the startup currents of the inverter, peak currents, etc. See here:

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

 

1 hour ago, David27 said:

If I sacrifice the A/C's, then the 2 batteries will be suitable.??

If you sacrifice the A/Cs then the energy storage capacity of two batteries should be sufficient to power your loads through loadshedding, however your battery bank would still be under-specced for the inverter. I have never tried to run my Multi with only two batteries, so I can't definitively tell you what issues (if any) you'll encounter. You could always start with two, and if you get DC ripple, BMS or other warnings then add more.