System Design Review

[Simpleone71]

Here is the system I am looking to build, and I would appreciate everyone letting me know of any wrongs or better methods to do things. I will be mounting it on a piece of oak plywood that has been covered with ceramic paper that is rated at 2300 F. I am also going to use a raspberry pi 4 / touchscreen with VenusOS to monitor it with a USB to VE.Can cable and USB to VE.direct cable for the inverter and MPPT.

A couple of questions I already have in mind would I benefit any from using a battery shunt for monitoring also? I am looking to use the BMS on the EG4 batteries to communicate with the Venus OS, so I felt it was unnecessary to buy the Victron shunt.

Also, If I added one more battery to the EG4 cabinet, would everything be the same? In other words, have I allowed for a little bit of future growth in this setup?

Here is what I am after mostly a backup power source for near (or direct) hurricanes and summer thunderstorms to run a few switches/wi-fi, etc. and my freezer and fridge. I calculated needing around 8.5 kwh a day. I would keep the computer stuff plugged in directly to it, but would need to manually plug in the freezer and fridge.

 

[marionw]

If you are spending money on a solar system why not use it 24/7.

Can you install a subpanel next to your existing "Main" panel that can be fed from the new inverter or the "Main" panel.
6-8-10 breaker subpanels are not that expensive. Install two "Mechanically Interlocked" breakers in this subpanel to permit power from either the main panel or the inverter, not both at the same time, one or the other.

Install two "Mechanically Interlocked" breakers in the "Main" panel. One breaker feeds the subpanel and the other breaker feeds the inverter such that if you have "Grid" power going to the inverter you cannot have grid power going to the subpanel.

If the TV show NCIS were still being produced Gibbs would have rules on the use of Solar Systems:
Rule XXX; Once solar bites you in the butt, you will want to expand your system.
Rule XXX; If your significate other (if you have one, else rule above applies) realizes your solar hobby is a great thing, you will be allowed to expand.

There are a number of Victron experts on this forum @sunshine_eggo being one of them.

Build the system with future expansion in mind and to also use the system for everyday use, even if it is only to power several small loads.

 

[Simpleone71]

I like the suggestion and even as I have it now, would be using it daily. I would keep my computer stuff plugged into it using the batteries at night and solar during the day. That may not sound like much, but I work in IT and have several servers, etc.

What would really make my project easier and cheaper is that my panel is in the garage. If I placed the batteries, inverter, MPPT in the garage, I could easily do what you suggest and for a cheaper price. Right now I will need to run wire in the attic from one end of my house to the other and to do what you suggest run a 2nd wire back to the panel. I am letting the electrician handle this part, but I imagine it is very big wire size that will be super expensive per foot.

How well does this stuff hold up if it is in a garage in south Georgia with 100 degree summers?

I may take your suggestion also, but make it a phase 2 to my project.

 

[marionw]

You would simply move existing circuits from the main panel to the subpanel (i.e. electrical outlets in the room that supplies your computers).
You would not need to run a new circuit to your "computer room".
You would be able to power the subpanel from the inverter or the main panel"

 

[Simpleone71]

Ok, I see what you are saying now. Thanks for the suggestion

 

[Rocketman]

Your solar mppt is very oversized for your current solar…
4x 550w = 2200w / 48v = 45amps.
A mppt 150/45 will handle your current array, but the 150/70 will allow future expansion.

One note: the future panels should be the same as the current ones, if they have different electrical specs there is a penalty- how much of a penalty depends on how different they are. Does your supplier think they will have more of these panels in stock in the future- if unknown- you may want to buy two more now, and hook them up in 2s3p - you will need three mc4 fuses. (All arrays over 3p must be fused on each string).

6x 550w = 3300w / 48v = 68.75amps

With six panels your charge controller will be almost full- with eight in 2s4p it will be overpaneled, but the Solar charge controller can handle that and will just clip all power over 70amps, you have good wiring to handle eight panels- can you fit them at your place?

 

[Simpleone71]

Thanks for all the excellent information. I knew my MPPT was oversized, I got a good deal on two models up and was looking to future-proof this somewhat. Even the inverter, 5000v is a size up from what I need currently.

The panels are Renology, so I hope that makes them easy to get in the future, but maybe can go ahead and grab two more as phase 2 to this project. For now, the panels will be ground-mounted, and I do have room for two more. I have to have "approval" from my HOA if I ever decide to have them mounted on the roof.

Hopefully the rest of my design looks good, especially in regards to wire size and fuses. I'm new at all of this and it has been a bit of a humbling experience