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DC side diagram HELP


Dylan
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Hi all,

Still crunching the numbers for solar, and its expensive and looking at different options... To get anywhere near a ROI I need about 7 - 10kWh saving from the system, which I am sure(read hope) it can do.

I have attached the proposed DC side of the installation consisting of focusing around multigrid II in ESS, I will add the AC side as well down the line.

One of my problems is there is absolutely no place inside the house for the equipment, okay maybe the battery's so it will all have to be installed in a 900x700 electrical IP65 enclosure with fans outside.

Have highlighted in red 4 questions and would appreciated some input if I am going to far or not far enough, obviously I am trying to keep costs down already at 92k for what I have laid out in the attachment.

Some other info, have gone for two grids 4x300W north and 4X300W east ish, am playing around with a grid tied inverter however its 10-15k more than mppt and cant get enough panels in series for voltage needed.

 

Thanks

DC layout.pdf

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1. I have a Mersen fused disconnect just like this installed. I have 160A, but it is a 24V system. 125A sounds good.

2. I prefer that my MPPT can be isolated from the battery independently, so I would put a breaker between the MPPT and the busbar. I am unsure whether you really need a breaker on the PV side of the MPPT, since you already have DC protection in the form of fuses, and since nothing bad happens to the MPPT if you open the breaker battery side (it happens all the time when BMSes disconnect the battery), so in my case I simply have DIN-mount fuse holders before the MPPT and breakers after it.

3. I have an additional fuse (Megafuse type) between my busbars and the Multi. Smaller Multis has this built in, for the larger ones you must install one yourself. So yes... extra fuse at point 3.

4. Just put a small inline fuse in the wire going to the colour control. 1A is ample, the CCGX uses less than a quarter of that.

Edited by plonkster
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1 hour ago, plonkster said:

1. I have a Mersen fused disconnect just like this installed. I have 160A, but it is a 24V system. 125A sounds good.

Thanks, do you have a local link for the one you use?

1 hour ago, plonkster said:

2. I prefer that my MPPT can be isolated from the battery independently, so I would put a breaker between the MPPT and the busbar. I am unsure whether you really need a breaker on the PV side of the MPPT, since you already have DC protection in the form of fuses, and since nothing bad happens to the MPPT if you open the breaker battery side (it happens all the time when BMSes disconnect the battery), so in my case I simply have DIN-mount fuse holders before the MPPT and breakers after it.

I guess the cheapest option is to then just move the breaker, however must just get a higher amp rating

 

Thanks for the input

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19 minutes ago, Dylan said:

Thanks, do you have a local link for the one you use?

https://thepowerstore.co.za/products/fuse-holder-for-mega-fuse

OnTrack also has some in the shop. Current Automation too. Just watch out, there is a cheaper 32V version and a more expensive one for higher voltages :-)

Oh hang on... wrong fuse. I have that one (above) between busbar and inverter.

This one on the battery side: https://www.sonopsolar.co.za/product/2-pole-battery-fuse-holder/

I was unsure whether I needed a fuse in both lines. I eventually went with just one in the positive side.

Edited by plonkster
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