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puskarpraveen avatar image
puskarpraveen asked

multiplus-ii 48v/5000/70-50 AC-IN cable specs

Hi,

I have a multiplus-ii 48v/5000/70-50 connected with a 14kWh battery.

I am looking forward to installing it in my garden shed which is approximately 17 Mtrs away from the meter box.


The plan is to charge the battery when it is sunny(with solar power) or use the grid when the power rates are cheaper(I have dynamic contract).

I am going to use Use AC-IN only, grid parallel topology with VM-3p75ct as the grid meter. I.e. only one cable running from my meter box to the garden shed.

My question is regarding the AC cable size for the AC-IN.

What is the recommended size?

If i do the math, 5000Va ~ 4000w

and 4000w/220v = 18.8 Amp

Also, I see the documentation referring to 50 Amp current protection required for AC-IN.

These values don't add up.

What am I missing here ?



Multiplus-IIESSac coupling
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mjs500 avatar image mjs500 commented ·

50 Amp current protection required for AC-IN. the transfer switch inside multiplus-ii 48v/5000/70-50 is rated at 50 amps ! but as you are go to be using multiplus-ii single ended no need for 50 amp mcb

do not for get to use bidirectional mcb and RCD or RCBO

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puskarpraveen avatar image puskarpraveen mjs500 commented ·
So I am considering a 6 mm2 cable with 25 Amp protection with bidirectional MCB and RCD/RBCO.


On another note, the inverter is rated as 5000w which is ~4000w, what if my house demands 4400w, will the inverter limit itself at 4000w, and the rest 400w will be pulled from the grid?

Is there a setting of such kind in ESS.

Or the inverter will stop and my house will start using the grid power instead.


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phoenix avatar image phoenix puskarpraveen commented ·

If you're using a 25A MCB, you need a cable rated for 25A. According to this site https://www.elandcables.com/cable-calculator 20m of 2.5mm2 copper either buried or in free air is adequate in the UK. If you are in any doubt seek a qualified person.

You can limit the output power of the inverter in ESS. If the house demands more it comes from the grid.

I imagine you're buying a GX or some other display. Does your WiFi stretch OK to the shed . Personally I'd run a cable for the energy meter.

Note that you will not be able to use the MP during a power cut if you only wire to AC in, unless you intend to run an extension lead back to the house for these rare events.

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Mike Dorsett avatar image Mike Dorsett commented ·
14Wh is a small size for the battery - perhaps you mean 14kWh?
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puskarpraveen avatar image puskarpraveen Mike Dorsett commented ·
yes, it is 14kwh.
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2 Answers
Alexandra avatar image
Alexandra answered ·

@puskar.praveen

The 50A suggestion is assuming that you have loads on the output and want to run full loads, pass through loads and charge the battery.

You obviously have a different use case and would have to size accordingly.

The inverter will feed back what you limit it to or up to its inverting power if you are only sending from the battery (unless derated for heat).

If you are not using the output you can in settings switch that off as well.

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puskarpraveen avatar image
puskarpraveen answered ·

I haven't experienced any power outages in the Netherlands recently, so power outage is not a concern for me at the moment. I have decided to use VM-3p75ct, which connects via WiFi, instead of ET112. The distance between the shed and the main power connection is 17 meters. I have hired an electrician to take care of the calculation fo wire guage and installation process.

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atebee avatar image atebee commented ·

Just for information, you can use a CT clamp on an extended cable to to grid metering from the MPII. A lower cost solution than the VM-3P75CT.

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