Help choosing equipment

DIY
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1

Hello everyone,

This is my first post on this forum, as I’ve only just discovered it, and I think I’ve come to the right place.

I’d like to treat myself to a nice gift by installing a good system with the following specifications:

  • 15 × 500 Wp DMEGC solar panels, facing due south on the roof (3 strings of 5)
  • 1 × 6000 VA MultiPlus-II
  • 3 × Pylontech US5000 batteries
  • 1 × Cerbo GX
  • 1 × Lynx Distributor

The idea:

  • A large part of my consumer unit would be on the IN side (and therefore not backed up). For this, I already have a 63 A circuit breaker connected to the busbar of the main LV switchboard (yes, I built a large consumer unit because a major house extension is currently under way :wink: )
  • One circuit from the consumer unit will need to be backed up (a few lights, one socket in the consumer unit, the blinds, fridges/freezers, the heating system, …). This circuit has a 30 mA RCD at its head.
  • On very sunny days, I send up to 3000 W to an electric heating element to heat a 1,000-litre buffer tank (domestic hot water + underfloor heating).
  • Only the PV panels are on the roof; the rest of the installation is concentrated in a plant room (maximum distance between the batteries and the inverter: 2 m).

For the next steps, I need your advice and expertise:

  • Help choosing the MPPT(s); even using Victron’s sizing tool, I’m not certain I’ve got it right.
  • Mandatory and/or missing protections on the AC and DC sides.
  • Sizing of the cable cross-sections and fuses for the Lynx Distributor.
  • Sizing of the cable cross-sections to the PV panels (maximum 20 m).
  • Battery wiring arrangement (in parallel with a single connection to the Lynx, or should each battery be connected to the Lynx via its own fuse?)
  • Is a neutral-to-earth bonding contact required on the backed-up side (I’ve seen/read that this is needed for other inverter brands)?
  • Is a mandatory Consuel inspection required?

I think I’ve covered everything.

Many thanks in advance to anyone who reads this and takes a little time to reply :ok_hand: .

For information, I’ve obtained quotes from several companies, and none of them specifies the same equipment, so I don’t want to make the wrong choices. I think this is where the best experts are.

2

Switchgear is also dictated by local regulations.

Each string of solar panels should be at least fused with a breaker at the minimum. Maybe an SPD.
I am assuming you have the 450/200 or maybe 3 separate mppts?

Either way, the basic fusing and cable size is in the manual for those.

All items should have a DC fuse and batteries a fused disconnect or a fuse and disconnect.

Make a drawing for your self, even if it is paper a pencil and some boxes and start planning it out.

3

You may want to engage someone to design the system properly as there are lots to consider e.g. the type of MCB or RCBO which should min be bi-directional Type A or even B if the inverter is not fully isolated (not to be confused with curve rating) depending on regs and should be dual poles for the AC side to ensure 100% isolation, ensuring other RCD’s are not “blinded” if in place etc. etc. etc. You realy need someone on site to to a full and proper assessment of the complete picture.

4

You might consider a mixture of DC-PV e.g. RS450/100 ir MPPT 250/xx and AC-PV eg Fronius Primo.
The AC-PV will be used directly with 98% efficiency, while DC-PV is efficient to charge battery.
Or alternatively a Multi RS 6000 plus Fronius.
Fronius is officially supported, while other brands might work with some tinkering.

BTW there is no MP2 6000VA.
Either MP2 6k5 Watt or 8000VA.
Please check the transfer relais if you want to connect your loads on AC_out for grid failure.