Connection steps (so you don’t miswire)

Step A — Make 3 series strings

String1: P1 + to P2 –

String2: P3 + to P4 –

String3: P5 + to P6 –

Each string now has:

one free + (from the first panel)

one free – (from the second panel)

Step B — Combine in parallel (combiner box)

Bring all three string + into separate fuses/breakers then join to PV+ OUT

Join all three string – to a negative busbar then to PV– OUT

Step C — Add safety isolation

Put a DC isolator (disconnect switch) between combiner and controller PV input

Step D — Controller to pump

Connect U/V/W to pump U/V/W

Bond earth/ground to pump body and controller earth

4) My recommended parts (Nigeria-friendly, installer standard)

A) PV combiner & protection (must-have)

PV combiner box (3-in / 1-out) with:

3 × string fuses (typical 15A each, depends on panel Isc)

DC surge protection (SPD Type 2) on PV input

DC breaker or isolator (63A is common on PV side, but size depends on current)

B) Cable sizes (practical)

These are conservative and work well:

Panels to combiner (each string):

6mm² PV cable (good for rooftop runs)

Combiner to controller (main PV feed):

10mm² if distance is moderate

16mm² if distance is long (or you want less voltage drop)

Controller to pump (downhole cable):

Use proper submersible pump cable sized for distance/depth

 (90m head often means a long run — voltage drop matters)

C) Grounding & lightning (you’ve seen what small lightning can do)

1–2 earth rods (good copper-bonded)

Bond:

panel frames/rails

combiner box earth

controller earth

pump body earth