Electrical design and installation of solar pumps

Panels fixing (on 
the support)
Fixing the panels on the support must prevent theft, making it as difficult as possible to remove them. 
For this, the following prevention measures are commonly used:
•
Place the panels at a height (on a roof, on the water tower if the surface allows it, ...)
•
Surround the park of panels with a wire fence (with barbed wire at the top of the fence if there’s a major risk of 
theft).
•
Weld stirrups on the stand to block the panels.
•
Use anti-theft nuts if it is possible to supply them (split nuts or nuts with special head requiring a special key to 
unscrew), or use socket screws and plug the screw head with putty when the nuts are inaccessible. 
In case of welding very close to the panels, protect the panels before welding so they are not damaged.
Grounding/
Earthing
• 
The panels must be connected to the support with same size of wire than solar panel cables, and the support must 
be connected to the ground using a 16 mm² cable.

---

15
SOLAR PUMPING
Guidelines - Electrical design and installation of solar pumps
3
 
PROTECTION CABINET
The protection box is essential on all pumping sites where the operating voltage (at the pump) is higher than 120V. The 
installation of a cabinet concerns almost all pump systems as this voltage is reached even on small installations (4 panels of 
250Wp).
The protection cabinet is used to:
•
Protect equipment from overload (fuses)
•
Switch off the installation to perform maintenance via a main switch ON / OFF
•
Protect the installation from lightning strikes and surges (surge arresters - SPD)
•
Create a central point of grounding
•
On some high power pumping systems, it also used to connect the different strings of solar panels together, and 
accumulate their power in a single output that will power the controller or the inverter
FIGURE 4:
DIAGRAM OF A EUROPEAN STYLE CABINET FOR 3 PANEL STRINGS
1 Fuse per string 
of panel
(on the + side)
1 Common bus 
bar (on the - side)
ON/OFF
contactor
Surge Protection 
Device (SPD) / 
Lightning arrestor
FIGURE 5:
EXAMPLE OF A US STYLE CABINET 
(same components than figure 4) 
ON/OFF contactor
1 Common bar 
(on the -)
1 Earth/Ground bar
(under the - bar) 
1 Fuse per panel string
(on the +)
Lightning arrestor
Protection cabinet
Solar pumping 
inverter cabinet
ON/OFF contactor 
lever
Internal view
External view