Direct answer: Protect a solar pump inverter with a system, not a single device: surge protective devices (SPDs) on the DC side and, where a backup source connects, on the AC side; a single, correctly bonded earthing system; short, separated cable runs; and a pre-storm disconnect order carried out before lightning is overhead. No SPD makes a system lightning-proof, and an SPD without earthing cannot do its job. All electrical work must be completed by qualified electrical personnel, following the model manual and local electrical rules.
Where a Surge Reaches a Solar Pump System
A surge does not need a direct strike on the inverter. Lightning near a long PV string, a long pump cable or an overhead supply line can induce a voltage spike in those conductors. Switching on a grid or generator backup, and faults elsewhere on a shared supply, can also send a transient into the system. That is why outdoor pumping systems are exposed in two directions at once: the PV array is a large, exposed conductor network, and the pump cable runs a long distance to the borehole or tank. The IP65 Solar Pump Inverter: Outdoor Installation Without a Control Cabinet guide makes the same point for outdoor mounting: a sealed enclosure is not, by itself, surge protection.
Think of protection in layers. The SPD diverts a surge to earth. Earthing gives that surge a path. Cable routing reduces how much surge is picked up in the first place. Disconnecting before a storm removes the live paths altogether. If any layer is missing, the remaining layers carry more than they should.
Verified Voltage Windows: Check Before You Choose an SPD
An SPD must be selected for the actual system voltage class, not for a generic solar system. The table below uses only figures published on the product pages for the QB100-PV Solar Pump Inverter and the IDEEI IP65 Solar Pumping VFD. Confirm the branch you bought before ordering any protective device, because the same product family covers very different DC ranges.
| Product branch | PV input on the product page | Output |
|---|---|---|
| QB100-PV, 220V models | DC 180–450V | Single-phase 220V or 3-phase 220V |
| QB100-PV, 400V models | DC 250–900V | 3-phase 380–400V |
| IP65 series, 220V branches | Recommended DC 200–400V; maximum DC 440V | 220V |
| IP65 series, 380V branch | Recommended DC 300–750V; maximum DC 900V | 380V |
Two checks follow from that table. First, the string voltage in cold, bright conditions must stay inside the branch range; a string that is already near the maximum leaves no margin when a transient arrives. Second, the SPD voltage class must match the branch, not the pump power. A device chosen for a 220V branch does not belong on a 400V branch, and vice versa. The QB100-PV product page also lists verified drive protections — PV overvoltage, overcurrent and over-temperature derating — but those are protections inside the drive. They do not replace an external SPD, as explained in the FAQ below.
SPD Placement: DC, AC Backup and Earthing
Fit SPDs where surges enter, as close as practical to the equipment they protect, with short earth leads. Long, looped SPD leads reduce the protection the device can provide, so the physical layout matters as much as the device itself. The IP65 installation guide lists surge protective devices on the DC side — and on the AC side where grid or generator backup connects — as part of a complete outdoor installation, alongside a DC disconnect, DC and AC fusing and correctly sized cables.
| Location | What to fit | Why it matters |
|---|---|---|
| DC side, at the array combiner or inverter input | DC SPD matched to the branch voltage class | Diverts a PV-side surge before it reaches the MPPT input |
| AC side, where grid or generator backup connects | AC SPD matched to the backup supply class | Protects the backup input path, which is a second surge entry point |
| Earthing bond | SPD earth, array frames and inverter protective earth bonded to the same earthing system | Gives a diverted surge one common path to earth instead of a path through the drive |
After fitting, record the SPD type, its location and the state of its status indicator. An SPD that has absorbed a large surge may need replacement even if the pump still runs. Check the indicator after every storm, and treat a changed indicator as a failed device, not as a cosmetic fault.
Earthing and Cable Routing
Earthing is the part of surge protection most often treated as an afterthought, and it is the part an SPD depends on. Bond the PV array frames, the inverter protective earth, the SPD earth and any metal enclosure or pole to the same earthing system, following the model manual and local rules. Do not leave the SPD earthed to a separate, isolated rod while the inverter is earthed elsewhere: a surge then has a voltage difference to drive current through, rather than a single path away from the equipment. The IP65 guide states the same rule plainly for outdoor work: a solid earth connection is non-negotiable outdoors, where lightning exposure is higher.
Cable routing is the second half of the same job. Keep DC and AC cables separated where practical, avoid large loops between conductors, and avoid running pump or PV cables in long parallel runs alongside other services for no reason. Keep cable glands matched to cable diameter, facing down on outdoor units, and seal every unused entry, so water cannot enter the enclosure and degrade the terminations that the SPD is protecting. For the full wiring order, see How Do I Wire a Solar Pump Inverter to Panels and a Pump?, which covers isolation, earthing, the DC disconnect, pump cable and PV string checks in order.
How to Protect a Solar Pump Inverter: Lightning Checklist
- Confirm the branch and voltage class. Record the QB100-PV or IP65 branch, the PV input range from the table above, and the string voltage. Select SPDs for that class, not for pump power alone.
- Fit DC and AC SPDs at the entry points. Place the DC SPD at the combiner or inverter input and, where backup connects, an AC SPD on the backup path. Keep SPD leads short and direct.
- Bond everything to one earthing system. Bond array frames, inverter earth, SPD earth and metalwork together, and have the earthing checked by qualified personnel. Do not skip this step because an SPD is fitted.
- Route cables without large loops. Separate DC and AC runs where practical, avoid unnecessary parallel runs, and finish glands and unused entries correctly.
- Check the disconnect order before storm season. Confirm, from the manual, the order for stopping the pump, opening the AC backup disconnect and opening the DC disconnect, and label both disconnects.
- Before a storm, disconnect in order. Stop the pump, open the AC backup disconnect if one is fitted, then open the DC disconnect. Leave the system isolated. Never work on conductors while lightning is overhead.
- After the storm, inspect before restarting. Check SPD indicators, glands, cable entries and visible damage. Replace any SPD whose indicator has changed.
- Restore in reverse order, after checks. Confirm polarity, string voltage and earthing as in the wiring guide, then close the DC disconnect, then the AC disconnect, then restart the pump and watch the first run.
- Record the event. Note the date, which indicators changed, what was replaced and the restart result. That record is what makes the next storm a routine check instead of a diagnosis.
For the seasonal routine that surrounds this checklist — seals, glands, heatsink clearance and storm-season inspections — see What Maintenance Does a Solar Pump Inverter Need Each Season?.
Frequently Asked Questions
Can an SPD make a solar pump inverter lightning-proof?
No. An SPD reduces the surge that reaches the drive; it does not make the system immune to a direct strike or to every transient. Earthing, routing and disconnection before a storm are part of the same protection, and a direct strike can still damage equipment. Treat an SPD as risk reduction, not as a guarantee.
If I install an SPD, do I still need earthing?
Yes — this is the trap. An SPD works by diverting a surge to earth. Without a bonded earthing system, the diverted surge has no safe path, and the SPD cannot protect the inverter as intended. Earthing is not an optional extra that an SPD replaces; it is the path the SPD uses.
Where should the SPD go: at the array or at the inverter?
At the entry points to the equipment being protected, as close as practical to it: the DC SPD at the combiner or inverter input, and an AC SPD where a grid or generator backup connects. A single SPD far from the inverter, connected by long looped leads, gives weaker protection than the same device fitted close to the input it protects.
Should I disconnect the system before a thunderstorm?
Yes, if you can do so safely before the storm arrives: stop the pump, open the AC backup disconnect, then open the DC disconnect, and leave the system isolated. Do not touch disconnects, cables or the inverter during the storm itself. If lightning is already overhead, stay away from the equipment and check it only after the storm has passed.
How do I know an SPD has failed after a storm?
Check its status indicator first, then look for visible damage and test the system only after the inspection steps in the checklist above. A changed indicator means the device has operated and should be replaced by qualified personnel, even if the pump appears to run normally. Record the replacement so the next inspection starts from a known state.
Does the QB100-PV built-in PV overvoltage protection replace an external SPD?
No. The QB100-PV product page lists PV overvoltage, overcurrent and over-temperature derating as verified drive protections. Those functions protect the drive under operating conditions; they are not an external surge diversion path for lightning-induced transients on long PV or backup cables. Use both: the drive protections, and SPDs fitted and earthed as described above.
Planning a storm-exposed installation? Send IDEEI the pump nameplate, PV string data, branch and cable length, and contact us for a matched selection and wiring guidance. Pricing is provided on inquiry.