Fuses for pumps

Fuses for pumps are an important part of both safety and operational protection.
They should protect the motor, wiring and control equipment against overload and short circuit — but they should not trip at normal starting current.

Here is a clear overview so you know what type of fuse you need, how to size it, and what additional protection you can combine with it 👇

1. Why you need a fuse for a pump

Protect the motor windings from overcurrent.

Prevent fire or damage to cables in the event of a short circuit.

Protect the electronics (pressure switch, control, capacitors) against voltage faults.

Ensure that the pump does not continue to run in the event of a fault (e.g. stuck rotor).

2. Common fuse types for pumps

a) Circuit breaker (miniature circuit breaker)

The most common type in household and agricultural installations.

Type Function Suitable for
B-characteristic Fast tripping time – trips at 3–5× rated current Electronics, small pumps (up to ~1 kW)
C-characteristic Slower – withstands 5–10× rated current Most common for motors/pumps (starting current is allowed to pass)
D-characteristic Extra slow (10–20× rated current) Larger pumps or three-phase with high starting current

💡 Most water pumps (1-phase) do best with a C fuse, e.g. 10 A or 16 A depending on power.

b) Fuse (Diazed, Neozed, gG/gL)

Classic fuse that is still used in many pump centers.

gG/gL fuse protects against both short circuit and overload.

Very reliable, withstands high starting currents better than a circuit breaker.

Requires a fuse holder, and is not resettable.

Example: 10 A gG for a 0.75 kW pump, 16 A gG for a 1.5 kW pump.

c) Motor protection switch / motor protection (thermal relay)

This is not a fuse, but is used together with the fuse.

It protects against long-term overload and phase failure.

Adjusted to the pump’s rated current (e.g. 3.2–5 A).

Switches off if the current is too high.

Always recommended for permanently installed pumps (especially three-phase).

d) Fuse in control equipment / control box

Smaller glass fuses or flat-pin fuses are found in:

electronic controls (e.g. Presscontrol, Grundfos PM1/PM2, Wilo control boxes),

level switches, relay cards or starter boxes for submersible pumps.

These should always be replaced with the same amperage and type (slow/fast) according to the manufacturer’s manual.

3. Sizing – how to choose the right size

Step 1: Check the pump rating

On the nameplate you will find:

Power (kW)

Current (A)

Voltage (230 V or 400 V)

Step 2: Select fuse by rated current
Pump power Typical rated current (1-phase 230 V) Rec. fuse
0.37 kW 2.5 A 6 A C-characteristic
0.55 kW 3.8 A 10 A C-characteristic
0.75 kW 4.8 A 10 A C-characteristic
1.1 kW 6.4 A 13–16 A C-characteristic
1.5 kW 8 A 16 A C-characteristic

For three-phase pumps, the currents are lower per phase, but C16 A or C10 A are almost always used depending on the power.

4. Recommended additional protection

Protection Function Comment
Earth fault circuit interrupter (30 mA) Personal protection, closes in case of leakage current Required for all 230 V outdoor installations
Motor protection Protects against overload/phase failure Adjusted to the pump’s rated current
Surge protection Protects electronics (control boxes, Presscontrol) Recommended in areas exposed to lightning
Fuse in control box Protects electronics internally Always replaced with the same type as the original