015395 66193
sales@flowjet.co.uk
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Use this guide to estimate the electric motor power required to drive a high-pressure pump and compare common motor frame sizes.
Motor horsepower calculator
The approximate motor horsepower required can be calculated using:
Motor power required
7.89 HP
approx. 5.9 kW
Example calculation
For a pressure washer pump delivering 20 LPM at 150 Bar:
20 × 150 ÷ 380 = 7.89 HP
The calculated requirement is approximately 7.9 HP. The next suitable standard motor size would normally be 10 HP / 7.5 kW, subject to the pump manufacturer’s specifications.
This calculation provides an estimate and includes an allowance for normal system and drive losses. Always check the pump’s stated power requirement before selecting a motor.
Common electric motor frame sizes
| IEC Frame Size | Approximate Length | Approximate Width |
|---|---|---|
| Frame 90 | 120 mm | 140 mm |
| Frame 100 | 140 mm | 160 mm |
| Frame 132 | 140 mm | 220 mm |
| Frame 160 | 210 mm | 250 mm |
Scroll the table sideways to see all columns.
Important compatibility checks
Motor dimensions can vary according to the manufacturer, power rating, mounting arrangement and whether the motor has a short or long frame. Before ordering, check:
- Required motor power in HP or kW
- Motor operating speed, such as 1450 or 2800 RPM
- Single-phase or three-phase electrical supply
- IEC frame size
- Foot-mounted or flange-mounted configuration
- Shaft diameter and shaft length
- Pump flange and coupling compatibility
- Motor voltage, current and electrical connection
Check that the pump can be removed
Before purchasing a replacement electric motor, make sure the pressure-washer pump can be successfully removed from the existing motor.
Pumps and couplings can sometimes seize onto the motor shaft through corrosion or long-term use. If the pump cannot be removed without damage, you may also require a replacement pump, flange, coupling or complete Motor Pump Unit (MPU).
Do not select a motor based only on its horsepower or frame number. Always compare the complete motor dimensional drawing with the available mounting space and pump connection.
For help checking compatibility with a pressure-washer pump, contact Flowjet Cleaning Equipment LTD on 015395 66193 or email sales@flowjet.co.uk.
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