What ‘in tolerance’ means for a UK commercial lift
UK commercial passenger lifts are typically specified to a levelling tolerance of ±5 mm at the sill. Anything worse is a defect. Wheelchair-accessible lifts under Approved Document M require ±5 mm as an accessibility criterion, not just a comfort one. A lift that has drifted to ±20 mm is a tripping hazard and — for a workplace duty holder — an actionable defect.
Encoder drift on modern gearless drives
Modern gearless commercial lifts (Otis Gen2, KONE MonoSpace, Schindler 3300) use a rotary encoder on the motor shaft to know exactly where the car is. Encoders drift over years, especially in humid or high-vibration installations. Symptom: gradual, consistent under-shoot or over-shoot at every landing. The controller can be re-taught the shaft in a service visit — usually a 2-hour job.
Brake wear on geared traction lifts
Older geared traction lifts (still common in UK office blocks built before 2010) use a drum brake that grips the drive shaft to hold the car at a landing. As the brake shoes wear, they take longer to grip, and the car settles a few millimetres past the intended stop. Symptom: over-shoot going up, under-shoot going down, worsening steadily over months. Brake service is routine and part of any UK PPM (planned preventative maintenance) contract.
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Describe your symptom →Rope stretch on traction lifts
Steel-rope traction lifts stretch over the first few years of service, then stabilise. A recent installation showing progressive levelling error is usually rope stretch — the engineer re-teaches the shaft and the problem clears. A long-serving installation showing sudden levelling error is not rope stretch — it's an encoder, brake or controller fault.
Hydraulic seal wear on hydraulic lifts
Hydraulic commercial lifts sag between calls as oil bleeds past the piston seals. On a healthy lift this is a few millimetres per hour, corrected by a ‘re-level’ feature that jogs the pump when a load is added at a landing. On a lift with worn seals, the re-level is triggered constantly, the reservoir warms up, and eventually the pump cannot keep up. Seal replacement is a major service item on hydraulic lifts and is a good indicator that the lift is approaching a modernisation decision.
Priority and escalation
Stop — call an engineer
Levelling problems are not ‘wait until the next service’ issues if:
- The error is more than 10 mm on any landing.
- The error is worse on some landings than others (indicates encoder or shaft-position problem).
- Any user has tripped over the sill.
- The lift is on an accessible route in a public building.
Log a callout, document the error at each landing, and expect the engineer to want to re-teach the shaft as part of the visit.
Frequently asked questions
- How do I measure the levelling error?
- A spirit level and a steel rule across the car sill and the landing sill will show the step within 1 mm. Take a photo at each landing and put the ruler in the shot — the engineer can then see the pattern before arriving.
- Is a re-level jog after arriving at a landing a fault?
- A single short re-level with a heavy load (a trolley wheeled in, three passengers stepping in) is normal on hydraulic lifts. Repeated re-levels on an empty car are a fault.
- Can levelling be fixed remotely?
- Some newer commercial lifts (Otis Gen360, KONE 24/7 Connect) can be re-taught remotely by the manufacturer. Older lifts require an engineer on site.
- Does poor levelling affect LOLER reports?
- Yes — the thorough examination checks levelling tolerance and a defect exceeding tolerance will be recorded. Persistent levelling error can trigger a ‘serious defect’ note that requires the lift to be taken out of service until fixed.
- Is levelling worse on a lift that has just been serviced?
- It shouldn't be. If it is, the shaft-teach step of the service was skipped or rushed. Insist the engineer returns to complete it — this is inside the visit scope, not an extra charge.