Liftronic hydraulic residential lift_False pit safety switch faulty
This elevator is in a two-story church in Wentworthville. Liftronic’s hydraulic elevator, designed for residential elevators, with a load of 300kg and a speed of 0.3m/s.
When the client found us, the elevator had been out of service for three weeks. He stated that the previous maintenance company had repaired it for three days but failed. The customer recalled that it was said to be a problem with the lift door light curtain so he hoped we could replace the light curtain anyway.
On the first day, we replaced the light curtain, but as we realized before, the light curtain would only affect door operation, so the replacement did not solve the problem.
We explained the problem to the customer, and the customer agreed that we could continue with troubleshooting.
The next day, we noticed that the elevator always played up when running up to a certain area. It indicated the safety circuit was disturbed and high likely the transmission cable was faulty. Before seeking for a spare wire, our first task is to locate the faulty point.
After testing and investigation, we located the fault point that was caused by the poor contact of a safety switch in the pit. Because of this, whenever the elevator ran upwards, it would encounter the mechanism connected to this switch and break the safety circuit accidentally.
Also, we found the long-term on and off malfunctions lead to carbon deposits on the contacts of a relay, which need to be replaced.
The reason why the previous maintenance personnel thought the problem was the light curtain is because the control system of this hydraulic residential lift relies on the signal from the safety circuit to maintain the door closing command when the elevator is running. When the safety circuit was disturbed and the door closing signal was lost, it looked like the light curtain played up which made the technician think that the light curtain had a problem.
Remedies:
- replace the damaged relay.
- fix the false pit safety switch
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