CET Door Operators & Interlocks 2 — Questions and Answers
Question 1: What is the maximum allowable hoistway door unlocking zone as specified by ASME A17.1?
- 3 inches above or below the landing
- 6 inches above or below the landing
- 9 inches above or below the landing
- 12 inches above or below the landing (Correct answer)
Correct answer: 12 inches above or below the landing
ASME A17.1 permits the hoistway door to be unlocked within 12 inches above or below the landing level.
Question 2: Which component physically prevents a hoistway door from being opened from the landing side unless the car is in the unlocking zone?
- Door restrictor
- Interlock mechanism (Correct answer)
- Retiring cam
- Door closer
Correct answer: Interlock mechanism
The interlock mechanism is the device that prevents hoistway door opening from the landing side when the elevator car is not in the unlocking zone.
Question 3: On a high-speed door operator, what is the primary function of the door nudging feature?
- Speeds up door closing when an obstruction is detected for an extended period (Correct answer)
- Prevents the door from closing when passengers are detected
- Reverses the door if resistance exceeds a set threshold
- Sounds an alarm when the door is blocked
Correct answer: Speeds up door closing when an obstruction is detected for an extended period
Door nudging reduces closing speed and sounds a warning signal to clear obstructions that have held the door open beyond the preset time.
Question 4: What type of interlock is designed so that the locking member engages BEFORE the electrical contact is made during door closing?
- Gravity interlock
- Positive lock interlock
- Sequence interlock (Correct answer)
- Spring-loaded interlock
Correct answer: Sequence interlock
A sequence interlock requires the mechanical locking element to engage before the electrical contact closes, ensuring positive locking before the car can move.
Question 5: When adjusting a door operator's closing force, the maximum kinetic energy for a power-operated horizontally sliding door must not exceed:
- 2.5 ft-lbs (Correct answer)
- 7.5 ft-lbs
- 10 ft-lbs
- 15 ft-lbs
Correct answer: 2.5 ft-lbs
ASME A17.1 limits the kinetic energy of a power-operated horizontally sliding door to 2.5 ft-lbs to protect passengers from injury.
Question 6: A door operator motor that runs continuously but the door does not move is MOST likely caused by:
- A failed door contact
- A broken drive belt or chain (Correct answer)
- An open interlock circuit
- A faulty controller relay
Correct answer: A broken drive belt or chain
If the motor runs but the door doesn't move, the mechanical link between the motor and door panel — such as a belt or chain — is likely broken.
Question 7: What is the purpose of the retiring cam on a car door operator?
- Engages the hoistway door coupling when the car arrives at a landing (Correct answer)
- Limits the speed of the car door during closing
- Provides the electrical interlock signal to the controller
- Prevents the hoistway door from bouncing open after closing
Correct answer: Engages the hoistway door coupling when the car arrives at a landing
The retiring cam extends when the car approaches a landing to mechanically engage the hoistway door coupling device, enabling the car door operator to open the hoistway door.
CET Door Operators & Interlocks 2
What is the maximum allowable hoistway door unlocking zone as specified by ASME A17.1?