Chiller Technician interview questions for employers
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How do you diagnose a low refrigerant charge in a centrifugal chiller?
A qualified chiller technician identifies low refrigerant charge by observing elevated discharge temperatures and fluctuating suction pressures during standard operation. They look for oil foaming in the sight glass as an early indicator of system leaks. A proper answer details the use of a digital gauge manifold to check saturation temperatures against actual liquid line temperatures to verify subcooling values. The applicant should explain using ultrasonic leak detectors to pinpoint pinhole failures in condenser tubes or gasket seals. Ask them how they confirm the leak source before adding refrigerant. A red flag appears if the candidate suggests simply topping off the refrigerant without finding the leak or calculating the exact subcooling deficit required for system stability.
What steps do you take when troubleshooting a high pressure cutout trip?
The technician must verify if the high pressure trip results from non-condensables or fouled heat exchanger surfaces. They check the cooling tower water temperature and verify the condenser water pump operation to ensure sufficient heat rejection flow. A strong answer describes checking the approach temperature between the condenser leaving water and the refrigerant condensing temperature. If the approach is high, tubes require cleaning or mechanical descaling. Ask the candidate to explain their process for purging air from the system if the high pressure persists despite clean tubes. A red flag occurs if the applicant suggests bypassing the safety switch or resetting the control circuit without first confirming water flow and heat transfer conditions.
Which EPA certifications do you hold for handling industrial refrigerants?
Technicians must possess an EPA Universal certification to manage the high volume of refrigerants found in commercial and industrial chillers. They should demonstrate familiarity with recovery equipment capable of handling R-123 or R-134a without atmospheric venting. The candidate should mention their experience with recovery cylinders and the documentation requirements for refrigerant logging. Ask them how they handle the transfer of refrigerant during major overhauls or vessel repairs. They must describe using scale-based weight tracking to ensure accurate logging of reclaimed material. A red flag arises if the candidate lacks current EPA documentation or shows confusion regarding the specific handling procedures for low pressure versus high pressure refrigerants under federal environmental regulations.
How do you organize the sequence of an evaporator tube bundle replacement?
Replacing tubes requires planning the isolation of the water circuit and the recovery of refrigerant from the vessel. The technician must explain the use of tube pullers to remove damaged segments and the installation of new tubes with correct expansion tools to prevent future leaks. They should describe the testing sequence including hydrostatic leak testing before closing the end bells. Ask the applicant about the specific torque requirements for end bell bolts to prevent gasket failure under operating pressure. Proper work flow involves cleaning the tube sheets and ensuring the head alignment remains true during reassembly. A red flag appears if the candidate ignores water side isolation or fails to mention pressure testing the assembly before charging.
Are you comfortable with the travel requirements and variable shift rotations?
Chiller service often demands responses to emergency failures during off-hours or travel to remote industrial sites. The candidate must clarify their availability for on-call rotations and their willingness to accept overnight stays when multiple days of service are needed. A meaningful response outlines how they manage their time and communicate site status updates to the dispatch team. Ask them how they prioritize multiple service calls when systems remain down during peak production cycles. They should show an understanding of the necessity for reliable transportation to carry specialized diagnostic tools and rigging equipment. A red flag is raised if the technician refuses standby duty or lacks the physical endurance to handle unexpected late-night calls for equipment recovery.
What information do you include in a formal service handover report?
A service report must provide clear data for the client and the next technician on the schedule. The candidate should include the suction and discharge pressures, approach temperatures, motor amp draws, and any diagnostic codes pulled from the controller. They need to document the quantities of refrigerant or oil added during the visit. Ask the applicant to explain how they communicate pending repairs or needed parts to the facility manager. They should describe providing a summary of the equipment condition and any recommended preventative maintenance tasks required to avoid future downtime. A red flag occurs if the report contains vague statements or omits critical sensor readings that help track the degradation of chiller performance.
How do you calibrate chilled water flow sensors and pressure transducers?
Calibration ensures the chiller controller receives accurate inputs for load calculation and safety limits. The technician should explain the use of a multimeter or field calibrator to verify the 4-20 milliamp signal from sensors to the control board. They need to describe cross-referencing sensor output with an independent reference gauge to check for signal drift. Ask the candidate how they address persistent errors where the display shows a value different from the actual physical measurement. They should discuss checking for wire corrosion and ensuring proper shielding to minimize electrical noise in the signal path. A red flag arises if the candidate suggests ignoring minor deviations or relies solely on the software display without verifying actual physical values.
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