CFESA Warewashing Equipment — Questions and Answers
Question 1: What is the minimum final rinse temperature required at the dish surface for a high-temperature commercial dishwasher to achieve proper sanitization?
- 140°F (60°C)
- 160°F (71°C)
- 180°F (82°C) (Correct answer)
- 212°F (100°C)
Correct answer: 180°F (82°C)
NSF/ANSI 3 and FDA Food Code require a minimum 180°F (82°C) at the dish surface during the final rinse cycle to achieve sanitization in high-temperature machines. The booster heater raises incoming water to meet this threshold.
Question 2: A flight-type dishwasher is producing cloudy glassware despite correct water temperature. Which cause should be investigated FIRST?
- Worn conveyor belt sprockets
- Insufficient rinse-aid concentration or malfunctioning chemical dispenser (Correct answer)
- Failed booster heater element
- Clogged scrap collector screen on the prewash tank
Correct answer: Insufficient rinse-aid concentration or malfunctioning chemical dispenser
Cloudy or spotted glassware in an otherwise correctly-temped machine is the classic symptom of inadequate rinse-aid. The surfactant in rinse-aid sheets water off the glass surface; without it, mineral deposits and detergent film dry on the glass.
Question 3: A undercounter glasswasher is tripping its thermal overload repeatedly. After confirming the motor windings are good, what is the most likely mechanical cause?
- Worn door gasket allowing steam loss
- Pump impeller jammed with broken glass or debris (Correct answer)
- Insufficient detergent concentration
- Control board sending incorrect cycle timing signals
Correct answer: Pump impeller jammed with broken glass or debris
A jam in the wash/rinse pump impeller causes the motor to draw locked-rotor amperage, rapidly heating the windings and tripping the thermal overload. Broken glass, bottle caps, and silverware are common culprits in glasswashers.
Question 4: When sizing a booster heater for a commercial dishwasher, which specification is the PRIMARY determining factor?
- The incoming cold-water line diameter
- The volume of final-rinse water per hour and the required temperature rise (ΔT) (Correct answer)
- The amperage rating of the dishwasher's main control panel
- The detergent manufacturer's recommended chemical concentration
Correct answer: The volume of final-rinse water per hour and the required temperature rise (ΔT)
Booster heater capacity (kW) must be matched to the gallons-per-hour of final-rinse flow multiplied by the BTU/hr required to raise incoming water temperature to 180°F. Undersizing results in chronic sanitization failures.
Question 5: What is the purpose of the scrap screen or pre-flush trough in a commercial conveyor dishwasher?
- To filter detergent before it enters the wash tank
- To remove food soil from dishes before the main wash cycle to prevent tank contamination (Correct answer)
- To capture loose silverware so it is not conveyed through the machine
- To measure the volume of water used per rack
Correct answer: To remove food soil from dishes before the main wash cycle to prevent tank contamination
The scrap screen/pre-flush zone removes gross food debris from dishes before they enter the wash tank. Without it, soil would rapidly contaminate the wash water, reducing detergent effectiveness and requiring more frequent tank changes.
Question 6: A technician is servicing a chemical-sanitizing (low-temperature) commercial dishwasher. What is the correct method to verify adequate sanitizer concentration in the final rinse?
- Use a calibrated infrared thermometer to verify 180°F surface temp
- Test the final rinse with the appropriate chemical test strips (e.g., chlorine test strips for chlorine-based sanitizers) (Correct answer)
- Measure rinse pressure with a gauge and compare to spec
- Check the sanitizer pump motor amperage draw
Correct answer: Test the final rinse with the appropriate chemical test strips (e.g., chlorine test strips for chlorine-based sanitizers)
Low-temperature machines rely on chemical sanitizers (typically 50–100 ppm chlorine or equivalent quaternary ammonia) rather than heat. The only direct verification method is chemical test strips matched to the sanitizer in use. Temperature measurement is irrelevant in this system type.
CFESA Warewashing Equipment
What is the minimum final rinse temperature required at the dish surface for a high-temperature commercial dishwasher to achieve proper sanitization?