NATE Light Commercial Exam Questions with Correct Answers Graded A+

NATE Light Commercial Exam Questions with Correct Answers Graded A+ Which of the following measurements would be needed to determine oil furnace combustion efficiency? a. net stack temperature and CO2 concentration b. net stack temperature and CO concentration c. stack temperature and indoor temperature d. stack temperature and fuel pressure -Ans a. net stack temperature and CO2 concentration When combustion is being tested on an oil furnace, high level of smoke and can be corrected by: a. Adjusting the barometric damper. b. Opening the air shutter. c. Adjusting the primary control. d. Closing the air shutter. -Ans b. Opening the air shutter A common problem with restaurant units is their location near kitchen exhaust. This could cause high discharge pressure in the cooling mode because: a. Return air filter becomes plugged. b. Grease plugs the evaporator. c. Grease plugs the condensate line. d. Grease plugs the condenser coil. -Ans d. Grease plugs the condenser coil. When a heat pump is in the cooling mode of operation, the check valve at the indoor coil should be: a. Modulating. b. Half open. c. Fully closed. d. Fully open. -Ans c. Fully closed. The technician make a service call in answer to a complaint of little or no cooling from an R-22 rooftop air conditioning unit. Upon checking pressures when the unit is running, the technician finds: · Suction pressure 48 psig · Discharge pressure 190 psig · Superheat 0°F The problem most likely occurs because the: a. Evaporator coil is iced up. b. Unit is full of non-condensables. c. Dirty condenser coil. d. Unit is overcharged. -Ans a. Evaporator coil is iced up. The result of properly converting a natural gas furnace to LP using the factory kit will: a. Decrease the pressure and the orifice size b. Decrease the pressure and increase the orifice size c. increase the pressure and the orifice size d. increase the pressure and decrease the orifice size -Ans d. increase the pressure and decrease the orifice size At least 24 hours before you start up a system that has been shut down for a long time, you must energize the crankcase heater, in order to: a. reduce the viscosity of the oil b. reduce the amount of refrigerant that may be in the compressor c. warm the compressor so that it will work more efficiently d. heat the refrigerant so that it will work more efficiently -Ans b. reduce the amount of refrigerant that may be in the compressor In checking a restaurant, a technician find difficulty in opening the front doors. Providing that kitchen exhaust and make-up air are balanced properly, which of the following adjustments should be made? a. the blower speed should be decreased b. System BTU capacity should be increased c. The space temperature set point should be increased d. The minimum outdoor air setting should be checked -Ans d. The minimum outdoor air setting should be checked A furnace is rated at 120,000 Btu input, but produces 100,000 Btu output. The percentage that exists as lost heat is: a. 12% b. 17% c. 22% d. 20% -Ans b. 17% Air that is pre-mixed with the gas in the burner is called: a. primary air b. dilution air c. secondary air d. supply air -Ans a. primary air