21 HVAC Service & When to Refer Practice Questions & Answers

Every HVAC Service & When to Refer practice question from the CAMT Apartment Maintenance Practice Test, with the correct answer and a short explanation.

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1. A technician replaces the return-air filter in an apartment air handler and notices an arrow printed on the filter frame. How should the filter be positioned in the rack?
- A.With the arrow facing the access panel so the size stays readable
- B.With the arrow pointing away from the blower, back toward the return grille
- C.With the arrow pointing toward the blower, in the direction air travels✓ Answer
- D.With the arrow pointing upward regardless of how the cabinet is mounted
The arrow marks the direction air travels through the media, so it must point toward the blower. The filter carries its reinforced backing on the downstream face so the media cannot bow under the pull of the blower; installed backwards it can deform, tear, and let dirt pass through onto the evaporator coil.
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2. An apartment air conditioner has gone a long time without a filter change and the filter is matted with dust. Beyond poor air circulation, what is the technician most likely to find if the condition continues?
- A.Reduced airflow across the coil, which can ice the coil and strain the blower✓ Answer
- B.A colder supply air stream, because less air passes over the cold coil surface
- C.Higher airflow at the registers, because air is forced through a smaller area
- D.Cleaner coils, because the loaded filter captures more of the dust in the air
A loaded filter restricts return airflow, so less air crosses the evaporator coil. With too little heat picked up from the air, the coil surface falls below freezing and ice forms, while the blower works against higher resistance. The same restriction in heating lets the heat exchanger overheat.
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3. The correct filter size for an apartment air handler is out of stock, and a slightly smaller filter is on the shelf. A technician considers wedging it into the rack. Why is this the wrong choice?
- A.A smaller filter raises static pressure and starves the return duct of air
- B.A smaller filter cannot hold its shape and will be pulled into the return grille
- C.A smaller filter blocks the condensate drain opening inside the blower cabinet
- D.Air bypasses around the edges of the filter and carries dirt onto the coil✓ Answer
A filter only cleans the air that is forced through it. Any gap at the edge of the rack becomes the path of least resistance, so unfiltered air slips past and deposits dirt on the evaporator coil, where the film of dirt insulates the coil and cuts heat transfer. Order the correct size rather than improvise.
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4. A resident on a lower floor reports a brown stain spreading across the bedroom ceiling. The apartment directly above has its air handler in a closet over that bedroom, and the air conditioner is running. What should the technician check first?
- A.The refrigerant line insulation where it enters the upstairs wall
- B.The condensate drain line, drain pan and pan overflow, for a blockage✓ Answer
- C.The domestic water supply line feeding the upstairs bathroom fixtures
- D.The roof flashing above the upstairs unit for wind-driven rain damage
A running evaporator coil condenses water continuously, and that water must leave through the drain pan and drain line. When the line or the pan outlet clogs, the pan fills and spills into the ceiling cavity below, which is exactly how a blocked condensate line first shows up as a stain in the apartment underneath.
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5. A resident reports the air conditioner suddenly stopped running. The thermostat display works, the breaker is on, and the technician finds standing water in the pan under the air handler. What is the most likely explanation?
- A.The compressor overload tripped because the pan lost its water seal
- B.The blower motor seized after water reached the return air filter rack
- C.The thermostat lost its batteries and cannot send a call for cooling
- D.The pan float switch opened the control circuit to stop water damage✓ Answer
A float or overflow switch sits in the pan and opens the low-voltage control circuit when water rises, deliberately shutting the equipment down before the water can reach the ceiling below. The thermostat still has power, which is why it looks normal. The technician clears the drain, empties the pan, and confirms the switch resets.
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6. The condensate drain line leaving an air handler includes a trap near the cabinet. What is the purpose of that trap?
- A.It keeps cabinet air pressure from blowing or pulling through the drain line✓ Answer
- B.It slows the water down so the drain line cannot overflow at the pan
- C.It collects sediment so the outdoor end of the line stays clear
- D.It vents sewer gas away from the closet where the unit is installed
The drain pan sits inside a cabinet that the blower holds at a pressure different from the room. Without a water seal in the trap, that pressure difference pushes or pulls air through the drain line instead of letting water run out, so the pan backs up and eventually overflows even though nothing is clogged.
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7. Water is dripping from the small auxiliary drain line that ends above a window on the outside of the building. What does this tell the technician?
- A.The secondary pan has cracked and the whole pan must be replaced now
- B.The primary condensate drain is blocked and needs to be cleared✓ Answer
- C.The condensate pump has failed and must be replaced right away
- D.The auxiliary line was routed too low and should be re-piped upward
The auxiliary or secondary drain is a backup that carries no water at all when the system is healthy. It is deliberately terminated somewhere conspicuous so that visible dripping serves as an early warning that the primary drain has stopped working, before water finds the ceiling instead.
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8. A resident complains the apartment never gets cool and the unit runs all day. The technician finds a tall bookcase pushed flat against the return-air grille in the hallway. What is the correct next step?
- A.Close half of the supply registers to push more air to the bedroom areas
- B.Clear the space at the return grille and tell the resident why✓ Answer
- C.Call the HVAC contractor to add a second return grille in the hallway
- D.Set the thermostat fan switch to ON so the blower never stops running
The blower can only deliver the air it is able to draw in. A blocked return starves the system, so the coil gets too little airflow, capacity drops, and the unit runs continuously without satisfying the thermostat. This is a routine service fix, and telling the resident why keeps the obstruction from returning.
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9. During a turn, a technician finds supply registers in two vacant bedrooms closed and a balancing damper in the trunk duct nearly shut. Why does this matter for the cooling system?
- A.Closed registers raise the return air temperature and shorten each cycle
- B.Closed registers force the condenser fan to run at a higher speed
- C.Closed dampers cause the thermostat to switch itself into heating
- D.Total airflow through the equipment drops, reducing cooling capacity✓ Answer
Closing registers and dampers does not redirect air for free; it adds resistance and the blower simply moves less air overall. Less air across the evaporator coil means less heat is absorbed, capacity falls and the coil can ice. A turn inspection should reopen registers and restore dampers to their balanced position.
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10. During seasonal maintenance a technician finds the outdoor condensing unit packed with grass clippings and surrounded by shrubs grown against the cabinet. What is the effect on the system, and the correct action?
- A.Heat cannot leave the coil; clean the coil and cut back the clearance✓ Answer
- B.Cold air cannot enter the coil; wrap the cabinet to hold heat inside it
- C.The fan reverses direction; replace the fan motor and clear the shrubs
- D.The coil freezes solid; wash it with a strong solvent and restart the unit
The condenser's whole job is to reject the heat picked up indoors, and it does that by passing outdoor air across its fins. Clippings and shrubs block that air, so the heat has nowhere to go, capacity falls and the unit runs long. Cleaning the coil and restoring clearance around the cabinet is routine preventive maintenance.
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11. A technician opens an air handler closet and finds the evaporator coil covered in a solid block of ice while the system is calling for cooling. What is the correct next step?
- A.Leave the unit running so the ice melts while the apartment keeps cooling
- B.Switch cooling off, run the fan to thaw the coil, then check filter and airflow✓ Answer
- C.Aim a heat gun at the coil until the ice clears and then close the panel
- D.Chip the ice off the coil with a screwdriver and restore the unit to service
Ice blocks the fins so no air can pass, and nothing about the system can be judged until it is gone. Running the blower with cooling off melts the ice safely, and the technician then looks for the airflow causes within a maintenance technician's scope, a dirty filter, blocked return or dirty coil, and refers the unit if airflow proves normal.
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12. A resident reports no cooling. The technician arrives and the thermostat display is blank. What should be checked before assuming the equipment has failed?
- A.The condensate drain line for standing water at the outside end
- B.The condenser fan blade for damage from debris in the cabinet
- C.Thermostat batteries and the power supplied to the thermostat✓ Answer
- D.The supply registers in every room for a closed damper blade
A blank display means the control has no power, and a control that cannot send a call for cooling produces exactly the same complaint as broken equipment. Restoring thermostat power is inside routine service, and checking it first prevents an unnecessary contractor call for a unit that is perfectly sound.
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13. A resident complains the living room is uncomfortable and the system short cycles. The technician sees the thermostat mounted directly above a floor lamp and close to a supply register. Why is this a problem?
- A.The thermostat wiring picks up interference from the lamp circuit nearby
- B.The thermostat batteries drain faster from the warm air rising past it
- C.The thermostat senses local heat and air, not true room temperature✓ Answer
- D.The thermostat loses its low-voltage signal when the register is open
A thermostat controls the system from the air touching its sensor, so it must sit where that air represents the room. Heat rising from the lamp makes it call when the room is already comfortable, and cold supply air blowing on it makes it satisfy early, which is what produces the short cycling and the complaint.
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14. A resident says the vents blow air all the time but the air is not always cold, and asks the technician to fix the unit. The thermostat fan switch is set to ON. What should the technician do?
- A.Leave the switch on ON and schedule a contractor to inspect the system
- B.Explain the setting, move the fan switch to AUTO, and verify cooling✓ Answer
- C.Turn the system off at the breaker until a contractor can look at it
- D.Leave the switch on ON and replace the thermostat with a new one
With the fan switch on ON the blower runs continuously, including during the long stretches when the cooling side is off, so room-temperature air keeps coming out of the registers. In AUTO the blower runs only with a call for cooling. This is a control-setting complaint, not an equipment fault, and it is resolved on the spot.
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15. A technician calls a work order in to an HVAC contractor and reports that the unit is not blowing any air at all, although the outdoor unit is running. Which component's job is the technician describing as failing?
- A.The compressor, which raises the pressure of the refrigerant vapor
- B.The condenser, which rejects heat from the refrigerant outdoors
- C.The metering device, which controls refrigerant flow into the coil
- D.The blower, which pulls air from the return and pushes it through the ducts✓ Answer
Moving air is the blower's function: it draws air from the return plenum and pushes it across the coil and out through the supply ducts. Naming the failing function correctly, rather than guessing at a refrigerant problem, tells the contractor to arrive prepared for the indoor air-moving side of the system.
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16. During preventive maintenance on a belt-drive blower, the technician hears a squeal at start-up and finds the belt glazed and loose. What is the appropriate action for a maintenance technician?
- A.Leave the belt alone and log it for the contractor's seasonal visit
- B.Tighten the belt as far as the adjustment allows while it is running
- C.Spray belt dressing on the running belt to quiet the squeal for now
- D.Lock out power, then replace the belt and set the tension correctly✓ Answer
A glazed, loose belt slips on the sheaves, so the blower turns slower than it should and airflow falls off long before the belt finally breaks. Replacing it and setting proper tension is ordinary preventive maintenance, and it is done only after the power is locked and tagged out so the blower cannot start on a call.
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17. An older blower motor in an apartment air handler has oil ports at each end bell. What is the correct approach during preventive maintenance?
- A.Oil the ports only once the motor has already begun to squeal loudly
- B.Pack the ports with heavy grease because the oil escapes too quickly
- C.Oil the ports generously every visit so the bearings never run dry
- D.Oil the ports as the equipment maker directs, with power locked out✓ Answer
Sleeve bearings need a specific lubricant in a specific quantity; too much oil runs out of the bearing, collects dust and can reach the windings, while grease will not flow into the bearing at all. Following the equipment maker's instructions with the power locked out keeps the motor safe to reach and correctly served.
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18. At the seasonal changeover inspection, a technician runs the heat in each apartment for the first time since spring. In one unit a brief burning-dust smell clears within minutes and the supply air is warm. What should the technician do?
- A.Replace the heat exchanger before the heating season gets started
- B.Tell the resident to run the heat continuously for a full day now
- C.Shut the gas off at the meter and tag the furnace as unsafe to use
- D.Note the normal first-run smell and finish the inspection checklist✓ Answer
Dust settles on a heat exchanger over a summer of disuse and burns off during the first firing, which is why the smell is brief and then gone while the unit heats normally. That is different from a fuel odor or from soot and a sounding alarm, either of which would call for shutting the appliance down instead.
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19. A technician suspects an apartment air conditioner has a refrigerant leak and wants to connect a gauge set to the service ports to look at pressures. The technician is not EPA Section 608 certified. What is the correct action?
- A.Do not connect the gauges; refer the unit to a certified technician✓ Answer
- B.Connect the gauges after a supervisor gives verbal permission on site
- C.Connect the gauges but recover any refrigerant into an open container
- D.Connect the gauges, since only adding refrigerant requires certification
EPA defines a technician to include anyone who attaches or detaches hoses and gauges to measure pressure, so simply gauging a sealed system is regulated work that requires certification. Recognizing that the job has crossed out of routine maintenance and belongs to a certified technician is itself the competency being tested.
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20. While checking a gas furnace in an occupied apartment, a technician smells gas near the equipment. What is the correct sequence of actions?
- A.Get everyone out without using switches or phones, then call from outside✓ Answer
- B.Light the pilot to burn off the gas that has collected in the space
- C.Use a cell phone in the room to call the utility before leaving it
- D.Turn on the exhaust fan and open windows, then keep working carefully
A gas smell means an ignitable mixture may already be present, and any switch, phone or two-way radio can produce the spark that sets it off. The rule is absolute: do not operate electrical devices, get people out, shut the gas off only if the valve can be reached safely, and make the call from outside the building.
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21. A resident reports the carbon monoxide alarm sounding whenever the gas furnace runs, and the technician sees soot and a yellow flame rolling out at the burner opening. What should the technician do?
- A.Shut the furnace down, ventilate, and call a licensed contractor✓ Answer
- B.Adjust the burner air until the flame is blue and leave it running
- C.Seal the cracked heat exchanger and return the furnace to service
- D.Reset the alarm, change the filter, and let the furnace keep running
Soot, yellow flame and a sounding alarm all point to incomplete combustion, which produces carbon monoxide inside an occupied home. This is a life-safety condition, not a service adjustment: the appliance comes out of service, the space is ventilated, and it stays off until a licensed heating contractor evaluates it.
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Practice questions based on the published NAAEI CAMT domains — Essential Trade Skills, Compliance, Facilities Operations, and Professional Development & Collaboration — and on standard trade practice. CAMT and NAAEI are marks of the National Apartment Association; this site is not affiliated with or endorsed by NAA or NAAEI. Code requirements, licensing boundaries and permit rules vary by jurisdiction and revise on a cycle, so none is tested here as a recalled figure — always verify the code having jurisdiction and use a licensed contractor where the work requires one. Confirm current program requirements with NAAEI before testing. About the CAMT credential →

1. A technician replaces the return-air filter in an apartment air handler and notices an arrow printed on the filter frame. How should the filter be positioned in the rack?

2. An apartment air conditioner has gone a long time without a filter change and the filter is matted with dust. Beyond poor air circulation, what is the technician most likely to find if the condition continues?

3. The correct filter size for an apartment air handler is out of stock, and a slightly smaller filter is on the shelf. A technician considers wedging it into the rack. Why is this the wrong choice?

4. A resident on a lower floor reports a brown stain spreading across the bedroom ceiling. The apartment directly above has its air handler in a closet over that bedroom, and the air conditioner is running. What should the technician check first?

5. A resident reports the air conditioner suddenly stopped running. The thermostat display works, the breaker is on, and the technician finds standing water in the pan under the air handler. What is the most likely explanation?

6. The condensate drain line leaving an air handler includes a trap near the cabinet. What is the purpose of that trap?

7. Water is dripping from the small auxiliary drain line that ends above a window on the outside of the building. What does this tell the technician?

8. A resident complains the apartment never gets cool and the unit runs all day. The technician finds a tall bookcase pushed flat against the return-air grille in the hallway. What is the correct next step?

9. During a turn, a technician finds supply registers in two vacant bedrooms closed and a balancing damper in the trunk duct nearly shut. Why does this matter for the cooling system?

10. During seasonal maintenance a technician finds the outdoor condensing unit packed with grass clippings and surrounded by shrubs grown against the cabinet. What is the effect on the system, and the correct action?

11. A technician opens an air handler closet and finds the evaporator coil covered in a solid block of ice while the system is calling for cooling. What is the correct next step?

12. A resident reports no cooling. The technician arrives and the thermostat display is blank. What should be checked before assuming the equipment has failed?

13. A resident complains the living room is uncomfortable and the system short cycles. The technician sees the thermostat mounted directly above a floor lamp and close to a supply register. Why is this a problem?

14. A resident says the vents blow air all the time but the air is not always cold, and asks the technician to fix the unit. The thermostat fan switch is set to ON. What should the technician do?

15. A technician calls a work order in to an HVAC contractor and reports that the unit is not blowing any air at all, although the outdoor unit is running. Which component's job is the technician describing as failing?

16. During preventive maintenance on a belt-drive blower, the technician hears a squeal at start-up and finds the belt glazed and loose. What is the appropriate action for a maintenance technician?

17. An older blower motor in an apartment air handler has oil ports at each end bell. What is the correct approach during preventive maintenance?

18. At the seasonal changeover inspection, a technician runs the heat in each apartment for the first time since spring. In one unit a brief burning-dust smell clears within minutes and the supply air is warm. What should the technician do?

19. A technician suspects an apartment air conditioner has a refrigerant leak and wants to connect a gauge set to the service ports to look at pressures. The technician is not EPA Section 608 certified. What is the correct action?

20. While checking a gas furnace in an occupied apartment, a technician smells gas near the equipment. What is the correct sequence of actions?

21. A resident reports the carbon monoxide alarm sounding whenever the gas furnace runs, and the technician sees soot and a yellow flame rolling out at the burner opening. What should the technician do?