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Engineer Building Facilities practice questions

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Question 1Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A facility technician is performing quarterly maintenance on a constant-volume air handling unit. The pre-filter and final filter differential pressure readings have risen steadily and now exceed the manufacturer's recommended final resistance. What is the most appropriate action?

  1. Reset the filter alarm and continue operating until the next quarterly service.
  2. Wash the filters with water and reinstall them after drying.
  3. Increase fan speed to compensate for the higher resistance.
  4. Replace the filters and record the new baseline differential pressure. Correct answer.

Explanation

Filter loading raises the pressure drop across the media, reducing airflow and increasing fan energy. Once the measured differential pressure exceeds the manufacturer's final resistance, the filters should be replaced and a clean baseline recorded. Washing or resetting the alarm does not restore the designed airflow.

Question 2Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

Occupants report a loud banging noise in the domestic water piping immediately after solenoid valves close on the laundry equipment. Which condition most directly explains this symptom?

  1. Sudden flow stoppage creating a pressure surge in the pipe Correct answer.
  2. Excessive static pressure in the building's rooftop water tank
  3. A failed pressure relief valve on the domestic hot water heater
  4. Air entrainment in the chilled water loop serving the air handlers

Explanation

Water hammer is a pressure surge caused by a rapid change in water velocity when a valve closes quickly. The surge travels through the piping and produces the banging noise. Installing water-hammer arrestors or slowing valve closure reduces the effect.

Question 3Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a building's electrical distribution system, what is the primary function of a ground-fault circuit interrupter in a wet location?

  1. Limit the maximum short-circuit current available at the receptacle
  2. Detect a line-to-neutral current imbalance and trip the circuit Correct answer.
  3. Provide backup overcurrent protection for the panelboard main breaker
  4. Prevent the equipment grounding conductor from carrying fault current

Explanation

A GFCI compares the current flowing on the line and neutral conductors. If the difference exceeds the trip threshold, usually about 4 to 6 milliamps, it opens the circuit to reduce shock risk. It is not intended to provide short-circuit or backup overcurrent protection.

Question 4Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A traction elevator's overspeed governor is being checked during a scheduled maintenance visit. The mechanic trips the governor manually and observes that the safety gear does not set. Which item should be investigated first?

  1. Governor rope tension and safety-gear linkage Correct answer.
  2. The machine-room ventilation fan airflow rate
  3. The car door operator closing speed setting
  4. The counterweight guide-rail lubrication level

Explanation

If the governor rope is loose or the safety-gear linkage is seized, tripping the governor will not pull the safeties into the guide rails. The governor rope tension and linkage should be checked before condemning the governor itself.

Question 5Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A draw-through air handling unit with a cooling coil has water pooling in the drain pan and overflowing onto the ceiling tiles. The drain line is clear and sloping correctly. Which installation error is the most likely cause?

  1. The condensate trap is too shallow for fan negative pressure. Correct answer.
  2. The cooling coil is oversized for the design airflow through the unit.
  3. The return-air damper is stuck in the fully open position.
  4. The chilled water supply temperature is too high at part load.

Explanation

A draw-through air handler operates the coil and drain pan under negative pressure. The condensate trap must have enough height to offset that suction; otherwise water cannot drain and the pan overflows. A shallow trap can also air-lock and stop flow.

Question 6Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

An automatic transfer switch is programmed to transfer a building's motor loads to a diesel generator. Before allowing the transfer, the controller checks that generator voltage and frequency are within set limits. Why is this check important for the connected induction motors?

  1. It allows the motors to be started without overload protection.
  2. It ensures the motors receive a supply that limits current and overheating. Correct answer.
  3. It guarantees the motors will operate at synchronous speed after transfer.
  4. It prevents the motors from running in reverse during the transfer.

Explanation

Induction motor speed follows supply frequency, and abnormal voltage or frequency can increase current and heating. The transfer switch verifies the generator is within acceptable limits before connecting sensitive motor loads. This prevents the motors from seeing an unstable source during transfer.

Question 7Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A commercial building has a reduced-pressure-zone backflow preventer on the domestic water service. During a no-flow test with normal upstream pressure, the relief valve discharges continuously. Which condition is the most likely cause?

  1. The building's water softener is in its regeneration cycle.
  2. The first check valve is fouled and passing water. Correct answer.
  3. The downstream check valve is stuck in the open position.
  4. The supply pressure upstream of the assembly is too low.

Explanation

In an RPZ assembly, the relief valve opens when the first check does not hold differential pressure across the zone. A fouled first check is a common cause of continuous discharge during a no-flow test. The assembly must be repaired and retested by a certified tester.

Question 8Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A centrifugal water chiller operating at steady load shows evaporator pressure and chilled-water supply temperature well below setpoint, while condenser pressure is normal. Which condition best explains these readings?

  1. High condenser-water entering temperature at the tower
  2. Fouled condenser tubes reducing heat rejection
  3. A restricted expansion valve or low refrigerant charge Correct answer.
  4. An excess refrigerant charge in the chiller circuit

Explanation

Low evaporator pressure and low chilled-water temperature with normal condenser pressure indicate the evaporator is starved of refrigerant. A restricted expansion valve or low charge reduces refrigerant flow into the evaporator. Excess charge or condenser problems would typically raise condenser pressure.

Question 9Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A base-mounted end-suction pump serving a condenser-water loop draws from an open cooling-tower basin 6 m below the pump inlet. The pump emits a crackling noise, discharge pressure fluctuates, and the suction gauge reads near the vapor pressure of water. Which root cause is most consistent with these observations?

  1. Available net positive suction head is below the pump's required NPSH. Correct answer.
  2. The pump shaft is misaligned with the motor.
  3. The pump is operating beyond the right-hand end of its curve.
  4. The discharge check valve is installed backward.

Explanation

Cavitation occurs when the absolute pressure at the pump inlet falls to the vapor pressure of the liquid. The available net positive suction head is then below the pump's required NPSH, and vapor bubbles collapse as the fluid moves to higher pressure. The crackling noise and fluctuating discharge pressure are classic symptoms.

Question 10Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A hydraulic elevator in a low-rise building stops short of the floor and then levels slowly. The oil temperature is normal, and the pump runs continuously while the car is stationary. Which fault should be investigated?

  1. A misadjusted door interlock in the car station
  2. A failed governor overspeed switch in the machine room
  3. A worn traction sheave liner on the machine
  4. A leaking down valve or cylinder packing Correct answer.

Explanation

In a hydraulic elevator, a leaking down valve or cylinder packing allows the car to settle or stop short of the floor. The pump may run continuously trying to maintain pressure and level the car. Traction sheave, door interlock, and governor faults do not fit a hydraulic unit with these symptoms.

Question 11Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A 480 V molded-case circuit breaker feeding a rooftop fan motor trips after about four minutes of drawing roughly 1.5 times its rated current. Which protective element inside the breaker is responding?

  1. The inverse-time thermal element sensing sustained overcurrent Correct answer.
  2. The ground-fault sensing module detecting leakage to earth
  3. The instantaneous magnetic element sensing a short circuit
  4. The shunt-trip coil receiving a remote opening command

Explanation

A current of about 1.5 times the breaker rating that persists for minutes is an overload, not a short circuit. The thermal element heats gradually and opens the breaker on an inverse-time curve, so higher overloads trip faster. Magnetic instantaneous elements respond to very high fault currents, ground-fault modules respond to leakage current, and shunt trips respond to a remote electrical signal.

Question 12Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A domestic hot-water system is equipped with a closed expansion tank on the cold-water inlet to the water heater. What is the tank's primary O&M purpose?

  1. To maintain a minimum recirculation flow through the hot-water return
  2. To store a reserve of hot water for peak morning demand
  3. To separate sand and sediment before water enters the heater
  4. To absorb the expansion of heated water and limit relief-valve discharge Correct answer.

Explanation

In a closed domestic hot-water system, water expands as it is heated and has nowhere to go because backflow prevention isolates the system from the street main. The expansion tank provides an air cushion that absorbs that volume change and keeps pressure below the relief-valve setting. Without a functioning tank, the temperature-and-pressure relief valve may discharge repeatedly or the system may experience pressure spikes.

Question 13Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a traction elevator, what is the main function of the counterweight?

  1. To keep the car level when the doors are open
  2. To balance car weight and reduce the machine's net load Correct answer.
  3. To tension the governor rope during normal travel
  4. To provide emergency braking if the overspeed governor trips

Explanation

The counterweight is sized to roughly balance the weight of the empty car plus a portion of the rated load. This reduces the torque the traction machine must produce and lowers the power needed to move the car. It does not provide braking, leveling, or governor-rope tension; those functions belong to other elevator components.

Question 14Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A cooling tower serving a condenser-water loop has white scale on the fill and the condenser-water conductivity is climbing above the setpoint. Which water-treatment adjustment is most appropriate?

  1. Increase the blowdown rate to remove dissolved solids Correct answer.
  2. Close the tower bypass to raise the basin temperature
  3. Add more makeup water continuously to dilute the basin
  4. Reduce the chemical biocide feed to lower conductivity

Explanation

Rising conductivity means dissolved solids are concentrating because evaporation leaves minerals behind. Increasing blowdown sends more of that concentrated water to drain and replaces it with fresh makeup, which lowers conductivity and reduces scaling potential. Biocide feed controls biological growth rather than dissolved solids, and continuous dilution without controlled blowdown wastes water and chemicals.

Question 15Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A belt-driven centrifugal exhaust fan develops a high-pitched squeal and leaves black dust around the sheaves. Belt tension is within the manufacturer's range. What is the most likely cause?

  1. A failed motor bearing allowing the shaft to drop
  2. An undersized motor running at service factor
  3. Fan wheel imbalance producing axial vibration
  4. Sheave misalignment causing belt sidewall wear Correct answer.

Explanation

Black rubber dust around the sheaves plus a squeal points to the belt rubbing against the sheave sidewalls. When pulleys are misaligned, the belt runs at an angle and wears rapidly even if tension is correct. Bearing failure, wheel imbalance, and motor sizing produce different symptoms such as growling, vibration, or overload trips rather than belt dust.

Question 16Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A UPS battery string uses valve-regulated lead-acid blocks. During a routine impedance test, one block shows internal resistance roughly three times the string average. What is the most appropriate interpretation?

  1. The charger is overcharging the entire string
  2. The UPS load is too small for the battery rating
  3. The block is degraded and needs capacity testing or replacement Correct answer.
  4. The block is fully charged and the reading is normal

Explanation

A block with much higher internal resistance than its stringmates is likely suffering from aging, dry-out, or grid corrosion. Such a block can pass a float-voltage check yet collapse under discharge, so it should be capacity-tested and scheduled for replacement if it fails. The charger and load size affect the whole string rather than one outlier block.

Question 17Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A domestic-water booster pump set with a diaphragm pressure tank short-cycles rapidly whenever fixtures are closed. The pump's pressure switch settings are correct. What should the technician check first?

  1. The water meter's pulse output wiring
  2. The building's peak water demand calculation
  3. The pressure-tank precharge and bladder integrity Correct answer.
  4. The pump impeller diameter against the design curve

Explanation

Rapid cycling at low or no flow usually means the pressure tank has lost its air cushion because the bladder is ruptured or the precharge is wrong. With little stored volume, the pump bumps between cut-in and cut-out pressures. Impeller diameter and demand calculations affect capacity, not short cycling with correct switch settings.

Question 18Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A three-phase motor starter has one blown fuse in the disconnect. The motor continues to run on the remaining two phases. What is the likely result?

  1. The motor draws high current on two phases and overheats Correct answer.
  2. The motor speed increases to synchronous speed
  3. The starter's overload heaters reset automatically
  4. The motor draws balanced current but produces more torque

Explanation

With one fuse open, the motor is single-phased and no longer has a balanced three-phase supply. It cannot develop uniform rotating torque, so the remaining phases draw excessive current and the winding overheats quickly. Overload heaters may eventually open, but they do not reset automatically to protect the motor.

Question 19Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A 480 V variable-frequency drive trips on DC-bus overvoltage whenever a high-inertia supply fan decelerates quickly. The incoming voltage is stable. Which corrective action is most appropriate?

  1. Bypass the drive and run the fan across the line at full speed
  2. Lengthen the deceleration ramp or add a dynamic braking resistor Correct answer.
  3. Increase the drive's carrier frequency to reduce motor heating
  4. Raise the motor overload setting to allow more current

Explanation

When a high-inertia fan is decelerated quickly, the motor acts as a generator and energy flows back into the drive's DC bus. If that energy cannot be dissipated or returned, bus voltage rises until the drive trips. Extending the deceleration ramp reduces the regeneration rate, and a braking resistor provides a path to dissipate excess energy.

Question 20Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a primary-secondary chilled-water plant, the bridge line flow reverses and runs from the secondary return into the secondary supply during peak demand. What does this indicate?

  1. Primary pump flow exceeds secondary pump flow and the bridge is overcooling
  2. The chillers are fully loaded and the primary loop is decoupling correctly
  3. Secondary flow exceeds primary production, so return water bypasses into the supply Correct answer.
  4. The secondary pump has lost prime and the bridge is acting as a vent

Explanation

The bridge decouples the constant-flow primary loop from the variable-flow secondary loop. If secondary flow exceeds the primary flow available, the extra flow must come through the bridge from the secondary return into the secondary supply. That bypasses warmer return water into the supply, raising the chilled-water temperature and reducing the plant's useful capacity.

Question 21Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a building's HVAC system, what is the primary function of a differential pressure switch installed across the supply air filter bank?

  1. To verify that the condensate drain pan is draining freely.
  2. To alarm when the filter becomes loaded and airflow resistance rises. Correct answer.
  3. To detect refrigerant leaks in the cooling coil and stop the unit.
  4. To measure duct static pressure and control the supply fan speed.

Explanation

A filter differential pressure switch monitors the pressure drop across the filter bank. As dust accumulates, the pressure drop increases and the switch triggers a dirty-filter alarm. Duct static pressure control uses a separate static-pressure sensor, refrigerant leak detection uses a refrigerant sensor, and drain-pan verification uses a float switch.

Question 22Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

What is the purpose of a temperature and pressure relief (T&P) valve on a domestic hot-water storage tank?

  1. To mix cold water with hot water to maintain a constant outlet temperature.
  2. To discharge water if tank temperature or pressure exceeds safe limits. Correct answer.
  3. To isolate the tank from the building water supply during maintenance.
  4. To prevent backflow of hot water into the cold-water supply.

Explanation

A T&P valve is a safety device that opens when either the stored water temperature or the tank pressure exceeds its setpoint. It relieves water to a drain to prevent tank rupture or scalding. A mixing valve controls outlet temperature, an isolation valve is for maintenance, and a backflow preventer protects the potable supply.

Question 23Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

What is the primary function of oil buffers installed at the bottom of an elevator hoistway?

  1. To absorb the car's or counterweight's kinetic energy after bottom overtravel. Correct answer.
  2. To guide the elevator car along the guide rails and reduce lateral sway.
  3. To apply braking force during normal stops at each floor.
  4. To tension the governor rope and detect overspeed.

Explanation

Oil buffers are energy-absorbing devices located at the pit bottom. They are designed to safely stop the car or counterweight if it overtravels the bottom terminal landing. Guide shoes guide the car, the machine brake stops the car normally, and the governor tension sheave keeps the governor rope taut.

Question 24Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A chilled-water air handling unit's coil freeze stat trips repeatedly in cold weather. The unit has a modulating outdoor-air damper and a preheat coil. Which condition is the most likely cause?

  1. The supply fan is running at excessive speed.
  2. The outdoor-air damper is stuck at its minimum position.
  3. The condensate drain trap is blocked.
  4. The preheat coil control valve is stuck closed. Correct answer.

Explanation

The freeze stat protects the cooling coil from freezing when cold outdoor air enters the unit. If the preheat coil valve is stuck closed, cold outdoor air is not tempered before reaching the cooling coil, so the freeze stat trips. An outdoor-air damper at minimum reduces cold air intake, and fan speed or a blocked drain trap do not directly cause coil freezing.

Question 25Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A base-mounted centrifugal pump in a chilled-water loop is cavitating. The suction pressure gauge reads below the pump manufacturer's minimum. Which action directly addresses the low suction pressure?

  1. Clean the suction strainer and check the suction valve is open. Correct answer.
  2. Throttle the discharge valve to reduce pump flow.
  3. Increase the pump speed to raise discharge pressure.
  4. Open the air vent on the pump casing and leave it open.

Explanation

Cavitation occurs when the available suction pressure falls below the pump's required net positive suction head. A common cause is a restricted suction line, such as a clogged strainer or a partially closed suction valve. Throttling discharge or increasing speed would not correct the suction restriction, and leaving a vent open would admit air.

Question 26Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A three-phase induction motor serving a rooftop exhaust fan draws current that is 12% higher on one phase than on the other two. The line-to-line voltages are balanced. Which is the most likely cause?

  1. The fan belt is tensioned too tightly.
  2. A loose connection in one motor circuit conductor. Correct answer.
  3. The variable-frequency drive is operating in bypass mode.
  4. The motor is oversized for the fan load.

Explanation

With balanced supply voltages, a current imbalance usually indicates a problem in the motor or its circuit, such as a high-resistance connection, a damaged winding, or a single-phasing condition. A loose connection increases resistance on that phase and causes the current imbalance. Oversizing, belt tension, and bypass operation do not typically cause a current imbalance with balanced voltage.

Question 27Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A building's main electrical service transformer has a high oil-temperature alarm. The transformer is a liquid-filled unit with forced-air cooling. Which action is most appropriate for the facility engineer to take first?

  1. Add oil to the transformer to raise the oil level.
  2. Check cooling fan operation and transformer load current. Correct answer.
  3. Immediately de-energize the transformer and call the utility.
  4. Reset the alarm and continue normal operation without investigation.

Explanation

A high oil-temperature alarm on a forced-air-cooled transformer often results from failed cooling fans or an overload. The first step is to confirm fan operation and check the load current against the transformer rating. De-energizing immediately may be unnecessary, adding oil does not address the heat source, and resetting without investigation risks insulation damage.

Question 28Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A domestic-water booster pump set with a variable-frequency drive maintains constant pressure. The pump runs continuously at low speed even when no fixtures are open. The pressure sensor is calibrated. Which is the most likely cause?

  1. The pressure tank is waterlogged.
  2. The VFD is set to hand mode.
  3. A leaking bypass valve around the pump. Correct answer.
  4. The pump impeller is worn.

Explanation

Continuous low-speed operation with no fixture demand means the pump is still seeing flow. A leaking or stuck-open bypass valve allows water to circulate back to the suction side, so the controller keeps the pump running. A waterlogged tank causes short cycling, a worn impeller reduces performance, and hand mode would run at a fixed speed rather than low speed.

Question 29Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A VAV air handling unit with an air-side economizer uses outdoor-air, return-air, and mixed-air dampers. During mild weather, the economizer fails to modulate and the mixed-air temperature remains close to return-air temperature even when outdoor air is cooler. The actuator and damper linkages move freely. Which control fault is most likely?

  1. The supply fan VFD is operating at minimum speed.
  2. The cooling coil valve is stuck open.
  3. The return fan is oversized for the system.
  4. The outdoor-air changeover sensor is failed or mis-set. Correct answer.

Explanation

The economizer controller decides whether to use outdoor air based on an outdoor-air enthalpy or dry-bulb changeover sensor. If that sensor fails or is set incorrectly, the controller may keep the economizer disabled and the mixed-air damper in the minimum position, so mixed-air temperature stays near return-air temperature. Fan speed, cooling coil valve position, and return fan sizing do not prevent damper modulation when the changeover sensor calls for free cooling.

Question 30Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a primary-secondary chilled-water plant, the secondary loop is variable-flow with two-way valves at the coils. The secondary pump is controlled to maintain differential pressure at the critical zone. If the differential pressure sensor is located at the pump discharge instead of the critical zone, what is the most likely operating result?

  1. The pump will over-supply at part load and increase bridge bypass, lowering delta-T. Correct answer.
  2. The chiller will short-cycle because the primary loop flow increases.
  3. The secondary pump will run at lower speed and starve the critical zone.
  4. The primary pumps will run in reverse due to the reversed sensor signal.

Explanation

The differential pressure sensor tells the secondary pump controller how much pressure to maintain. If the sensor is at the pump discharge, the controller holds a higher pressure than needed at the critical zone. At part load, the two-way valves close and the excess pump pressure is relieved through the bridge line, increasing bypass flow and lowering the plant delta-T. The pump will not run slower, the chiller is not directly short-cycled, and the primary pumps do not reverse.

Question 31Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

In a traction elevator, the car governor is driven by a rope from the car and mounted in the machine space. What is its safety function?

  1. It detects car overspeed and trips the safety gear to stop the car mechanically. Correct answer.
  2. It limits the rate of car acceleration by modulating the traction machine current.
  3. It limits the total travel of the car so that it cannot overrun the top landing.
  4. It holds the car at a landing with the doors open by clamping it to the guide rails.

Explanation

The governor is a mechanical overspeed device driven by a rope from the car. When the car exceeds its tripping speed the governor grips the rope and pulls the safety gear, forcing wedges against the guide rails to stop the car. A switch in the governor also removes power from the machine.

Question 32Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A domestic water service entering a building that has a boiler, chemical treatment and a fire sprinkler system is fitted with a reduced-pressure-zone (RPZ) backflow preventer. What does this device protect?

  1. The downstream piping system from water hammer caused by fast-closing solenoid valves.
  2. The public water main from contamination by water flowing back out of the building. Correct answer.
  3. The building's plumbing fixtures from excessive static pressure carried in the street main.
  4. The domestic water heater from thermal expansion stresses during each heating cycle.

Explanation

An RPZ is a testable backflow preventer with two independent check valves and a relief valve between them. It keeps water that has been inside the building, where it may pick up boiler chemicals or stagnant sprinkler water, from being drawn back into the public supply. If either check leaks, the relief valve dumps water rather than letting the contamination pass upstream.

Question 33Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A chilled-water air handling unit has its condensate drain piped to a floor drain. Why must the drain line include a P-trap?

  1. To isolate the drain line from the sanitary sewer during a backup in the building drain.
  2. To reduce the noise of condensate dripping into the drain pan during operation.
  3. To stop air blowing out of the pan and let condensate drain against fan pressure. Correct answer.
  4. To trap debris so that the drain pan outlet does not become blocked with sediment over time.

Explanation

The drain pan sits on the suction side of the supply fan, so it is at a negative pressure relative to the room. Without a trap, room air is pulled in through the drain and the condensate cannot leave the pan. The trap must be deep enough that its water column exceeds the fan's negative static pressure.

Question 34Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A water-cooled centrifugal chiller runs at design load. Condenser-water entering temperature, condenser-water flow and refrigerant charge are all at design values, but the condenser approach temperature has risen from 1.5 K to 4 K over several months. What is the most likely cause?

  1. The chiller is low on refrigerant charge, so the condenser is starved of gas.
  2. The condenser tubes are fouled on the water side, reducing heat transfer. Correct answer.
  3. The compressor is unloading because the chilled-water load has dropped below design.
  4. The cooling tower is supplying water colder than the design entering temperature.

Explanation

Approach temperature compares the condensing temperature with the leaving condenser-water temperature at fixed conditions. A rising approach means the condenser is rejecting heat less effectively, most often because scale or biofilm has built up on the water side of the tubes. Charge and loading problems would show up as abnormal subcooling or suction pressure, not as a rising approach alone.

Question 35Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

Two identical centrifugal pumps are piped in parallel in a chilled-water secondary loop. Starting the second pump raises total flow by only about 60 percent instead of 100 percent. Which statement best explains this?

  1. Pumps in parallel share head, and a steep system curve limits the flow gain. Correct answer.
  2. Pumps in parallel add their heads, so the second machine raises pressure rather than total flow.
  3. The second pump runs at a lower speed because of voltage drop in its branch feeder cable under load.
  4. A partly open bypass around the second pump returns most of that pump's flow to the suction header.

Explanation

Parallel pumps operate at a common head and their individual flows add at that head. The operating point is where the combined pump curve meets the system curve; if the system curve is steep, a modest flow increase demands a large head increase and the second pump cannot double the flow. Parallel arrangements therefore give the best gain on flat, low-resistance systems.

Question 36Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A 480 V feeder to a 75 kW induction motor shows phase voltages of 480 V, 470 V and 478 V. What is the main concern for the motor?

  1. The overload relay will trip because the total current exceeds the motor service factor.
  2. The voltage imbalance produces a much larger current imbalance, causing overheating and requiring derating. Correct answer.
  3. The motor will run at a lower power factor but with no meaningful heating risk.
  4. The motor insulation will fail immediately because of the phase-to-phase overvoltage.

Explanation

Unbalanced phase voltages create a negative-sequence component that produces a disproportionately large current imbalance, commonly six to ten times the voltage imbalance. The rotor and stator heat quickly and the motor must be derated per NEMA guidance. The usual causes are unequal single-phase loading or a loose or corroded connection upstream.

Question 37Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A hydraulic elevator stops at a landing, but over several minutes the car sinks about 30 mm and has to re-level before the doors will cycle. The cylinder, packing and visible piping show no external oil leakage. What is the most likely cause?

  1. The down valve or check valve in the power unit is leaking internally back to the tank. Correct answer.
  2. The governor rope is too slack, so the safety gear is dragging on the guide rails.
  3. The oil in the tank is cold and contracting, so the car settles as the oil cools.
  4. The rupture (pipe-break) valve is throttling the down flow while the car travels between floors.

Explanation

A hydraulic elevator holds the car by trapping oil in the cylinder with the check valve closed. If the check valve or down valve does not seat, oil leaks back to the tank while the pump is off and the car settles. Because there is no external leakage, the fault is inside the power unit valve block.

Question 38Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A domestic hot-water storage tank is held at 80 degrees C and a thermostatic mixing valve at the tank outlet delivers 48 degrees C to fixtures in a care facility. What is the primary purpose of this arrangement?

  1. To keep the stored water below 60 degrees C so that scale does not form on the tank lining.
  2. To store water hot enough to control Legionella while limiting fixture delivery temperature to prevent scalding. Correct answer.
  3. To increase the usable capacity of the tank by blending cold water at the tank outlet.
  4. To hold a constant recirculation flow rate in the hot-water return line during light load.

Explanation

Hot-water storage above 60 degrees C limits Legionella growth in the tank, but water at that temperature will scald at a fixture. A thermostatic mixing valve blends cold water at the outlet so distribution stays near 48 to 50 degrees C. This gives both pathogen control in the tank and a safe delivery temperature.

Question 39Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

On a 35 degree C day, an air-cooled screw chiller shows high discharge pressure, subcooling well above design, normal superheat and normal evaporator pressure, with all condenser fans running. Which cause fits these readings best?

  1. An undercharge of refrigerant, which leaves part of the condenser flooded with liquid.
  2. An overfeeding expansion valve, which floods the evaporator and raises suction pressure.
  3. A failed condenser fan motor, so that no air at all moves across the condenser coil.
  4. Restricted condenser airflow or a fouled coil, which is holding liquid in the condenser. Correct answer.

Explanation

High discharge pressure together with abnormally high subcooling shows liquid is backing up in the condenser because heat rejection is restricted. With fans at full speed, the usual causes are a fouled or blocked coil, recirculation of hot air, or a coil blocked by debris. Normal superheat and suction pressure make charge and metering faults unlikely.

Question 40Building systems operation and maintenance (HVAC, mechanical, electrical, plumbing, elevators)

A 480 V building distribution system is high-resistance grounded through a neutral grounding resistor rated 5 A. A single line-to-ground fault occurs on one outgoing feeder. What is the expected behaviour?

  1. The feeder breaker trips at once because the ground-fault current is far above its instantaneous pickup setting.
  2. It keeps running on alarm, with fault current limited to about 5 A, until the fault is cleared. Correct answer.
  3. The grounding resistor turns the ground fault into a bolted three-phase fault, so the main breaker opens without delay.
  4. Every phase-to-neutral load on the system is disconnected automatically until the resistor is switched out of the circuit.

Explanation

High-resistance grounding limits line-to-ground fault current to a few amperes, well below the level that would trip a feeder breaker. The system is allowed to keep running so that processes are not interrupted, but an alarm is raised and the fault must be located quickly. A second ground fault on another phase would create a phase-to-phase fault and trip the circuit.

Question 41Facility management, supervision, and staff administration

A facility manager is preparing the annual operating plan for a multi-tenant office building. Which task belongs to facility management rather than to a trade-level maintenance activity?

  1. Calibrating a differential pressure transmitter
  2. Resetting a fire alarm panel after a trouble signal
  3. Replacing a failed bearing on the supply fan
  4. Setting the O&M budget and staffing plan Correct answer.

Explanation

Facility management coordinates budgets, staffing, service levels, and work processes; it does not normally perform trade-level repairs itself. Setting the O&M budget and staffing plan is a core management deliverable.

Question 42Facility management, supervision, and staff administration

A work order system receives four requests at the same time in an occupied office building. Which request should be classified as an emergency priority in a facility management program?

  1. Scuffed paint on a corridor wall
  2. A stained ceiling tile in a vacant office
  3. A flickering fluorescent lamp in a storage room
  4. An impaired fire sprinkler system Correct answer.

Explanation

An impaired fire sprinkler system threatens occupant life safety and may violate fire code, so it is an emergency priority. Cosmetic or routine lighting issues can be scheduled later.

Question 43Facility management, supervision, and staff administration

A facility manager is hiring a contractor for elevator maintenance. Which document defines the contractor's responsibilities, performance standards, and reporting requirements?

  1. Scope of work (SOW) Correct answer.
  2. Request for information (RFI)
  3. Submittal register
  4. Punch list

Explanation

The scope of work defines the contractor's services, performance standards, schedule, and reporting requirements. A punch list records closeout deficiencies, an RFI clarifies design information, and a submittal register tracks product data.

Question 44Facility management, supervision, and staff administration

A facility manager wants to measure whether the maintenance team is completing scheduled preventive maintenance tasks within the assigned time window. Which KPI is most appropriate?

  1. Mean time to repair (MTTR)
  2. First-time fix rate
  3. PM compliance percentage Correct answer.
  4. Work order backlog in hours

Explanation

PM compliance compares completed preventive maintenance tasks with those due in the scheduled window. It directly shows whether scheduled work is being completed on time; MTTR, first-time fix rate, and backlog measure different aspects.

Question 45Facility management, supervision, and staff administration

An operating engineer has arrived late for three consecutive shift turnovers, delaying the outgoing engineer. What is the most appropriate first step for the facility supervisor?

  1. Ignore the lateness because the engineer's technical work is strong
  2. Issue a written warning without discussion to establish discipline
  3. Meet privately, discuss the pattern, and document it Correct answer.
  4. Move the engineer permanently to a different shift

Explanation

Progressive supervision starts with a private, documented discussion to identify the cause and set clear expectations. Formal discipline or reassignment should follow only if the behavior continues.

Question 46Facility management, supervision, and staff administration

A facility requires two operating engineers on site from 06:00 to 18:00, seven days per week. Each full-time engineer is scheduled for five 8-hour shifts per week. How many FTE engineers are needed to fill the two on-site positions before adding relief for leave and training?

  1. 3.6 FTE
  2. 4.2 FTE Correct answer.
  3. 5.6 FTE
  4. 4.8 FTE

Explanation

Two positions times 12 hours times seven days equals 168 engineer-hours per week. At 40 hours per FTE, 168 divided by 40 equals 4.2 FTE before any relief for leave or training.

Question 47Facility management, supervision, and staff administration

A facility manager wants annual performance reviews for building engineers to be defensible and consistent. Which practice best supports that goal?

  1. Compare engineers against each other rather than against written criteria
  2. Keep written criteria and documented observations Correct answer.
  3. Ask only the building tenants for informal comments
  4. Rely on the supervisor's overall impression from the past few weeks

Explanation

Defensible reviews rely on pre-established criteria and ongoing documented observations rather than recent impressions or peer ranking. Tenant feedback can be one input, but it should not replace documented performance evidence.

Question 48Facility management, supervision, and staff administration

A maintenance technician nearly falls from a portable ladder because the ladder was not secured. No injury occurred. What is the most appropriate supervisory response?

  1. Remove all portable ladders from the building permanently
  2. Investigate, retrain staff, and document corrective action Correct answer.
  3. Counsel the technician informally and let work continue
  4. Take no action because no one was injured

Explanation

Near misses are leading indicators of injury risk, so the supervisor should investigate causes, correct the practice, retrain, and document the action. Ignoring the event or only counseling informally leaves the hazard in place.

Question 49Facility management, supervision, and staff administration

An HVAC filter budget was built on four changes per year for 20 air-handling units at $30 per filter. Midyear, construction dust forces six changes per year. Which action is the most appropriate facility management response?

  1. Reduce the number of AHUs maintained to keep filter costs flat
  2. Charge the extra filters to the construction contractor without documentation
  3. Continue four changes per year to stay within budget
  4. Revise PM frequency and request a documented budget adjustment Correct answer.

Explanation

The facility manager should align PM frequency with actual operating conditions and manage the cost variance through a documented budget adjustment. Skipping required filter changes or cutting maintenance scope would harm equipment and reliability.

Question 50Facility management, supervision, and staff administration

A central plant has two licensed boiler operators; both are eligible to retire within 18 months, and no other staff hold the required license. Which staffing risk should the facility manager address first?

  1. No licensed-operator succession or cross-training plan Correct answer.
  2. The cost of uniforms for boiler room staff
  3. The number of parking spaces assigned to plant staff
  4. The frequency of boiler room housekeeping inspections

Explanation

Losing both licensed boiler operators would threaten continuous coverage and code compliance, so succession and cross-training are the priority. Uniform costs, parking, and housekeeping are minor compared with loss of required operator coverage.