HVAC Certification Preparation Quiz

The correct answer highlights common reasons for dimming lights upon compressor start up, including high voltage, high current draw, or low line voltage amp draw. Faulty wiring, a malfunctioning breaker switch, and an issue with the compressor motor are all potential causes but not the most common reasons for this specific issue.

Increasing the heat anticipator resistance results in the thermostat keeping the heating system on for longer periods of time, leading to longer heating cycles.

The correct way to install a vibabsorber is to position it parallel to the crankcase and perpendicular to the crankcase closest to the compressor. This orientation helps in effectively absorbing vibrations and reducing noise levels.

When installing a roof top unit, the most important thing to consider is accessibility to ensure easy maintenance and servicing in the future.

A P-trap should always be installed on the larger suction line to prevent air from entering the system.

Poor oil return on low load is often caused by an oversized smaller suction riser, which can lead to improper oil circulation in the system.

When replacing a shaft seal on a inline booster pump, the motor is typically the first component to be removed to access the shaft seal for replacement.

Chilled water coils are designed to have cool water entering at the bottom and warm water leaving at the top to maximize the cooling efficiency.

The chemical pot in a closed loop water system is typically located at the system supply point to properly treat the water in circulation.

When vapor is removed from R-404A, the process of fractionation occurs, leading to the separation of the various components within the refrigerant mixture.

In a double riser plumbing system, the trap should be installed in the larger line to ensure proper drainage and prevent clogs.

When replacing a hermetic compressor, the low side components should be tested to a pressure of 150 psi as part of proper troubleshooting and maintenance procedures.

When a pneumatic valve is in the full open position, the most likely cause is a ruptured diaphragm, which fails to control the valve position effectively.

The correct way to calculate the total watts consumed in this scenario is by multiplying the watts of each fan by the number of fans to get 1000 watts. Then, by adding the 1000 watts to the initial 100,000 Btu's converted to watts, you get the total of 30,291 watts.

When a system is charged with R/22 and experiences overload, high temperature is usually the cause as it indicates that the system is getting too hot which leads to shutdown.

The correct calculation for CFM with a 7.5 ton HVAC system and 10% make up air is multiplying 7.5 tons by 400 CFM and then taking 10% of that result, which equals 300 CFM. Therefore, the correct answer is 300 CFM.

A double suction riser is required when there is a risk of oil entrainment at minimum capacity load, as it helps prevent this issue from occurring.

When the defrost time clock is wired in parallel with the time clock switch, they both receive the same input voltage and operate independently. This allows for both devices to function effectively without interfering with each other's operations.

When the outdoor ambient stat is set above ambient, the dampers are designed to close to regulate the temperature and maintain desired conditions. Additionally, the compressor should come on to provide cooling as needed.

When a defective liquid line solenoid valve is found, the correct procedure is to recover the refrigerant before replacing the faulty valve. Bypassing the valve or continuing operations with a defective one can lead to system inefficiency and potential safety hazards. Ignoring the issue or attempting to repair the valve without proper refrigerant recovery is not a recommended course of action.

The EPR valve is typically installed at the evaporator with the higher temperature to control the refrigerant flow and maintain optimal performance.

The vapor barrier of a walk-in cooler is typically positioned between the outer wall and the insulation to prevent moisture from entering the insulation material.

When troubleshooting a VAV box that is pneumatically controlled and not working, the first things to check in order are the thermostat (T-stat), actuator, and linkage. These components are crucial in ensuring proper functioning of the VAV box and can help identify the root cause of the issue.

To change the rotation of a single phase motor, the correct method is to internally change the start winding lead. This adjustment directly impacts the direction of rotation without the need to adjust external speed control settings, switch winding positions, or modify the power source.

When putting a system into a vacuum, it is important to install schrader valves to control the pressure within the system and prevent air from entering.

When the fan starts up, the increase in airflow will cause an increase in pressure as measured by the manometer. However, the velocity and pressure as measured by the velometer will decrease due to the effect of the fan pulling air away from that point.

When humidity stat contacts are pitted, the best course of action is to set a wider range on the control and increase the humidifier differential to compensate for the pitting.

Fouling in a water-cooled condenser can be caused by various factors, but one common reason is when the subcooling is too low, affecting the efficiency of the condenser.