SKA Rating Assessor

Correct: According to the International Mechanical Code (IMC), equipment must be listed and labeled by an approved agency, and field modifications must not compromise this status. Furthermore, Section 304.1 requires that equipment and appliances be supported on a level surface of noncombustible material or a fire-resistance-rated assembly. The mounting must be designed to support the weight of the equipment and prevent damage to the building structure.

Incorrect: The suggestion that integrity is based on a shipping manifest is incorrect as it ignores the listing and labeling requirements for the actual installation. The claim that field modifications automatically void integrity is too broad, as modifications can be approved if they meet code and listing standards. Vibration isolators are not a universal requirement for all units. Focusing solely on electrical grounding or static weight ignores the fire-resistance and noncombustible requirements for mounting surfaces.

Takeaway: Mechanical equipment must maintain its listing and labeling through any modifications and be mounted on a level, noncombustible, or fire-rated surface that ensures structural stability.

Correct: According to the International Mechanical Code (IMC) Section 304.11, moving parts of mechanical equipment, including fan blades and belts, must be protected by guards when located within 7 feet of the floor or working level. The code specifies that these guards must be constructed to prevent a 0.5-inch diameter sphere from passing through, which serves as a critical safety control to prevent accidental injury to personnel.

Correct: According to the International Mechanical Code (IMC) and International Plumbing Code (IPC), Reduced Pressure Zone (RPZ) backflow preventers must have their relief port discharge through an air gap. This physical separation is critical because it prevents a cross-connection where waste or contaminated water could be siphoned back into the potable water supply if the waste line backs up or if there is a drop in supply pressure.

Incorrect: Equipping the line with a solenoid valve is incorrect as it introduces a point of failure and does not address the cross-connection risk. While glycol may require specific disposal considerations, the primary mechanical code violation for an RPZ is the lack of an air gap, not the absence of a neutralizer. Routing the discharge outdoors without an air gap still violates the requirement for an indirect waste connection and does not protect against back-siphonage from the discharge point itself.

Takeaway: RPZ relief ports must always utilize an atmospheric air gap to ensure the integrity of the backflow prevention and protect the potable water supply.

Correct: According to the International Mechanical Code (IMC), specifically regarding exhaust systems and ventilation, makeup air must be provided to replace air being exhausted. If makeup air is not provided, the building develops a negative pressure (vacuum effect), which can cause doors to stick, backdrafting of combustion appliances, and reduced exhaust fan performance. Providing makeup air in a volume that balances the exhaust ensures the system operates within design parameters and maintains the structural integrity of the building environment.

Incorrect: Increasing static pressure does not solve the underlying pressure imbalance and may exacerbate the difficulty of opening doors or cause mechanical strain on the fan motors. Gravity-actuated dampers are used to prevent backflow but do not address the lack of replacement air for the exhaust system. Synchronizing return air fans with HVAC cycles focuses on thermal comfort and efficiency rather than the specific mass-balance requirement of an exhaust-heavy environment.

Takeaway: Proper mechanical balancing requires the introduction of makeup air to compensate for exhausted air, preventing negative pressure issues and ensuring system efficacy.

Correct: The primary function of a thermostatic expansion valve (TXV) is to act as a metering device that regulates the amount of liquid refrigerant entering the evaporator. It does this by sensing the temperature and pressure at the evaporator outlet and adjusting the flow to maintain a constant superheat. This ensures that the evaporator surface is used efficiently while preventing liquid refrigerant from returning to the compressor, which could cause mechanical failure.

Incorrect: Regulating discharge pressure is a function of the condenser or head pressure control systems, not the expansion valve. Converting vapor to liquid is the thermodynamic process that occurs in the condenser, whereas the expansion valve handles the pressure drop of liquid refrigerant. Monitoring crankcase temperature to prevent oil dilution is the role of a crankcase heater or an oil management system, not a metering device like a TXV.

Takeaway: A thermostatic expansion valve optimizes evaporator efficiency and protects the compressor by modulating refrigerant flow to maintain a constant superheat at the evaporator exit.

Correct: According to the International Mechanical Code (IMC), specifically Section 605 on Air Filters, the code requires that all of the scheduled amount of air passes through the filter. To achieve this, the code mandates that filter racks be constructed and installed in a manner that prevents the passage of unfiltered air. This ensures the integrity of the air distribution system and protects downstream components from dust and debris accumulation.

Incorrect: The suggestion that differential pressure gauges are required for all filter housings is incorrect, as these are typically design preferences or required only in specific high-performance environments, not a general IMC requirement for all filter racks. The claim that a 10 percent leakage rate is acceptable is false; the code does not provide a permissible percentage for bypass but rather requires the prevention of unfiltered air passage. Finally, the requirement for sealing is not limited to HEPA-rated systems; the IMC applies the standard for preventing unfiltered air bypass to all air filter installations in mechanical systems.

Takeaway: The International Mechanical Code requires filter racks to be constructed and installed to ensure all air passes through the filter media, effectively prohibiting unfiltered air bypass.

Correct: According to the International Mechanical Code (IMC) Section 507.4.1, canopy-type hoods must be designed and located such that the edge of the hood extends a horizontal distance of not less than 6 inches beyond the edge of the cooking surface on all open sides. This ensures the proper capture and containment of grease-laden vapors and heat plumes.

Incorrect: The 12-inch requirement is often a best-practice recommendation for heavy-duty or high-heat appliances but is not the minimum prescriptive code requirement for standard canopy hoods. The 3-inch and 9-inch options are incorrect as they do not align with the specific safety standards established by the IMC for adequate capture area, which is strictly set at a minimum of 6 inches.

Takeaway: Type I canopy hoods must maintain a minimum 6-inch horizontal overhang on all open sides to comply with IMC safety standards for grease and heat capture.

Correct: The International Mechanical Code (IMC) requires that refrigeration systems be protected by pressure-limiting devices to prevent the pressure from exceeding the design pressure of the components. Bypassing these controls is a critical safety violation that overrides operational or efficiency concerns, as it removes the primary safeguard against vessel rupture or explosion.

Incorrect: Focusing on asset management or depreciation schedules ignores the immediate physical safety and code compliance risks. Attributing relief valve discharge to expansion valve sizing is technically inaccurate in this context, as the discharge is a direct result of high pressure that the bypassed switch should have mitigated. Prioritizing energy efficiency monitoring over safety-critical pressure controls misaligns the auditor’s risk assessment with the severity of the potential impact.

Takeaway: Safety-critical pressure controls in chiller systems are mandatory under the International Mechanical Code and their bypass represents a high-priority risk to life and property.

Correct: According to the International Mechanical Code (IMC) and the International Plumbing Code (IPC), the discharge pipe for a temperature and pressure (T&P) relief valve must not be threaded at the terminal end. This requirement is a critical safety control designed to prevent the installation of a plug or cap on the end of the pipe, which would render the safety relief valve useless and potentially lead to a boiler explosion if the tank over-pressurizes.

Incorrect: Constructing the pipe from rated CPVC is acceptable as long as the material meets the temperature and pressure requirements of the system. Terminating the pipe at an indirect waste receptor within the same room is a standard and compliant method of discharge, provided it is above the floor and visible. Maintaining the same diameter as the valve outlet and ensuring no traps or valves are present are both mandatory code requirements to ensure unobstructed flow during an emergency discharge.

Takeaway: To prevent unauthorized capping of a safety device, the International Mechanical Code strictly prohibits the use of threaded ends on temperature and pressure relief valve discharge piping.

Correct: According to the International Fuel Gas Code (IFGC) and the International Mechanical Code (IMC), appliances are categorized based on vent pressure and the potential for condensation. Category I appliances operate with a non-positive vent pressure, while Category IV appliances operate with positive vent pressure and produce significant condensate. Mixing these categories in a standard Type B vent is prohibited because the positive pressure from the Category IV unit can force flue gases back through the Category I appliance, and the corrosive condensate from the Category IV unit will damage a vent not rated for such conditions.

Incorrect: Increasing chimney height does not resolve the fundamental pressure and moisture compatibility issues between different appliance categories. Using standard BTU venting tables is inappropriate because those tables are designed for atmospheric or fan-assisted Category I appliances, not positive-pressure condensing units. Installing a backflow preventer at the flue collar is not a code-approved method for reconciling the venting requirements of disparate appliance categories and does not address the material degradation caused by acidic condensate.

Takeaway: Venting systems must be matched to the specific appliance category, and positive-pressure Category IV appliances must generally be vented independently of negative-pressure Category I appliances to ensure safety and vent integrity.