HVAC/ACR International Mechanical Code
Five Important Changes to the 2021 International Mechanical Code (IMC)
The new 2021 International Mechanical Code (IMC) has been published and is available to adopt. There are 33 significant changes to eight chapters in the Code’s 2021 edition. While the scope of this article does not cover all of the changes, there are five items that should be noted for new construction and renovation.
Condensate Discharge
Whenever condensate drains or lines are connected directly to a plumbing system, serious health hazards can occur. For instance, sewer gas could permeate from the drains and fill the entire space of a structure. To alleviate sewer gas build-up and other health-related issues, the IMC has adopted new language regarding the use of condensate lines. In the new language, except where discharging to grade, condensate lines can be located only in floor sinks, floor drains, trench drains, mop sinks, hub drains, standpipes, utility sinks, or laundry sinks. Direct connections to the sewer system are no longer permitted.
Mechanical Ventilation in Apartments
Improved language regarding ventilation in apartments (R2 dwellings) can be found in Chapter 4, Ventilation. These dwelling units are required to meet the appropriate air leakage requirements in the International Energy Conservation Code, resulting in minimal air infiltration. Therefore, all dwelling units, such as apartments, must be mechanically ventilated. Openable windows and doors, which typically count as natural ventilation, cannot be the sole source of changing air in the dwelling.
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Pressure Testing Refrigerant Lines
In large commercial occupancies such as grocery stores, refrigeration is a necessary part of the business model. Coolers, refrigerators, and freezers line several isles containing produce, frozen food, meat, and dairy products. Connecting these indoor components to compressor and condenser units requires several hundred feet of refrigerant lines. These lines are typically field-installed copper pipe with many brazed joints. Pressure testing connections before beginning equipment startup is essential. The cost of refrigerant, malfunctioning equipment, environmental hazards, and the safety of occupants are good reasons to ensure leakproof refrigeration systems. Additionally, most mechanical codes and the Environmental Protection Agency (EPA) require pressure tests for new piping installations.
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Medium Pressure Gas Piping Systems
When properly installed, fuel gas is a safe energy source for cooking, heating, clothes drying, and exterior lighting. It is available to serve residential and commercial buildings in the form of natural and liquified petroleum gas. Although these two fuel gases have different characteristics and work under slightly different manifold pressures, appliances can be converted to use either type. Adequately sizing the gas delivery piping is mandatory for safe operation. The piping cannot leak and must provide enough fuel for combustion to each appliance burner.
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Venting Systems for Mid-Efficiency Furnaces
A vent is defined as a pipe or conduit that contains a passageway for conveying combustion products and air to the atmosphere. Products of combustion contain carbon dioxide, water, and sometimes carbon monoxide. Therefore, it is important to safely vent a gas furnace.
Modern gas furnaces are available with efficiencies that range from 80% to 98% Annual Fuel Utilization Efficiency (AFUE) ratio. Furnaces that are 90 to 98% AFUE are considered very efficient and utilize a category 4 vent system. This means that the flue gases operate under a positive vent stack pressure with a low vent gas temperature, causing the gases to condense before discharging from the vent. Venting materials used for category 4 furnaces are those recognized by the furnace’s installation instructions such as stainless steel, PVC, and ABS. Furnaces one tier lower in efficiency use more traditional venting methods than the 90+% units. Even though these systems are associated with conventional chimneys and vents, special attention must be given to their installation.
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Duct Leakage Tests
The International Code Commission (ICC) mandated HVAC duct leakage testing for the first time in the 2009 International Energy Conservation Code (IECC). Since the first leakage test requirement was rolled out, extensive testing procedures and equipment have remained in the Code. Obviously, the scope of the IECC is to conserve energy. Leaking conditioned air to unconditioned spaces is wasteful and unnecessary. There are many duct sealing systems available that will fill most of the small openings around duct fittings. To seal ducts and conduct a leakage test, a HVAC contractor, engineer, or HERS rater use these specialized tools and metho
