4.2 Cooling Equipment, Heat Pumps & Solar Thermal

Cooling & Refrigeration is about 2 percent of the M2 and Heat Pumps & Solar Thermal about 4 percent. The inspector mistake is treating every outdoor box as “just HVAC.” A condensing unit, a water-source heat pump, a ground loop, and a solar-thermal collector array are four different code paths.

Factory-built cooling equipment is accepted through 2024 IMC 1101.2 and Table 1101.2 when it is listed, labeled, and installed to the listing and the manufacturer’s instructions. Air-conditioning equipment and split-system air conditioners and heat pumps are tested to UL 1995 or UL/CSA 60335-2-40. Packaged terminal air conditioners and heat pumps are tested to UL 484 or UL/CSA 60335-2-40. 918.2 repeats the same UL 1995 or UL/CSA 60335-2-40 pair for electric heat pumps. High-probability equipment using Group A2L, A2, A3, or B1 refrigerant must comply with UL 484, UL/CSA 60335-2-40, or UL/CSA 60335-2-89 (1101.2.1) — that sentence is why the new mildly flammable residential and light-commercial splits show a 60335-2-40 mark instead of a 1995-only plate.

Cooling coils, condensing units, and packaged DX

A cooling coil in an air handler is a refrigerant evaporator. Indoor installation still follows Chapter 3: 306.1’s 30-by-30 control-side working space, 304.1’s on-site instructions, and Section 307 condensate (primary drain, Table 307.2.2 size, ⅛-in-12 slope, and 307.2.3 auxiliary protection where overflow can damage the building). The coil’s refrigerant charge counts toward Chapter 11 quantity limits if it sits in an occupied space — that calculation is the next section.

A condensing unit or packaged DX rooftop unit is outdoor equipment. 303.6 requires an outdoor listing. 304.10 still elevates grade-mounted equipment 3 inches on an approved pad or 6 inches if suspended. 306.1 still wants a level 30-by-30 space at the control side — a unit shoved against a penthouse wall so the service panel cannot open is a fail even if it cools. Airflow clearances (coil face, condenser discharge, and the distance to walls or screens) come from the listing and the manufacturer’s instructions; 304.2 makes those instructions control when they are more restrictive than a generic IMC clearance idea. Combine that with access, rooftop platforms, and guards.

Heat-rejection equipment that is a cooling tower, evaporative condenser, or fluid cooler is 2024 IMC 908. Factory-built cooling towers are listed to UL 1995 or UL/CSA 60335-2-40 (908.1). 908.2: ready access. 908.3: locate the equipment so vapor plumes do not enter occupied spaces, and keep plume discharges not less than 5 feet above or 20 feet away from any ventilation inlet to a building. 908.5 sends the water supply and backflow protection to the IPC. 908.6: drains, overflows, and blowdown are indirectly connected to an approved disposal location. 908.8.2: drift eliminators with a maximum drift rate of 0.005 percent of circulated water flow. Refrigerant inside a closed heat-rejection circuit still goes to Chapter 11 (908.7).

Heat pumps: air-source, water-source, ground-source

An air-source heat pump is a refrigeration appliance that reverses to heat. Inspect it as listed outdoor or indoor equipment (303.6 / 303.5), with 306.1 access, 304.10 elevation, and 307 condensate from the indoor coil and, where the listing produces it, from the outdoor unit in heat mode. The 2024 IMC does not publish a standalone “crankcase heater required below X °F” sentence. Crankcase heaters, base-pan heaters, and other freeze-protection devices are enforced through 304.1 — install them when the listing and the manufacturer’s installation instructions require them for that climate and that application. If the instructions call for a heater and it is missing or not wired, the installation is not per the listing.

A water-source heat pump uses a building hydronic loop as the heat sink and source. The refrigerant side is Chapter 11 equipment. The water side is Chapter 12 hydronic piping — the same family as boilers and hydronic systems. 1202.3: materials rated for the operating temperature, pressure, and fluid. 1205.1.5: shutoff valves on connections to mechanical equipment and appliances. 1208.1: hydronic piping systems are tested hydrostatically at 1½ times the maximum system design pressure, but not less than 100 psi, for not less than 15 minutes. 1207.1: the flash point of a transfer fluid shall be not less than 50°F above the maximum system operating temperature.

A ground-source heat pump loop is 2024 IMC 1210, not a casual “plastic pipe in the yard.” 1210.2: reused pipe, fittings, valves, and other materials shall not be permitted. 1210.4 / Table 1210.4 accept CPVC, PEX, PE-AL-PE, HDPE, PP-R, PVC, and PE-RT to the listed standards (HDPE commonly ASTM D3035 / F714 / CSA C448 / NSF 358-1). Underground joints must be approved for buried applications (1210.6). HDPE joints are heat-fusion (ASTM D2657), electrofusion (ASTM F1055), or stab-type inserts (ASTM F1924) — not hose clamps. 1210.8: install to ANSI/CSA/IGSHPA C448 and the manufacturer’s instructions. 1210.8.1: a potable-water connection gets IPC backflow protection. 1210.8.9: where the loop enters the building, mark it “GROUND-SOURCE HEAT PUMP LOOP SYSTEM” and state any antifreeze by name and concentration. 1210.8.10: antifreeze and other chemicals shall be chemically compatible with the pipe, fittings, and mechanical systems.

1210.10 Tests is the number you will be asked. Before connection-header trenches are backfilled, the assembled loop system shall be pressure-tested with water at 100 psi (689 kPa) for 15 minutes, in which time there shall not be observed leaks. Flow and pressure-loss testing shall be performed, and actual flow rates and pressure drops compared to calculated design values. If either differs by more than 10 percent, identify the cause and take corrective action. 1210.11: piping to be embedded in concrete is pressure-tested before the pour and held at the proposed operating pressure during the pour. Do not substitute the Chapter 12 1½-times hydronic test for the 1210.10 loop test — both can apply to different parts of the same job (buried loop versus indoor hydronic piping).

Solar thermal — do not inspect it as photovoltaic

A solar thermal system uses sunlight to heat a fluid for space heating, domestic water, pool heating, or process heat (1401.1). It is not a photovoltaic array, inverter, or rapid-shutdown inspection. 1401.4: solar thermal equipment shall conform to this chapter and ICC 900/SRCC 300; systems shall be listed and labeled to ICC 900/SRCC 300 and installed to the manufacturer’s instructions and that standard. 1401.4.1 / 1402.8.1.1: collectors and panels are listed and labeled to ICC 901/SRCC 100.

Relief and over-temperature. 1402.3: components containing pressurized fluids shall be protected against pressures and temperatures exceeding design limitations with pressure-and-temperature relief valves or pressure-relief valves. System components shall have a working-pressure rating not less than the relief setting. 1402.3.1: each section in which excessive pressure can develop shall have a relief device located so the section cannot be valved off from that device. Relief valves follow 1006.6; indirect solar-loop relief valves also follow ICC 900/SRCC 300. 1402.3.2: components that can see vacuum need a vacuum rating or vacuum-relief valves. 1402.8.7: liquid single-phase systems get expansion tanks sized to Section 1009, plus extra acceptance volume equal to the liquid in the collectors and the piping above the collectors.

Freeze. 1402.4: protect components from freezing of heat-transfer liquids at the lowest ambient temperature the system will see, in accordance with ICC 900/SRCC 300. Drain-back systems (1402.4.1) must gravity-drain to a non-freezing location and hold a horizontal slope in the direction of flow of not less than ¼ unit vertical in 12 units horizontal (2 percent). Freeze-protection valves (1402.4.2) shall discharge without creating a hazard or structural damage.

Potable isolation. 1401.2 sends potable supplies to the IPC, with an exception only where the entire solar piping system is part of the potable distribution system and every component is listed for potable water. 1402.5.1: water supplies of any type shall not be connected to the solar heating loop of an indirect system (service inlets/outlets on that loop are not a fill connection to the building water). 1402.8.4.1: heat exchangers using a nonfood-grade fluid shall be double-wall construction with an air gap open to the atmosphere between the walls, and the discharge location shall be visible. 1402.8.4.2: a single-wall exchanger is limited to food-grade heat-transfer fluid. 1403.1: the fluid flash point shall be not less than 50°F above the design maximum nonoperating (no-flow) temperature attained in the collector. 1403.5: a flammable liquid or gas shall not be used as a heat-transfer fluid. 1404.3: label drain and fill valves as “Potable Water,” “Food-Grade Fluid,” “Nonfood-Grade Fluid,” or “Toxic.”

1402.2: roof-mounted collectors shall not obstruct roof hatches, chimneys, smoke vents, or other roof-mounted appliances. 1402.6: equipment exposed to vehicular traffic is installed not less than 6 feet above the finished floor unless protected from vehicle impact. 1402.8.5.1: hot-water storage tanks are insulated to not less than R-12.5. 1402.8.6.1: isolation valves on the solar loop.