IMC 304.1 / Manufacturer installation instructions

IMC 1203.4

Dissimilar metals (steel to copper) require dielectric unions to prevent galvanic corrosion. Without them, the pipe joint will corrode and fail within 2-5 years.

IMC 1205.1.6

This is a correct closed-loop arrangement, but note which code actually governs it. IMC 1009 is titled "Hot Water Boiler Expansion Tank" and sits in Chapter 10, whose scope is boilers, water heaters and pressure vessels — it does not reach a chilled water loop. Chilled water is scoped into Chapter 12, Hydronic Piping, and Chapter 12 imposes no expansion-tank requirement at all: the tank is an engineering necessity, not an IMC command. The section that actually decides this scenario is IMC 1205.1.6, which requires shutoff valves only at connections to NONDIAPHRAGM-type expansion tanks — so a diaphragm tank with no isolating valve is compliant, and that contrast is the thing worth remembering. The tank absorbs expansion across the loop's own temperature range, including warm-up and shutdown, not "as it heats" the way a boiler loop does. Two details here are good engineering practice rather than code: connecting at the pump suction puts the point of no pressure change where it belongs so the pump adds pressure to the loop, and the air separator upstream keeps entrained air out of the tank.

IMC 304 / Manufacturer Specs

The installation meets the manufacturer's minimum clearances. Equipment clearances are determined by the manufacturer's listing and installation instructions, which are enforced by code. As long as the actual clearances meet or exceed the listed minimums, the installation is compliant.

IMC 307.2 / ASHRAE

CRAH condensate drains must have a P-trap to prevent pressurized under-floor air from blowing back through the drain line. Without a trap, the raised floor plenum pressure will force air through the drain, preventing condensate from draining and potentially causing water damage.

IMC 307.2.2

This is a proper installation. When gravity drainage is not possible, condensate pumps are an accepted solution. The key requirement is the overflow safety switch — if the pump fails, the unit must shut down to prevent water damage. Discharge to a laundry sink is an approved indirect waste receptor.

IMC 401.5

Outdoor air intakes and return air openings must have corrosion-resistant screens (min 1/4" mesh) to prevent entry of birds, rodents, and large debris.