Crestline Mechanical Specification / California T-24

Crestline Mechanical Plans / SMACNA

A 10"x10" duct has only 100 sq inches of cross section. At 1,520 CFM, duct velocity would be approximately 2,190 FPM — far exceeding the 1,200 FPM maximum for occupied-space return ducts. The plans call for a 22"x22" RA duct (RA22X22-1520) with 484 sq inches providing approximately 450 FPM velocity.

Crestline Mechanical Specification

Wrong insulation type. While the thickness (0.5 inch) meets the minimum, mineral wool (PI-A) is unacceptable for refrigerant suction lines. The spec requires PI-B (elastomeric/rubber) because refrigerant suction lines operate below the dew point and will condense moisture from the surrounding air. Elastomeric insulation is closed-cell and acts as its own vapor barrier, preventing moisture from reaching the cold pipe. Mineral wool is open-cell and would absorb moisture, lose its insulating value, and cause corrosion on the copper suction line. The wet, degraded insulation would also drip onto equipment and ceiling tiles below.

Crestline Mechanical Specification / ASTM C1136

PVC jacketing is not permitted on outdoor pipe insulation per Crestline specifications. PVC degrades under UV exposure, becomes brittle, and cracks, allowing moisture infiltration that destroys the insulation. Aluminum or stainless steel jacketing is required for outdoor applications.

Crestline Mechanical Specification / SMACNA

Duct liner is NOT allowed inside kitchen supply ducts, regardless of NRC rating or installation quality. Grease-laden air can saturate fiberglass liner, creating a fire hazard and breeding ground for bacteria. The Crestline spec explicitly prohibits internal duct liner on kitchen supply ductwork. Noise reduction in kitchen duct systems must be achieved through external duct wrap, sound attenuators, or duct silencers mounted upstream of the kitchen branch.

Crestline Mechanical Specifications

Pre-insulated piping transitions must terminate a minimum of 2'-0" inside the building per the Crestline specifications. At only 1'-0" inside, the transition is too close to the building envelope — moisture can migrate along the pre-insulated carrier pipe from outside, and the joint between pre-insulated and standard piping is exposed to temperature fluctuations from the nearby wall penetration. The 2'-0" minimum ensures the transition is fully within the conditioned space, allowing proper inspection access and preventing condensation issues at the insulation changeover point.

Crestline Mechanical Specifications / ASME B31.9

Ball valves are not permitted underground per the Crestline specifications. All underground valves must be gate valves. Gate valves are preferred underground because they provide a full-port opening with minimal pressure drop when fully open, and their rising stem or position indicator makes it easy to verify valve position from above the valve box. Ball valves underground are problematic because the handle position can be ambiguous through a valve box access, and ball valve seats can be damaged by debris common in underground installations. The ball valve must be replaced with a gate valve of the same size and pressure rating.