Crestline Mechanical Specification / ASTM C1136

Crestline Mechanical Plans / NFPA 37

The exhaust height is 2 feet below the minimum requirement. Per the Crestline mechanical plans (with engine-exhaust termination governed by NFPA 37), generator room exhaust must terminate a minimum of 10 feet above grade. At 8 feet, the exhaust outlet is only slightly above head height — carbon monoxide and diesel particulates from the generator exhaust could affect pedestrians, maintenance workers, or be drawn into nearby building openings. The 12-foot distance from the property line meets the 10-foot minimum requirement, but the height must be corrected by raising the exhaust stack an additional 2 feet to reach the 10-foot minimum.

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 / California T-24

This installation meets code. In Climate Zone 3, the minimum R-value for supply and return ducts located outside the building is R-8. The contractor correctly used DW-B insulation with a metal jacket, which is required for exterior duct applications to protect the insulation from weather, UV damage, and physical abuse. If this project were in Climate Zone 5 or higher, R-12 would be required instead of R-8.

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.