Refrigerated Warehouse Title 24 Requirements
A refrigerated warehouse of 3,000 square feet or more is a covered process, with its own insulation table, evaporator and condenser requirements and acceptance tests. Separate refrigerated rooms count together if one refrigeration system serves them.
The threshold aggregates across rooms
Three thousand square feet triggers the requirements — but it is not only measured as a single warehouse. Refrigerated spaces whose areas sum to 3,000 square feet or more are caught when they are served by the same refrigeration system.
That is the detail that surprises people. Four 800-square-foot cold rooms on one rack is 3,200 square feet and inside the section, even though no individual room is close to the threshold. Separate systems serving each room would be assessed separately.
Insulation is specified by room temperature
Freezers and coolers get different numbers, and the gap is wide:
- Freezer roof and ceiling — R-40
- Freezer walls — R-36
- Freezer floor — R-35, or R-20 where productive refrigeration heating is used
- Cooler roof and ceiling — R-28
- Cooler walls — R-28
These are far above anything in the ordinary building envelope. A freezer floor is insulated at all, which a normal slab is not, and R-40 in a roof is roughly twice a conditioned building's requirement. The reason is the temperature difference: a freezer at −10°F in a Central Valley summer is fighting a gradient no office ever sees.
Underslab heating is restricted, not banned
Electric resistance heat shall not be used for underslab heating — with one exception. It is permitted where it is thermostatically controlled and disabled during the summer on-peak period.
The purpose of underslab heat is to stop the ground beneath a freezer freezing and heaving, which is a genuine structural problem. The code does not deny the need; it denies the combination of resistance heat and on-peak summer operation, which is the most expensive way to meet it at the worst possible time for the grid.
Evaporators: motors, fans and static pressure
Evaporator fan motors under 1 horsepower must be electronically commutated, or reach a minimum motor efficiency of 70 per cent. Multi-compressor systems require variable-speed fans. And the applied static pressure drop across evaporators shall not exceed 0.5 inches of water.
That last figure is a coil selection constraint rather than a control setting. It cannot be commissioned in later — it is decided when the equipment is chosen.
Condensers: three specific limits
Air-cooled condenser fin density must be no greater than 10 fins per inch. The minimum condensing temperature setpoint must be 70°F or lower. And all condenser fans must be continuously variable speed.
The fin density limit reads oddly until you consider maintenance: tightly packed fins foul and are hard to clean, so a condenser that looked efficient on paper degrades in service. The condensing temperature limit forces the system to take advantage of cool nights instead of holding a fixed high head pressure year-round.
Five acceptance tests can apply
Refrigerated warehouses carry the heaviest acceptance testing in the covered process family: evaporators and fan motor controls, evaporative condenser controls, air cooled condensers, variable speed screw compressors and underslab heating each have their own NRCA-PRC form. Evaporator fan motor controls are tested to the procedure in NA7.10.2.
All of them carry the -F suffix, so a field technician may perform them — no certified acceptance test technician is required for covered process work.