3.3.5 Door Limit Switch Optional limit switch to indicate when a door is open on the booth. If a door is in the open position, micro switch contact is opened which breaks the circuit for the paint air solenoid. 3.3.6 Air Makeup Unit (Optional) The air makeup unit (AMU) supplies filtered, heated atmospheric air. This unit may be heated by natural gas, LP gas, steam coils or hot water coils. The temperature of the AMU discharge air is controlled by a temperature controller. The airflow capacity of the fan and motor are matched to the airflow capacity of the spray booth exhaust fans. Some air makeup units also have the capability to provide a paint cure cycle. This cycle, employed after the paint spraying operations are complete, typically involves supplying air that is heated to the paint area of the booth to decrease paint cure times. 3.4 Exhaust Filter Manometer Manometer is used to measure pressure drop across exhaust filters to indicate the condition of the filters. 3.5 Air Solenoid Valve The function of this valve is to interrupt supply of compressed air to painting equipment under certain conditions. This is done to prevent painting from occurring when the booth is not operating as designed or if any booth doors are open. The air solenoid valve is electrically interlocked with booth intake and exhaust fans. If optional switches are purchased, it is also interlocked with product doors and personnel doors. lf a fan is not operating properly, or if a door is open, the air solenoid valve will shut off flow of pressurized air to spray gun. Unit should be installed downstream of any regulators and filters and upstream of painting equipment. It should be located near fitting to which painting equipment connects in order to ensure rapid loss of supply pressure. 3.6 Control Panel The spray booth may be equipped with an optional electrical control panel. Electrical schematics are located inside the control panel. Also shown on this drawing is the wiring required for installation. No spare parts are provided with control panel. Panel and its associated wiring must be installed by a licensed electrician. The cabinet that houses controls is either NEMA 1 or NEMA 12 rated. It is not suitable for installation in a Class I, Division II area. Refer to Chapter 6 in the NFPA 33 Standard and consult with the local authority having jurisdiction for definition of this area for paint spray booth.
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