volts motor controls, switches, wiring, accessories, and motor controllers,
in a UL listed NEMA 250, Type [1] [4] enclosure. Tank-mounted air
compressors shall be manufactured to comply with UL listing requirements.
Air compressors shall have manufacturer's name and address, together with
trade name and catalog number, on a nameplate securely attached to the
equipment. Each compressor shall [start and stop automatically at upper
and lower pressure limits of the system] [regulate pressure by constant
speed compressor loading and unloading] [have a "manual-off-automatic"
switch that, when in the manual position, the compressor loads and unloads
to meet the demand and, in the automatic position, a time delay relay
allows the compressor to operate for an adjustable length of time unloaded,
then stops the unit]. Guards shall shield exposed moving parts. Each
duplex compressor system shall be provided with [automatic alternation
system] [manual alternation system]. Each compressor motor shall be
provided with an across-the-line type magnetic controller, complete with
low-voltage release. An intake air filter and silencer shall be provided
with each compressor. Aftercooler and moisture separator shall be
installed between compressors and air receivers, to remove moisture and oil
condensate before the air enters the receiver. Aftercoolers shall be
either air or water cooled, as indicated. The air shall pass through a
sufficient number of tubes to affect cooling. Tubes shall be sized to give
maximum heat transfer. Water to unit shall be controlled by a solenoid or
pneumatic valve, which opens when the compressors start and closes when the
compressors shut down. Cooling capacity of the aftercooler shall be sized
for the total capacity of the compressors. Means shall be provided for
draining condensed moisture from the receiver by an automatic float type
trap. Capacities of air compressors and receivers shall be as indicated.
2.17.2
Medical Compressed Air (Oil-Free Type) Compressors
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NOTE: Oil-free air is required for dental
operatories and operating, delivery, and recovery
rooms. Quantities of air required will be
determined by procedures in TM 5-838-2 or AFM 88-50.
Oil-free compressors will be sized so that the
total air supplied by all units will not exceed 120
percent of the normal air requirement as determined
by TM 5-838-2. Multiple compressors of the 6 to 7.5
kW (7-1/2 to 10 horsepower) range are suggested, in
lieu of the larger power range of 15 kW (20
horsepower) or greater to provide more flexibility.
Generally, the pressures required at the installed
equipment or point of usage are as follows: Dental
operatories, 552 kPa (80 psig); operating, delivery,
and recovery rooms, 345 kPa (50 psig); laboratory
deck or counter-mounted service fixtures, 207 kPa
(30 psig). Reciprocating type air compressors
should be avoided, except in foreign or desert
applications. Delete references to this type of
compressor where not utilized. Refer to ETL
1110-3-379 dated 30 November 1987 for requirements
for compressed air and vacuum systems for dental
facilities.
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Compressors shall have the capacity indicated. Compressor shall be
[centrifugal] [or] [liquid-sealed rotary type] [or] [reciprocating
teflon-ring type designed so that no oil is administered to the air
SECTION 15405A
Page 57
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