SECTION 2
®SULLAIR®
8
3700 Operator’s Manual and Parts List
2.2 DESCRIPTION OF COMPONENTS
Refer to Figure 2-1 and Figure 2-2. The components 
and assemblies of the air compressor are clearly shown. 
The complete package includes compressor, electric 
motor, starter, compressor inlet system, 
compressor discharge system, compressor 
lubrication and cooling system, capacity control 
system, microprocessor controller, aftercooler, a 
combination separator and trap, all mounted on a 
heavy gauge steel frame. 
On air-cooled models, a fan draws air into the enclosure 
over the fan and main motors through the combined 
aftercooler and fluid cooler thereby removing the 
compression heat from the compressed air and the 
cooling fluid, and forces it out the top of the machine. 
On water-cooled models, a shell and tube heat 
exchanger is mounted on the compressor frame. Fluid is 
piped into the heat exchanger where compression heat 
is removed from the fluid. Another similar heat 
exchanger cools the compressed air.
Both air-cooled and water-cooled versions have easily 
accessible items such as the fluid filter air/oil separator 
and control valves. The inlet air filter is also easily 
accessible for servicing. 
2.3 SULLAIR COMPRESSOR UNIT, 
FUNCTIONAL DESCRIPTION
Sullair air compressors feature the Sullair compressor 
unit, a single-stage, positive displacement, flood 
lubricated-type compressor. This unit provides 
continuous compression to meet your needs.
The 3700 Series compressors are factory-filled with 
Sullube lubricant. For more information on fluid fill, 
consult Section 3, SPECIFICATIONS.
Sullair 24KT compressors are filled with a fluid that 
rarely needs to be changed. Use only Sullair 24KT fluid 
in the event that a fluid change is required.
Sullair recommends that a 24KT sample be taken at the 
first filter change and sent to the factory for analysis. 
This is a free service. The sample kit with instructions 
and self-addressed container is to be supplied by your 
Sullair dealer at start-up. The user will receive an 
analysis report with recommendations.
Fluid is injected into the compressor unit hoses and 
mixes directly with the air as the rotors turn, 
compressing the air. The fluid flow has three basic 
functions: 
1. As coolant, it controls the rise of air temperature 
normally associated with the heat of compression.
2. Seals the clearance paths between the rotors and 
the stator and also between the rotors themselves.
3. Acts as a lubricating film between the rotors allowing 
one rotor to directly drive the other, which is an idler.
After the air/fluid mixture is discharged from the 
compressor unit, the fluid is separated from the 
air. At this time, the air flows through an 
aftercooler and separator then to your service 
line while the fluid is being cooled in preparation 
for reinjection.
NOTE
With a Sullair compressor, there is no 
maintenance or inspection of the internal 
parts of the compressor unit permitted in 
accordance with the terms of the 
warranty.
SU_0000021
CAUTION
Mixing of other lubricants within the 
compressor unit will void all warranties.
SU-0000022