STSH Series Product Overview

STSH

The STSH series are single-stage, oil-injected screw air compressors available with either a star-delta starter or an inverter (VFD) starter. The motor drives the screw assembly via a V-belt. All STSH units are controlled by the AirMASTER FORM controller (UL certified). Electrical panels are designed and built to UL 508A and CSA C22.2 No. 14 standards (UL certified: NITW.E532921 & NITW7.E532921).

Key Specifications

Specification	Value
Compressor Type	Single-stage, oil-injected rotary screw
Starter Types	Star-delta or inverter (VFD)
Drive	V-belt (motor to airend)
Cooling	Air-cooled (axial fan); water-cooled optional
Controller	AirMASTER FORM (UL certified)
Min. Ambient Temperature	+33.8°F (+1°C)
Max. Ambient Temperature	+104°F (+40°C)
Max. Operating Temperature	+230°F
Max. Altitude	3,280 ft above sea level
Max. Humidity	80%
Electrical Standards	UL 508A / CSA C22.2 No. 14 (NITW.E532921 & NITW7.E532921)

System Components

Oil System

The oil system consists of the screw assembly, separator tank, spin-on separator element (vertical/upward-flow), thermostatic valve, oil cooler, and oil filter element. A one-way check valve in the scavenge line returns separated oil from the separator element back to the oil circuit. Oil quantity is controlled via an orifice at the screw assembly inlet. If seasonal temperature swings are extreme, contact South-Tek for orifice diameter verification.

▲ Attention In continuous operation at ambient temperatures above +104°F (+40°C), oil entering the screw assembly should be at or above +122°F (+50°C). If the oil is too cold, water vapor will condense in the separator, causing corrosion and oil degradation that can seriously damage the screw assembly.

Cooling System

An axial fan draws cooling air through the cabinet. Hot exhaust air must be ducted to the exterior and must not recirculate to the compressor intake. Duct air resistance must not exceed 50 Pa (5 mm H₂O). The user is responsible for installing the appropriate duct at the hot air outlet.

Suction Control Valve — RB60E Series (NC Solenoid)

▲ Attention — STSH Unique The STSH uses the RB60E suction control valve with an NC (normally-closed) solenoid valve. This is the opposite logic from the STS and STSD/STSP/STSP2 families (which use NA solenoid valves). Do not cross-reference valve behavior or service procedures between model families without verifying the valve type on the unit.

• Loading: When the NC solenoid energizes, it opens. The pressurized air from the separator tank discharges through the suction control valve mouth discharge holes. This allows the suction flap to open and air intake to begin.
• Unloading: When the NC solenoid de-energizes, it closes. The NO valve control air closes. Separator tank air and NO valve control air discharge from the suction valve mouth. The suction flap closes and air intake stops.
• Reloading: When pressure drops to the lower setpoint, the NC solenoid energizes again, reopening the suction flap.
• Auto-stop: If pressure does not reach the lower setpoint during the idle period, the compressor stops. The NC solenoid de-energizes and the NO valve discharges separator tank pressure through the suction valve mouth.

V-Belt Drive

The motor drives the airend via V-belts. Belt tension must be inspected every 2,000 hours. See the V-Belt Inspection & Replacement article for the full procedure. Always replace the complete belt set together and use the same brand and specification on all grooves.

Approved Oil — Lupamat LPM 46 / LPM 68

Property	Lupamat LPM 46	Lupamat LPM 68
Viscosity Class	ISO VG 46	ISO VG 68
Viscosity @ 40°C	46 cst	68 cst
Viscosity @ 100°C	7.2 cst	9 cst
Flash Point	+252°C	+255°C

Check the label on the compressor to confirm which grade is fitted at the factory. Never mix oils.

Optional Features

• Water-cooled heat exchanger: Installed on the oil circuit inside the cabinet. Heats process water using hot compressor oil. Water circuit must be active before first startup. Water quality requirements apply — see section 2.3.1 of the STSH manual.
• Separator tank oil heater (125W): Warms oil in cold weather before startup. Automatically controlled based on oil/air temperature sensor readings. When ambient temperature drops below +32°F (0°C), the compressor control system prevents startup automatically.

Forklift Lifting

STSH cabinet compressors have legs at the base creating a gap for forklift access. Center forks under the cabinet at the designated forklift point. Verify forks pass fully through to the other side before lifting. Never lift by the cabinet sides.

Related Articles

• STSH Maintenance Schedule
• V-Belt Inspection & Replacement
• First Start-Up & Commissioning Checklist
• Safety Precautions & Symbols

For technical support or commissioning, contact South-Tek Systems: [phone] or [e-mail]