The Hoffman Controls 903-S120/277 three Phase SCR Controllers are designed to function as a Master/Slave system. The Master or Slave will be identified as either a two triac (902 Series) or three triac (903 Series) Controller, which may be connected in the line or inside the Delta or Wye respectively. The Master Controller includes a multiple input Logic that is capable of driving up to 18 902-Series or 12 903-Series SCR Controls. (Consult factory for applications requiring more circuits.) Each three phase Master or Slave requires a separate three phase circuit connected to its specific KW load. Additional circuits (loads) require slaves only. Only one Master is required for each thermostat input. Each three phase Master or Slave Controller may be connected up to the maximum current or KW load described in Table-1. The proportional 24V AC control circuit, when energized, provides “zero firing” of line voltage phases. This feature suppresses Radio Frequency Interference (RFI). The Controllers consist of a “zero firing” line voltage load circuit section, with a 28 Amp maximum rating. A 901-D Series Logic is mounted atop the heat sink to accommodate the multiple input signal wiring for driving the master
Power Switch Section:
Each Master or Slave Controller is built with a separate line voltage “zero firing” crossover at each triac. The crossover logic is independent of the low voltage 901-D Series Logic. The 24V AC proportional output is factory wired on Masters to each “zero firing” power switch contained within the extruded aluminum heat sink. The power switch section may contain two or three “zero firing” triac circuits depending on the model selected. Each triac circuit of the Master or Slave is rated at 28-amps maximum. Selecting a two or three triac Controller allows the flexibility of matching the Controller to a three phase circuit. Additional three phase loads may be controlled by paralleling Slave Controller circuits as required.
Hoffman Controls 903-S120/277 Features:
- Factory wired and assembled three phase Controller.
- 28 amps maximum rated triac circuit.
- Optional two or three triac power switch.
- Separate low voltage logic externally mounted.
- 901-D accepts multiple input signals.
- 901-DP pneumatic input directly accepted by “on board” transducer.
- All inputs factory calibrated.
- “Zero firing” contactor applications (RFI).
- 48 amp/line rating (Max. approved by U.L.) (See Table 1).
- Compact modular design
Hoffman Controls 903-S120/277 Specifications:
- 902 or 903 – Master
- 902-S or 903-S – Slave
- Current, Max./Triac Circuit – 28 Amps
- 902 Series (Master or Slave) – 2
- 903 Series (Master or Slave) – 3
- 902 or 903 Series – 120/277 – 120V
- 902 or 903 Series – 120/277 – 208/240V
- 902 or 903 Series – 120/277 – 277V
- 902 or 903 Series – 347/480 – 347V
- 902 or 903 Series – 347/480 – 480V
- 902 or 903 Series – 600 – 600V
- Voltage Limitations – +10%, –15%
- Heat Sink – 50°C (120°F)
- Control Panel – 75°C (167°F)
- Voltage input – 24V AC
- Voltage output – 24V AC
- Power 902 Series – 4.0 VA
- Power 903 Series – 6.7 VA
- Terminal Blocks – 30 Amps
- Max. Wire Size – #10 A.W.G.
Dimensions (L x W x H)
- 902 Series – 8” x 5.75” x 4”
- 903 Series – 12” x 5.75” x 4”
U.L. Recognized – File #E47100
C.S.A. Certified – 95430