INTRODUCTION

Three-input BE3 temperature relays use resistance

temperature detectors (RTDs) to monitor remote

temperatures. When any of three monitored temperatures

exceeds a preset limit, the corresponding relay output

operates. A dc metering output indicates the highest

temperature of the three RTDs. BE3 temperature relays are

available for use with 10 Ω copper or 100 Ω platinum RTDs.

OPERATION

Three temperatures are monitored through RTDs connected

at the nine-position front panel connector. RTD connections

are labeled A, B, and C. Three user-adjustable controls are

located on the front panel: SET 1. SET 2. and SET 3. Each

setpoint is adjustable from 50 to 100% (±3%) of the RTD

temperature range. When a setpoint is exceeded, the

corresponding TRIP LED lights and the relay output

energizes. Each RTD has a corresponding LED to identify

which RTD has exceeded the temperature setpoint. For

example, if the temperature of RTDs B and C exceeds the

trip level, the B and C TRIP LEDs light and the relay output

energizes. A green LED labeled AUX indicates the power

supply status. Figure 1 illustrates the BE3-49R controls,

indicators, and terminals.