The Honeywell 51120841-101, also cataloged as the 51120841 SPDT Control Relay, operates as a dedicated hardware component for physical circuit isolation and load switching within industrial control systems. This MR series assembly establishes electromechanical contact switching pathways to route pilot-duty signals and power circuits based on external control voltage commands.
Hardware Specifications
Parameter
Specification
Model
51120841-101
Brand
Honeywell
Series
MR Series
Origin
United States
Weight
0.2 lbs (0.09 kg)
Dimensions
2 in x 2 in x 1.5 in (5.08 cm x 5.08 cm x 3.81 cm)
Operating Temp
Standard industrial control enclosure environmental limits
Product Type
Electromechanical Control Relay
Contact Arrangement
SPDT (Single Pole, Double Throw), Form C execution
Contact Current Rating
10 A maximum resistive load handling
Coil Control Voltages
Multi-voltage input pins: 24 V AC/DC, 115 V AC, or 230 V AC
DC Operating Range
18 to 30 VDC continuous coil activation limits
Status Indicator
Integrated red LED (Illuminates upon active coil energization)
Mounting Configuration
Integrated hardware for DIN-rail or flat panel mounting
Process Control Instrumentation and DCS Communication
The control relay acts as a robust physical isolation barrier between sensitive low-voltage microprocessors and high-voltage field actuator elements. When integrated alongside digital outputs from a distributed control system, the module isolates the logic card from inductive back-EMF spikes generated by large solenoids or motor starters.
Frequently Asked Questions
Q: How does the multi-voltage coil terminal configuration operate without causing internal short circuits?
A: The relay frame utilizes separate, dedicated physical terminal pins for each specific control voltage rating (24 V AC/DC, 115 V AC, and 230 V AC). Electrical wiring must only be terminated to the single target voltage pin and common neutral/ground pair required for the application; energizing multiple coil input pins concurrently will destroy the internal coil windings.
Q: What is the mechanical state of the SPDT contacts when control power is lost to the module coil?
A: The SPDT contact array utilizes a spring-return Form C architecture. Upon a total loss of coil control voltage, the internal armature immediately returns to its de-energized state, opening the Normally Open (NO) circuit path and closing the Normally Closed (NC) circuit path to execute a predictable fail-safe state.
