Model 21M 3-Phase Monitor (Manual Reset, 190-480 VAC)
The Model 21M 3-Phase Monitor provides essential protection for industrial systems. Operating across a 190-480 VAC range, this device detects critical conditions including phase loss, phase reversal, over/under voltage, and voltage unbalance. Its manual reset functionality ensures controlled system restarts after a fault, preventing automatic re-energization until inspected. Users can adjust trip delay times for over, under, and unbalance conditions from 1-30 seconds, allowing for application-specific tuning to minimize nuisance trips. The unit also features a restart delay adjustable from 1-500 seconds. With a compact design (2.98" L x 1.77" W x 2.45" H) and a 5-year unconditional warranty, the Model 21M offers reliable performance and system integrity. It is compatible with both Wye and Delta systems, requiring no neutral connection, simplifying installation.
Universal 3Ph Monitor
Specifications
| Model Type | Manual Reset |
|---|---|
| Operating Voltage | 190-480 VAC |
| Power Consumption | 3.7W at 480V |
| Auto Ranges | Yes |
| Monitored Conditions | Phase Loss, Phase Reversal, Over/Under Voltage and Voltage Unbalance |
| Frequency | 50/60Hz |
| Type of Measurement | RMS |
| Under Voltage Trip | 90% ±1% (% of setpoint) |
| Under Voltage Reset | 93% ±1% (% of setpoint) |
| Over Voltage Trip | 110% ±1% (% of setpoint) |
| Over Voltage Reset | 107% ±1% (% of setpoint) |
| Voltage Unbalance Trip | 2-8%, adjustable (conforms to NEMA) |
| Voltage Unbalance Reset | Trip setting minus 0.7% |
| Trip Delay Time (Over, Under, & Unbalanced) | 1-30 sec., adjustable |
| Trip Delay Time (Single-Phasing Faults Unbalance > 15%) | 1 sec., fixed |
| Trip Delay Time (Reverse Phase) | 1 sec., fixed |
| Restart Delay | 1-500 sec., adjustable |
| Manual Reset Input | 5V open circuit/500µA short circuit |
| Output Contacts | SPDT 10A at 240VAC resistive |
| Operating Temperature | -20° to +140° F |
| Humidity Tolerance | 0-97% w/o condensation |
| Enclosure Material | Noryl plastic |
| Mounting | 8-Pin Socket (**sold separately) |
| Recommended Socket | 51x120 |
| Additional Options | /SG = Silver with Gold Flash Contacts |
| Agency Approval | UL Recognized (U.S. and Canada) (For use in a Pollution Degree 2 Environment) |
| Neutral Connection | Not required |
| System Compatibility | Wye or Delta systems |
| Recommended Fuse | 1A 600VAC |
| Warranty | 5-year Unconditional Warranty |
