Mercoid Controls — Electronic Alarm
Mercoid Series EDA
Electronic Differential Alarm Controller
Dual relay outputs • 4–20 mA input • Adjustable setpoints & deadband • NEMA 4X • UL/CSA
Overview
The Mercoid Series EDA is an electronic differential alarm controller designed to accept a standard 4–20 mA process signal and provide dual relay outputs for independent high and low alarm setpoints. Each relay has its own independently adjustable deadband (differential), eliminating nuisance trips caused by process fluctuation near the setpoint.
The Series EDA is the electronic complement to Mercoid’s mechanical pressure and level switches, providing the flexibility of a transmitter-based system with the simplicity of a dedicated alarm controller. LED indicators for power, high alarm, and low alarm status provide at-a-glance process monitoring without requiring a separate display.
Available in 24 VDC and 120/240 VAC supply versions, with NEMA 4X standard enclosure and an explosion-proof NEMA 7/9 option for Class I, Division 1 hazardous locations. DIN rail or panel mount installation suits both control panel and field-mounted applications.
Key Features
- Electronic differential alarm with adjustable setpoints
- Dual relay outputs for high and low alarm service
- LED indication for power, high alarm, and low alarm status
- Compatible with 4–20 mA transmitter inputs
- Field-adjustable deadband (differential) on each setpoint
- NEMA 4X enclosure standard; explosion-proof option available
- DIN rail or panel mount installation
- Wide supply voltage range: 24 VDC or 120/240 VAC
- Relay contacts rated 5A @ 120/240 VAC, SPDT
- UL and CSA listed
Specifications
| Parameter | Value |
|---|---|
| Input Signal | 4–20 mA (2-wire or 3-wire transmitter). |
| Supply Voltage | 24 VDC ±10% or 120/240 VAC, 50/60 Hz (specify). |
| Power Consumption | 5 VA maximum. |
| Relay Outputs | Two SPDT relays (High Alarm, Low Alarm). 5A @ 120/240 VAC resistive. |
| Setpoint Range | 0–100% of input span, independently adjustable. |
| Deadband (Differential) | 0.5–10% of span, independently adjustable per relay. |
| Response Time | < 100 ms. |
| Indication | LED: Power (green), High Alarm (red), Low Alarm (amber). |
| Enclosure | NEMA 4X standard. Optional NEMA 7/9 explosion-proof. |
| Mounting | DIN rail (35 mm) or panel mount. |
| Operating Temperature | –20 to 60°C (–4 to 140°F). |
| Electrical Connections | Screw terminal, 12–22 AWG. |
| Conduit Connection | 1/2″ female NPT (explosion-proof model). |
| Agency Approvals | UL, CSA. |
Typical Applications
Level Alarms
High and low level alarms on tanks and vessels using submersible or float transmitters.
Pressure Monitoring
Dual-setpoint pressure alarms on process lines with 4–20 mA pressure transmitters.
Flow Alarms
Low-flow and high-flow alarms using differential pressure or magnetic flowmeter outputs.
Temperature Alarms
Over-temperature and under-temperature alarms with RTD or thermocouple transmitters.
Pump Protection
Dry-run protection and high-pressure cutout for pump systems.
Boiler Monitoring
Steam drum level alarms in conjunction with Mercoid float level transmitters.
Popular Models
| Model Number | Description |
|---|---|
| EDA-1-24DC | Electronic differential alarm, 24 VDC supply, NEMA 4X enclosure. |
| EDA-1-120AC | Electronic differential alarm, 120 VAC supply, NEMA 4X enclosure. |
| EDA-1-240AC | Electronic differential alarm, 240 VAC supply, NEMA 4X enclosure. |
| EDA-1-24DC-XP | Electronic differential alarm, 24 VDC supply, explosion-proof NEMA 7/9. |
Custom configurations available. Contact Northeast Controls for special requirements.
Mercoid Series EDA
Electronic Differential Alarm