Description
ICM Controls ICM550 Multi-Functional Defrost Timer — Timed or Manual
The ICM550 is a solid-state defrost time clock for commercial refrigeration (walk-in coolers and freezers). It lets you schedule defrosts in 15-minute increments and end them either on time or by a defrost-termination input. High-capacity relays switch the defrost heaters and condenser-fan/compressor circuits directly, and a simple front panel makes setup fast.
Key Features
Timed or Manual Termination
Run defrosts for a set duration or terminate early via the termination input (“X–N”).
Versatile Scheduling
Adjustable cycle length from 15 minutes to 23 hours 45 minutes in 15-minute steps.
High-Power Relay Outputs
Separate outputs for heaters and fan/compressor, contacts rated up to 40 A (NO) / 30 A (NC) at 240 VAC.
I/O Status at a Glance
Green LED for refrigeration mode, red LED for defrost mode, the control monitors all inputs and outputs.
Drop-in Replacement
“Drag-and-drop” form factor replaces many Intermatic/Grässlin, Paragon, and Precision mechanical defrost clocks.
Weatherproof Version
Order ICM550-ENC for a factory NEMA 4X enclosure that’s easy to mount and lockable.
How the Operating Modes Work
Mode A: During the timed defrost, the load is OFF and the backup (defrost) source turns ON. After the timer expires, the unit returns to normal refrigeration. Use this when replacing controls that open the refrigeration circuit during defrost.
Mode B: During the timed defrost, the load is ON along with the backup source (contact configuration matches those legacy timers). After the timer expires, operation returns to normal. Select the mode to mirror the timer you’re replacing.
Quick Specifications
| Supply voltage / frequency | 120–240 VAC, 60 Hz |
| Relay forms & ratings | SPDT & SPST; NO 40 A @ 240 VAC, NC 30 A @ 240 VAC |
| Defrost timing range | 15 min – 23 h 45 m (15-min increments) |
| Termination input | Short X → N to end defrost |
| Status indication | Green = refrigeration, Red = defrost |
Common Replacements
- Intermatic/Grässlin DT040, DT140, DTAV40/DTAV40M, DT-B, DTMV, DTSX;
- Paragon 8041, 8045, 8047, 8141, 8143, 8145, 8245, 8247;
- Precision 6041, 6045, 6047, 6141, 6145.
- Always verify wiring and contact action when cross-referencing.
Size / Versions
- ICM550 (mechanism only): open-board with bracket; fits many panel enclosures.
- ICM550-ENC: factory NEMA 4X weatherproof enclosure, approx. 8.75″ × 6.50″ × 2.75″
More About the ICM550
Unlock Custom Fan & Defrost Logic
By default, the ICM‑550 restores evaporator fan operation immediately after defrost termination. For professionals looking to delay fan reactivation—allowing coil temperature to normalize and protecting the product load—you can add an ICM‑255 fan delay timer downstream of the fan output.
The ICM‑255 supports both:
On-delay (“delay on make”) to postpone fan start after a defrost
Off-delay (“delay on break”) to continue fan operation post-cycle for air purging
This modular approach gives you precise control over fan behavior—especially valuable in low-temp or humidity-sensitive environments.
Terminal “X” = Field Control at Your Fingertips
The ICM‑550 supports full termination control via Terminal X. Here’s how to use it:
- X → N: Field-terminate defrost instantly for testing or diagnostics.
- Floating X: Defrost runs strictly on the preset time interval.
- F/T Stat to X: Allows temperature-based termination plus optional fan delay via accessory modules.
These wiring options allow for fast adaptation in both new installs and legacy equipment, without changing out main boards.
Installation Tips: Best Practices for Long-Term Reliability
Most issues with “dead timers” or failed defrost advance are tied to install conditions. For long-term performance:
- Ensure the timer motor receives correct line voltage (check N-to-1 power).
- Inspect all terminals for heat damage or mislanded wires before energizing.
- In systems where the timer motor’s neutral path routes through the defrost heater or bi-metal, understand that timer advance may pause between cycles—a normal condition based on circuit design.
