ICM401A – PHASE LOSS AND REVERSAL MOTOR PROTECTOR (LOW CONTROL VOLTAGE)

ICM Controls 3-phase line voltage monitor that continuously watches a 180-600 VAC three-phase line for phase loss and phase reversal, with unbalance monitored as a percentage of input voltage. It uses 24 VAC control voltage wired to the Y and C terminals; when all conditions are in range a green LED lights and Y-OUT is energized. On a phase loss or reversal a red fault LED lights and Y-OUT de-energizes, re-energizing automatically once the fault clears. Cutting the on-board jumper sets it for 50 Hz operation.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• Function3-phase monitor - loss, reversal, unbalance
• Line voltage180-600 VAC
• Control voltage18-32 VAC (24 VAC to Y and C)
• Frequency50/60 Hz (jumper cut for 50 Hz)
• OutputRelay, SPST
• Contact rating6 A N.O. @ 32 VAC max
• ResetAutomatic once fault clears
• IndicatorsGreen = OK, red = fault
• ConstructionEpoxy coated
• Dimensions1" H x 3" W x 3.25" L
• Cross-reference (Supco)TPMP2
• Cross-reference (Mars)32536

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• 401A

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

Where does an HVAC surge protector go?

Hardwired at the outdoor disconnect, on the line side, not the load side. Line side keeps it working even when somebody pulls the block for service. Leads land in parallel across L1 and L2 with the green on the ground lug, and keep them short and straight, because extra length adds inductance and slows the clamping response. Shut off the breaker and pull the disconnect before you open the box.

What ratings should I look at?

Two numbers. Surge current capacity in kA is how much energy it can soak up before it is used up, and 25kA to 50kA per mode is a reasonable residential range. Voltage protection rating is what it lets through, and lower is better. Then look for a status light. Green means the metal oxide varistors are intact. Dark, red or amber means they are spent and the device is now just a box on the wall.

Do I really need one in Dallas?

More than most places. DFW gets spring and summer storm activity plus heavy grid load across a cooling season that runs March into October, and utility switching transients come with that territory. An inverter or communicating system with a variable speed board is far more sensitive to transients than an old single-stage unit, and one of those boards runs several hundred dollars against a protector that costs a fraction of it.

Will it protect against low voltage or brownouts?

No, and that is the myth worth killing. A surge protective device clamps spikes going up. It does nothing about sagging voltage, single phasing, rapid short cycling or a welded contactor. Those call for a line voltage monitor or a compressor protection module, which is a different part on different terminals.