Relay Specialties, Inc. - Macromatic

To protect the environment and provide safe water, municipalities rely on treatment plants, pumping stations, lift stations and water towers. Mile of underground infrastructure supply, collect and treat water. Gravity pipelines augmented by lift stations move wastewater through the system. In these applications, industrial controls and relays monitor and protect the pumps and compressors in the systems.

Macromatic Relays Used For Water and Wastewater Management

Alternating relays equalize run times on multiple pump systems.
Time Delay Relays have built-in timing to control automated operation.
Three-Phase Monitor Relays protect equipment from damage due to voltage faults.
Intrinsically Safe Barrier Relays protect circuits and control loads in hazardous locations.

Manufacturers of HVAC equipment use relays to protect and control critical system components. The correct sequencing and timing of fans, blowers, condensers, pumps, and compressors ensures efficient and safe operation. Relays also protect the motors in these systems from adverse conditions providing reduced downtime, lower operating costs, and extended life.

Common Challenge

Lift stations with duplex pump control are used in municipal and commercial wastewater systems throughout the United States. Their operation is critical, raising wastewater to a higher elevation to continue its flow to the treatment facility. The simplicity of alternator-based relay control makes the systems easy to maintain for decades. One issue with lift stations, however, is power outages caused by storms that can shut-down the system. This sequence of events is the last thing wanted:

Water continues to flow into the well, potentially becoming close to full.
The level controller (floats, level sensors, etc.) then calls for both pumps to run.
When power is restored both contactors start in unison.
The inrush current of normal induction motors causes the main breakers to trip.

The Macromatic Solution

If a lift station fails, wastewater can back up into nearby homes and businesses and overflow into the surrounding environment. A Macromatic Time Delay Relay provides a simple solution to avoid tripping the main breakers. By setting the timer to the ON DELAY – TIMED AND INSTANEOUS function, the start-up of the second pump can be delayed.

The instantaneous relay function is wired to the first motor starter, and the timed relay function is wired to the second motor starter. With that time delay set to 10 seconds, the lift station restarts only one pump, with the other pump starting ten seconds later. As a result, the circuit breakers will not trip when power is restored.

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