Using a 16M Direct Acting Relay for Pump Up or Pump Down

The 16M relay is one of the most common relays used for level control. It can be used to control a single level or a differential. Typically when working with differential level service, a direct acting relay is used for “pump down” or “drain” applications, and an inverse acting relay is used for “pump up” or “fill” applications. Direct acting relays are more commonly sold in comparison to inverse acting relays, but because the relay has both a normally open and a normally closed contact, a direct acting relay is capable of being used for either “pump up” or “pump down” service.

“Pump Up” Example:

In the example shown above, the direct acting relay is wired for a “pump up” application. While the media level is below the high level probe, the relay is not energized, but because the normally closed contact is closed, it will call for the pump to operate and raise the media level. When the media level reaches the high probe, the relay becomes energized and opens the normally closed contact, shutting off the pump. The relay remains energized until the media level falls below the low probe at which time the relay is deenergized and the normally closed contact becomes closed again, causing the pump to operate and raise the media level.

“Pump Down” Example:

In the example shown above, the direct acting relay is wired for a “pump down” application. While the media level is below the high level probe, the relay is not energized, and because the normally open contact is open, the pump will not operate. When the media level reaches the top probe, the relay becomes energized and the normally open contact becomes closed, causing the pump to turn on and lower the media level. The relay remains energized until the media level falls below the low probe at which time the relay is deenergized and the normally open contact becomes open again, stopping the pump from draining the tank.