Heat-Timer® Corporation

PLL (Pump Lead-Lag Control)

Pump Lead-Lag Control for 2 and 3-Pump Systems


The PLL control is a lead pump rotation control. It operates in multiple modes that satisfy many single or multiple pump applications. It is designed to run and power up to three pumps. In addition, it connects to flow switches to check for pump flow and activate the alarm outputs when needed.

Rotation: The PLL offers three different system pump rotation modes that include flow checking and alarming. The PLL has built-in lead pump timed rotation and alternate rotation. The timed-rotation offers two options, 1 day and 7 days rotation. :

  • 2-Pump 1-Call/1-Flow
  • 2-Pump 2-Call/1-Flow (VFD Pumps)
  • 3-Pump 1-Call/1-Flow

Boiler Feed Systems: In this mode, the PLL operates boiler pumps in a two-boiler system. An auxiliary pump is used to replace any failed boiler pump. The PLL will also activate a solenoid valve to direct the flow to the newly activated pump.

Alarm and Flow Check: The PLL changes the lead pump on flow failure. In addition, it triggers the pump’s alarm and excludes that pump from rotation and activation until the Alarm Reset is pressed.

Pump Exercise: The PLL can be used to lubricate seals on wet seal pumps and prevent pump seizure after long inactive periods. It does that by running any pump for a few seconds if that pump was inactive for an extended period.

PLL (Pump Lead-Lag Control) 926825-00
Vis-U-Larm 925011-00

Connected the control to power correctly but no display or LED is on.
Most controls are equipped with a fuse on the back of the main board to help protect the control against power surges. Check the fuse on the back of the control using a continuity meter. If continuity does not exist, replace the fuse with the same fuse size and rating.

Related Products