Roth Southeast Variable Pumping


  • In a condenser water heat pump system, the heat in the building is rejected into the condenser water that is pumped to each heat pump.
  • The heat is then carried in the water to the cooling tower where the heat is rejected to the atmosphere through the cooling tower.
  • In a typical design, from 5 years ago or older, the pumps that moved this water through the system were constant volume. Constant volume means that water is pumped through every unit, even if it is not running.
  • A unit will have approximately 3 gallons of water per minute per ton of air conditioning pumped through it.
  • New technology, with variable frequency drives and controls, allow us to more efficiently control this water flow. Pumping water consumes horse power (i.e. electricity). New variable speed pumping systems reduce the water pumped though the system by using a control valve that stops the water from flowing through a unit that is
    not operating.
  • A typical unit that is sized properly would only need to run 2/3rds of the time. In addition to this, condo/ apartment/ hotel buildings tend to have people that are away or at work for long periods of time where the systems will have even less run time.
  • Another common issue at these types of buildings is that the system is actually over pumping or pumping more than is required. This new type of control allows you to also get energy savings by controlling this condition
    as well.
  • The variable pumping system uses the existing pumps, but slows them down so they pump less water.
  • By pumping less water, the motor consumes less horsepower.
  • Typically these pumps run 24/7, so reducing the horsepower by just one horsepower is an annual savings of $525. In addition, the slower these pumps run, the less wear there is on the pump seals and bearings.

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