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How to Use a Chiller or Heat Pump Externally

Read all about how to use an Aermec chiller or heat pump externally …

Can a heat pump with reversible water side (WRL, NXW, WWM) be used as reversible heat pump (seasonal changeover heat pump)?

Two types of water cooled units are able to do this:

  1. Heat pumps with reversible water side (often called water cooled chiller)
  2. Heat pumps with reversible refrigerant side

Heat pumps with reversible water side are conventionally used for cooling only applications. Heat pumps with reversible refrigerant side can be used for cooling operation during summer and heating operation during winter by reversing the operation with reversing valve on the refrigerant circuit. To differentiate between these two types, heat pumps with reversible water side are called water cooled chillers and heat pumps with reversible refrigerant side are called water cooled reversible heat pumps.

Can heat pumps with reversible water side unit be used as reversible heat pumps?

Yes, heat pumps with reversible water side (sometimes referred to as a chiller) can be used as a seasonal changeover heat pump. Some modifications on the hydraulic circuit must be made in order to use this model/version as heat pump.

The unit allows the management of both hydraulic circuits: condenser and evaporator. Therefore, it could be used as chiller or heat pump. The commutation between chiller and heat pump operation is obtained by managing the hydraulic circuit.

Capture1Modifications need to be made such as installing a few 3-way valve external to the unit.

Capture2

Caution should be used during the winter as the unit on the source side should always operate within the operating envelope.

Capture3Water setpoint limits:

  Description Value
Chiller Minimum Minimum limit set point for the unit in cooling mode 40°F
Chiller Maximum Maximum limit set point in cooling mode 64°F
Heat Pump Minimum Minimum limit set point in heating mode / heat pump mode 77°F
Heat Pump Maximum Max limit setpoint in heating mode 131°F

A variable flow pump is recommended to be installed on the geothermal side. If there are on-off pumps with 3 speeds, the modulating valve should be installed in order to regulate head pressure. Unit controller can control this modulating valve by 0-10V output. The modulation of the geothermal side flow rate is used to stabilize the condensing pressure. In heat pump mode/heating mode with head pressure control the opening of the valve or the speed of the inverter pump is fixed.

The unit controller controls the return water temperature of the system, or the outlet temperature (adjustable parameter). The control is divided between hot water production (winter), and cold-water production (summer).

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Aermec is distributed by Master Distributor Mits Airconditioning Inc. in North America