PAK’nSAVE – OPA 2100 Humidity Intelligence

PAK'nSAVE Wairau Road in Glenfield was opened on 3rd May 2009. In 2019 the store was looking to undertake the replacement of their existing air conditioning system, two Temperzone R410a refrigerant rooftop package units. As part of Foodstuffs North Island Ltd, they adhere with a wider initiative to reduce their carbon footprint while installing more energy efficient systems. Along with HVAC system upgrade, PAK’nSAVE Wairau Road was also looking to upgrade to Trans-critical CO2 refrigeration systems and energy efficient lighting solutions to reduce overall energy consumption and reduce carbon emissions.

The HVAC solution needed to maintain consistent humidity levels, typically around 50% RH, 22 DB, to keep glass cases clear and to avoid using excess energy by adding load to the refrigeration cases. Older refrigeration cabinets can require extra defrost which results in reduced cooling, has the potential to spoil product and produce condensate which could result in floor slippage. Effectively maintaining consistent humidity levels can avoid these issues.

Fonko NZ, HVAC Mechanical and Trans-critical CO2 Commercial Refrigeration specialists, wanted to use Temperzone’s new OPA2100 humidity intelligence systems to meet the humidity control and energy efficiency requirements of this project. To meet the low GWP requirement for this project Fonko engaged Temperzone to develop our first R32 refrigerant OPA2100 system. R32 has a GWP (675) which is less than a third of the currently used refrigerant R410A (GWP of 2,088). The R32 unit also required less refrigerant charge than the R410a version which resulted in an overall reduction of GWP of around 75% per kW of cooling.

Two OPA2100 units were commissioned in late 2019, these were among the very first commercial R32 products installed in the NZ market. Each with a capacity range of 15 ~ 200kW, equipped with 4 independent refrigeration systems featuring inverter compressors and EC fans, they are specifically designed to target dew point temperature. Dew point is the temperature to which air must be cooled in order to produce condensation (dew). It represents how much moisture is in the air: the higher the dew point temperature, the greater the atmospheric moisture content. Traditionally air conditioning is controlled solely on temperature however the OPA 2100 is unique as it also focuses on moisture content in air leading to precise cooling applications. The OPA2100 has been designed to control the room conditions with an innovative focus on humidity. By considering the humidity levels, the space temperature can be maintained in the most efficient way.

Utilising four independent systems allows precise control over the temperature as well as moisture levels of the air being supplied. The unit controller compares the customer setpoint for heating and cooling as well as the required RH% with the current room conditions which in turn automatically activates the specific control mode. The on-board controller calculates the dew point and then ramps the inverter compressor to control the indoor coil temperature in order to remove moisture only when required.

The OPA2100 uses precise evaporator control, when latent removal is required, each individual inverter is controlled so that the evaporating temperature is below the dew point. During cooling if the space doesn’t call for moisture removal compressor speeds are reduced which results in reduced power input to cool the space.

The control offers a unique approach based on an intuitive algorithm that adjusts compressor speeds as the room load changes. This approach plays perfectly to part load efficiencies by drastically reducing the energy demand on the building and improving comfort conditions due to curbing out extreme high and low temperature fluctuations when a unit is running to meet the target setpoint.

The units feature heat reclaim water coils to be connected to the refrigeration chillers. With the upgrade to new Trans-critical CO2 refrigeration systems, the heat reclaim coils will utilise the reject heat for the first stage of heating.

Economisers were installed for ventilation and economy cycle to reduce power input when outdoor conditions are favourable.

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