APPLICATION
VRF

Swegon can easily integrate a VRF refrigerant coil module to the supply air side of the cabinet. The outside air is first conditioned by the Swegon energy recovery wheel and then this air is further conditioned by the VRF coil. The VRF coil can be used for DX cooling only, or for heat pump applications (heating and cooling). Swegon electronic controls are advanced and flexible which allows for easy integration with the VRF controls and sequences.

Since the Swegon energy recovery wheel is so efficient, it does a significant portion of the sensible and latent cooling of the outside air (see chart above). This high efficiency wheel translates into a “high capacity wheel”, allowing the VRF condensing tonnage to be reduced which significantly decreases the installation cost. Also, in the heating mode, the Swegon high efficiency energy recovery wheel provides safe and warm air temperatures entering the VRF coil. For example: with Outside Air Temperatures of -20F to 0F, the Leaving Air Temperature off the wheel will be in the 50F-60F range meaning that the VRF heating coil will see entering air temps of 50F to 60F. This is all done with no pre-heating of the air before it enters the Swegon energy recovery wheel.

If reheat is needed to provide neutral air to the space during cooling mode, Swegon can easily package differing methods of reheat. A reliable, cost-effective, and functional solution is to provide Face and Bypass reheat as shown above. Swegon varies the cooling capacity signal to the VRF condensing unit to provide accurate control of the DX cooling coil to fully cool and dehumidify the air through the coil. A small amount of bypass air (that has been cooled and dehumidified by the energy recovery wheel), mixes with the air coming through the DX coil. This method is very reliable and allows a reduction of the VRF condensing tonnage since not all the air is flowing through the DX coil. This reduction in VRF condensing tonnage provides a installation cost advantage to the customer.

With the Face and Bypass method, the chart above shows the significant capacity of cooling and dehumidification of the Swegon energy recovery wheel. The VRF DX coil performs further cooling and dehumidification of the air. The mixed air temperature is a combination of the bypass air and the air off the VRF DX coil. The Face and Bypass method significantly simplifies the refrigeration system with less controls and sensors, less refrigeration piping, and less refrigeration coils. Also, Swegon’s advanced controls save even more energy with automatic reset of the DX coil leaving air temperature setpoint based upon outside air enthalpy. As outside air enthalpy becomes more moderate, the DX coil leaving air setpoint is relaxed which allows for less compressor run-time. This automatic reset can significantly decrease VRF condensing unit compressor run-time during shoulder months and other moderate times of the year.

Swegon can also provide reheat by using a Wrap Around heat pipe method. Swegon’s modular cabinet allows for easy integration of various types and sizes of wrap around pipes.

With the Wrap Around Heat Pipe application, the chart above again shows the significant portion of cooling and dehumidifying that the Swegon energy recovery wheel performs. The pre-cooling portion of the Wrap Around Heat Pipe provides sensible cooling of the air. The VRF DX coil then provides further cooling and dehumidification of the air. The air is then re-heated with the heating portion of the Wrap Around Heat Pipe. Swegon’s modular cabinet makes the Wrap Around Heat Pipe application a simple and reliable approach to reheating the air.

Swegon can also easily package with a “water cooled” VRF condensing unit. Along with the water cooled VRF condensing unit, the Swegon package can optionally employ a highly intelligent method of reheat called Condenser Water Reheat, shown in the chart above. With Condenser Water Reheat, Swegon controls a water pump and a 3-way mixing valve. By reducing the condenser water flow rate to the condensing unit via the 3-way mixing valve, the condenser water at the VRF unit warms up. This warmer condensing water is then pumped to a hot water coil module in the Swegon unit which provides re-heating of the chilled air coming off the VRF DX coil. This is a very efficient and highly intelligent manner in which to reheat chilled air because heat that would normally get rejected to the condenser water and then through a cooling tower is now being re-directed to reheat the chilled air. This ultimately reduces run-time and capacity of the cooling tower which reduces the building owners installed cost and reduces the owners energy consumption.

The chart above shows how the Condenser Water Reheat conditions the outside air. Again, the Swegon energy recovery wheel performs sensible and latent capacity. The VRF DX coil provides further cooling and dehumidification. Then the hot water coil (Condenser Water Reheat coil) provides the final re-heating of the air to neutral conditions. The Swegon controls makes this an easy integration package.