Year round comfort for sustainable Quick restaurants

Quick is a chain of fast food restaurants of Belgian origin, who are currently redesigning their restaurant concept. Among the requirements for new franchises are improved sustainability and reduced energy use, which includes high efficiency air conditioning and heat recovery.

For a new restaurant in Mersch in the Grand Duchy of Luxembourg, Reznor PREEVA air handling units were selected. This series of fully customizable air handlers have a gas fired, closed combustion heat exchanger. PREEVA air handlers are available for natural gas or for propane and exist in indoors versions (SDH, SHH) or outdoors versions (RDH, RHH).

One of the two PREEVA units is an RDH outdoor rooftop unit with a heating capacity of 73 kW and a standard thermal efficiency of 91% (net calorific value). For this installation, an optional heat recovery section was integrated in the PREEVA RDH. The cross flow heat exchanger in the heat recovery section was installed above the hoods in the kitchen, so that the heat from the extracted air can be transferred to the stream of fresh air being brought into the building. In a cross flow heat exchanger, there is no direct contact between the streams of fresh air and extracted air, so that no odours are brought into the premises. With the fresh air pre-heated, less energy is required to bring it to comfort temperature, thereby considerably reducing energy consumption.

This installation also required another PREEVA unit, an RHH with a heating capacity of 55 kW. The difference between an RDH and an RHH is that the RHH's gas fired heat exchanger has an extra section in which flue gases condense, so that the energy contained in the water vapour in the flue gases, is also used. This gives the RHH heat exchanger a thermal efficiency of 102 % (NCV).

For the Quick installation, both the PREEVA RDH and RHH have an optional cooling coil which is connected to a Reznor RZCHA heat pump. The selected RZCHA has a cooling capacity of 95 kW and a heating capacity of 105 kW. However, below certain ambient temperatures, the efficiency of a heat pump in heating mode will not be optimal. For this reason, the controls of the PREEVA units and the RZCHA are set up so that the gas fired heating section of the PREEVA takes over as soon as a set point has been reached. This way, the PREEVA RDH and RHH in conjunction with the RZCHA, will always give the end user the highest heating efficiency, even at low ambient temperatures.

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