Heat recovery occurs when we extract the heat from a chiller to use in an application rather than wasting or dumping it outdoors or into a geoloop. Heat recovery is available with air to water units as well as water to water units. If a building has a cooling load and a heat recovery chiller we will use heat recovery any time there is a call for heating and cooling at the same time. This is free heating which provides tremendous energy savings and greatly lowers the carbon footprint as fossil fuels are not used to produce the hot water anytime we are using heat recovery.
Heat recovery is available in different capacities typically 25-40% or 100%. 25-40% is called a desuperheater and 100% is called total heat recovery. Heat recovery is only available when there is a cooling load and there is a call for heating at the same time. It is heat recovery not simultaneous heating and cooling as some manufacturers call it, as there are units that can provide true simultaneous heating and cooling with any amount of heating and any amount of cooling whenever you need it. When there is a call for both the simultaneous unit will provide heat recovery.
A simple example is a 100 ton chiller with desuperheater. When the chiller is providing 100 tons of cooling the desuperheater will provide 40 tons or 480,000 Btus of free heat. If the load drops to 50 tons the amount of heat recovery from the desuperheater drops to 20 tons or 240,000 Btus. If the chiller has no cooling load there is no heat recovery available, so no cooling no heating. The same is true for 100% heat or total heat recovery, as the load on the chiller drops the amount of heat recovery drops proportionally. A true simultaneous unit will allow you to have up to 100% heating even if there is no cooling.
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