7.8 Optional Equipment Piping
7.8.1 Free-Cooling Coil
The free-cooling coil is a secondary coil located downstream of the DX coil. The free-coiling coil does not
operate at the same time as the DX coil. A temperature sensor is factory-mounted to the free-cooling
piping. If the water temperature is less than the set temperature (usually 45°F [7.2°C]), the 3-way valve
opens to allow chilled water flow to the free-cooling coil and the compressor is locked off. If the water
temperature is above the set temperature, the 3-way valve closes (bypasses) and enables the compressor.
To keep deposits from building up in the free-cooling coil, an adjustable timer is factory-set to flush every
400 minutes.
NOTE: If the free-cooling coil is piped to an open water tower, a CU/NI (copper-nickel) type coil must
be ordered to prevent corrosion of the copper tubes; or a heat exchanger must separate the tower
water from the free-cooling loop.
On water-cooled systems, the free-cooling coil outlet can be field piped to the condensing unit inlet,
provided a 3-way regulating valve has been installed within the water/glycol condensing unit (see Figure
7.17 below).
Figure 7.17 Optional free-cooling coil (3-way valve) on water/glycol units
7.8.2 Hot Water Reheat Coil
Building hot water can be piped to a factory-installed hot water reheat coil, located downstream of the
cooling coil. A factory-installed solenoid valve opens upon a call for reheat.
Vertiv | Liebert Mini-Mate2—5 ton User Manual| 52
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