Freeze Protection of Closed Circuit Cooler Coils
The simplest and most effective way of protecting the heat exchanger coil from freezing is to use an inhibited ethylene or
propylene glycol anti-freeze. If this is not possible, an auxiliary heat load and minimum flow rate must be maintained on
the coil at all times so that the water temperature does not drop below 10°C when the cooler is shut down. See Table 6 for
recommended minimum flow rates.
If an anti-freeze solution is not used, the coil must be drained immediately whenever the pumps are shut down or flow stops. This
is accomplished by having automatic drain valves and air vents in the piping to and from the cooler. Care must be taken to ensure
that the piping is adequately insulated and sized to allow the water to flow quickly from the coil. This method of protection should
be used only in emergency situations and is neither a practical nor recommended method of freeze protection. Coils should not
be drained for an extended period of time, as internal corrosion may occur.
When the unit is in operation during freezing weather, some type of capacity control is normally required in order to keep water
temperatures from dropping below 10°C. Operating dry with a remote sump is an excellent way of reducing unit capacity at low
temperatures. Other methods of capacity control include two-speed motors, VFDs and fan cycling. These can be used individually
or in combination with dry/remote sump operation.
Table 6 - Closed Circuit Cooler Minimum Recommended Flow Rate
Closed Circuit Cooler
Standard Flow Series Flow
Footprint
LPS LPS
ATW, eco-ATW & eco-ATWE Products
0,9 m wide units — 1,7
1,2 m wide** 4,7 2,4
2,3 m x 2,6 m 9,4 4,7
2,4 m x 2,7 m to 2,4 m x 6,4 m 10,1 5,1
4,9 m wide 20,2 10,1
3 m x 3,6 m & 3 m x 5,6 m 11,9 6,0
3 m x 7,3 m; 3 m x 11,0 m; 6,1 m x 3,6 m; 6,1 m x 5,5 m 23,8 11,9
6,1 m x 7,3 m; 6,1 m x 11,0 m 47,4 23,8
3,6 m x 3,6 m; 3,6 m x 4,2 m; 3,6 m x 5,5 m; 3,6 m x 6,1 m 14,7 7,4
3,6 m x 7,3 m; 3,6 m x 8,6 m; 3,6 m x 11,0 m; 3,6 m x 12,9 m 29,3 14,7
7,3 m x 3,6 m; 7,3 m x 4,2 m; 7,3 m x 5,5 m; 7,3 m x 6,1 m 29,3 14,7
7,3 m x 7,3 m; 7,3 m x 8,6 m; 7,3 m x 11,0 m; 7,3 m x 12,9 m 58,6 29,3
CATW Products 8,9 4,5
LRW Products
1,2 m wide units 3,8 1,9
1,6 m wide units 6,0 3,0
2,4 m wide units 9,4 4,7
LSWA Products
1,2 m wide units 4,2 1,9
1,6 m wide units 6,0 3,0
LSWA 91 to LSWA 135 9,4 4,7
LSWA 116 to LSWA 174 11,9 6,0
LSWA 232 to LSWA 348 23,8 11,9
Dual Fan Side Units
LSWA 182 to LSWA 270 16,7 8,4
ESWA Products
2,4 m wide units 15,0 7,5
3,6 m wide units 20,9 10,5
Minimum Flows
** Not available as eco-ATWE
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