11
Operation and Maintenance Instructions
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 5
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 5 - 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
Troubleshooting: see Bulletin 116-E, pages 26-29
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