14
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
** Not available as eco-ATWE
Closed Circuit Cooler
Footprint
Minimum Flows
Standard
Flow
GPM
Series Flow
GPM
Standard
Flow
l/s
Series Flow
l/s
ATWB Products, eco-ATW & eco-ATWE
3’x3’**
4’ wide units**
7’ wide units
8.5’x7.5’
8.5’x9’ to 8.5’x21’
17’x12’, 17’x14
10’x12’, 10’x18’
10’x24, 10’x36’, 20’x12’, 20’x18’
20’x24’, 20’x36’
12’x12’, 12’x14’, 12’x18’, 12’x20’
12’x24’, 12’x28’, 12’x36’, 12’x40’
24’x12’, 24’x14’, 24’x18’, 24’x20’
24’x24’, 24’x28’, 24’x36, 24’x40’
—
74
140
148
160
320
188
376
752
232
464
464
928
26
37
70
74
80
160
94
188
376
116
232
232
464
—
4.7
8.8
9.3
10
20
11.9
23.7
47.4
14.6
29.3
11
58.5
1.6
2.3
4.4
4.7
5
10
5.9
11.9
23.7
7.3
14.6
11
29.3
LRWB Products
3’ wide units
5’ wide units
8’ wide units
60
94
148
30
47
74
3.8
5.9
9.3
1.9
3
4.7
LSWE Products
4’x6’, 4’x9’, 4’x12’, 4’x18’
5.5’x12’, 5.5’x18’
8’x12’, 8’x18’
8’x24’, 8’x36’
10’x12’, 10’x18’
10’x24, 10’x36’
66
94
148
296
188
376
30
47
74
148
94
188
66
94
148
296
188
376
30
47
74
148
94
188
ESW4 Products
8.5’x6’-LP
8.5’x9’, 8.5’x12’, 12’x12’-LP, 12’x12’-SP
8.5’x18’, 12’x12’-LF, 12’x12’-SF, 12’x18’-LF, 12’x18’X-SF
12’x18’X-LP, 12’x18’X-SP
12’x18’X-LF, 12’x18’X-SF
14’x22’
100
160
240
320
480
440
50
80
120
160
240
220
6.3
10.1
15.1
20.2
30.3
27.8
3.2
5
7.6
10.1
15.1
13.9
