23
6.5 - Anti-freeze
In areas where entering loop temperatures drop below 4.4
°
C or
where piping will be routed through areas subject to freezing,
anti-freeze is needed.
Alcohols and glycols are commonly used as anti-freeze agents.
Freeze protection should be maintained to 8.3 K below the lowest
expected entering loop temperature. For example, if the lowest
expected entering loop temperature is -1.1
°
C, the leaving loop
temperature would be -5.6 to -3.9
°
C. Therefore, the freeze
protection should be at -9.4
°
C (-1.1
°
C -8.3
°
C = -9.4
°
C).
IMPORTANT: All alcohols should be pre-mixed and pumped
from a reservoir outside of the building or introduced under
water level to prevent fuming.
Calculate the total volume of fluid in the piping system (see
Table 9). Use the percentage by volume in Table 10 to determine
the amount of anti-freeze to use. Anti-freeze concentration should
be checked from a well mixed sample using a hydrometer to
measure specific gravity.
6.5.1 - Freeze protection selection
The -1.1
°
C FP1 factory setting (water) should be used to avoid
freeze damage to the unit.
Once anti-freeze is selected, the JW3 jumper (FP1) should be
clipped on the control to select the low temperature (anti-freeze
-12.2
°
C) set point to avoid nuisance faults.
6.6 - Cooling tower/boiler systems
These systems typically use a common loop maintained at 15.6
to 32.2
°
C. Carrier recommends using a closed circuit evaporative
cooling tower with a secondary heat exchanger between the
tower and the water loop. If an open type cooling tower is used
continuously, chemical treatment and filtering will be necessary.
Table 9 - Approximate fluid volume (l) per 30 m of
pipe
Pipe
Diameter, in
Volume, l
Copper
1
15.5
1-1/4
24.2
1-1/2
34.8
Rubber hose
1
14.8
Polyethylene
3/4 IPS SDR11
10.6
1 IPS SDR11
17.0
1-1/4 IPS SDR11
30.6
1/2 IPS SDR11
41.3
2 IPS SDR11
68.1
1-1/4 IPS SCH40
31.4
1-1/2 IPS SCH40
41.3
2 IPS SCH40
64.4
Legend
IPS
- Internal pipe size
SCH - Schedule
SDR - Standard dimensional ratio
Note: Volume of heat exchanger is approximately 3.78 litres.
Table 10 - Anti-freeze percentages by volume
Anti-freeze
Minimum temperature for freeze protection,
°
C
-12.2
-9.4
-6.7
-3.9
Methanol (%)
25
21
16
10
100% USP food grade
Propylene glycol (%)
38
30
22
15
6.7 - Ground coupled, closed loop and plateframe
heat exchanger well systems
These systems allow water temperatures from -1.1 to 43.3
°
C.
The external loop field is divided up into 51 mm polyethylene
supply and return lines. Each line has valves connected in such
a way that upon system start-up, each line can be isolated for
flushing using only the system pumps. Locate air separation in
the piping system prior to the fluid re-entering the loop field.
