Antifreeze, Cooling tower/boiler systems – Carrier 50RTG User Manual
Page 18
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6. Open the return valve to send a pressure surge through
the loop to purge any air pockets in the piping system.
7. A noticeable drop in fluid level will be seen in the flush
cart tank. This is the only indication of air in the loop.
NOTE: If air is purged from the system while using a 10 in.
PVC flush tank, only a 1 to 2 in. level drop will be noticed
since liquids are incompressible. If the level drops more than
this, flushing should continue since air is still being com-
pressed in the loop. If level is less than 1 to 2 in., reverse the
flow.
8. Repeat this procedure until all air is purged.
9. Restore power.
Antifreeze may be added before, during or after the flushing
process. However, depending on when it is added in the
process, it can be wasted. Refer to the Antifreeze section for
more detail.
Loop static pressure will fluctuate with the seasons. Pres-
sures will be higher in the winter months than during the warm-
er months. This fluctuation is normal and should be considered
when charging the system initially. Run the unit in either heat-
ing or cooling for several minutes to condition the loop to a
homogenous temperature.
When complete, perform a final flush and pressurize the
loop to a static pressure of 40 to 50 psi for winter months or 15
to 20 psi for summer months.
After pressurization, be sure to remove the plug from the
end of the loop pump motor(s) to allow trapped air to be
discharged and to ensure the motor housing has been flooded.
Be sure the loop flow center provides adequate flow through
the unit by checking pressure drop across the heat exchanger.
Compare the results to the data in Table 16.
Table 16 — 50RTG Coaxial Water Pressure Drop
Antifreeze —
In areas where entering loop temperatures
drop below 40 F or where piping will be routed through areas
subject to freezing, antifreeze is needed.
Alcohols and glycols are commonly used as antifreeze
agents. Freeze protection should be maintained to 15 F below
the lowest expected entering loop temperature. For example, if
the lowest expected entering loop temperature is 30 F, the leav-
ing loop temperature would be 22 to 25 F. Therefore, the freeze
protection should be at 15 F (30 F – 15 F = 15 F).
Calculate the total volume of fluid in the piping system. See
Table 17. Use the percentage by volume in Table 18 to deter-
mine the amount of antifreeze to use. Antifreeze concentration
should be checked from a well mixed sample using a hydrome-
ter to measure specific gravity.
FREEZE PROTECTION SELECTION — The 30 F FP1 fac-
tory setting (water) should be used to avoid freeze damage to
the unit.
Once antifreeze is selected, the JW3 jumper (FP1) should
be clipped on the control to select the low temperature (anti-
freeze 13 F) set point to avoid nuisance faults.
Table 17 — Approximate Fluid Volume (gal.)
per 100 Ft of Pipe
LEGEND
NOTE: Volume of heat exchanger is approximately 1.0 gallon.
Table 18 — Antifreeze Percentages by Volume
Cooling Tower/Boiler Systems —
These systems
typically use a common loop maintained at 60 to 90 F. The use
of a closed circuit evaporative cooling tower with a secondary
heat exchanger between the tower and the water loop is recom-
mended. If an open type cooling tower is used continuously,
chemical treatment and filtering will be necessary.
Ground Coupled, Closed Loop and Plateframe
Heat Exchanger Well Systems —
These systems al-
low water temperatures from 30 to 110 F. The external loop
field is divided up into 2 in. 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. Air separation should be located in the
piping system prior to the fluid re-entering the loop field.
UNIT
50RTG
GPM
WATER TEMPERATURE (F)
30
50
70
90
Pressure Drop (ft. H
2
O)
03
4.0
3.1
2.8
2.8
2.8
6.0
6.1
5.3
5.3
5.3
8.0
9.9
8.9
8.9
8.9
10.0
14.3
12.9
12.9
12.9
04
5.5
4.2
3.4
3.4
3.4
8.5
8.9
7.8
7.8
7.8
11.5
14.8
13.2
13.2
13.2
14.0
20.5
18.6
18.6
18.6
05
7.0
8.1
5.3
5.3
5.3
11.0
16.9
11.2
11.2
11.2
15.0
28.5
18.9
18.9
18.9
18.0
38.8
25.6
25.6
25.6
07
10.0
3.4
2.3
2.3
2.3
15.0
10.1
6.7
6.7
6.7
20.0
16.0
10.7
10.7
10.7
24.0
22.3
14.9
14.9
14.9
08
11.0
4.5
3.5
3.5
3.5
17.0
9.4
8.1
8.1
8.1
22.0
14.2
12.7
12.7
12.7
27.0
20.0
18.2
18.2
18.2
10
14.0
8.3
5.5
5.5
5.5
22.0
17.6
11.7
11.7
11.7
30.0
29.4
19.7
19.7
19.7
36.0
39.9
26.7
26.7
26.7
12
17.0
4.8
3.2
3.2
3.2
25.0
9.4
6.0
6.0
6.0
34.0
13.1
10.3
10.3
10.3
40.0
22.0
13.5
13.5
13.5
15
21.0
5.2
2.9
2.9
2.9
32.0
10.7
7.4
7.4
7.4
42.0
17.4
11.6
11.6
11.6
51.0
24.3
16.5
16.5
16.5
20
31.0
10.6
6.4
6.4
6.4
47.0
21.2
13.1
13.1
13.1
62.0
34.2
20.8
20.8
20.8
74.0
46.2
28.0
28.0
28.0
IMPORTANT: All alcohols should be pre-mixed and
pumped from a reservoir outside of the building or
introduced under water level to prevent fumes.
PIPE
DIAMETER (in.)
VOLUME (gal.)
Copper
1
4.1
1.25
6.4
1.5
9.2
Rubber Hose
1
3.9
Polyethylene
3
/
4
IPS SDR11
2.8
1 IPS SDR11
4.5
1
1
/
4
IPS SDR11
8.0
1
/
2
IPS SDR11
10.9
2 IPS SDR11
18.0
1
1
/
4
IPS SCH40
8.3
1
1
/
2
IPS SCH40
10.9
2 IPS SCH40
17.0
IPS
— Internal Pipe Size
SCH — Schedule
SDR — Standard Dimensional Ratio
ANTIFREEZE
MINIMUM TEMPERATURE FOR
FREEZE PROTECTION (F)
10
15
20
25
Methanol (%)
25
21
16
10
100% USP Food Grade
Propylene Glycol (%)
38
30
22
15