34
Table 25 — 50PC070 Typical Unit Operating Pressures and Temperatures
LEGEND
Unit Start-Up Heating Mode
NOTE: Operate the unit in heating cycle after checking the
cooling cycle. Allow 5 minutes between tests for the pressure
or reversing valve to equalize.
1. Turn thermostat to lowest setting and set thermostat
switch to HEAT position.
2. Slowly turn the thermostat to a higher temperature until
the compressor activates.
3. Check for warm air delivery at the unit grille within a few
minutes after the unit has begun to operate.
4. Check the temperature of both supply and discharge wa-
ter. Compare to Tables 14-25. If temperature is within
range, proceed. If temperature is outside the range, check
the heating refrigerant pressures in Tables 14-25.
5. Once the unit has begun to run, check for warm air deliv-
ery at the unit grille.
6. Check air temperature rise across the coil when compres-
sor is operating. Air temperature rise should be between
20 and 30°F after 15 minutes at load.
7. Check for vibration, noise and water leaks.
Flow Regulation —
Flow regulation can be accom-
plished by two methods. Most water control valves have a flow
adjustment built into the valve. By measuring the pressure drop
through the unit heat exchanger, the flow rate can be deter-
mined. Adjust the water control valve until the desired flow
rate is achieved. Since the pressure constantly varies, two pres-
sure gages may be needed in some applications.
An alternate method of flow regulation is to install an auto-
matic flow control valve. These valves feature a removable
cartridge that controls the maximum flow through the valve as-
sembly. Automatic flow control valves should be sized for the
specific flow for each application.
Flushing —
Once the piping is complete, units require final
purging and loop charging. A flush cart pump of at least 1.5 hp
is needed to achieve adequate flow velocity in the loop to purge
air and dirt particles from the loop. Flush the loop in both
directions with a high volume of water at a high velocity. Fol-
low the steps below to properly flush the loop:
1. Verify power is off.
2. Fill loop with water from hose through flush cart before
using flush cart pump to ensure an even fill. Do not allow
the water level in the flush cart tank to drop below the
pump inlet line to prevent air from filling the line.
3. Maintain a fluid level in the tank above the return tee to
avoid air entering back into the fluid.
4. Shutting off the return valve that connects into the flush
cart reservoir will allow 50 psig surges to help purge air
pockets. This maintains the pump at 50 psig.
5. To purge, keep the pump at 50 psig until maximum
pumping pressure is reached.
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, the level drop will only be 1 to 2
in. since liquids are incompressible. If the level drops
more than this, flushing should continue since air is still
being compressed 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 on
page 35 for more detail.
Loop static pressure will fluctuate with the seasons. Pres-
sures will be higher in the winter months than during the
warmer months. This fluctuation is normal and should be con-
sidered when charging the system initially. Run the unit in
either heating 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 psig for winter months or
15 to 20 psig 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
ENTERING
WATER
TEMP (°F)
WATER
FLOW
(GPM/TON)
COOLING
HEATING
SUCTION
PRESSURE
(PSIG)
DISCHARGE
PRESSURE
(PSIG)
WATER
TEMP
RISE (°F)
AIR TEMP
DROP
(°F) DB
SUCTION
PRESSURE
(PSIG)
DISCHARGE
PRESSURE
(PSIG)
WATER
TEMP
DROP (°F)
AIR TEMP
RISE (°F)
30
12.0
—
—
—
—
68-84
256-313
5-7
19-23
16.0
—
—
—
—
73-89
261-319
4-5
20-25
40
12.0
117-143
182-222
15-19
21-26
81-99
277-339
7-8
22-26
16.0
114-139
170-208
11-14
22-27
86-105
283-346
5-6
23-28
50
12.0
120-147
215-263
15-18
20-25
93-114
299-365
8-9
24-29
16.0
117-143
201-246
11-14
21-26
99-121
305-373
6-7
25-31
60
12.0
123-150
248-304
14-17
20-24
106-129
321-392
9-11
26-32
16.0
119-146
232-284
11-13
21-25
113-138
327-400
7-8
28-34
70
12.0
126-154
282-344
14-17
19-24
118-145
342-418
10-12
29-35
16.0
122-149
263-322
10-13
20-25
126-154
349-427
8-9
30-37
80
12.0
129-157
315-385
13-16
19-23
131-160
364-444
11-14
31-38
16.0
125-153
294-360
10-12
19-24
139-170
371-454
8-10
33-40
90
12.0
132-161
348-426
13-16
18-22
143-175
385-471
12-15
33-41
16.0
128-156
326-398
10-12
19-23
152-186
393-480
9-11
35-43
100
12.0
134-164
382-466
12-15
17-21
—
—
—
—
16.0
131-160
357-436
9-11
18-22
—
—
—
—
DB
—
Dry Bulb
—
—
No Operation in This Temperature Range
WARNING
To avoid possible injury or death due to electrical shock,
open the power supply disconnect switch and secure it in
an open position before flushing system.