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5. Operate unit in the cooling cycle first, then the heating
cycle. Refer to Table 13 for unit operating limits. Al-
low 15 minutes between cooling and heating tests for
pressure to equalize.
NOTE: Two factors determine the operating limits of a unit:
entering-air temperature and water temperature. Whenever
any of these factors are at a minimum or maximum level,
the other two factors must be at a normal level to ensure
proper unit operation. See Tables 14-25.
Table 13 — Operating Limits
LEGEND
*Antifreeze solution is required at these fluid temperatures.
Scroll Compressor Rotation —
It is important to
be certain compressor is rotating in the proper direction. To
determine whether or not compressor is rotating in the prop-
er direction:
1. Connect service gages to suction and discharge pressure
fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge
pressure should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge
pressure does not rise to normal levels:
1. Turn off power to the unit. Install disconnect tag.
2. Reverse any two of the unit power leads.
3. Reapply power to the unit and verify pressures are correct.
The suction and discharge pressure levels should now move
to their normal start-up levels.
When the compressor is rotating in the wrong direction, the
unit makes more noise and does not provide cooling.
After a few minutes of reverse operation, the scroll com-
pressor internal overload protection will open, thus activating
the unit lockout. This requires a manual reset. To reset, turn the
thermostat on and then off.
NOTE: There is a 5-minute time delay before the compressor
will start.
Unit Start-Up Cooling Mode
1. Adjust the unit thermostat to the warmest position.
Slowly reduce the thermostat position until the compres-
sor activates.
2. Check for cool air delivery at unit grille a few minutes
after the unit has begun to operate.
3. Verify that the compressor is on and that the water flow
rate is correct by measuring pressure drop through the
heat exchanger using P/T plugs. Check the elevation and
cleanliness of the condensate lines; any dripping could be
a sign of a blocked line. Be sure the condensate trap in-
cludes a water seal.
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 cooling refrigerant pressures in Tables 14-25.
5. Check air temperature drop across the coil when com-
pressor is operating. Air temperature drop should be
between 15 and 25°F.
Table 14 — 50PC007 Typical Unit Operating Pressures and Temperatures
LEGEND
AIR LIMITS
STANDARD
UNIT
EXTENDED
RANGE
OPTION
COOLING
Minimum cooling entering air db/wb F
68/57
68/57
Maximum cooling entering air db/wb F
95/85
98/85
Minimum cooling entering fluid
temperature F
50
50
Water loop typical coil entering fluid
range temperature F
70/90
70/90
Maximum cooling entering fluid
temperature F
100
110
HEATING
Minimum heating entering air db F
50
50
Maximum heating entering air db F
80
80
Normal water coil entering fluid range F
50-80
25-80*
Minimum water coil entering Fluid F
50
20*
db
—
Dry Bulb
wb —
Wet Bulb
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
1.4
—
—
—
—
65-80
282-344
6-7
14-17
1.9
—
—
—
—
73-89
294-359
3-4
15-18
40
1.4
106-129
146-178
17-21
18-22
80-98
299-365
7-9
16-20
1.9
102-124
133-162
10-13
19-23
89-108
311-380
4-5
17-21
50
1.4
115-141
180-220
17-20
17-21
95-116
315-385
9-11
19-23
1.9
111-135
163-200
10-12
18-23
105-128
329-402
5-7
20-24
60
1.4
124-152
213-261
16-19
17-21
109-133
332-406
11-13
21-26
1.9
120-146
194-237
10-12
18-22
121-148
346-423
6-8
22-27
70
1.4
134-163
247-302
15-19
17-20
124-151
349-427
12-15
23-28
1.9
128-157
225-275
9-11
18-21
138-168
364-444
7-9
25-30
80
1.4
143-175
281-343
14-18
16-20
138-169
366-447
14-17
26-31
1.9
137-168
255-312
9-11
17-21
154-188
381-466
8-10
27-33
90
1.4
152-186
315-385
14-17
16-19
153-187
383-468
16-19
28-34
1.9
146-179
286-350
8-10
17-20
170-208
399-487
9-12
29-36
100
1.4
161-197
349-426
13-16
15-19
—
—
—
—
1.9
155-190
317-387
8-10
16-20
—
—
—
—
DB
—
Dry Bulb
—
—
No Operation in This Temperature Range