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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 proper direction:
1.
Connect service gauges to suction and discharge pressure
fittings.
2.
Energize the compressor by using the thermostat or DDC
control to put the unit in cooling mode.
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 compressor
internal overload protection will open, thus activating the unit
lockout. This requires a manual reset. To reset the lockout, turn the
thermostat on and then off or power cycle the unit power feed.
NOTE: There is a 5-minute time delay before the compressor will
restart.
COOLING MODE START-UP
1.
Using the thermostat or DDC control, operate the unit in the
cooling cycle. Refer to Table 18 for operating limits. Allow
the unit to run for a minimum of five minutes and record the
operating data.
2.
Check for water leaks and vibration.
3.
Check for cool air delivery at unit grille a few minutes after
the unit has begun to operate.
Table 19 — 50PC007 Typical Unit Operating Pressures and Temperatures
ENTERING
WATER
WATER
FLOW
TEMP (°F)
(GPM/TON)
1.4
30
1.9
1.4
40
1.9
1.4
50
1.9
1.4
60
1.9
1.4
70
1.9
1.4
80
1.9
1.4
90
1.9
1.4
100
1.9
LEGEND
DB
— Dry Bulb
—
— No Operation in This Temperature Range
COOLING
Suction
Discharge
Pressure
Pressure
(PSIG)
(PSIG)
Rise (°F)
—
—
—
—
106-129
146-178
102-124
133-162
115-141
180-220
111-135
163-200
124-152
213-261
120-146
194-237
134-163
247-302
128-187
225-275
143-175
281-343
137-168
255-312
152-186
315-385
146-179
286-350
161-197
349-426
155-190
317-387
4.
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 includes a
water seal.
5.
Check the temperature of both supply and discharge water.
Compare to Tables 19-31. If temperature is within range,
proceed. If temperature is outside the range, check the cooling
refrigerant pressures in Tables 19-31.
6.
Check air temperature drop across the coil when compressor
is operating. Air temperature drop should be between 15 and
25°F.
7.
Disable cooling mode and wait a period of 5 minutes to allow
system pressures to equalize.
HEATING MODE START-UP
1.
After waiting for a period of 5 minutes after the cooling cycle,
use the thermostat or DDC control to operate the unit in the
heating cycle. Refer to Table 18 for operating limits. Allow
the unit to run for a minimum of five minutes and record the
operating data.
2.
Check for water leaks and vibration.
3.
Check for warm air delivery at unit grille a few minutes after
the unit has begun to operate.
4.
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.
5.
Check the temperature of both supply and discharge water.
Compare to Tables 19-31. If temperature is within range, pro-
ceed. If temperature is outside the range, check the cooling
refrigerant pressures in Tables 19-31.
6.
Check air temperature rise across the coil when compressor is
operating. Air temperature rise should be between 20°F and
30°F.
7.
Disable heating mode.
Water
Air Temp
Suction
Temp
Drop
Pressure
(°F) DB
(PSIG)
—
—
58-68
—
—
62-72
17-21
18-22
71-81
10-13
19-23
77-87
17-20
17-21
88-98
10-12
18-23
95-105
16-19
17-21
105-115
10-12
18-22
114-124
15-19
17-20
125-135
9-11
18-21
135-145
14-18
16-20
146-156
9-11
17-21
159-169
14-17
16-19
169-179
8-10
17-20
186-196
13-16
15-19
—
8-10
16-20
—
44
HEATING
Discharge
Water
Air Temp.
Pressure
Temp.
Drop (°F)
(PSIG)
Rise (°F)
275-285
5-6
280-290
3-4
290-300
7-8
296-306
4-5
308-318
7-8
315-325
4-5
324-334
9-10
331-341
5-6
340-350
10-11
348-358
6-7
356-366
12-13
366-376
7-8
374-384
13-14
386-396
8-9
—
—
—
—
19-23
20-24
22-26
23-27
25-29
27-31
28-32
30-34
32-36
33-37
35-39
37-41
39-43
41-45
—
—
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