Reznor MAPSII Series REDA Users Manual - Manual (Page 18)

Form O-MAPS II, P/N 209179 R7, Page 18
 Step 10. System Startup
Assure voltage to compressor does not drop below minimum allowable
voltage (eg. 187 volts for 230/208-3-60, 415 volts for 460/3/60, 518 volts
for 575/3/60) during the period the compressor is trying to start. If a low
voltage or voltage imbalance condition exists, the electrical problem
must be determined and corrected prior to operating the unit.
Voltage Imbalance - Voltage imbalance is becoming a more common
problem. In a 3-phase system, excessive voltage imbalance between
phases will cause motors to overheat and compressors to fail. Maximum
allowable imbalance is 2%. To determine voltage imbalance, measure and
record the voltage of all three phases. Take the measurements at the com-
pressor terminals with the compressor operating.
Voltage Imbalance Formula:
If the imbalance is within the 2% tolerance, voltage imbalance is not a
problem and the system may be operated. If the imbalance exceeds the
2% tolerance, follow the procedures below.
Solutions to Voltage Imbalance - The cause for a voltage imbalance
problem can originate at the power company or can be caused inside the
building. Try the following on-site solution to determine if the problem can
be easily resolved.
Roll the connections at the compressor terminals one forward. Connect the
wire now on Terminal 1 to Terminal 2, 2 to 3, and 3 to 1. Re-measure and
re-calculate the voltage imbalance. If the imbalance is within 2%, the sys-
tem may be operated.
If the imbalance is not within tolerance, roll the connections one more for-
ward. Re-measure and re-calculate the voltage imbalance. If the imbalance
is within 2%, the system may be operated. If the voltage imbalance still
exceeds 2%, do not start the system. Contact the building owner or person
responsible to have an electrician analyze the buildings's power supply and
load distribution.
 Step 11. Check Superheat and Subcooling
Superheat is the verification that the evaporator coil is properly using the
refrigerant supplied. Too much superheat indicates that the coil is under-
charged. Too little superheat indicates that the coil is overcharged and
potentially flooding liquid refrigerant to the compressor.
Subcooling is the measurement of liquid refrigerant stored in the con-
denser coil. Too much subcooling indicates a system overcharge. Too
little subcooling indicates a system undercharge and may not provide the
thermal expansion valve with a full column of liquid refrigerant for proper
operation.
Two important requirements before checking superheat/subcooling:
1) This unit has fully intertwined refrigerant circuits and each circuit MUST
be isolated before measuring its temperature. Another active circuit will
influence the reading and make it impossible to determine accurate super-
heat and subcooling.
2) If the circuit is equipped with an optional hot gas bypass valve, the valve
must be disabled before measuring superheat and subcooling. Disable
the hot gas bypass valve by removing the cover and adjusting the spring
Compressor
Maintenance
Checklist,
Steps 1-13 (cont'd)
Key: V1, V2, V3 = line voltages as measured
VA (average) =
(V1 + V2 + V3)
3
VD = Line voltage (V1, V2, or V3) that deviates farthest from average (VA)
Formula: % Voltage
Imbalance =
[100 x (VA - VD)]
VA
Saturation
Temperature
Pressure
(psig)
(ºF) (ºC) R-22 R-407C
0 -17.8 24 19.5
5 -15.0 28.2 23.6
10 -12.2 32.7 28.0
15 -9.4 37.7 32.7
20 -6.7 43 37.9
25 -3.9 48.7 43.6
30 -1.1 54.9 49.6
35 1.7 61.4 56.2
40 4.4 68.5 63.2
45 7.2 76 70.7
50 10.0 84 78.8
55 12.8 92.5 87.5
60 15.6 101.6 96.8
65 18.3 111 106.7
70 21.1 121.4 117.2
75 23.9 132 128.4
80 26.7 144 140.4
85 29.4 156 153.1
90 32.2 168.4 166.5
95 35.0 182 180.8
100 37.8 196 195.8
105 40.6 211 211.8
110 43.3 226.4 228.7
115 46.1 243 246.5
120 48.9 260 265.3
125 51.7 278.4 285.2
130 54.4 296.8 306.1
135 57.2 317 328.2
140 60.0 337.3 351.4
145 62.8 359 375.9
7.0 Compressor
Maintenance
and
Replacement
(cont'd)