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507232-04 7/2017
E-Charge Verification - Approach Method - AHRI
TESTING
1-Using the same thermometer, compare liquid
temperature to outdoor ambient temperature.
Approach Temperature = Liquid temperature (at
condenser outlet) minus ambient temperature.
2-Approach temperature should match values in table 13.
An approach temperature greater than value shown
indicates an undercharge. An approach temperature
less than value shown indicates an overcharge.
3-The approach method is not valid for grossly over or
undercharged systems. Use tables 7 through 12 as a
guide for typical operating pressures.
TABLE 13
APPROACH TEMPERATURES
420S, 540S
8°F + 1 (4.4 + 0.5)
420H, 480H, 6°F + 1 (3.3 + 0.5)
480S 9°F + 1 (5.0 + 0.5)
600S 7°F + 1 (3.9 + 0.5)
F-Compressor Controls
1- High Pressure Switch (S4, S7, S28, S96)
The compressor circuit is protected by a high pressure
switch which opens at 640 psig +
10 psig (4413 kPa +
70 kPa) and automatically resets at 475 psig + 20 psig
(3275kPa +
138 kPa).
2- Low Pressure Switch (S87, S88, S97, S98)
The compressor circuit is protected by a low pressure
switch. Switch opens at 40 psig +
5 psig (276 + 34
kPa) and automatically resets at 90 psig +
5 psig (621
kPa +
34 kPa).
3- Crankcase Heater (HR1, HR2, HR5, HR11)
Units have compressors which contain a belly band
compressor oil heater which must be on 24 hours
before running compressors. Energize by setting
thermostat so that there is no cooling demand, to
prevent compressor from cycling, and apply power to
unit.
4- Low Ambient Pressure Switch (S11, S84, S85, S94)
Switch maintains adequate discharge pressure by
de-energizing condenser fan when liquid pressure falls
below 240 psig +
10 (1655 kPa+69). Switch closes to
energize condenser fan when pressure rises to 450
psig +
10 (3103kPa + 69).
Condenser fans 1, 2, and 3 are energized when
compressor 1 or 2 are operating. Condenser fans 4, 5,
and 6 are energized when compressor 3 or 4 are
operating. See figure 32.
CONDENSER FANS
FIGURE 32
41
52
63
1
2
3
4
CONDENSER
FANS
COMPRESSORS
TOP VIEW OF UNIT
The Unit Controller de-energizes condenser fan 2
(K68) and 5 (K152) when outdoor temperature drops
below 55°F (13°C).
The Unit Controller de-energizes condenser fan 1
(K10) and 6 (K153) when outdoor temperature drops
below 40°F (5°C).
S11 and S84 pressure switches (in refrigerant circuits 1
and 2 respectively) are in parallel; any ONE switch will
maintain operation of condenser fan 3 (K149).
S85 and S94 pressure switches (in refrigerant circuits 3
and 4 respectively) are in parallel; any ONE switch will
maintain operation of condenser fan 4 (K150).
5- Freezestats (S49, S50, S53, S95)
Switches de-energize compressors when evaporator
coil temperature falls below 29°F (-2°C) to prevent
evaporator freeze-up. Switches reset when evaporator
coil temperature reaches 58°F (15°C).
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