Specifications
Page 10
2-Crankcase Heaters HR1 and HR2
(-1353 only)
GCS24-1353 units use belly band type heaters. Heater HR1
is installed around compressor B1, heater HR2 is installed
around compressor B2. Crankcase heater wattage varies by
compressor manufacturer. See unit rating plate for specific
electrical data.
3-High Pressure Limit S4 and S7 (all units)
The high pressure limit is a manually reset SPST N.C. switch
which opens on a pressure rise. All GCS24 units are
equipped with this limit. The switch is located in the compres
sor discharge line and is wired in series with the compressor
contactor.
S4 is wired in series with the first stage compressor contactor
and S7 is wired in series with the second stage compressor
contactor.
When discharge pressure rises above 410±10 psig (indicat
ing a problem in the system) the switch opens and the respec
tive compressor is de-energized (the economizer can contin
ue to operate.) After the problem has been found and cor
rected, reset the switch by pushing in the switch button.
4-Low Ambient Switch S11 and S84
(all units)
The low ambient switch is an autoreset SPST N.O. switch
which allows for mechanical cooling operation at low outdoor
temperatures. All GCS241353/1603 units are equipped with
this switch. The switch is wired in series with the condenser
fan relay, low ambient relay and condenser fan contactor. In
the early models the switch is located in the compressor dis
charge line next to the high pressure switch. In the late models
the switch is located in the liquid line next to the drier.
S11 is wired in series with the first stage condenser fan B4
and S25 is wired in series with second stage condenser fan
B5.
When discharge pressure drops below 150±10psig the switch
opens and the condenser fan is de-energized. This intermit
tent fan operation results in high evaporating temperature
which allows the system to operate without icing the evapora
tor coil and losing capacity. The switch automatically resets
when pressure in the discharge line rises above 275±10 psig.
5-Low Pressure Switch S87 & S88 (all units)
The low pressure switch is an autoreset SPST N.C. switch
which opens on a pressure drop. All GCS24 units are
equipped with this switch. The switch is located in the com
pressor suction line and is wired in series with the high pres
sure switch and compressor contactor.
S87 (first stage) is wired in series with first stage compressor
contactor and S88 (second stage) is wired in series with sec
ond stage compressor contactor.
When suction pressure drops below 25±5 psig (indicating low
pressure) the switch opens and the compressor is de-ener
gized. The switch automatically resets when refrigerant is
added and pressure in the suction line rises above 55±5 psig.
6-Thermometer Well (all units)
All units are factory equipped with a thermometer well (figure
7) for charging the unit. The well is used to accurately mea
sure the temperature of the liquid line. The temperature mea
sured is then used to calculate the approach temperature. Ap
proach temperatures are compared to tables printed in the
charging section of this manual to determine the correct
charge. Thermometer wells are equipped with a gauge port
for high pressure gauge connection.
FIGURE 7
THERMOMETER WELL
THERMOMETER WELL
LIQUID LINE GAUGE PORT
LIQUID LINE
To accurately measure the temperature of the liquid line, the
well should be filled with a light mineral oil before using. This
will ensure good heat transfer to thermometer.
7-Freezestats S49 and S50 (all units)
Each evaporator is equipped with a low temperature limit
(freezestat) located on the suction tube at the bottom of each
evaporator. S49 is located on the first stage evaporator coil
and S50 is located on the second stage evaporator coil.
Each freezestat is wired in series with its respective compres
sor contactor coil. Each freezestat is a SPST auto-reset limit
which opens at 29°F + 3°F on a temperature drop and closes
at 58°F + 4°F on a temperature rise. To prevent coil icing,
freezestats open during compressor operation to temporarily
disable the respective compressor until the coil warms suffi
ciently to melt any accumulated frost.
If the freezestats are tripping frequently due to coil icing, check
the unit charge, airflow and filters before allowing unit back in
operation. Make sure to eliminate all conditions which might
promote evaporator ice buildup.