Page 26
FIGURE 14
1
2
3
4
SUCTION
POCKET
SUCTION
ORBITING SCROLL
STATIONARY SCROLL
SUCTION
SUCTION
DISCHARGE
POCKET
SUCTION
INTERMEDIATE PRESSURE
GAS
CRECENT SHAPED
GAS POCKET
HIGH PRESURE GAS
FLANKS SEALED
BY CENTRIFIGUAL
FORCE
MOVEMENT OF ORBIT
3-Evaporator Coil
All CHA/CHP16/20 units have a single slab evaporator
coil. The CHA16 coils have two rows of rifled copper tubes
fitted with ripple-edged alum
inum fins and the CHP16/20 coils have three, A Thermal
Expansion Valve (TXV) feeds multiple parallel circuits
through the coil. See figure 15.
4-Condenser Coil
All CHA/CHP16/20 units have a single condenser coil. Each
coil in all units has up to two rows of copper tubes fitted with
ripple-edged aluminum enhanced fins.
5-Freezestat Switch S49
All CHA/CHP16/20 model units are equipped with a low
temperature freezestat switch S49. S49 is wired in series
with high pressure switch S4 and compressor contactor K1.
S49 is a SPST N.C. auto-reset switch which opens at 29ºF ±
3 ºF (-1.7ºC 1.7 ºC) on temperature drop and closes at 58ºF
± 4 ºF (14.4ºC ± 2.2 ºC) on a temperature rise. To prevent coil
icing, S49 opens during compressor operation to temporariĆ
ly disable the compressor until the coil warms sufficiently to
melt any accumulated frost.
If S49 trips frequently due to coil icing, check the unit charge,
air flow and filters before allowing unit back in operation.
Make sure to eliminate conditions which might promote ice
build up.
6-High Pressure Switch S4
High pressure switch S4 is standard on all CHP16/20 model
units. S4 is a manually reset SPST N.C. high pressure
switch which opens on pressure rise. The switch is located
on the discharge line and wired in series with compressor
contactor K1. When discharge pressure rises above
450±10 psig (3103 kPa± 69 kPa) the switch opens and the
compressor is de-energized (the economizer can continue
to operate). After the problem has been found and corĆ
rected, the switch can be reset by pushing-in the switch butĆ
ton.
EVAPORATOR PLUMBING
CHP16/20-030/036 SHOWN
FIGURE 15
EQUALIZER
LINE
EXPANSION
VALVE
SENSING
BULB
LIQUID
LINE
7-Reversing Valve L1
All CHP16/20 units are equipped with refrigerant reversing
valve L1. L1 has a 24VAC solenoid coil used to reverse reĆ
frigerant flow during unit operation. L1 is connected in the
vapor line of the refrigerant circuit. Internal thermostat wiring
energizes L1 during cooling demand and de-energizes durĆ
ing heatingdemand. When thermostat selection is out of
cooling mode L1 is de-energized.
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