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8-Drier
All CHP16/20 units have a biflo with filter drier located in the
liquid line of each refrigerant circuit at the exit of the conĆ
denser coil. The drier removes contaminants and moisture
from the system.
9-Defrost Thermostat S6
Defrost thermostat S6 works in conjunction with defrost conĆ
trol CMC1 to initiate defrost. The switch is a SPST N.O. therĆ
mostat located on the liquid line between the outdoor coil
distributor and the outdoor coil thermal expansion valve. It
remains open during normal cooling and heating operation
(to prevent defrosting) and defrost timer CMC1 continues to
accumulate time. When outdoor coil temperature drops beĆ
low 35
°
F + 4
°
F, the switch closes and the defrost circuit is
enabled (call for defrost). If S6 is closed when CMC1 checks
for defrost (every 30, 60 or 90 minutes) then defrost relay K4
is energized. S6 remains closed until liquid line temperature
rises above 60
°
F + 5
°
F.
Defrost thermostat S6 is intended only to initiate defrost.
Pressure switch S46 is used to terminate defrost. Once deĆ
frost starts, contacts K4Ć3 close to latchĆin K10 and K4. TypĆ
ically S6 will open before the end of the 14 minute defrost
period leaving relay K4 energized through contacts K4-3.
10-Defrost Pressure Switch S46
Defrost pressure switch S46 is a SPST N.C. pressure switch
located in the compressor discharge line.
The purpose of the latch circuit is to ensure thorough defrost
by forcing defrost relay K4 to terminate only when S46 is satĆ
isfied or after the 14 minute defrost time period. When disĆ
charge (head) pressure during defrost rises above
10psi (1896
69 kPa) the switch opens. At 275psi (1896
kPa), the condensing temperature of HCFCĆ22 refrigerant is
approximately 125
°
F (52
°
). Head pressure builds rapidly
due to the outdoor fan being disabled during defrost. By the
time head pressure is elevated to 275psi (1896 kPa), the
condensing temperature is elevated to the point that the outĆ
door coil is defrosted.
If S46 opens during defrost, defrost is terminated (K4 is deĆ
energized). S46 automatically resets (closes) when the unit
resumes heating operation and discharge (head) pressure
drops below 10psi.
11-Low Ambient Bypass Relay K58
Optional low ambient bypass relay K58 is a N.O. DPDT relay
with a 24VAC coil. K58 is wired in parallel with compressor
reversing valve (L1). When L1 is energized in the cooling
cycle, K58 is also energized, opening K58-1. Therefore,
K58-1 is always closed during heating demand bypassing
low ambient switch S11. This allows the fan to operate durĆ
ing heating demand and to cycle during cooling demand.
12-Low Ambient Switch S11
Optional low ambient switch S11 is an auto-reset SPST N.O.
pressure switch which allows for mechanical cooling operaĆ
tion at low outdoor temperatures. S11 is located in the liquid
line prior to the indoor coil section. When liquid pressure
rises to 275
10 psig (1896
69 kPa), the switch closes
and the condenser fan is energized. When liquid pressure in
the refrigerant circuit drops to 150
10 psig (1034
69
kPa), the switch opens and the condenser fan is de-enerĆ
gized. This intermittent fan operation results in higher evapĆ
orating temperature allowing the system to operate without
icing the evaporator coil and losing capacity.
C-Condenser Fan and Indoor Blower
1-Condenser Fan and Blower Motor B4
See specifications section of this manual for the specificaĆ
tions of condenser fans used. In all CHP units. the condensĆ
er fan is energized by contactor K1 and condenser contacĆ
tor K10. In all CHA units the condenser fan is controlled by
contactor K1.
2-Capacitors C1 & C12
All three phase model units use singleĆphase PSC outdoor
fan motors which requires a run capacitor. C1 is located in
the compressor compartment. Single phase units use a dual
capacitor C12 instead of C1. The dual capacitor is shared
between the compressor and outdoor fan. Ratings for caĆ
pacitors will be on outdoor fan motor nameplate.
3-Blower Motor B3 & Capacitor C4
All CHA/CHP16/20 series units use singleĆphase PSC blowĆ
er motors. A single run capacitor C4 is mounted on the blowĆ
er housing. Ratings for capacitor will be on motor nameĆ
plate. All motors use multiple speed taps. Typically, the high
speed tap is energized during compressor operation and a
lower speed tap is energized during heating operation. See
motor nameplate or ELECTRICAL DATA section for motor
specifications.