heat for the heating mode of operation. The heart of
(6) A circuit breaker, in the two power lines to
the electrical control system is the control panel
the compressor, with an auxiliary switch in the
primary line to the control voltage, provides for
where a selector switch, thermostatic control and
protection against compressor overloads. In the
toggle switch are used to manually select the
event of compressor overload, the circuit breaker
various modes and conditions of operation. Four
basic modes of operation are available.
t r i p s , opening both the two lines to the compressor
b. Cooling Cycle. The selector switch, when
and the control circuit.
placed in the cooling mode, provides power to a
(7) A pressure switch operated by the
control voltage transformer. This transformer
refrigerant system discharge pressure by-passes the
r e d u c e s the 115 volt power to a safe 30 volts. The
fan speed toggle switch during high temperature
r e d u c e d ac voltage is rectified to a pulsating dc and
c o o l i n g operation of automatically switch the fan to
high speed operation. The fan automatically
used to operate the system control circuits. The
c o n t r o l voltage operates relays and solenoids, which
switches to low speed upon a drop in pressure.
in turn connects the power voltage to the com-
(8) A time delay relay prevents simultaneous
compressor motor and fan motor start-up. When
pressor motor and to the fan motor. The toggle
the selector switch is placed in the cool position the
switch on the control panel controls the speed of the
two speed fan motor (when S-7 is open).
compressor motor starts 15 seconds after the fan
c . V e n t i l a t i n g C y c l e . In the ventilating cycle, of
o p e r a t i o n , the control voltage is switched off from
( 9 ) A time delay relay prevents the fan motor
f r o m starting directly on high speed, The time delay
c e r t a i n relays and solenoids which de-activates bdth
of 15 seconds allows the fan motor to attain low
the refrigerant and heating circuits. The fan motor
speed RPM before switching to high speed.
circuit is kept energized in this mode and may be
operated in either low speed or high speed.
Malfunction Isolation Procedure
d. Low Heat Cycle. In the low heat mode of
a. General. When malfunctions occur in the air
operation, the selector switch energizes a set of
conditioner procedures are provided to aid the
heaters with the single phase power. The heat is
technician in locating the faulty component. The
distributed with the fan motor in either low speed
procedures are designed around the three primary
or high speed operation.
f u n c t i o n s that the air conditioner accomplishes: air
e. High Heat Cycle. In the high heat mode of
flow, cooling or heating.
o p e r a t i o n , a second set of heaters is controlled by a
b . Air Low. A i r f l o w d i r e c t l y a f f e c t s c o o l i n g o r
t h e r m o s t a t i c a l l y controlled relay. The second set of
h e a t i n g and in the event of any type failure the air
h e a t e r s is identical to the set used in the low heat
flow should be checked first.
cycle; thus providing twice the low heat wattage
(1) Place the selector switch in the VEN-
output in the high heat mode.
T I L A T E position and check for air flow by feel and
f. Electrical System Protection. S e v e r a l
listening for fan motor operation.
protection devices are included in the electrical
(2) If motor operates but flow is insufficient,
check grille louver position, check filters and
screens for cleanliness, then check fan blades for
( 1 ) One 2 amp fuse is installed in the primary
v o l t a g e line to the control voltage transformer and
( 3 ) If fan motor fails to operate at low speed,
protects the control voltage transformer and rec-
with HI-LO switch in the LO position and the
tifier from overload.
selector switch contacts S/W2; 2 to B, relay K7,
(2) One five amp fuse is installed in the dc
contacts 4 to 5 and 7 to 8, circuit breaker CB
control voltage line. This fuse protects the control
contacts B1 to B2 and the fan motor thermal
relays and components from overload.
protector for continuity. Check capacitor C1 to
(3) Thermal protectors are included on the
insure that is not defective.
compressor motor and on the fan motor to protect
(4) Place HI-LO switch in the HI position. If
the motors and input circuits from overload and
fan motor fails to operate at high speed in the
ventilate mode, check the following components.
(4) A thermal protector is included in the
(a) Circuit breaker auxiliary switch;
heater circuit and installed near the heaters to
continuity from C to N.O.
p r o t e c t them
(b) Fuses F1 and F2: continuity.
overheating from failure of air flow.
(c) S e l e c t o r s w i t c h : c o n t i n u i t y f r o m
(5) A high and a low pressure safety cutout
S/W2, 2 to B.
t u r n s off the cooling operation in the event of high
(d) T o g g l e s w i t c h S 7 : c o n t i n u i t y .
or low pressure in the refrigerant system. The
( e ) Time delay relay K9: continuity from 2
cutouts operated from the refrigerant system
p r e s s u r e , control the voltage to the electrical control
(f) F a n s p e e d r e l a y K 7 : c o n t i n u i t y f r o m 1 5
to 16, 3 to 4 and 6 to 7.