Malfunction Isolation Procedure

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

motor.

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.

5-11.

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,

system to

protect

against

overloads

and

check grille louver position, check filters and

overheating.

screens for cleanliness, then check fan blades for

( 1 ) One 2 amp fuse is installed in the primary

looseness.

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

overheating.

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

from

faiIure

the

event

(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

to 3.

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

circuits.

to 16, 3 to 4 and 6 to 7.

5-6