Alto-Shaam QC-40 User Manual download pdf (Page 8)

Even though the fan LED’s are illuminated on the relay board, the

terminator must be satisfied before the fans will operate.

NOTE: IF THE EVAPORATOR COIL 1 OR EVAPORATOR COIL 2 RTD

SENSOR IS DISCONNECTED OR DEFECTIVE, THE FAN LED’S

OR THE EVAPORATOR FANS WILL NOT BE ENERGIZED. THE

RTD CONNECTIONS ARE LOCATED, IN THE LOWER RIGHT

CORNER OF THE CPU BOARD AT THE J6 PLUG (

FIGURE 14).

The defrost heaters are powered by the

relay board, through the J3 and J4 plugs on

the upper middle of the relay board (

Figure

15). L

is continuously supplied to the

defrost heaters and L

is switched by the "ice

cube" relays with protection by the 4A fuses

or 6.3A fuses in the model QC-40 (F7-F12).

goes to the defrost terminator, located on

a plate above the evaporator, and which

closes at 30 degrees F (-1 degree C) and

opens at 60 degrees F (16 degrees C). The

evaporator fan(s), solenoid(s) or

compressor(s) are not energized when the

unit is in either one of the defrost modes.

NOTE: IF THERE IS NO POWER THROUGH ANY OF THE RELAYS, INITIALLY ENSURE THE RELAY PINS

AND SOCKETS ARE CLEAN AND PROPERLY SEATED. THERE IS A RETAINING STRAP ACROSS

THE TOP OF THE RELAY TO KEEP IT FROM VIBRATING LOOSE IN THE SOCKET. TO TEST THE

RELAY COIL, USE A MULTI-METER SET TO THE OHMS SCALE. TEST ACROSS THE 2 VERTICAL

PINS. THE RESISTANCE READING SHOULD BE APPROXIMATELY 150 OHMS RESISTANCE.

The Manual Defrost time is factory pre-set for 20 minutes. When the unit is in the Manual Defrost mode, the

control will time down and the heater(s) will be activated until the defrost

terminator senses 60 degrees F (16 degrees C). At that time, the defrost

heater(s) will be de-energized and the control will finish timing down to zero.

The Control Display will read "Defrost Finished." Push the “D” key to return

to the Main Menu screen. In the Automatic Defrost mode the unit will go

into defrost whenever the evaporator fans are running for at least a 6-hour

cumulative period of time, the unit has been in the hold mode for at least 15

minutes, and the internal cavity temperature is not above 35 degrees F (1,7

degrees Celsius. When in the Automatic Defrost mode, the unit will go into

defrost, after the above conditions are met until the defrost terminators reach

60 degrees F (16 degrees C). At that time the Control Display will read

"Defrost Finished" and the unit will continue in the hold cycle.

The refrigerant solenoid valves are powered by the relay board through the

J5 plug which is located on the upper right corner of the relay board (

Figure

16). L

is continuously supplied to the solenoid coil and L

is switched by the

solid state relays on the relay board, with protection by the 300MA fuses (F13-

F14). If there is 208/240VAC supplied to the solenoid coils and the solenoid

valve is not opening, the coil may be defective. To check for a defective coil,

disconnect the leads to the coil. Using a multimeter set to the OMH’s scale,

measure between the 2 terminals. There should be 780 OHM’s resistance.

NOTE: DO NOT APPLY POWER TO A COIL THAT IS NOT MOUNTED

TO THE SOLENOID VALVE. THIS ACTION WILL CAUSE THE

COIL TO MELT.

Figure 14

DEFROST

HEATER

FUSES

6-3A

FUSES

FOR

QC-40

MODEL

DEFROST

HEATER

RELAYS

IS ALWAYS

ENERGIZED. L

IS SUPPLIED BY

THE SOLID STATE

RELAYS TO

PROPER FAN

DEPENDING ON

MODEL NUMBER.

Figure 15

COIL 1

RTD SENSOR

LEADS

COIL 2

RTD SENSOR

LEADS

Figure 16

300MA

FUSES

SOLID STATE

RELAYS

IS ALWAYS

ENERGIZED. L

SUPPLIED BY THE

SOLID STATE

RELAY TO THE

PROPER SOLENOID.

RIGHT

LEFT

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 19 20

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Alto-Shaam QC-40 User Manual Page 8

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