Alto-Shaam QC-50 Operations Instructions download pdf (Page 20)

4.5 TROUBLE-SHOOTING GUIDELINES - CONTROL

#8400 Installation & Maintenance Manual - Pg. 18

PROBLEM

Alphanumeric display is blank.

If power is connected to the unit and the

main circuit breaker is on, the display on

the control should be illuminated with a

green tinged background.

Unresponsive control.

If the control does not respond to operator key

presses or the screen on the display appears

frozen or sluggish.

Control not receiving correct power.

If the green light located on the middle bottom

edge of the circuit board is not illuminated.

Power Failure Threshold is set too low.

Electronic control operates but fans, heaters,

and solenoids are not getting power.

No power to the relay board.

If all or a portion of the four green lights on

the relay board are not illuminated.

Excessive chill time.

— Fans not operating.

Manual defrost operational — automatic

defrost does not function.

Manual and automatic defrost does

not function.

Condensing units are not getting power or

do not function.

Display indicates

Please Close Door with the

door fully closed.

Unit will hold at refrigeration temperature

but will not Auto-Chill.

POSSIBLE CAUSE

Control needs to be reset.

Control not receiving correct power.

Power failure threshold is set too low.

Control board is faulty.

Control needs to be reset.

Power failure threshold is set too low.

Control board is faulty.

The control continuously measures a fraction of the

input power supplied to the unit. When this

fraction drops below 1.25 - 1.30 Vdc (converted to

DC) the control determines power is on the verge of

failing, saves all important data to battery memory

back-up, and prepares for a power failure.

Relay board may not be receiving full power.

One of the power supplies on the relay board may

not be functioning.

The power cable between the electronic control and

the relay board may not be properly connected

The control cable between the relay board and the

electronic control may not be properly connected

Control transformer may be incorrectly wired.

POSSIBLE SOLUTION

Press the yellow reset button located within the

locked keyboard door.

Press the yellow reset button

1. Check connector J12 to the right of light along with

other three connecting wires for secure connections.

2. Check the AC voltage across the two end wires on

the connector with a voltmeter for a reading of 22 to

26 VAC. If there is no voltage or the voltage appears

low, check power connector on the relay board inside

electrical enclosure. Also check electronic filter,

transformer, and the two fuses at the bottom of relay

board. See installation instructions.

Turn the trim-pot screw to adjust the amount of input

power used by the control to determine power failure.

1. Open the locked keyboard and locate the blue trim-

pot marked P12 just above the battery at the bottom

of the circuit board.

2. Place voltmeter red lead on the pin-connector

marked J22 (PFI) approximately 5" (127mm) under

the blue trim-pot.

3. Place voltmeter black lead on the metal nut in the

center of the board.

5. Adjust the trim-pot with a screwdriver until the

voltage of the DC-Voltmeter reads 1.70 to 1.85 volts.

Check connections on both ends of the control cable.

Make certain there is power to the relay board.

Check connections.

Check electronic filter.

Check the transformer. See installation

instructions.

Check the coil mounted fan terminator switch.

Check the fan fuses.

Check the connections between the fans and the

relay board.

Verify set-up menu for automatic defrost is set at

YES. See Booklet No. 265,

Cook/Chill Operation

and Procedures.

Check heater fuses.

Check the large, transparent, coil-type relays on

the relay board and make certain each relay is

secure in the socket.

Check the control cable for good connections.

Check the over-pressure switch on the pressure

control. This switch opens when an over-

pressure occurs and must be manually reset.

Check the compressor SC15 and SC20 fuses

located in the fuse blocks on the left side-wall on

the inside of the electrical enclosure.

Check for a faulty solid-state compressor relay by

measuring the voltage across the output side of the

relay. If the voltage reads near zero, the relay is

closed. If the voltage reads very close to line voltage,

the relay is open. Open and close these relays using

the diagnostic program (4.2) with a voltmeter to

determine if the relay is opening and closing.

Adjust the door switch.

Make certain the food probes are being inserted into

the food BEFORE starting the auto-chill cycle.

Loose connection

Control transformer incorrectly wired.

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Alto-Shaam QC-50 Operations Instructions Page 20

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