Despatch LAD Series WITH PROTOCOL PLUS User Manual

Page 66

Difficulty

Probable Cause

Suggested Remedy

Improper airflow

Fan motor failure

Fan wheel seated too low on
fan shaft

Unbalanced fan wheel

Replace fan motor.

Adjust fan wheel for 3/16" clearance between
wheel and inlet ring.

Replace fan wheel.

Excessive
vibration

Dirty fan wheel

Unbalanced fan wheel

Clean fan.

Replace fan wheel.

Oven will not
control at
setpoint

Hi-limit set too low

Protocol malfunction

SSR malfunction

Air friction of recirculation fan

Set the Hi-limit higher

Replace control.

Replace SSR and/or check control output voltage.

Open exhaust air vent. Unit will not control below
minimum operating temperature with vent closed.

Heater does not
shut down until
temp. reaches
the Hi-limit
setting

Protocol malfunction

SSR malfunction

Replace Protocol

Replace SSR

NOTE: The circuit board mounted on the control panel has three status LED indicators
to help troubleshoot if the oven is not heating (LAD1-42 only).

A.

If LED 1 is not lit, check 2F and 3F (control fuses), or power switch.

If LED 1 and LED 3 are lit but not LED 2, check high limit (and optional door
switch, if installed).

If all three LEDs are lit, check 1F and 4F (heater fuses), SSR, heater, and heater
relays.