Testing Auxiliary Limit; Checking Flame Rollout Switch - Daikin DBG Series Service Instructions Manual

SERVICING
S-301 TESTING AUXILIARY LIMIT
The auxiliary limit control is a preset nonadjustable control
mounted in the blower compartment area.
It is connected in series with the rollout switch wiring to the
gas valve. If its temperature should be exceeded, it will open,
interrupting the voltage to the gas valve causing it to open.
An additional limit (primary limit) control is required for safety
control of high temperature within the furnace or ductwork.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do so
may cause property damage, personal injury
or death.
1. Remove the wires from the auxiliary limit control terminals.
2. Using an ohmmeter, test for continuity across the two
terminals. No reading indicates the control is open. Push
the red reset button, test again - if still open, replace the
control.
3. If limit tests open, allow unit to cool and retest.
4. If still open, replace the control.
AUXILIARY LIMIT SWITCH
PLACEMENT FOR
BELT DRIVE MODELS
AUXILIARY LIMIT SWITCH
PLACEMENT FOR
DIRECT DRIVE MODELS
TESTING AUXILIARY LIMIT CONTROL
S-302 CHECKING FLAME ROLLOUT SWITCH
DCG units are equipped with a temperature-activated manual
reset control. This control is mounted to the manifold assembly
and is wired in series with the auxiliary limit and gas valve.
The control is designed to open should a flame roll out occur.
An over firing condition or flame impingement on the heat
shield can also cause the control to open.
If the rollout control has opened, the circuit between the igni-
tion control and gas valve will be interrupted and the ignition
control module will go into lockout. The servicer should reset
the ignition control by opening and closing the thermostat
circuit. The servicer should look for the ignitor glowing which
indicates there is power to the ignition control. The servicer
should measure the voltage between each side of the rollout
control and ground while the ignition control is try to power
the gas valve.

CHECKING FLAME ROLLOUT SWITCH

Limit Switch Operation (Applies to Primary, Auxiliary,
and Roll Out Limits) DSI systems.
43