S-302 Checking Flame Rollout Switch - Daikin DP14UM 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.
AUX. LIMIT
High Voltage!
Disconnect all power before servicing or
installing. 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.
28
WARNING
Testing Auxiliary Limit Control

S-302 Checking Flame Rollout Switch

DP14UM/DP16UM 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
ignition 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 sparking 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.