4
Manual
Reset
Limit
Switch
Figure 4
DGAT Series
Blower
Combustion
Fan Motor
Burner
Observation
Cover
Gas
Valve
System
Switch
Ignitor
Control
Ignition System —
Automatic Ignition Furnaces
The furnace is equipped with an ignitor and has no pilot
burner. When the wall thermostat calls for heat, the furnace
combustion fan starts. In approximately 30 SECONDS,the
ignitor energizes, t he gas valve admits gas to the main
burnerandthegasisignited.
If ignition does not occur, the ignitor will continue to operate
for a pproximately 7SECONDS.After30 SECONDS (the
combustion fan still running) the ignitor will energize again.
If ignition does not occur, the ignitor will continue for 7SE-
CONDS, and shut off. In approximately 30 SECONDS the
ignitor will attempt ignition again.
If ignition does not occur after three attempts, the system
will lock out. The system must then be manually reset by
turning t he wall thermostat to a point below room tempera-
ture, after waiting for 1MINUTE.
THE FURNACE CONTROLS AND THEIR FUNC-
TION
1. System Switch --- this system switch turns ON or OFF
the 120 volt electrical circuit that powers the furnace
controls and the blower motor. The system s witch must
be turned ON for the furnace to operate. Turn the
switch to OFF when oiling the blower motor, cleaning
the blower, etc.
2.
Fan Switch --- this fan switch is a temperature sensing
device. When t he furnace heats up, the switch auto-
matically turns the blower on. On the off---cycle, when
the furnace cools down, the sw itch turns the blower off.
3.
Limit Control --- this furnace is protected by two (2)
high temperature limit switches. The lower limit switch
is an automatic reset type.
IMPORT ANT
THE UPPER LIMIT SWITCH NEAR LEFT SIDE OF
BL OWER IS A MANUAL RESET TYPE LIMIT
SWITCH. (SEE FIGURE 4). IF BURNER DOES NOT
FUNCTION, TURN SYSTEM SWITCH TO OFF AND
PUSH RESET BUTTON IN CENTER OF LIMIT
SWITCH.
If the upper limit switch trips again soon after resetting,
turn the furnace System Switch to the OFF position and
call your authorized service technician.
CAUTION
THE CHUTE TO LEFT OF BLOWER IS HOT. USE
CARE WHEN RESETTING LIMIT SWITCH TO AVOID
BURNS TO HAND AND ARM.
4.
Gas Valve
--- gas valves are 100% shut---off type and
will fail safe if for some reason the gas is turned off or
the pilot goes out. They are also of the modulating or
“step-- open” type which means they open to a “low
fire” position and after a few seconds “step-- open”to
“high fire”.
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