Desa DNV40NB - Manual (Page 16)

16 201835
DIRECT-VENT NATURAL GAS HEATER
DYNAVENT ®
TROUBLESHOOTING
Continued
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The electronic system is made up of two
parts: the ignition control and the glo bar.
The ignition control is the brain of the elec-
tronic system. It has several functions:
1. When the blower reaches full r.p.m., a
24-volt circuit is completed to the ig-
nition control. (Check across yellow
and orange wires.)
2. The red and blue wires at the ignition
control are the 120-volt input for the
glo-bar circuit. When the 24-volt cir-
cuit is completed, the ignition control
will complete the 120-volt circuit to the
glo bar and it begins to glow. (Check
this circuit across the two white wires
at the ignition control.)
3. After approximately 20 seconds, a 24-
volt circuit is completed through the ig-
nition control to the gas valve. (This cir-
cuit is checked from brown wire at ig-
nition control to a neutral ground.) This
circuit opens the valve, gas flows to the
burner and is ignited by the heat from
the glo bar.
Note: Glo bar remains on.
4. When the burner flame is established,
the sensing probe will sense the pres-
ence of burner flame and open the glo-
bar circuit. The glo bar will then stop
glowing.
It is important to determine the type of
problem being experienced. Then the proper
checkout procedure can be made. The fol-
lowing is a list of problems, how to identify
in which area the problem is located, and
how to correct it.
WARNINGS:
• Never connect unit or ignition
circuit to 230 volts.
• Never operate unit with glo bar
touching burner or any other
ground. Damage to ignition
control will occur.
• Be sure sensor probe never
touches glo bar. This will dam-
age ignition control.
• If the ignition control is defec-
tive, it must be replaced. It is
not field-repairable.
CAUTION: Do not attempt to
repair the ignition control. This
may alter it and cause it to oper-
ate incorrectly.
IGNITION FAILURES
OBSERVED PROBLEM
No heat (continued)
POSSIBLE CAUSE
7. Blower not operating
8. Short cycling (motor goes on and off)
REMEDY
7. A. Check power supply to furnace
B. Check electrical connections at furnace
C. With thermostat points closed, check for cir-
cuit completion at motor. If voltage is present,
replace motor. If no voltage is present at mo-
tor, check for:
• 24 volts on secondary coil or transformer. If
no voltage, replace transformer.
• If 24 volt transformer okay, check for circuit
completion across contacts on time delay
relay. Allow three to five seconds for con-
tact to close
• If circuit across contacts okay, check conti-
nuity of wiring in motor circuit
8. A. Check thermostat. Contacts should remain
closed. If contacts are breaking:
• Check thermostat anticipator setting. It
should be between .75 and 1.0
• If anticipator setting okay, check amp draw
across thermostat. If amp draw exceeds .65,
check amp draw across coil of valve and time
delay relay.
Note: On initial operation of glo
bar, there is a momentary surge of approxi-
mately 4.0 amps
• If amp draw is within limits, check for shorts
in thermostat wiring
• If wiring is okay, replace thermostat