Crown Verity DSC Series - Manual (Page 23)

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DSC Series 4.0 Maintenance • Troubleshooting Guide
Symptom Possible Cause Corrective Action
Burning of gas-air mixture
inside plenum (flashback).
Rumbling noise present.
• Heater mounted at incorrect angle.
• Excessive drafts.
• Gas leaking at orifice.
• Separation of ceramic grids.
• Ceramic grids cracked.
• Mount at a 0˚- 30˚angle from horizontal.
• Relocate heater or shield from draft.
• Check with leak detector solution.
• Replace burner.
• Replace burner.
Delayed ignition. • Electrode out of specification.
• Low gas pressure.
• Partially blocked orifice.
• Improper orifice size.
• Incorrect gas.
• See ignition system insert.
• See Section 2.0, Gas Supply.
• Clean or replace gas orifice.
• Consult distributor.
• See unit rating plate.
Low ceramic surface
temperature or excessive
rollout.
• Dirty or plugged burner ceramics.
• Partially blocked orifice.
• Low inlet gas pressure.
• High or low manifold gas pressure.
• Foreign matter in venturi tube.
• Excessive dark spots on burner.
• Gas supply piping too small.
• Incorrect gas.
• See periodic maintenance instructions.
• Remove and clean.
• See Section 2.0, Gas Supply.
• Adjust main valve regulator as specified.
• See periodic maintenance instructions.
• See periodic maintenance instructions.
• Increase inlet pressure or replace piping.
• See unit nameplate.
Control system overheating. • Heater not mounted correctly.
• Heater mounted too close to
ceiling.
• Mounting angle 0°- 30°. Level left to right.
• Observe clearance to combustibles.
Gas odor. • Loose pipe connection. • Check connections. Tighten as necessary.
Heater cycles repeatedly. • Heater located in drafty area.
• Low gas pressure.
• Thermostat located in drafty area.
• Defective flame electrode or circuit
board.
• Relocate or shield from draft.
• See Section 2.0, Gas Supply.
• Relocate thermostat.
• Replace electrode and/or circuit board.
No spark; no ignition. • Lack of 24V incoming voltage.
• Open high voltage wire.
• Improper electrode gap.
• Loose or open wire connection.
• Poor or no equipment ground.
• Unit in “safety lockout” mode.
• Defective control module.
• Check power supply.
• Isolate and check resistance, replace if
open.
• See Ignition System specifications.
• Check all wires, tighten or replace.
• Check all connections, provide positive
earth ground.
• Interrupt power source, repeat trial
for ignition.
• Replace circuit board.
Heater lights, and “locks
out” after approximately 10
seconds.
• Poor or no equipment ground.
• Polarity is reversed.
• Low gas pressure.
• Electrode not sensing.
• Heater mounted at incorrect angle.
• Defective control module.
• Check all connections, provide positive
earth ground.
• Correct wiring.
• See Section 2.0, Gas Supply.
• Relocate or replace if electrode is defective.
• Mounting angle 0˚- 30˚.
• Replace circuit board.
Spark is present. No main
gas operation. Unit “locks
out”.
• Gas valve in “OFF” position.
• Defective gas valve.
• Defective control module.
• Turn to “ON” position.
• Isolate and check for resistance, replace
if reading open.
• Replace circuit board.
Heater will not shut off. • Defective thermostat or wiring.
• Gas valve stuck or open.
• High gas pressure.
• Replace thermostat or repair wiring.
• Replace gas valve.
• See Section 2.0, Gas Supply.
Chart 4.1 • Troubleshooting Guide