Understanding Ignition Failures

No Ignition, rough or starved ignition, or Initial ignition and immediate failure

(Lean Condition)

Possible cause:

Fuel; Not enough

-gas line too small

-gas line obstructed

-failed primary/secondary regulator

-test system gas pressure drop at ignition.  If more than 1in of WC drop gas line may be too small, obstructed, or failed primary/secondary regulator

-test pressure if pressure difference from one end of line to the other.  If large difference the gas line is too small or obstructed.  If little to no difference the regulator may have failed or be incorrectly sized.

-gas shut off closed

Turn gas on

-Failed appliance gas valve

-Improper manifold/pilot gas pressure

Test gas pressure when valve is energized.  Adjust to rated pressure.  If there is no pressure when energized or pressure doesn’t change when adjusting, replace valve.

-Obstructed gas/pilot orifice

Clean or replace related orifice

-Dirty burner/pilot burner

Clean or replace affected burner

No ignition, rough ignition, flame to large, or flame lifts off burner at ignition

(Rich Condition)

Possible Cause: Too Much Fuel

-gas pressure to high

-test incoming gas pressure against data plate.  If too high adjust regulator or contact regulators responsible party.  If pressure got to high, appliance gas valve may also need replaced

-test manifold pressure.  If too high adjust appliance gas valve.  If pressure doesn’t adjust replace gas valve.

-Orifice to large

-Check design size of gas orifice and replace if necessary

No Ignition or rough ignition

-Dirty Fuel

-All pressures, orifices, correct amount of air and correct spark could indicate dirty fuel.  Have fuel tested for cleanliness.  (LP or Oil typically, maybe bottom of tank or too much moisture present?)

No Ignition, rough ignition, pulsating/woofing ignition

(Can have symptoms of Rich Condition)

Possible Cause: Low Airflow of Fuel/Air Mix

-partially blocked intake or exhaust vent

-

-Check for partially blocked intake or exhaust vent (pressure switch can still make depending on equipment).  Modulating boilers in particular use pressure switch only to sense the combustion blower is moving air and not necessarily the correct amount.

- partially blocked inducer/combustion blower

-remove and inspect inducer/combustion blower for deteriorated or broken intake, wheel, or housing

-clogged or partially clogged condensate drain

-clean condensate trap and drain to ensure there isn’t a backup of water into the heat exchanger.

-Partially blocked or leaking heat exchanger

-usually able to determine by testing via a combustion test.  If no ignition at all is possible, it can be tested with confirmed good inducer and venting disconnected.  If pressure isn’t within requirements of equipment the heat exchanger may need replaced or cleaned.

No Ignition, rough ignition,

(Lean Condition)

Possible Cause: Too Much Airflow of Fuel/Air Mix

-Typically, the lean condition is caused by not enough gas, but incorrect combustion blowers or parts could potentially cause this

-Check that parts are all correct including all Combustion Air Orifices an correct parts if incorrect.

No Spark

-incorrect spark gap

-replace or re-gap spark ignitor depends on the ignitor and manufacturer if it is able to be re-gaped

-faulty burner/pilot ground

Repair internal appliance ground

-faulty spark generator

-replace spark generator whether it is a stand-a-lone part or if it is an integrated generator

-incorrect placement in relation to the burner

-Reposition ignitor according to manufacturer’s recommendation

-Broken ceramic or deteriorated spark rod

-Replace ignitor

Hot Surface ignitor doesn’t heat up

-Broken ignitor element

-test for correct resistance in ignitor.  Replace if not in tolerances for ignitor

-Faulty ignition module

-test if correct voltage is at ignitor in the correct ignition sequence

Appliance ignites but fails to sense flame

-No dedicated ground

-install dedicated ground to the appliance from the panel.  Also check that the panel has an earth ground rod installed.

NEUTRAL IS NOT GROUND.  FOR MOST SUCCESSFUL FLAME SENSING A DEDICATED GROUND IS NECESSARY.

- Dirty or faulty flame sensor

-clean or replace flame sensor

-if ignitor and flame sensor are integrated replace ignitor

-faulty ignition control

-replace faulty ignition control or integrated control board.