York Package Units: DNA
Re: Pilot Lights but Burners Won't Ignite
These package gas/electric units use a Honeywell Smart Valve for ignition.
- Sequence Of Operation
- On a call for heat, the fan timer board starts the inducer fan motor and sends 24V through the pressure switch to the Smart Valve.
- When the Smart Valve receives a demand for heat it powers the 24V glow plug and opens the pilot valve.
- When a pilot flame is sensed, the Smart Valve opens the main valve to allow gas flow to the burners.
Qty |
Possible Causes: |
1 |
Bad Smart Valve |
|
Dirty Flame Sensor |
|
Clogged Pilot Orifice |
|
Clogged Burners |
CHECKOUT:
1. Check Pilot Flame
- Observe the pilot flame to ensure that it comes into steady contact with the flame sensor.
2. Check Gas Pressure
- Check the Inlet Gas Pressure.
-
- No or Very Low Pressure = Gas Supply Issue
- Re-apply power to the unit.
- Energize a call for heat.
- Monitor inlet pressure while the glow plug energizes.
3. Check Pilot Orifice
- Disconnect the aluminum pilot tubing from the gas valve.
- Energize a call for heat.
- Ensure that gas comes out of the pilot gas port.
- No Pilot Gas = Bad Smart Valve
- Pilot Gas Present ⇒ Blow through the pilot tubing to ensure the pilot orifice is clear.
- Pilot Orifice Clear ⇒ Increase Pilot Gas Pressure
4. Check Flame Sensor
- Disconnect the pilot tubing from the gas valve (if not already disconnected).
- Remove the two screws that mount the pilot assembly to the burner manifold.
- Carefully remove the pilot assembly along with the pilot tubing.
- Clean the flame sensor. BE CAREFUL NOT TO BREAK THE GLOW PLUG!
- Re-install the pilot assembly and re-connect the pilot tubing.
- Energize a call for heat.
- Ensure that the pilot lights and the main burners ignite.
- Pilot + No Main Gas = Bad Smart Valve
- Pilot + Main Gas + No Main Flame = Clogged Burners ⇒ Remove burners and clean burner wings.