Vermont Casting DBT36 - Manual (Page 25)

10002789/0 -25- DBT33/DBT36/DBT39
TROUBLE SHOOTING THE GAS CONTROL SYSTEM
SIT NOVA 820 MILLIVOLT VALVE
Note: Before trouble shooting the gas control system, be sure external gas shut off is in the "On" position.
WARNING: BEFORE DOING ANY GAS CONTROL SERVICE WORK, REMOVE GLASS FRONT.
SYMPTOM POSSIBLE CAUSES CORRECTIVE ACTION
1. Spark ignitor will not light A. Defective or misaligned Using a match, light pilot. If pilot lights, turn off pilot and
electrode at pilot. push the red button again. If pilot will not light - check gap
at electrode and pilot-should be 1/8" to have a strong spark.
B. Defective ignitor (Push Button) Push Piezo Ignitor Button. Check for spark at electrode and
pilot. If no spark to pilot, and electrode wire is properly
connected, replace ignitor.
2. Pilot will not stay lit after A. Defective pilot generator 1. Check pilot ame. Must impinge on thermocouple/
carefully following lighting (thermocouple), remote wall thermopile. Note: this pilot burner assembly utilizes both-
instructions. switch. a thermocouple and a thermopile. The thermocouple
operates the main valve operation (On and Off). Clean
and or adjust pilot for maximum ame impingement on
thermopile and thermocouple.
B. Defective automatic valve Turn valve knob to "Pilot". Maintain ow to pilot; mil
liv olt meter should read greater than 10 mV. If the reading
is okay and the pilot does not stay on, replace the gas
valve. Note: An interrupter block (not supplied) must be
used to conduct this test.
3. Pilot burning, no gas to A. Wall switch or wires defective Check wall switch and wires for proper connections.
main burner Jumper wire across terminals at wall switch, if burner
comes on, replace defective wall switch. If okay, jumper
wires across wall switch wires at valve, if burner comes
on, wires are faulty or connections are bad.
B. Thermopile may not be 1. Be sure wire connections from thermopile at gas valve
generating sufcient terminals are tight and thermopile is fully inserted into pilot
millivoltage. bracket.
2. One of the wall switch wires may be grounded. Remove
wall switch wires from valve terminals if pilot now stays
lit, trace wall switch wiring for ground. May be grounded
to replace or gas supply.
3. Check thermopile with millivolt meter. Take reading at
thermopile terminals of gas valve. Should read 250-300
millivolts (minimum 150) while holding valve knob de-
pressed in pilot position and wall switch "Off". Replace
faulty thermopile if reading is below specied minimum
C. Plugged burner orice. Check burner orices for debris and remove.
D. Defective automatic valve Turn valve knob to "On", place wall switch to "On" millivolt
operator. meter should read greater than 100 mV. If the reading is
okay and the burner does not come on, replace the gas
valve.
4. Frequent pilot outage A. Pilot ame may be too low Clean and/or adjust pilot ame for maximum ame
problem. or blowing (high) causing the impingement on thermopile and thermocouple.
pilot safety to drop out.
B. Possible blockage of the vent Check the vent terminal for blockage (recycling the ue gases)
terminal.