!WARNING!: Maintenance should be performed by trained personnel only.
Incorrect maintenance may result in improper operation and serious injury. The unit should be inspected before each use and at least annually.
All components should be regularly checked as follows:
High Limit Switch
The high limit switch should be checked to ensure the burner will shutdown if supply air temperature exceeds 220’F This can be done by placing an operating unit behind the test unit so its discharge air is drawn into the supply air of test unit.
Gas Valve Delay Timer (DF1500)
This timer should be regularly checked to ensure proper high fire operation. To do this, turn unit onto
MANUAL-HIGH FIRE. After 15 seconds, unit should go from low to high fire.
Air Proving Switch
Remove 1/4” aluminum tubing from inside chamber ( behind fan blade) and blow out with air pressure to ensure no obstructions are inside tube. Replace tube, then with a minimum of 12” X 12” piece of cardboard, place at the top center of the end plate screen. Start unit with gas off. The unit should run for 15 seconds without the burner on light coming on, or the ignition controller LED light flashing then shut off. If the blower on light does come on, replace air switch.
Ignition Controller
With gas off, start machine. Red light on controller should flash for 1 second then stay off. After 5 seconds, ignitor should spark for 4 seconds, then red light should flash 3 times then unit will shut down. With gas on, start unit. Once flame is proven, turn off yellow handled ball valve. Once controller senses flame loss, it should try for ignition (spark) for 4 seconds, then flash red 3 times to indicate flame failure.
Flame Current Check Single Spark and Sense
To measure flame current, disconnect the input voltage, and attach the leads from the multimeter with a DC microampere scale to FC+ and FC-terminals to the 35-70 flame sense test pins found on the Fenwal ignition controller. Reconnect the input voltage and initiate the call for heat. After sparking is complete and the flame
is established, the meter should read min. 1.0 DC microamperes or higher. If meter reads below “0” on the scale, meter leads are reversed. Disconnect power and reconnect meter leads for proper polarity.
Motor
To prevent motor overheating, ensure motor is clean and free of dust and dirt.
Thermostat
Check thermostat by turning unit to thermostat mode, unit should start and stop according to call for heat from
stat.
Spark plug
Should be checked regularly to ensure a good spark. Set gap at 1/16”.
Manifold-Gas leak testing
After removal for service or replacing components on the gas manifold, a gas leak test must be performed.
1.Close main gas firing valve on the gas manifold.
2.Connect your source of gas to the gas manifold.
3. Once connections are tightened, open source gas. Start unit
4. On each connection and fitting apply soap solution and check for bubbles. This will indicate a gas leak if bubbles continue to form.
5. Fix any leaks that are found by applying pipe dope to the leaking fitting or connection and retighten.
Check for leaks once repairs, if any, are made.
6. Open main gas firing valve and start the unit.
7. Once the unit is operating and the burner is running, redo the soap test to ensure gas fittings are tight.
8. Fix any leaks found.