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knowledge of possible problems, and the probable causes of each. With this knowledge, the techni-
cian should be able to isolate and correct any problem encountered.
Problems that are likely to be encountered can be grouped into five broad categories:
1. Ignition failures
2. Improper burner functioning
3. Improper temperature control
4. Controller-related problems
5. Autofill system problems.
The probable causes of each category are discussed in the following sections. A series of trouble-
shooting guides (decision trees) is also included at the end of the chapter to assist in identifying
some of the more common problems.
6.7.1 Ignition Failures
Ignition failure occurs when the ignition module fails to sense a flame within 4 seconds and locks
out. When this happens, the module sends 24 VAC through the interface board alarm circuit to the
controller and the trouble light on the timer control panel lights.
The three primary reasons for ignition failure, listed in order of probability, are:
1. Problems related to the gas and/or electrical power supplies.
2. Problems related to the electronic circuits.
3. Problems related to the gas valve.
PROBLEMS RELATED TO THE GAS AND/OR ELECTRICAL POWER SUPPLIES
The main indicator of a problem with the electrical power supply is that there are no indicator lights
illuminated on the unit. The main indication of a problem with the gas supply is failure of the unit to
fire. Verify that the gas line quick-disconnect fitting (if used) is properly connected, the unit is
plugged in, the main gas supply valve is open, and the circuit breaker for the unit’s electrical supply
is not tripped.
PROBLEMS RELATED TO THE ELECTRONIC CIRCUITS
If gas and electrical power are being supplied to the rethermalizer, the next most likely cause of igni-
tion failure is a problem in the 24 VAC circuit. First, verify that the drain valve is fully closed. (The
drain valve assembly includes a microswitch that must be closed for power to reach the gas valve.
Often, although the valve handle appears to be in the closed position, the microswitch is still open.)
If the drain valve is fully closed, refer to the troubleshooting guide
TROUBLESHOOTING THE 24 VAC
CIRCUIT
.
Some typical causes of ignition failure in this category include a defective sensing wire in the ignitor
assembly, a defective module, a defective ignition wire, or a defective ignitor. Occasionally an igni-