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XII Troubleshooting
The following pages contain troubleshooting charts for use in diagnosing control problems. If troubleshooting a CB502
control system, go to the box marked “Start” at the top of the chart on page 58 and follow the appropriate path though the chart
until a box with a list of possible causes is reached. If troubleshooting a R8285 control system, go to the box marked “Start”
at the top of the chart on page 62 and follow the appropriate path though the chart until a box with a list of possible causes is
reached.If the problem is known to be within the ignition system, go directly to the ingition system troubleshooting guide on
page 64. In using these charts, the following should be kept in mind:
1) These charts are only meant to be used by a professional heating technician as an aid in diagnosing control problems.
2) Where applicable, follow all precautions outlined in the appropriate lighting instructions on page 49.
3) In general, these charts assume that there are no loose or miswired electrical connections. Before using these charts, inspect
all electrical connections on the boiler to make sure that they are tight. Also, check the wiring on the boiler against the
appropriate wiring diagrams in the Wiring section.
4) The possible causes at the end of each branch in these charts are not listed in order of likelihood. All controls on the CWD
are tested at least once in the manufacturing process and a defective control or component is generally the least likely cause.
Before replacing a component, try to rule out all other possible causes.
5) If the charts indicate that the boiler transformer is defective, it is possible that this transformer has been destroyed by a short
circuit in the boiler wiring. Before replacing the transformer, carefully inspect all low voltage wiring on the boiler for places
where it is touching the frame of the boiler or wiring on the other side of the transformer.
6) If the charts indicate that one of the relays in the CB502 board or the R8285 are defective, it is possible that a second
transformer is present in the thermostat or zone valve circuit, resulting in the application of 48 volts across the relay coil. In
older buildings, this transformer may be hidden in a location far from the boiler. If this second transformer exists, it must be
found and removed before the relay is replaced.