XIII Troubleshooting
The following pages contain troubleshooting charts for use in diagnosing control problems. To use these charts, go to the box marked “Start” at the top of the chart on page 37 or 39 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 appropriate troubleshooting guide for the boiler (standing pilot on page 41 or intermittent ignition on page 42). 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 pages
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 diagram in Figures 18 - 21.
4)The possible causes at the end of each branch in these charts are not listed in order of likelihood. All controls on the CWI 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)These troubleshooting charts assume that the vent damper is closed at the beginning of the troubleshooting process. With the 120 volts applied to the boiler and no call for heat, the damper should go to the closed position. If it does not, do the following:
•Confirm that 120 volts is applied to the boiler and that there is no call for heat.
•Make sure that the switch on the damper is in the “automatic” position.
•Unplug the harness from the damper and check for 24 volts across pin #1 (blue) and pin #4 (yellow).
•If voltage is present, the damper is defective or there is an obstruction in the path of the damper blade.
•If no voltage is present, there is either a loose connection in the damper harness or the limit control (L8148E or L8124E) is defective.
6)If the charts indicate that the L8148E or L8124E is defective, do the following before replacing it:
•Check for 24 volts across TV and Z. If no voltage is present, the transformer in the L8148E or L8124E is defective. It is possible that this transformer has been destroyed by a short circuit in the boiler wiring. Before replacing the control, 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.
•If 24 volts is present across TV and Z, check for 24 volts between T and W. On L8148Es, if no voltage is present, make sure that the brass jumper is present between W and Z and that the screws holding this jumper in place are both tight. If the boiler is equipped with a L8124E, voltage will only be present across T and W when there is a call for heat AND the boiler water temperature high enough to satisfy the low limit.
•If not already done, temporarily replace the thermostat across TV and T with a jumper. If the boiler fires when this is done, there is a problem with the thermostat or zone wiring.
•If 24 volts is present across T and W and the relay in the L8148E or L8124E does not pull in, the relay in this control is probably defective. Inspect the coil of this relay for visible heat damage. If such damage is found, there is a good chance 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 L8148E or L8124E is replaced.
7)When checking voltage across damper harness pins, be careful not to insert the meter probes into the pins. Doing so may damage the pin, resulting in a loose connection when the harness is reconnected.
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