Traditional troubleshooting techniques may be outdated, but old-fashioned logic still works.
By Eric Johnson
This is a continuation of last month's discussion of secondary ground-fault protection, in which Johnson examined the industry's initial experiences with SCGFP and assessed the code's impact.
The fundamentals of harmonious ground-fault practices center on grounding. If functional service ground is present, everyone's happy. Prior to the SCGFP requirement, transformers would hum right along without a service ground, albeit under unsafe conditions. Now, they will trip.
With SCGFP circuitry, a proper earth ground must be supplied with the primary. Accept nothing but a wire for this ground path. Using conduit for bond/ground is not acceptable. If you are mounting channel letters at a distance from the power service, include longer primary tie-ins in preparation for an electrician's hook-up.
Frustration peaks during SCGFP-transformer installation when proper ground isn't supplied or is insecure. Without firm bonding connections and proper materials, there's no peace of mind. Ground verification is the first step in the SCGFP troubleshooting process.
The same care must be taken to verify polarity. SCGFP circuitry is polarity-sensitive. Make sure that neutrals are indeed neutral and hots, hot. Use a multimeter to confirm that the black wires are hot and the whites are neutral in all lengths extending back from the transformers to the panel. While inspecting wiring, verify that primary supply wires aren't commingled with secondary wires. Inadvertent bundling of these wires may also cause trips.
Site surveys assume more importance. If an installation crew encounters the unexpected, penalties paid in lost time or multiple visits will escalate. Double-check the intended location of transformers, secondary wiring, tube clearances, etc. Make sure that, if someone else provided the primary power service, it's what you need.
Troubleshooting with SCGFP
The "new reality" for modern neon work assumes that "old-style" traditional troubleshooting techniques won't be the most time-effective on service calls. Pre-SCGFP, the first step might have been to obtain a spark off the transformer. Today's experience dictates that, even if that comforting spark can be achieved, there's little indication of the fault's source. If the source isn't remedied, the neon remains unlit.
Before SCGFP, a serviceman could expect to see an arc, hear a buzz or smell the ozone. Fault-protected transformers more typically shut off before conditions worsen. So, other techniques must be used to complete the job expeditiously.
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