This book will help electric sign companies compete for extra income by servicing parking lot and security lighting for existing customers and new ones. The book includes merchandising planning, servicing ...
George explains more advanced wiring skills.
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By George Doll
Sign installers commonly handle the field wiring of remote neon letters and exposed luminous tubing. In past columns, we have sidestepped this more advanced skill in order to concentrate on the basics.
Now, within this new series, we will begin tackling the electrical requirements and issues that deal with field-installed neon.
To discuss field wiring, we must transform our minds. We are no longer primarily signmakers. We must envision ourselves as commercial electricians. Why? Because the National Electrical Code (NEC) prohibits installing a display with 1,000 or more volts in anything but a commercial location.
Where to begin?
For this series of articles, we'll assume we meet the criteria of "qualified persons" as defined by the NEC, have passed a state electrical examination and can legally pull the municipal electrical permits required to install branch-circuit wiring for this display from the panel box through the last electrode. Consequently, we can focus on only technical issues and exclude prerequisite governmental and testing issues.
Our first task in this project is to run branch circuits from the distribution panel (breaker box) to the sign location. This is the sign-branch circuit. A simple, 120-volt branch circuit has three conductors (hot/black, neutral/white and green/ground). This simple branch sign circuit can supply no other load.
This circuit cannot power a cash wrap or display lights for the windows below. The sign circuit supplies only the sign.
Now here's a nice trick. All sign circuits must have a minimum 20-ampere rating. However, because we are now addressing neon, that circuit can be increased to 30 amperes. Understanding this code provision can significantly reduce cost. $image1
More allowable amperage means fewer overall circuits. The branch circuits can be wired to 80% of their load. A 20-ampere circuit can be loaded to 16, while a 30-ampere circuit can be loaded to 24. The code states, "Where a branch circuit supplies continuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125% of the continuous load." A continuous load carries a maximum current for three hours or more.
The NEC allows using one circuit instead of running two, 20-amp circuits for three normal power-factor, heavy-duty, outdoor, 15,000V/60mA transformers. This saves us a breaker, a panel-box position (which can be golden) and also the additional conductors (copper = $) needed to create a second branch circuit.
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