Electrical Basics

Your customers may not be master electricians, but they know if their signs are reliable. Ignoring electrical guidelines during installation can cause nagging failures, which can lead to substantially higher maintenance costs and dissatisfied customers. Professional electricians typically dedicate separate circuits to signs (Fig. 1).

If a new sign is connected to the same circuit that operates other devices, the sign company is often needlessly called to service unrelated malfunctions. To determine the source of the problem, the serviceperson must locate and troubleshoot all devices connected to the same circuit. When the sign is the source of the problem, it may trip a circuit breaker that operates other, critical devices.

Additionally, overloaded circuits create long-term problems. The maximum electrical load for a circuit breaker is 80% of its rated capacity. Thus, installers shouldn’t exceed recommended electrical loads (Table 1) when connecting new signs. To estimate neon signs’ electrical loads, add the amp ratings of every transformer (Table 2), plus any other devices, such as flashers, chasers or rotators. Loads for fluorescent, high-output (HO) lamps typically range from 3 to 5 amps per ballast.

Without testing, use 4 amps per ballast to estimate total electrical load. To determine the exact operating load, clamp an "amprobe" meter around a primary wire while the sign is illuminated ("amprobe" has become a generic term for testing devices, although the term is the registered trademark of devices manufactured by Miramar, FL-based Advanced Test Products).

 

Table 1: 120V Circuit Loading (80% of Rated Fuse Capacity)
Breaker/fuse size	Load capacity
15 amps	12 amps
20 amps	16 amps
25 amps	20 amps
30 amps	24 amps

 

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Table 2: Neon Sign Circuit Loading
Transformer	Electrical load (approximated)
15,000V/30	12,000V/30
9,000V/30	7,500V/30
4 amps	3.2 amps
2.4 amps	2 amps

In many cases, No. 10 or 12 THHN wire is used for electric-sign branch circuits. But if a sign is located a substantial distance from the power source (the electrical panel), use a larger wire size to prevent an excessive voltage drop. As the trade-size number of wire decreases, the physical size (diameter) increases.

Table 3 shows how size requirements increase for a large, electric sign (15-amp load) in proportion to the branch circuit’s length. Undersized wires can cause chronic failures of fluorescent lamps, ballasts and neon transformers. Ensure grounding by installing metallic conduit in unbroken, electrically conductive pathways from electrical panels to the sign bodies.

Whether conduit is installed inside a building or buried underground to supply an outdoor sign, its continuity must be maintained, and connections between individual conduit sections must be firm and secure.

 

Table 3: Wire Sizes for a Large Sign at Various Distances from the Panel (15-Amp Load, 120V, Single-phase Power)
Length	Wire size
0-65 ft	#12
65-110 ft.	#10
110-180 ft.	#8
180-280 ft	#6
280-450 ft.	#4

Although most electric signs incorporate fluorescent ballasts or neon transformers, retro-style signs may also incorporate incandescent lightbulbs. To calculate loads for these signs, convert watts to amps. Calculate the maximum wattage by multiplying the line voltage (typically 120V) by the maximum allowable amps for a particular circuit.

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Because a standard, 20-amp circuit has a 16-amp load capacity, the maximum load is approximately 2,000 watts. For a 15-amp circuit, 1,500W is the approximate load limit. Poor connections contribute to high-voltage arcing in neon signs. GTO wires are usually connected to a transformer’s secondary posts by wrapping the wire’s stripped end around the post and fastening it with a nut and cup washer.

Inaccessible transformers often lead to wire-attachment errors. Nuts may not be fully tightened, or the tightening pressure has pushed the wire out from beneath the cup-washer, leading to faulty primary or secondary connections. Rather than reaching blindly through a small access door to attach a wire to the transformer, use a crimp-type electrical terminal (Fig. 2), which simply attaches to the end of a wire. The wire then slips easily onto the post for a secure connection.

Use crimping, rather than ordinary pliers, to fasten the terminal securely. The essential, green wire Many antique signs I’m restoring for the American Sign Museum (Cincinnati) weren’t originally equipped with mechanical-ground (green) wires. Simple, two-wire systems were considered adequate in the early 20th Century. In fact, older homes’ original wiring, known as "knob and tube," includes only two conductors.

Today, every 120V circuit requires a three-wire feed, which includes a green wire to ground electrical devices’ metal portions. A neutral line break in a two-wire system can electrocute anyone who touches the device. When the neutral line is open, the green wire provides a backup pathway to ground.

Similarly, a serviceperson who touches an ungrounded, energized sign can receive a shock sufficient to knock him down from a ladder. But it’s not enough merely to have a green wire — you must connect it securely. Neon transformers may incorporate terminal posts for green wires, but the mechanical ground may also be directly attached to the sign cabinet via bolts or screws.

Prior to adoption of ground-fault protection, the primary connections for neon transformers could be reversed without affecting operation. But fault-protected transformers will not operate unless the primary polarity is correct. Switching controls Selecting the proper power switch for a new sign is extremely important to your customer’s convenience and safety.

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Time clocks switch signs on and off at preset times during the day. However, a time clock must be adjusted periodically and twice a year for standard or daylight savings time. Also, the tiny, on/off "trippers" that attach to the clock’s dial face must be securely fastened to maintain proper switching times. Additionally, small, electric, clock motors sometimes fail after a few years of use and must be replaced.

Use dusk-to-dawn photocell controls, sometimes called "electric eyes," only for all-night sign operation on busy streets. Allow signs on streets with little overnight traffic to sleep from 11 p.m. to 6 a.m, which decreases electrical consumption, electrical failures and required maintenance. But when business owners want to eliminate the need to adjust time clocks — or remember to throw manual switches — a photocell may be an acceptable solution.

Discuss these switching options with your customers to select the most suitable control. If ordinary circuit breakers provide the means of switching, and a sign requires more than one circuit, the sign’s breaker switches should be located next to each other vertically, in the panel. The switches should also be connected by a throw-bar that actuates them simultaneously. If not, the owner may inadvertently illuminate only a portion of the sign.

Internal wiring

Be sure to protect internal wires and connections when building a fluorescent, cabinet sign. Protect ballast wires from sharp edges by using plastic bushings at various points where the wires pass through metal. Modern sign ballasts incorporate thin wires that can be easily cut or chafed. Limit the number of internal connections when building new signs in your shop or repairing older signs in the field.

Run secondary wires, without splices, from the ballast case to the socket-wire connections. Don’t splice GTO cables in neon signs — an additional connection point increases the likelihood of failure. Also, avoid placing wires at the bottom of outdoor signs, where rainwater accumulates. Moisture that enters wire-nut connections causes many electrical failures, particularly in fluorescent signs.

Don’t leave excessively long wires inside raceways. Wires that don’t fit easily into a raceway are usually unnecessarily long. Folding, bunching or jamming wires inside raceways makes it difficult for servicepeople to install the raceway covers. Signs of distinction Product durability helps maintain your competitive advantage and customer approval.

Computers have leveled the playing field, but many sign builders still aren’t savvy about electrical designs. Leading sign professionals, however, understand that thoughtful electrical design represents the foundation of successful projects.