OE1G Series Channel Letter Eneon®
Neon Power Supply
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Installation Guide
A trouble-free installation of Neon Power Supplies may require special care. This guide was prepared to help minimize installation problems and assure long life for the OE1G Series of Channel Letter Eneon products.
We feel it important to show the neon installer not only the conditions to avoid when using neon power supplies, but also why certain characteristics of neon power supplies sometimes create installation problems. We hope a better understanding of these characteristics will make the best installation method more apparent.
Characteristics of Neon Power Supplies
What are the primary differences between an electronic neon power supply and a conventional core and coil type neon transformer?
· Neon power supplies are much smaller and lighter.
· Conventional transformers operate tubing at 50 or 60 Hz (cycles per second), whereas neon power supplies operate tubing at “high frequency” (typically greater than 20,000 Hertz).
What is the primary difficulty encountered when operating neon tubing at high frequency?
· High frequency operation significantly increases the detrimental effects of “capacitive coupling” in a given neon display.
What is capacitive coupling?
· Any two electrical conductors electrically insulated from each other exhibit a property called “capacitance” between each other.
· When an AC voltage is applied between these conductors an “electric field” electrically “couples” the conductors even though they are insulated from each other. This coupling effectively allows an electrical current to flow from one conductor to the other[1]. The larger the AC voltage, the more current will flow. The higher the frequency of the AC voltage, the more current will flow. Also, the larger the value of capacitance between the conductors, the more current will flow.
· Several factors affect the value of the capacitance between these two conductors:
1. The closer the two conductors are together, the larger the value of capacitance.
2. The longer the conductors, the larger the value of capacitance.
3. The longer the two conductors are in the vicinity of each other, the larger the value of capacitance (for instance, if the conductors are parallel to each other, the capacitance between them is much larger than if they crossed at 90°).
4. Conductors separated by an air insulator yield the lowest the value of capacitance. Displacing air with most other types of insulators (such as ceramic, glass, insulating polymers) increases the capacitance beyond that of air.
What are some possibly troublesome situations in neon systems where capacitive coupling plays a role?
· GTO cable in a metallic conduit or raceway – the metallic conduit or raceway is one conductor and the GTO conductor is the other. Air and GTO insulation is the insulator.
· Neon tubing mounted on tube supports against a metal backing – the neon arc is one conductor and the metal backing is the other. Air is the insulator
· Two neon tubes situated parallel and close to each other. The neon arcs are the conductors. Tubing glass and air is the insulator.
How does capacitive coupling adversely affect neon installations?
· It “bleeds off” some of the current leaving the transformer before it actually reaches all the neon tubing. This effect is very small with a neon transformer, but can be very significant when a neon power supply is used.
What are the symptoms of excessive capacitive coupling?
· All or a portion of the display is dim -- “current starving.”
· Nuisance or false tripping of the secondary ground fault protection circuitry.
· Excessive current drawn for the neon power supply – causes premature failure of the power supply. The OE1G Series is immune to this problem.
· Neon arc instability (“bubbles”)
· Potential display failure when GTO cables and tubes are too close to each other (GTO and tubing damage can result).
· “Cross-talk” between neon power supplies (power supply overheating and nuisance tripping can occur if power supplies are located close to each other).
· Localized, short-term damage to GTO cable.
What can be done to reduce capacitive coupling or to reduce its effects?
· Minimize the length of all GTO cable runs.
· Elevate GTO cable at least 1.5 inches away from all metallic surfaces. Elevate more if possible.
· Do not under any circumstances run GTO cable in metallic conduit.
· Cross GTO cables at 90° -- never run GTO cables parallel to each other. Separate the cables as far as possible even when crossing at 90°.
· Separate any adjacent GTO cable runs as far as possible.
Note: GTO sleeving will not reduce capacitive coupling – it might even increase the coupling.
· Maintain maximum possible clearance (at least 1.5 inches) between any metal surface and neon segments.
· Minimize the number of “double-backs”.
· Increase distance between adjacent neon segments.
· Order of display section connections is important. Layout the neon to minimize the voltage between adjacent tubing sections. The longer the total tubing length between adjacent sections, the higher the voltage between them. For instance, wire double-stroke tubing sections from the outside in (See Figure 1).
· Separate neon power supplies from each other as far as possible.
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Bad - Section of tubing with highest voltage closest together. Tubing may be lit evenly. |
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Good - Sections of tubing with highest voltage to ground separated the greatest distance. |
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Figure 1
How do I properly load and wire to a neon power supply?
· Follow the guidelines for minimizing capacitive coupling effects.
· Use the tube loading chart as a good first guide (see Table 1). In no case should the power supply be overloaded past the loading chart recommendation. Overloading may cause the power supply to overheat or trip off. (Excessive capacitive coupling may make it necessary to shorten tubing length below Table 1 guidelines).
Note: OE1G power supplies output the same current regardless of tube load. For this reason, a milliammeter cannot be used for loading.
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For Red Neon Tubing: |
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Glass Diameter (mm) |
25 |
22 |
20 |
18 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
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Output Voltage Rating (kV) |
Maximum Tubing Length (Feet) |
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5 |
34 |
29 |
26 |
22 |
18 |
16 |
15 |
14 |
12 |
11 |
9 |
8 |
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7.5 |
53 |
45 |
40 |
35 |
28 |
26 |
23 |
21 |
19 |
17 |
15 |
13 |
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10 |
72 |
61 |
55 |
48 |
38 |
35 |
32 |
29 |
26 |
23 |
20 |
17 |
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Recommended Pressure |
6.0 |
7.0 |
7.5 |
8.0 |
9.5 |
10.0 |
10.5 |
11.0 |
12.0 |
13.0 |
14.5 |
15.0 |
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For Hg-Argon Tubing: |
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Glass Diameter (mm) |
25 |
22 |
20 |
18 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
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Output Voltage Rating (kV) |
Maximum Tubing Length (Feet) |
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5 |
39 |
33 |
30 |
26 |
21 |
19 |
18 |
16 |
14 |
13 |
11 |
10 |
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7.5 |
61 |
52 |
47 |
41 |
33 |
30 |
28 |
25 |
23 |
20 |
18 |
15 |
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10 |
84 |
72 |
64 |
56 |
45 |
41 |
38 |
34 |
31 |
27 |
24 |
21 |
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Recommended Pressure |
6.0 |
7.0 |
7.5 |
8.0 |
9.5 |
10.0 |
10.5 |
11.0 |
12.0 |
13.0 |
14.5 |
15.0 |
Table 1
· If applicable (i.e. in border tubing, smaller channel letters, or similar applications), make every effort to “balance” both the tubing load and the GTO cable runs. A balanced system minimizes nuisance tripping (See Figures 2 & 3).
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Unacceptable |
Marginal |
Best |
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Unbalanced GTO leads. Long runs of GTO at highest voltage to ground. May nuisance trip. |
Load & leads balanced but long leads at highest voltage to ground from power supply. |
Load & leads balanced, highest voltage leads short, longest leads at lowest voltage to ground. |
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Figure 2
· The voltage to ground is the lowest at the electrical center of a display. For this reason, place the longest runs of GTO cable near the electrical center of the display (See Figure 3).
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Unacceptable |
Marginal |
Best |
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One GTO lead very long and at highest voltage to ground. May nuisance trip and tubing may be dim. |
Equal (balanced) and long lead lengths, but longest leads at highest voltage to ground - tubing may be dim. |
Balanced tubing & leads, longest leads at lowest voltage to ground. |
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Figure 3
· If the display is mixed neon and argon tubing, attempt to connect the neon portion of the tubing directly to the transformer high voltage output. Since for a given length and diameter, neon tubing drops more voltage than argon tubing, connecting the neon tubing directly to the transformer drops the overall voltage to ground on the rest of the display in a shorter distance, thus reducing the effects of capacitive coupling.
· In some applications (POP-like displays, certain skeletal displays, etc.) it is impossible to balance either GTO or tubing. In such displays, do everything possible to shorten GTO jumps. In such cases, it is a good idea to connect the power supply to tubing near the center of the sign, connecting other tubing sections as you move outward. Also try to place longest runs of GTO near the electrical center of the display. This reduces the effects of capacitive coupling from the GTO to any metallic surface (See Figures 4, 5, 6).
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Might Trip Off |
Best |
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Figure 4
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Channel Letter Examples (not to scale nor meant to show proper clearances) |
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Unacceptable – long & unbalanced GTO. Likely to trip off |
Best - Balanced tubing & leads, longest leads at lowest voltage to ground. |
Very good. Double-stroke letter - Balanced tubing & short leads. |
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Figure 5
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Multiple Channel Letter with One OE1G Notice shortest possible leads from OE1G to tubing, longest interconnecting GTO leads nearer to center of display. (not to scale nor meant to show proper clearances) |
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Figure 6
· Do not mid-point ground the tubing. The power supply will trip off.
· If GTO cable is to be run through a hole in a metallic partition, leave at least ½” clearance between the surface of the GTO and the edges of the opening. Use an approved bushing to keep the GTO cable centered in the hole. When GTO is brought near the sharp edges of any electrically-conductive material, the GTO can degrade very quickly.
What are some indications of improperly loaded or wired neon power supply?
· Power supply trips off immediately or occasionally.
· A portion of the tubing is dim.
· Bubbles under extreme overload, some displays may show evidence of phenomenon -- shed load.
· Short-term GTO failures.
May OE1G products be dimmed?
· No
May OE1G products be flashed?
· Yes, but only with an electronic as opposed to mechanical flasher.
What causes the tubing to flash several times, then go out, when voltage is applied to the neon power supply?
· Flashing of the display is caused by:
1. A secondary ground fault somewhere in the display
2. A tubing overload.
3. Cracked or broken tubing, GTO not connected.
4. A direct short of the power supply outputs.
What is secondary circuit ground fault protection (SCGFP)?
· It is a function incorporated into a neon power supply that causes the power supply to trip off when a leakage current to ground of exceeds a certain value. This is a requirement of Underwriters Laboratories Standard UL 2161. The maximum “trip” point per UL 2161 is 15 milliamperes. UL 2161 was created in response to changes in the 1996 National Electrical Code. This requirement was created in an effort to reduce the number of fires believed to be of neon origin. All neon power supplies rated at greater than 2000 volts to ground and/or with greater than 33 milliamperes possible between any high voltage output lead and ground or from one output lead to any other.
· Incorporation of SCGFP can create “nuisance tripping” situation when using neon power supplies because of the adverse effects of capacitive coupling, so it is important to follow all the above guidelines to reduce capacitive coupling and/or to reduce its effects.
Note: The OE1G series incorporates a circuit to reduce the occurrence of nuisance tripping due to capacitive coupling.
Can neon power supplies successfully operate at the same high temperatures as conventional neon transformers?
· Neon power supplies are typically much more efficient than conventional transformer, so they contribute significantly less heat to the enclosure in which they are mounted. This simply means, all other things being equal, a neon power supply will run cooler than a transformer. However, since electronic components in any neon power supply are more sensitive to high temperatures than a neon transformer the published maximum operating temperatures should never be exceeded. As a rule of thumb, for every 10°C increase in the operating temperature of a neon transformer or power supply, its life expectancy is reduced by approximately 50%, so one should always strive to lower the operating temperature of the power supply as much as possible.
What can be done to lower neon power supply operating temperature?
· Allow good air flow over the power supply.
· Mount the power supply solidly to inside of a surface that is exposed to outside air on the opposite side.
· Reduce the neon tubing load in areas where very high temperatures are expected.
What can be done to extend the life of a neon power supply in very high temperature locations?
· The recommended maximum operating temperature for all France OE1G power supplies is -30 to 122°F (-34 to 50°C). So, at the maximum temperature of 122°F one can expect long life at 100% of rated tubing load. However, if 122°F is exceeded the power supply may still be used if tubing load is reduced. The following derating guide should be used:
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Ambient Temperature (°F) |
122 |
131 |
140 |
149 |
158 |
167 |
178 |
185 |
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Derating Factor (%) |
100 |
90 |
80 |
70 |
60 |
50 |
40 |
30 |
Table 2
Derating factor: The percent of the published full tubing load (per Table 2 above) that may be driven at the ambient temperature given in the chart.