What Does GTO Stand For?

One of the most common questions we receive is, "What does GTO stand for?"

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In the neon sign industry, GTO stands for Gas Tube Only. It is a specialized high-voltage cable designed specifically to connect neon sign transformers to the electrodes of gas-discharge tubes, such as neon and argon. The name emphasizes that this cable is intended exclusively for gas tube circuits—not for general electrical wiring.

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You may also come across references describing GTO as Gas Tube and Oil (burner ignition) cable. This is because similar cable constructions are also used in oil burner ignition systems.

 

GTO Voltage Ratings

The most common type of neon sign wire is GTO-15, which is rated for 15 kV. Since neon transformers are not manufactured with output voltages above 15 kV, GTO-15 is suitable for use with any conventional neon transformer.

 

Other available ratings include:

• GTO-10 – Rated for 10 kV

• GTO-5 – Rated for 5 kV

 

Lower-voltage GTO wire is often selected when a smaller, more flexible cable is preferred for improved appearance, ease of installation, or reduced cost.

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Interestingly, GTO-10 is approved for use with all electronic (solid-state) neon transformers, including the largest 12 kV models. In fact, many electronic neon transformers are factory-equipped with GTO-10 high-voltage output leads.

 

Types of GTO Wire

There are two primary types of GTO wire:

• "Regular" GTO  -  In installations where the National Electrical Code (NEC) requires additional insulation (sleeving), this wire must be installed inside a separate protective sleeve.

• "Integral Sleeve" GTO  -  Integral sleeve GTO incorporates a better insulating layer as part of the cable's construction. Because it is already recognized as providing the required protection, no separate sleeving is needed when the NEC calls for a sleeved installation.

 

Some installers choose to use both integral sleeve GTO and additional sleeving for added protection and peace of mind.

 

Construction and Flexibility

GTO wire typically uses a stranded copper conductor to withstand the high voltages produced by neon transformers while remaining flexible during installation.

 

Standard conductor sizes include:

• GTO-15: 14 AWG stranded copper

• GTO-10: 18 AWG stranded copper

 

Because GTO-10 uses a smaller conductor, it is generally more flexible than GTO-15, making it easier to route through tight spaces.

 

Most standard GTO-15 wire uses an approved thermoplastic insulation, while integral sleeve GTO is typically insulated with silicone for increased durability and flexibility.

 

Installation Guidelines

Always install GTO wire in accordance with the current National Electrical Code (NEC) and all applicable local electrical codes.

 

When routing high-voltage wiring, it is important to always keep GTO conductors separated from one another and from grounded metal surfaces.

 

Proper spacing helps:

• Prevent nuisance tripping of the ground-fault protection built into modern neon transformers.

• Minimize corona discharge.

• Reduce the risk of arcing and insulation breakdown.

 

Following these guidelines as well as all the NEC installation requirements will help ensure a safe, reliable, and code-compliant neon installation.