The lighting market offers various tombstone types, and many buyers question whether to use shunted or non-shunted. Choosing the right option for linear lamps is essential to avoid risks like electrical shorts and ensure overall system safety.
Using the wrong type could lead to a fire hazard, causing damage to both the tubes and tombstones or, in the worst-case scenario, endangering lives. Moreover, using the incorrect tombstones might void the UL listing on the lamp or reduce its overall lifespan.
In this post, we will delve into the differences between shunted and non-shunted and understand when to deploy each.
What Is a Light Tombstone?
In simple terms, a light tombstone is the physical interface where the tube meets electricity. It secures the tube and connects it to power. It serves as the interface between the tube and the power source, ensuring safe and efficient transmission of electricity.
Differentiating Shunted and Non-Shunted
It is easy to recognize shunted and non-shunted if you understand how they work.
Shunted Types
For shunted lamp holders, electrical contacts feature internal connections, creating a single track for the current to travel from the ballast through the tombstone to the lamp's pins. The two metal contacts in the lamp tombstone are connected together. The shunt, which is a small piece of conductive material, bridges the gap between the terminals, allowing electricity to flow without the need for external wiring to connect them.
Electrical Current Flow Explained:
Just supply power to one end of the lamp tombstone, and the current can pass through the internal connection to make the lamp tube work. For instance, some LED tubes only need to be plugged into a lamp holder with electricity at one end to light up, and the other end does not need to be connected to electricity.
One of the key features of shunted ones is their simplicity in wiring. Because the terminals are already linked together, they are usually used in fixtures where the bulbs are connected in parallel. However, shunted ones have limitations. They are not suitable for use with dimmers or other devices that require variable current control.
Non-Shunted Type
Non-shunted type provides separate contacts, allowing for multiple entry points for wires and creating dual tracks for the current to travel.
Electrical Current Flow Explained:
The current enters from one pin at one end of the lamp tube, passes through the internal circuit of the lamp tube, and then flows out from the pin at the other end, forming a circuit.
Non-shunted types are often used when bulbs are connected in series or when the lighting setup needs adjustable current, like with dimmer switches. In a series circuit, electricity flows through one bulb to the next, and non-shunted tombstones make that wiring possible. They also give better control over the electrical flow, making them a good fit for different types of lighting systems.
Visually, this distinction is apparent, but exceptions exist. To get an accurate result, use a voltage meter, which will react when contacted in a shunted lamp holder. Do not forget to set the voltage meter to "continuity" mode.
Shunted types distribute voltage using a single pair of wires, connecting it to two internal contacts. In contrast, non-shunted tombstones deliver voltage independently to each contact via a separate wiring path.
Different Points
Electrical Connection: The most significant difference is the presence or absence of a built-in electrical connection between the terminals.
Wiring Complexity: Shunted types are easier to wire because the terminals are already connected.
Application: Shunted tombstones are commonly used in parallel lighting circuits. Non-shunted tombstones are more suitable for series circuits and dimmable lighting systems.
Compatibility: Shunted ones are often limited to specific bulb types and wattages.
Quick View Comparison Table: Shunted vs Non-Shunted
