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Direct Wire LED T8 Tube Lights and What You Need to Know About Sockets.

Posted by Doug Root on May 02, 2016

If you’re looking to make the switch to LED but you need some help wiring T8 LED bulbs, read on to learn more about the installation process of  direct wire LED T8 tubes using these helpful tips and the LED tube light connection diagram below.

Sockets

Sockets

Non Shunted

Non Shunted

Non Shunted and Shunted Sockets

Non Shunted and Shunted Sockets

1. Most common type of sockets are
non-shunted and shunted. Non-shunted on the left
and Shunted on the right side.
Verify the type of socket, or ‘tombstone’.

2. Typical wiring for
N/L-Neutral/Load
Side, the other Socket
will have no Power.

3. To confirm which type of socket is in the existing fluorescent
fixture, a voltage meter should be set to “continuity”. If the two
tombstone socket contacts show positive continuity, power flows
between the contacts and the socket is shunted.

What You Need to Know

Some shunted sockets may have 2 entries like the non-shunted socket, or tombstone. The contacts in shunted sockets connect directly at the socket so power moves from one contact to the other.

Note: the “shunt” may be internal to the socket and may not be viewable like in the picture above. Before installation you must confirm which type of socket is in the existing fluorescent fixture.

As a general rule T8 fluorescent fixtures with an instant start ballast have non-shunted sockets and T12 fluorescent fixtures with a rapid start ballast usually have shunted sockets. However use a voltage meter to test "continuity". If the two socket contacts show positive continuity, power flows between the contacts and the socket is shunted.

Shunted sockets must be replaced with a non-shunted type for the LED retrofit to operate properly. If there is no continuity across the contacts, the tombstone sockets are non-shunted and can be used with the LED tubes.

We call these types of installations hard wired, ballast bypass or direct wire. The power is on one end; No driver or ballast required, as the driver is internally located inside of the plug and play or direct wire bypass tube light. After replacing the sockets, one socket will have the live power feed and the other socket will serve solely as a lamp holder, as shown in Figure 2 which features the LED tube light connection diagram. No power will be run to the other end.

led t8 non shunted wiring diagram

When wiring T8 LED bulbs, the reason this requires  non-shunted sockets is that the LED lamp is single end-powered. With shunted sockets, they work with fluorescent because you can utilize sockets on both ends of the fixture to complete the circuit. With LED you would have to put live AND neutral into the same side of the same socket, which would not work. With non-shunted sockets you can rewire and have one end live accepting the 120 or 277V circuit.

Pros & Cons

Pros – No need to replace or maintain the ballast any longer.
Cons – Safety concerns over someone down the line putting in a fluorescent tube and it malfunctioning or possibly exploding due to the direct line current not being regulated through a ballast. Currently there is a sticker that installers are instructed to be apply at the time of the retrofit to alert that the wiring of the LED bulbs has been altered. This method is also labor intensive and may void the UL classification. Relabeling required.
*Power must be turned OFF. Must Be done by Electrician.

It is imperative that one understands the system they are working with when retrofitting a fluorescent system to an LED direct wire system. For those of you who want to simply go LED but do not want to hassle with wiring T8 LED bulbs, then the "plug and play" option is the one you want.

Read more about plug and play LED T8 lamps here.

Get Expert Help from ALB

When you’re looking for the experience of seasoned lighting professionals, look no further than Atlanta Light Bulbs. We not only specialize in quality lighting from the most trusted brands in the industry, but in providing expert customer service to answer any questions you may have. For more information about wiring T8 LED bulbs, replacement tombstone sockets, or other lighting solutions, contact us today!

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