Are you upgrading to LED tube lighting? Choosing the right tombstones is essential for safety and performance. Non-shunted tombstones are a crucial component in modern lighting installations, especially for single-ended LED tubes. This guide will help you understand what non-shunted tombstones are, why they matter, and how to choose the best ones for your lighting project—ensuring efficiency, reliability, and peace of mind.
Shunted vs. Non-Shunted Tombstones: Comparison Table
| Attribute | Shunted Tombstone | Non-Shunted Tombstone |
|---|---|---|
| Internal Contact Connection | Contacts are internally connected (joined) | Contacts are separate (not joined) |
| Number of Wiring Tracks | Single track | Two separate tracks |
| Compatible Ballast Type | Instant-start ballasts | Rapid-start, programmed-start, dimming, or ballast bypass for LEDs |
| Typical Application | Fluorescent fixtures with instant-start ballasts | Fluorescent or LED retrofits (direct wire, single-end power) |
| Ballast Requirement | Often requires ballast to remain in fixture | Suitable for direct wire/bypass (LED conversions) |
| Electrical Safety | Cannot be used for split circuit/dual-end wiring | Allows safe split wiring to each lamp pin |
| Retrofit Suitability | Limited LED retrofit options | Preferred for LED ballast bypass retrofits |
| Replacement Need When Retrofitting to LEDs | Usually replaced | Often retained or newly installed |
| Visual Identification | May have only 2 wire entry points | Usually 4 wire entry points (but check with a voltage meter to confirm) |
Everyday Usage of Non-Shunted Tombstones
Non-shunted tombstones (also called non-shunted sockets or lampholders) are a critical part of many lighting fixtures—especially when it comes to upgrading traditional fluorescent lighting to energy-efficient LED technology. You most often use non-shunted tombstones in commercial, industrial, and office settings when retrofitting old fluorescent fixtures with new direct-wire or “ballast bypass” LED T8 or T12 tubes.
Here’s how you interact with them in daily scenarios:
- Fluorescent Fixtures: Non-shunted tombstones are used in rapid-start and programmed-start ballasts. Here, each pin of the lamp gets a dedicated wire, allowing the ballast to heat the cathodes independently and prolong lamp life.
- LED Retrofit Projects: When converting fixtures to direct-wire LEDs, you generally need to remove the old rapid-start or instant-start ballast and install non-shunted tombstones. This is because LED tubes powered on a single end require independent connections to line (live/hot) and neutral.
- Lighting Maintenance: Facility managers, electricians, and savvy DIYers encounter non-shunted tombstones when troubleshooting or maintaining commercial lighting systems.
In essence: If you want safer, more energy-efficient lighting—without a ballast—non-shunted tombstones make it possible.
Benefits of Non-Shunted Tombstones
Why choose non-shunted tombstones for your retrofit or new install? Consider the following advantages:
- LED Compatibility: Most direct-wire LED tubes require non-shunted tombstones for safe operation. This is essential for single-end powered tubes, which need separate line and neutral connections.
- Enhanced Safety: Separate contacts minimize the risk of electrical shorts. Each pin is independently wired, which matches the requirements of modern LED tubes and avoids hazardous cross-connections.
- Longevity & Lamp Protection: Using the correct socket type reduces wear, prevents premature tube failure, and upholds the fixture’s UL listing or warranty.
- Electrical Flexibility: Non-shunted lamp holders allow for a range of wiring configurations—supporting advanced ballasts (programmed start, dimming) and facilitating easy future upgrades.
- Compliance: Many building codes and national standards require non-shunted sockets when retrofitting to LED for safety and UL compliance.
How to Choose the Right Non-Shunted Tombstones
Selecting the best non-shunted tombstone for your project goes beyond just picking one from the shelf. Use these criteria to make an informed, safe, and long-lasting decision:
1. Lamp Technology & Application
- If converting to direct wire/single-end powered LED tubes, non-shunted tombstones are a must.
- Confirm the LED tube manufacturer specifies non-shunted sockets for ballast bypass installation.
2. Fixture Compatibility
- Inspect your existing light fixture: Will the tombstone fit securely? Check size (mini or regular), mounting style (snap-in, slide-on, bolt-in) and pin spacing.
- Look for tombstones compatible with T8, T12, or T5 tube types as needed.
3. Wiring Capacity
- Make sure the socket accommodates the correct wire gauge, usually 18 AWG for lighting circuits.
- Non-shunted tombstones generally have four wire entry points (two per side)—this is an easy way to double-check, but always verify with a voltage (continuity) meter.
4. Certifications and Ratings
- Choose sockets that are UL-listed or certified to applicable standards.
- Opt for flame-retardant materials, good for high-heat environments (warehouses, industrial plants, etc.).
5. Mechanical Durability
- Select sockets with robust housing, solid spring contacts, and that won’t crack or lose tension with repeated tube changes.
- For locations with vibration or movement, look for locking or extra-secure models.
6. Project Volume and Cost
- For large retrofits, quantity packs may offer savings.
- Balance price with quality; inferior lampholders can cause connection failures and safety hazards.
Practical Tips & Best Practices for Non-Shunted Tombstones
- Always Turn Off the Power: De-energize the circuit at the breaker box before replacing or wiring tombstones.
- Test Existing Sockets: Do not rely solely on visual appearance to identify socket type. Use a continuity tester or multimeter. Place probes on both contacts—if you get a beep or continuity, it’s shunted; if not, it’s non-shunted.
- Label Modified Fixtures: After retrofitting for direct-wire LEDs, apply a clear sticker stating “Ballast Removed – Use Only Compatible LED Tubes – Do NOT Install Fluorescent Tubes” to avoid future confusion and hazards.
- Use Professional Installation if Unsure: Only qualified electricians should perform fixture rewiring or conversions, especially in commercial or high-voltage settings.
- Wiring: Insert wires firmly into the push-in connectors. Avoid leaving loose or exposed copper, and ensure a snug, reliable contact to prevent arcing.
- Match Your Tube Type: Double-ended LED tubes may not require fixture rewiring or non-shunted sockets; single-ended direct-wire tubes almost always do.
- Inspect Contacts for Wear: If upgrading an older fixture, check the metal contacts for corrosion or loss of spring tension. Replace any compromised tombstones.
- Check for Updates: LED technology evolves. Occasionally, new tubes offer compatibility with both socket types—read all installation instructions provided with your lamps.
- Quality Matters: Don’t compromise on safety or performance by choosing bargain, uncertified sockets, especially in areas of high use or critical applications.
Technical Comparison Table: Key Features of Non-Shunted Tombstone Models
| Feature | Standard Non-Shunted | Heavy-Duty Non-Shunted | Miniature Non-Shunted |
|---|---|---|---|
| Tube Compatibility | T8, T12 Bi-Pin | T8, T12 Bi-Pin, VHO | T5, Mini Bi-Pin |
| Contact Material | Phosphor-bronze or brass | Nickel-plated copper | Brass or copper alloy |
| Wire Size Accepted | 18 AWG (standard) | 18–14 AWG | 18–20 AWG |
| Mounting Type | Snap-in, slide-on, screw | Bolt/screw fastened | Snap-in or slide-on |
| Housing Material | Flame-retardant plastic | High-heat polycarbonate | Polycarbonate or nylon |
| Certification | UL Listed, CSA, CE | UL, CSA | UL, CE (some models) |
| Max Voltage/Current | 600V/660W | 600V/1200W | 600V/440W |
| Spring Design | Standard | Reinforced/Tight tension | Low-profile |
| Application Area | Office, schools, retail | Warehouse, factories | Under-cabinet, compact |
| Life Expectancy | 5–10 years typical | 10+ years | 3–8 years typical |
Actual features vary by manufacturer and specific fixture needs.
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Conclusion
Non-shunted tombstones are a vital—yet often overlooked—component when upgrading and maintaining modern lighting systems. With the shift toward energy-efficient LED tube technology, understanding the difference between shunted and non-shunted lampholders directly impacts your project’s safety, performance, and long-term reliability. By choosing the correct non-shunted model for your fixture and installation, you ensure compliance, electrical safety, and optimal operation for years to come.
Remember, the right tombstone not only holds your lamp in place but also ensures safe and proper electrical flow—don’t compromise on this small but crucial part of your lighting upgrade.
FAQ
-
What exactly is a non-shunted tombstone?
A non-shunted tombstone is a type of light socket (often called a lampholder) where the electrical contacts are NOT internally connected. Each lamp pin receives its own independent wire, enabling safe wiring for LED retrofits, especially single-ended direct wire tubes. -
Why do LED tubes often require non-shunted tombstones?
Direct wire (ballast bypass) LED tubes require separate line and neutral connections to the lamp. Non-shunted tombstones allow independent wiring to each pin, preventing electrical shorts and supporting the needs of modern LEDs. -
How can I tell if my current tombstones are non-shunted?
Use a voltage/continuity meter: turn power off, and place probes on both contacts of the same socket. No continuity (no beep or reading) means non-shunted; if there is continuity, it’s shunted. Visual checks alone aren’t always reliable. -
Can I use existing shunted tombstones with new LEDs?
Only if the LED tubes are specifically rated for compatibility. Most direct-wire/single-end powered LEDs require non-shunted sockets. Otherwise, you must replace shunted sockets with non-shunted ones for safety. -
What fixtures need non-shunted tombstones?
Fixtures being retrofitted for single-end powered, direct wire LED tubes, or original fixtures with rapid-start/programmed-start/dimmable ballasts require non-shunted tombstones. -
Are non-shunted tombstones safer than shunted sockets?
They provide safer, up-to-code wiring for split-circuit and single-end power applications. This reduces risk of electrical shorting or fires during LED retrofits. -
Can I convert a shunted tombstone into a non-shunted one?
No. Shunted and non-shunted tombstones have different internal structures. It is not safe or practical to modify a shunted to a non-shunted; always use the correct, purpose-built socket. -
What size of wire do non-shunted tombstones accept?
Most accept 18 AWG wires, but heavy-duty or industrial models may support up to 14 AWG. Always check the product’s technical specifications. -
How long do non-shunted tombstones last?
Quality non-shunted tombstones typically last 5–10 years or more, depending on usage frequency, environment, and installation quality. -
Are non-shunted tombstones compatible with both T8 and T12 tubes?
Yes, many are universal for both T8 and T12 bi-pin tubes, but always verify tube compatibility (pin spacing and size) before installation.
By understanding and applying the information in this guide, you’ll be equipped to confidently upgrade or maintain your lighting system with the right non-shunted tombstones—ensuring safety, efficiency, and lasting performance.