Let's break down your lighting design and address your specific questions. Given the ceiling height and diverse area requirements, moving beyond the simple "75 lumens/sq ft" is a good idea. LEDs definitely warrant a more tailored approach.

Understanding LED Troffers and Brightness Are 2x4 4-bulb LED troffers going to be too bright? Possibly, especially with high-output LEDs. The key is lumens, not just the number of bulbs. Modern LED T8s can put out significantly more light than older fluorescent tubes. You absolutely cannot just assume a 4-bulb LED fixture will be the same brightness as a 4-bulb fluorescent one. Key

Check the lumen output per bulb on the LED T8s you're considering. Then multiply by the number of bulbs and consider the light distribution (see below).

Typical LED T8 Output

Decent LED T8 tubes can easily output 2000-3000 lumens each, and some even more. A 4-bulb fixture with 3000 lumen bulbs would be producing 12,000 lumens! This would likely be way too much for a break room.

Dimming

Consider using dimmable LED drivers and bulbs for flexibility, especially in the break room. This allows you to fine-tune the brightness to the desired level.

Fixture Spacing Rule of Thumb Simple Rule: Height-to-Spacing Ratio A common rule of thumb for fixture spacing is to use a height-to-spacing ratio. This ratio considers the distance from the light source to the work surface. General Purpose

For general area lighting, a ratio of 1:1 to 1.5:1 (Fixture height: Spacing).

High-Accuracy Work

For areas needing high light levels, a ratio of 1:0.8 or 1:1 is a good starting point.

Ceiling Height

In your case, with a 14'6" (14.5 ft) ceiling, the spacing for general areas would be approximately 14.5 ft - 21.75 ft apart. If you need high accuracy, fixtures are around 11.6ft-14.5ft apart.

Consider Light Distribution

This rule assumes a fairly wide, even light distribution pattern from the fixtures. If the fixtures have a narrow beam angle, you'll need to space them closer together to avoid dark spots. Check the fixture's light distribution curve.

Overlap

Plan for some overlap in the light coverage from each fixture. This helps to minimize shadows and create more even illumination.

Lumen Calculation for Specific Areas

Here's a more nuanced approach to lumen requirements for each area: Mechanics Area



Task

General repair, working on engines, etc.

Foot-Candles

Aim for 50-75 foot-candles on the work surface. This equates to roughly 500-800 lux.

Lumens per sq ft

75-100 Lumens per square foot (slightly higher than your initial estimate).

Considerations

Ensure good vertical illumination. This is critical when working on tall objects like engines. Focus your light on the work plane.

Fixture Selection

4-bulb troffers are probably the right type of fixture for this area, but choose lower-lumen LED T8 bulbs or use a 2- or 3-bulb fixture.

Break Room



Task

Relaxing, eating, casual meetings.

Foot-Candles

20-30 foot-candles on the table/counter surfaces. (200-300 lux)

Lumens per sq ft

20-30 lumens per sq ft.

Considerations

Lower light levels are preferred. Warm color temperature (2700K-3000K) is more inviting. Dimmable fixtures are highly recommended.

Fixture Selection

Consider smaller 2x2 or 1x4 troffers. Alternatively, a linear pendant with a frosted diffuser can create a more relaxed feel.

Paint/Fine Assembly Area



Task

Critical color matching, detail work, small parts assembly.

Foot-Candles

75-100 foot-candles on the work surface (800-1000 lux). Possibly higher for color matching.

Lumens per sq ft

80-120 lumens per sq ft.

Considerations

Excellent color rendering index (CRI) is essential. Aim for a CRI of 90 or higher. Even, shadow-free light is crucial.

Fixture Selection

4-bulb troffers are likely appropriate but you may need to increase light levels. Consider additional task lighting.

Machine Shop Area



Task

Operating machinery, precision work.

Foot-Candles

50-75 foot-candles on the work surface. (500-800 lux).

Lumens per sq ft

75-100 lumens per sq ft.

Considerations

Good vertical illumination is important. Ensure fixtures are shielded to prevent glare for machine operators. Resistance to vibration is important.

Fixture Selection

4-bulb troffers, possibly with additional task lighting near machines. Choose durable fixtures that can withstand the shop environment.

Detailed Calculation Example (Mechanics Area)


Area

Let's say the mechanics area is 20 ft x 30 ft = 600 sq ft.2.

Desired Foot-Candles

75 foot-candles.3.

Total Lumens Needed

600 sq ft 75 lumens/sq ft = 45,000 lumens.4.

Fixture Lumens

If you choose a 2x4 4-bulb troffer, and each bulb puts out 2500 lumens, the fixture provides 10,000 lumens.5.

Number of Fixtures

45,000 lumens / 10,000 lumens/fixture = 4.5 fixtures. Round up to 5 fixtures for good coverage.
6.

Fixture Spacing

Since the area is 20ft x 30ft, one way to spread the 5 fixtures is to put two fixtures along the 20ft length and three fixtures along the 30ft length. This would mean fixtures are ~10ft apart and ~10ft apart.

Important Considerations & Tips Color Temperature (CCT)

Choose appropriate color temperatures. 3500K-4000K (cool white) is generally good for work areas. 2700K-3000K (warm white) is better for break rooms.

Color Rendering Index (CRI)

Higher CRI (80+) is important for areas where color accuracy is crucial (paint/assembly).

Light Loss Factor (LLF)

Account for light loss over time due to dirt accumulation and lamp depreciation. Use a LLF of 0.7-0.8 in your calculations.

Reflectance

Higher reflectance values on walls and ceilings will improve light levels. Light color paint is preferred.

Controls

Dimmers, occupancy sensors, and daylight harvesting systems can save energy and improve the overall lighting experience.

Professional Consultation

For a complex project like this, consider consulting with a lighting designer. They can perform detailed calculations and create a lighting plan that meets your specific needs.

Safety and Approvals

Ensure all fixtures are UL listed and meet local electrical codes.

Summary

Don't stick with old formulas.1. Determine your room size.
2. What tasks are performed? Use a table to determine the Lux/FootCandles needed to appropriately light the space.3. Calculate total lumens needed.
4. Find fixtures that meet the lumen requirements.5. Determine the proper fixture spacing.
6. Adjust spacing based on obstructions.7. Test!By carefully considering the specific needs of each area, selecting appropriate LED fixtures, and using proper layout techniques, you can create a well-lit and efficient workspace for your customer. Good luck! Flag for review