31 May, 2015

So why aren't you buying LED bulbs right now?

Hey, they're getting cheaper to buy and they're cheaper to use.  I mean, what's the rub, Bub? With lifespan ratings of approximately 25,000–50,000 hours, an LED bulb lasts 2 to 4 times longer than a compact fluorescent (CFL) bulb, and 20 to 40 times longer than a common incandescent bulb.

Let's look at the place where I work, the historic Old Stone Church (Presbyterian) on Cleveland's Public Square (see picture below). The small chandeliers under the balcony each used four 100 watt incandescent bulbs which were replaced with 10 watt LED bulbs rated at 800 lumens -- 2700 Kelvin.

The Kelvin number used here is the color of white light produced, 2700K is a warm white or yellowish. Higher numbers start become "cooler" or more blue-ish. We removed 360 watts from each of the ten small chandeliers (3600 watts). Despite having a lower lumen rating than the incandescent bulbs, the LEDs are noticeably brighter in the fixtures and generate much less heat.

The eight large chandeliers in the sanctuary each held a number of incandescent bulbs for a grand total of 38,600 watts. After the LED replacements were installed, a total 3800 watts are used for the eight chandeliers. So now we are using about one-tenth of the power requirement of the previous light bulbs to light the main area. And again, much less heat output and noticeably brighter.

What the property management of the church looks for in this changeover is less labor costs as well as lower power usage. The more time between bulb replacements the better.

The process of changing bulbs in the large chandeliers requires someone to climb up five stories into the bell tower and crawl hands and knees through the ceiling on a narrow plywood ramp to each fixture.  A cable is unplugged and a hand-crank hoist lowers the chandelier so that the bulbs can changed while standing on the floor.  Then reverse the process to take the chandeliers back up. There are other fixtures in the parish building that require a scaffold to be assembled to reach the bulbs. So if you're not very fond of climbing, LED bulbs are the way to go.

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