Technologies > UPGRADING EXISTING T8 SYSTEMS

 

Introduction: The standard fluorescent T8 lighting system—once the model of efficiency—can itself be upgraded with newer, more efficient T8 lamp and ballast options. Potential energy savings can be as high as 18-30 percent—or more if lower light levels are acceptable. Newer T8 systems can offer other advantages, including longer lamp life, better lumen maintenance and higher color rendering capability.

Upgrade Options: A standard T8 system may include four-foot basic-grade 700 series lamps operated by 0.87 ballast factor generic electronic ballasts, installed in troffers and other fixtures over the past 10-15 years.

Several options can be considered to replace this system in an existing installation. Some options involve achieving target or lower light levels for a lower fixed wattage. Examples include energy-saving T8 lamps in 25W, 28W and 30W models operated on low (0.71-0.78) and normal (0.87-0.88) ballast factor instant-start or programmed-start ballasts.

Other options involve using high-lumen lamps with a low ballast factor ballast or using a high-lumen system and then reducing the size of the system (delamping). Examples include high-lumen T8 (“Super T8”) lamps with a low, normal or high (1.14-1.20) ballast factor ballast, or a dimming ballast.

Table 1. Operations for upgrading T8 lighting systems. Source: Lighting Wizards, 2005

LAMP FOR LAMP TABLE
opt-ions	lamp & ballast type	catalog initial lumens	catalog mean lumens	CRI	ballast factor (BF)	mean lumens with BF	# of lamps	mean lumens	mean lumens compared to basic & standard	system wattage	wattage savings compared to basic & generic electric ballast	mean lumens per watt
old hat	F34T12CW & Energy Saving Magnetic	2650	2300	62	0.89	2047	1	2047	90%	44	-47%	47
							2	4094		72	-24%	57
							3	6141		116	-33%	53
							4	8188		144	-26%	57
base case	Basic Grade 32W F32T8s & GEB (generic electronic ballast)	2800	2590	75 - 78	0.88	2279	1	2279	100%	30	0%	76
							2	4558		58	0%	79
							3	6838		87	0%	79
							4	9117		114	0%	80
1	Extra Efficient Instant Start & high-lumen 32W F32T8s	3100	2950	82 - 86	0.87	2567	1	2567	113%	28	7%	92
							2	5133		53	9%	97
							3	7700		80	8%	96
							4	10266		106	7%	97
2	Extra Efficient Instant Start & high-lumen 32W F32T8s	3100	2950	82 - 86	0.77	2272	1	2272	100%	25	17%	91
							2	4543		48	17%	95
							3	6815		72	17%	95
							4	9086		96	16%	95
3	Extra Efficient Program Start & high-lumen 32W F32T8s	3100	2950	82 - 86	0.71	2095	1	2095	92%	25	17%	84
							2	4189		46	21%	91
							3	6284		71	18%	89
							4	8378		91	20%	92
4	Extra Efficient Instant Start & 30W F32T8s	2850	2690	82 - 86	0.87	2340	1	2340	103%	27	10%	87
							2	4681		52	10%	90
							3	7021		77	11%	91
							4	9361		103	10%	91
5	Extra Efficient Program Start & 30W Lamps	2850	2690	82 - 86	0.71	1910	1	1910	84%	24	20%	80
							2	3820		43	26%	89
							3	5730		67	23%	86
							4	7640		86	25%	89
6	Extra Efficient Instant Start & 28W F32T8s	2750	2575	82 - 86	0.87	2240	1	2240	98%	25	17%	90
							2	4481		48	17%	93
							3	6721		71	18%	95
							4	8961		96	16%	93
7	Extra Efficient Instant Start & 25W F32T8s	2400	2280	82 - 86	0.86	1961	1	1961	86%	21	30%	93
							2	3922		43	26%	91
							3	5882		63	28%	93
							4	7843		82	28%	96
8	Extra Efficient Program Start & 32W F32T8s	3100	2950	82 - 86	0.60	1770	1	1770	78%	24	20%	74
							2	3540		44	24%	80
							3	5310		66	24%	80
							4	7080		88	23%	80
NOTES: 1) Mean lumens is at 40% of rated lamp life; 2) system wattages are based on 277V and may be slightly higher for 120V; 3) Basic and Standard
has typical 700 series F32T8 lamps and generic electronic ballast; 4) savings with 25-30W energy-saving F32T8 lamps is much less without extra-efficient
ballasts--typically, about half the lamp wattage difference; 5) the higher the CRI of the options can help offset fewer mean lumens; 6) many of the above
numbers are based on composites and exrapolations, so do not be concerned about small differences, like a difference of one or two in mean LPW;
7) wattage and ballast factor for some 0.60 BF programmed-start ballast are estimates; 8) more wattage can be saved with the 3100-lumen 32W F32T8s
with delamping--two 3100-lumen F32T8s with 1.15 BF draws 73W and can often replace three basic-grade F32T8s or four F34T12s; 9) it is highly
recommended to do your own calculations with specific lamps and ballasts.
© 2005 Stan Walerczyk, LC, Lighting Wizards.
Wattage and BF for some 0.60 BF program start ballasts are estimates.

Applications: If the existing lighting system has reached a point at which the ballasts are starting to fail, consider a lamp-ballast system upgrade with expanded options for maximum energy savings. As the electronic ballasts in these older projects reach the end of their life, it can be advantageous to replace them all at once and save even more energy. At 70-80 percent of their expected life, the failure rate for ballasts starts increasing. A typical commercial installation, operating about 4,000 hours per year, will enter this phase of system life between 10.5 and 12 years after installation. Since ballast replacement is already assured, the only cost to be justified is the incremental cost of choosing between standard and high-efficiency technology, rather than the total “parts and labor” cost of re-ballasting a new, or moderately new, installation.

If the existing lighting system is relatively new, consider replacing the standard 32W T8 lamps with energy-saving 25W, 28W and 30W T8 lamps.

Another ideal application involves previously over-lighted spaces, where there is an opportunity to reduce lamps and wattage.

In each of these cases, the higher the applicable energy rates or the more an existing space is over-lighted, the better the ROI and payback, and the greater the cost-saving opportunity for the owner.

Limitations: Energy-saving T8 lamp types (25W, 28W and 30W) were originally designed for use with instant-start ballasts. While widely used, instant-start ballast operation may result in shorter lamp life in applications where the lighting system is frequently switched, such as in spaces with occupancy sensors. Manufacturers have begun to address this issue with new programmed-start ballasts that are compatible with energy-saving T8 lamp types. Programmed-start ballasts are rapid-start ballasts that start the lamps using a method that decreases wear and tear on the lamp and increases its average life—highly suitable for use with frequently switched lighting systems. When selecting a programmed-start ballast, make sure it was designed, and is compatible, with the selected energy-saving T8 lamp type.

Another limitation is that energy-saving T8 lamps are not compatible with dimming ballasts. If dimming is desired or required, consider using high-lumen Super T8 lamps, as most are dimmable and most allow for the widest range of lumen output because they start higher than standard T8 lamps.

Energy-saving T8 lamps typically have minimum starting temperatures of 60°F or greater. If exposed to air colder than 60°F during operation, they may exhibit snaking or striation.

Super T8 Lamps: For clarification, high-lumen “Super T8” lamps are not subject to the above limitations. Super T8 lamps also offer higher maintained efficacy (lumens of light output per watt of electrical input) and, depending on the application, can result in the highest possible energy savings.

See also:

High-Efficiency Electronic Ballasts

Energy-Saving T8 and Super T8 Lamps

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