Part number MH175/U/M replaces 15556, 2020180010, 30721370199, 58041, 69549016903, 69549580411, 715060, M175U/MED, M175X/U/MED

Ballast Compatibility:

• Magnetic (core & coil) ballasts rated M57, 175W metal halide
• Electronic ballasts rated for 175W metal halide
• Multi-tap ballasts (120V, 208V, 240V, 277V, 480V) with M57 designation
• Probe-start and pulse-start ballasts (verify lamp compatibility — this is a probe-start lamp)

Common Fixture Brands:
Lithonia, RAB Lighting, Hubbell, Cooper Lighting, Philips Stonco, American Electric Lighting, Acuity Brands, MaxLite, Howard Lighting, Venture Lighting, TCP, Plusrite, Satco, GE, Sylvania, PhilipsNote: Always verify the ballast ANSI code (M57) and wattage (175W) match the lamp specifications. Using an incompatible ballast will cause lamp failure or unsafe operation.

Why does my metal halide bulb take so long to turn on?

Metal halide bulbs require a warm-up period of 2–5 minutes to reach full brightness — this is completely normal and inherent to HID (high-intensity discharge) technology. When you first turn on the lamp, an arc is struck between the electrodes inside the bulb. This arc heats the metal halide salts and mercury inside the lamp, which vaporize and produce light. As the lamp warms up, the light output increases and the color shifts from dim/bluish to bright white. This warm-up time is not a defect — it's how metal halide technology works. Additionally, if power is interrupted while the lamp is hot (even briefly), the lamp cannot immediately restrike. It must cool down for 10–20 minutes before the arc can be re-established. This "restrike time" is a limitation of standard metal halide lamps. If instant-on capability is critical for your application, consider pulse-start metal halide lamps (faster warm-up and restrike) or LED retrofits (instant on, no warm-up required).

Bulb won't light at all

Bulb flickers or cycles on and off

Significantly reduced light output (dimming over time)

Bulb takes excessively long to warm up

Color shift — light appears pink, orange, or off-color

Bulb shuts off randomly then restarts

Visible blackening inside the glass envelope

Bulb makes buzzing or humming noise

Light output noticeably uneven

Bulb worked briefly then failed

End of rated lamp life reached

Fixture produces less light than adjacent fixtures with newer bulbs

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Metal Halide (HID)