Must the HID ballast be removed?

Many products require ballast bypass, while some are ballast-compatible. Follow the exact listed lamp instructions rather than a general rule.

Can an E39 corn lamp fit every mogul-base fixture?

No. Verify base standard, voltage, dimensions, orientation, socket condition and enclosure suitability.

Why can a corn lamp overheat?

The existing housing may trap heat beyond the lamp’s rated condition. Driver losses, ambient temperature, orientation and airflow all matter.

Will equal lumens produce equal lighting?

No. Source geometry and the existing reflector change distribution, glare and uniformity. Evaluate the complete retrofitted luminaire.

What labels are needed after bypass?

Use the retrofit kit’s required markings so future maintenance knows the luminaire was rewired and which replacement is permitted.

What is an LED Corn Light Bulb?: Your Brightest Questions Answered

Q: What is an LED corn light bulb?

It is a multi-sided LED replacement lamp intended to distribute light around a cylindrical body. It is often used in HID retrofit applications.

2024-07-03

1. What a Corn Lamp Is

An LED corn lamp places many small LED packages around a cylindrical body to approximate the broad distribution of an HID lamp. It is commonly offered as a screw-base replacement for metal-halide or high-pressure-sodium lamps in high bays, post tops, wall packs and similar luminaires.

The shape alone does not guarantee compatibility. The complete retrofit must fit the housing, operate on the available electrical system, manage heat and produce a useful distribution through the existing reflector or refractor.

For related planning resources, review the CPS Lighting product center.

2. Start With the Existing HID System

Document the original lamp type, wattage, ballast, supply voltage, socket, burning position and luminaire condition. A degraded socket, brittle wiring or damaged enclosure should be corrected before conversion.

Compare the maintained lighting requirement rather than matching old input watts. Existing HID output may already have depreciated, so a visual side-by-side with an aged lamp can exaggerate the apparent improvement. A sample area and measured grid give a more defensible comparison.

Compatibility item	Why it matters	Common mistake	Verification
Base and socket	Mechanical/electrical connection	Assuming E39/E40 or E26/E27 are universal	Exact product and holder data
Ballast method	Determines wiring and losses	Leaving an incompatible ballast in circuit	Listed wiring diagram
Dimensions/orientation	Fit and thermal behavior	Checking diameter only	Housing measurement and label
Enclosure/temperature	Driver and LED reliability	Using an open-rated lamp in sealed housing	Application rating
Photometry	Coverage and glare	Matching only lamp lumens	Retrofit calculation or field test

Start With the Existing HID System detail

For related planning resources, review the lighting case library.

3. Base, Voltage and Ballast Bypass

Many corn lamps require ballast bypass and direct line voltage; others are designed for a particular ballast. Follow the exact wiring diagram and listing.

Bypass work changes the luminaire and should use an appropriate listed retrofit product and labels. Match E26/E27 or E39/E40 base, voltage and physical keying as specified—similar dimensions do not replace electrical verification. Qualified personnel should isolate, test and reconnect the circuit, then mark the luminaire to prevent later installation of an incompatible HID lamp.

For related planning resources, review the lighting news center.

4. Heat, Enclosure and Orientation

Corn lamps concentrate driver and LED heat inside an existing housing. Check the product’s maximum ambient temperature, enclosed-fixture suitability, permitted orientation and required free space.

A ventilated open fixture and a sealed post top are not equivalent. The lamp’s fan, if present, adds a moving maintenance component and may collect dust. Confirm maximum overall length and diameter, socket condition and center of gravity so the lamp does not contact lenses or overload a weak holder.

For related planning resources, review the CPS Lighting company profile.

5. Photometry After the Retrofit

The existing reflector was designed around another source position and geometry. A corn lamp can send light into the reflector, through the lens and sometimes directly outward, changing cutoff, glare and uniformity.

Fixture lumens or lamp lumens cannot predict the final result by themselves. For area and roadway applications, use a photometric file for the retrofitted luminaire where available, or measure a representative installation. Check uplight, high-angle intensity and dark zones as well as average illuminance.

For related planning resources, review the project consultation team.

6. Procurement and Installation Checklist

A procurement schedule should list original system, target light level, base, voltage, bypass method, dimensions, orientation, enclosure rating, temperature range, surge protection, warranty and certification. The DesignLights Consortium treats mogul screw-base HID replacements as an application with reference-housing requirements, illustrating why housing conditions matter.

Commission the retrofit by checking wiring labels, controls, startup, stabilized power, temperature and light levels. Keep spare lamps tied to the approved model so later maintenance does not introduce a different distribution or electrical design.

For related planning resources, review the CPS Lighting.