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CDM Lights: The Easy Way to Get UVA & UVB

CDM Lights: The Easy Way to Get UVA & UVB

Want bigger, bushier healthier plants with fruits and flowers that look, smell and taste better? Expose them to a broader light spectrum with more UVA & UVB. You can get it on a budget with CDM lights.

What’s a CDM Grow Light?

CDM (Ceramic Discharge Metal Halide) grow lights broaden your light spectrum to improve plant health and yield quality.

Specifically, CDM lights are known to emit lots of UVA & UVB.

Most of the systems we sell come with a Philips 930 Agro or 942 Daylight CDM lamp.


  • The 930 Agro can be used as a standalone or supplemental lamp and has a fuller light spectrum
  • The 942 Daylight lamp is a supplemental light only, with a bluer light spectrum.
MaxiBright Horizon 315W CDM Lighting System MaxiBright Horizon 315W CDM Lighting System

What are UVA & UVB?

UVA & UVB are both ultraviolet wavelengths of light that increase the production of terpenes, flavonoids, essential oils and even vitamin D.


Plants exposed to UVA & UVB:

  • Are bushier with shorter internodal spaces and more lateral branches
  • Have a better flavour and aroma
  • Produce a bigger yield
  • Have greater medicinal properties and pest resistance
  • Have more flowering sites
  • Develop bigger root networks that support heavier crops

More and more research shows how important these wavelengths of light are every day!

What CDM Lighting Systems are Available?

Most of the CDM's we sell use a 315W CDM Lamp, Maxibright Ballast and CDM Reflector.

You'll often see 'remote' and 'connect' versions of the same system.

  • In Connect systems, your ballast is fixed to your reflector
  • In Remote systems, you run your ballast remotely (maybe keep your ballast outside your tent).

The difference between each system really comes down to the reflector and what coverage area you want.

Focus Reflector


Run your light as a standalone fixture in a 0.75cm - 0.75cm - 1m x 1m area with this reflector (make sure you use the 930 Agro lamp) 

(remote reflector, remote system, connect system, connect reflector)

Horizon Reflector

Maxibright CDMMaxibright CDM

This reflector's great at preventing heat build ups. It's has a wide angle, so it slots nicely between two HID's in an 1.2m x 2.4m area without increasing your overall intensity by much - just your spectrum!

(remote reflector, remote system, connect system, connect reflector)

Euro Reflector


This is your budget reflector. This is another one you can slow between two HID lights to supplement your spectrum

(remote reflector, remote system)

How do you Position a CDM Grow Light?

It’s simple to fit them into your existing layout - just make sure you use the Horizon reflector. 

Option 1:

Simply slot 1 x Horizon CDM light between every 2 x 600W HID grow lights (if using as a supplemental light).

CDM SetupCDM Setup
CDM SetupCDM Setup

Option 2:

It’s possible to grow from start to finish under a 930 CDM lamp. The quality of yield vs. the power consumption makes this a great option for many growers. 

The best reflector for this is the Maxibright Focus Reflector in a 0.75m - 0.75m to 1m x 1m area. If you want to give it a try, you can buy your tent and light together as a complete kit.


How do they Connect to a Reflector?

CDM lamps don’t connect to a standard E40 reflector fitting. If you get a CDM lighting system or reflector from us, they'll either have an inbuilt CDM lampholder or we'll supply one with your kit. If you want to use a standard reflector that has an E40 fitting, you'll also need to buy a CDM lampholder.

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About the author

Ian's our Sheffield shop manager. He loves tinkering in the greenhouse. Drop by to see what he's growing.

GroWell Hydroponics Sheffield

Call GroWell Sheffield:
0114 243 9242

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