Garden & Greenhouse


G&G Product Review – The ARC Commercial CMH 315W

Posted August 1st, 2018 by Garden & Greenhouse in

When operating multiple lighting systems, an indoor horticulturist must have a lighting system that provides consistent light levels in an efficient manner. For large scale grow operations, the artificial light source must not only provide a certain level of intensity, but also deliver a consistent, balanced light spectrum. Of all the horticultural lighting technologies currently available, ceramic metal halide (CMH) lighting systems are becoming one of the most popular choices for commercial indoor growers. Ceramic metal halide systems provide commercial growers with intensity, a balanced spectrum and a good amount of the right kind of UV radiation. All in all, the balanced spectrum, incredible color rendition index (CRI), and longevity make CMH systems the most efficient and effective high intensity discharge (HID) systems on the market. Both indoor hobbyists and commercial indoor growers are reaping all the benefits CMH lighting systems have to offer.

Advantages of Ceramic Metal Halides (CMH)

Ceramic metal halide lamps contain a ceramic arc tube (much like a high pressure sodium lamp), but also use a mixture of halides and gases in the arc tube (much like a metal halide lamp). In other words, a ceramic metal halide is almost like a cross between a metal halide (MH) lamp and a high pressure sodium (HPS) lamp. CMHs are essentially a hybrid of MH and HPS technologies which is why they are able to produce such an intense, balanced spectrum of light. CMHs consume less power to produce the same light output as traditional HPS or MH HID technologies. This heightened efficiency is a big advantage for indoor horticulturists who are always searching for the maximum radiant output at the lowest electricity usage. Put another way, indoor growers are always searching for lighting technologies that provide the highest percentage of photosynthetically active radiation (PAR) per watt of energy consumed.

Although CMH technology offers a heightened efficiency over traditional HID lighting systems, it is the spectral output of this technology that is extremely impressive. Ceramic metal halides produce a full spectrum output with a color rendition index (CRI) rating around 90. CMH lighting systems are capable of delivering a spectrum very close to that of the sun, which has a CRI rating of 100. Not only is the CRI index of CMHs untouchable by other HID technologies, but the amount of PAR per watt of energy delivered by this technology is greater than other HID systems.

Another advantage of CMHs is they provide a strong amount of ultraviolet (UV) radiation. Although UV light is outside a human’s visual range, it provides multiple benefits in plant growth and plant development. CMHs actually produce all three types of UV spectrums (UV-A, UV-B, and UV-C). Since UV-C is very harmful to the eyes of humans, most CMH lamp manufacturers use a special glass which filters out the UV-C spectrum, while still allowing through the UV-A and UV-B spectrums. The final advantage of CMH lamp technology is longevity. Ceramic metal halide lamps have a longer life span than the standard metal halide. In fact, ceramic metal halide bulbs have a rated life span of 20,000 hours, whereas many horticultural specific HPS lamps have a rated life span of only 10,000 hours.

ARC Commercial CMH 315W Lighting System from Hydrofarm

The ARC Commercial CMH 315W lighting system is a complete, low-profile horticultural lighting system designed to meet the needs of commercial indoor growers. Due to its impressive full-spectrum output, the ARC Commercial CMH 315W system is the ideal lighting solution for both vegetative and flowering growth. The replaceable reflector that comes with the system is crafted from 95% reflective European aluminum and was specifically designed to distribute the CMH lamp’s photosynthetic photon flux (PPF) in a rectangular, traditional spread. This high quality reflector delivers high µmol/s when positioned closer to the plant canopy and a wider distribution of plant-usable light radiation when raised higher.

When purchasing an ARC Commercial CMH 315W system, a horticulturist can choose between a 3100K or 4200K lamp. Both lamps are top quality Philips brand CMH lamps. These lamps are able to produce excellent PPF, along with the optimal spectrums outside the PAR range which trigger photomorphogenic responses, such as increased essential oil production. In addition to the quality Philips lamps, the ARC Commercial CMH 315W system features a low frequency 50/60Hz square wave Philips brand ballast that is rated for 50,000 hours. The ARC Commercial CMH 315W system features massive thermal heat distribution fins on the ballast compartment to allow the internal electronic components to operate at the optimal temperature range and ensure an even longer ballast life. The ARC Commercial CMH 315W lighting systems are available in 208-240V, 277V, 347V, and 480V versions. In other words, regardless of the commercial facility, the ARC Commercial CMH 315W will be compatible.

Square Wave Technology

As previously mentioned, the ARC Commercial CMH 315W lighting system comes complete with a high efficiency, low frequency square wave ballast. Many electronic ballasts operate on a sine wave at high frequencies (120,000 Hertz). The square wave ballast inside of the ARC Commercial CMH 315W operates at a much lower frequency (50/60 Hz). The low frequency operation is easier on the internal electrical components, which leads to increased longevity of the entire unit. The low frequency operation also helps avoid harmonic distortion that could potentially cause a color shift in the light system’s spectral output. Put another way, lighting systems that operate on square wave technology are more consistent in spectral output and are much less likely to have any “shifts” in the spectrum during the life span of the bulb. Another advantage of the low frequency operation is that it will not cause any issues related to radio frequency (RF) interference. This is a common problem with ballasts that operate on high frequencies.

The ARC Commercial CMH 315W lighting system is just another example of how Hydrofarm continues to provide horticulturists with the very best equipment for growing plants indoors. Proudly designed and assembled in Petaluma, California, the ARC Commercial CMH 315W lighting system is the perfect solution for serious indoor horticultural hobbyists and/or commercial indoor growers. A true combination of innovative technologies come together in the ARC Commercial CMH 315W to form the ultimate complete lighting system package (the hanging hardware is even included). The impressive balanced spectrum, high CRI rating, and UV light produced by the ARC Commercial CMH 315W lighting system is sure to supply indoor crops with everything they need to flourish. From the trusted Philips brand ballasts and lamps to the 95% reflective aluminum reflector, this lighting package has everything an indoor grower needs to provide his or her garden with a harmonious blend of efficiency and effectiveness.

For more information call 800.637.9990 or visit

Read More Garden & Greenhouse Product Reviews

Click Here for  a Free Garden & Greenhouse Magazine Subscription

Click Here for a Free Garden & Greenhouse Email Newsletter Subscription