Growers Choice 315W CMH Lamp 3100K | 570 µmol/s SE Bloom Bulb

Growers Choice 315W CMH 3100K, a warm single-ended bloom lamp

This is the warm lamp in the Grower's Choice single-ended line, part CMH-315W/931/PGZX18/HO, sold under SKU GC315W3K01. The spec sheet rates it at 570 µmol/s and 37,000 lumens after 100 hours, which works out to 120 lm/W. Colour rendering is listed at CRI 90 or better. Rated life is 15,000 hours on ten-hour starts. It runs at 100V and 3.15A on a C182/O-rated or electronic ballast, with a 198V minimum open-circuit voltage. The base is PGZX18, the standard socket in single-ended 315W CMH reflectors. Grower's Choice rates it for open or enclosed fixtures and for any burning position. Maximum base temperature is 250°C and the bulb itself tops out at 350°C. The company says a phosphor coating on the outside of the arc tube shapes its spectrum. That coating is what pushes output toward the warm end.

How this 315W CMH bulb did in our own lamp test

In our ten-lamp CMH comparison it finished fifth on summed PAR, ahead of both Ushio lamps and several discontinued names. Its UV reading was the lowest of the group, though, so it is not the lamp to pick if short-wave light is the goal. That is worth knowing, because the maker's own copy leans on UV and far-red content. What it does well is photons per dollar in a warm, flower-friendly spectrum. At this colour temperature it sits in the bloom and transitional range and can still carry a veg room in a pinch. In a 4x4 tent, most growers start one lamp around 18 to 24 inches above the tops and come down after the stretch. Pair it with a low-frequency CMH ballast, since standard HPS and MH ballasts will not drive it. A red-enhanced 3K-R version exists in the same range for rooms that want more deep red late in flower. The cooler 4200K lamp from the same line is the better pick for dedicated veg. It is sold as a bare lamp, so the reflector, socket and ballast come separately.

Key Features

• 570 µmol/s Photon Flux: A published PPF figure lets you plan canopy intensity instead of guessing from lumens.
• 37,000 Lumens at 120 lm/W: High efficacy means more light per watt and less heat for the same output.
• Fifth of Ten in Our PAR Test: It beat both Ushio lamps on summed PAR in our side-by-side comparison.
• 3100K Bloom Spectrum, CRI 90+: Warm, broad output supports flowering and keeps plants easy to read under the lamp.
• 15,000-Hour Rated Life: Rated at ten-hour starts, it covers years of flower cycles before replacement.
• PGZX18, Any Burn Position: Fits standard single-ended 315W reflectors, open or enclosed, in any orientation.

Technical Specifications