There are a number of different lamps in this family, and each of them seem to have had spec sheets with minor variations released innumerable times. The bi-pin lamps appear to have been designed from a clean sheet of paper. These first used a PGZ18 base, and a T9 envelope. I was skeptical about the base design for a couple of reasons - it seemed like an answer in search of a question, and they were unbelievably difficult to source. The only manufacturer's that I could initially find were in Germany and Italy, and they had minimum order quantities ranging from hundreds to thousands of units. After several months of looking, I found a US company (Mitronix - https://lighting.mitronix.com/item/me...-halide/k577a?
) that started building them and they had a minimum order of 10. There were some problems with the first versions because Philips made a slight change in the base when they came out with the PGZX18 version for open-fixture usage and didn't publicize the change for some time. Mitronix replaced all of the bases at no charge after they got their design updated - they are an excellent company to do business with. After that was worked out, I found that the base design was far superior to the Edison (mogul) screw base. It indexes the internal supports of the lamp in exactly the same spot each time, so there is no shadowing from it. The lamp makes a partial turn in the socket and locks into place similarly to automotive lamps, so there is no possibility of under- or over-torquing the lamp in the socket. This is something that I would have appreciated numerous times at the top of a 40' ladder when trying to relamp fixtures in an industrial plant.
The PGZ18 T9 lamps have single jackets and are intended for use in enclosed fixtures ONLY. The CMH lamps operate at extremely high pressures and temperatures, ranging up to approximately 2500-3000 psi and the internal temperatures can reportedly range up to 1000° C. Lamp failures, while rare, are nothing to be screwed around with. These lamps are available in 3000K (Philips "930") and 4200K ("942") versions. The 930 is rated for 30,000 hours life, 37,800 initial lumens, 120 lumens/watt efficacy and 90% lumen maintenance at 10,000 hours. The 942 is rated for 24,000 hours life, 36,200 initial lumens, 115 lumens/watt efficacy, and 90% lumen maintenance at 10,000 hours.
The PGZX18 T12 lamps have double jackets and are designed for open fixture use. The "X" suffix denotes that the sockets are incompatible with the PGZ bases, and are designed to keep you from using an enclosed-rated lamp in an open fixture (the PGZ sockets accept both versions). I have been unable to find a domestic supplier for the PGZX socket. These lamps are also available in the 930 and 942 versions. The 930 is rated for 20,000 hours life, 36,200 initial lumens, 115 lumens/watt efficacy and 90% lumen maintenance at 10,000 hours. The 942 is rated for 20,000 hours life, 34,700 initial lumens, 110 lumens/watt efficacy, and 90% lumen maintenance at 10,000 hours.
All of the above lamps were designed for architectural use, so Philips came out with a lamp that had the spectrum optimized for horticultural use. They used the T12 design that could be used in open fixtures, and enhanced the spectrum significantly. This lamp, originally the "Agro" (part #415216) and subsequently renamed to "Green Power" (part # 41521-6) is 3200K with a substantial increase in the far-red portion of the spectrum. It is rated for 20,000 hours life, 33,000 initial lumens, 104 lumens/watt efficacy and 90% lumen maintenance at 8,000 hours. I've used both the standard 930 and the Agro/Green Power, and there is a measurable improvement.
There is also a mogul-base version of the lamp available, but only offered in a 4,200K version. It is rated for 20,000 hours life, 34,300 initial lumens, 109 lumens/watt efficacy and significantly different lumen maintenance with 87% at 5,000 hours. The UVA output of this lamp is roughly 3x that of the Agro/Green Power and the 930's, and 1.5x the 942 T lamps. This lamp is offered in a very reasonable kit with the ballast and socket from Advanced Tech Lighting, but be forewarned that it is a one-man shop who has a spotty reputation for timeliness - https://advancedtechlighting.com/cdmmw.htm
Some links to suppliers of the 315w Agro/Green Power. Check shipping costs - some of the suppliers make up for low prices with high shipping or only use UPS:
GrowGreenMi, $77.78 https://growgreenmi.com/philips-mastercolor-cdm-lamp-315-w-argo-p-3100-k?gclid=CL3e39i8lMMCFcECaQodIC wADg
BulbAmerica, $74.30 https://www.bulbamerica.com/products/...FRaBaQodX78Alg
Growershouse, $94.95, on sale now 10% off, but high shipping cost, https://growershouse.com/philips-mast...amp-t12-3100-k
Horticultural Resource, $79.79, decent shipping cost, https://www.horticulturesource.com/ph...12-cs--p13536/
Greener Hydroponics, $79.30, high shipping cost https://www.greenerhydroponics.com/Ph...-_p_81225.html
I haven't used a 4200K lamp yet, but here is something for people to consider:
Originally Posted by LargePrime
Readers may care to note that the 942 bulbs with the more blue (4200K) spectrum are considered by some to grow better than the agro 3100K.