10-watt, 16-watt and 28-watt 2D lamps may be operated in any position. 21-watt, 38-watt, 39-watt, and 55-watt 2D lamps must be used with the leg market (a) in the diagram below the bend (b), in order to avoid overheating the end of the cap marked (c).
4-Pin lamp minimum starting temperature is a function of the ballast. Most ballasts are rated with a minimum starting temperature of 50 degrees F (10 C). Ballasts are also available that provide reliable starting to 0 degrees F (-18C) and -20 F (-29C).