Rockwell Automation 1397 DC Drive Firmware 2.xx - Manual (Page 250)

Derating C–2
Publication 1397-5.0 — June, 2001
Altitude is also a factor in enclosure heat dissipation capability. All
heat dissipation capacities in Table C.A are based on an altitude of
3300 feet (1000 meter) or less. At higher altitudes, air density, fan
efficiency, and heat transfer efficiency are all decreased. Derate the
heat dissipation capacity of the enclosure by 3% for each additional
1000 feet above 3300 feet.
An alternative to heat dissipation through radiation and conduction
in totally-enclosed cabinets is to cool the cabinet air through air
conditioning. Since air conditioners are rated in terms of BTU/HR,
controller watts loss must be converted to BTU/HR. This is done by
multiplying watts loss by 3.413. Use this value to select an
appropriately - sized air conditioner.
If space heaters are required in cold or damp environments when the
Drive is not being operated, select space heaters to produce
approximately one-half of the heat dissipation capacity of the
enclosure.
Derating for High Altitude
Air Conditioning
Space Heaters