Juniper M120 Hardware Manual page 117

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System thermal output for maximally configured AC-powered router:
(Watts DC / AC power supply 110V input 85% efficiency) * 3.41 = BTU/hr
(2,068 / 0.85) * 3.41= 8296 BTU/hr
(Watts DC / AC power supply 220V input 89% efficiency) * 3.41 = BTU/hr
2,068/ 0.89) * 3.41 = 7923 BTU/hr
Current requirement adjustment for fans running at full speed (high temperature
environment or cooling component failure):
Calculated system current (X) – Cooling (normal) + Cooling (full speed) =
X A – 3.90 A + 5.11 A =
X A + 1.21 A
Input current from a DC source other than –48 VDC (based on maximum configuration;
applies to DC power supply only):
(–54 VDC input) x (input current X) = (–48 VDC input) x (input current Y)
54 x X = 48 x 43.1 A
X = 48 x 43.1 A/54 = 38.3 A
M120 Power Supplies Description on page 71
Replacing an M120 AC Power Supply on page 239
Replacing an M120 DC Power Supply on page 245
M120 Router Chassis Description on page 7
Chapter 9: Preparation Overview
91