Juniper M120 - Page 117

•
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
Related
Documentation
• 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
91Copyright © 2018, Juniper Networks, Inc.
Chapter 9: Preparation Overview