Juniper Networks Hardware Manual page 268

M120 Multiservice Edge Router Hardware Guide
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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 29
Replacing an M120 AC Power Supply on page 173
Replacing an M120 DC Power Supply on page 177
M120 Router Chassis Description on page 6
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