Lucent Technologies Lineage
®
2000 ECS/GPS Battery Plant J85500G-2
Issue 6 May 1999 Engineering, Planning and Ordering 3 - 13
The ampacity tables are given in the National Electrical Code
(NEC), starting with Table 310-16. These tables, together with
the appropriate notes, determine the current that will result in the
maximum allowable operating temperature for each wiring
method For instance, for the maximum temperature for Type
RHW wire is 75°C (167°F). The current that will result in that
temperature (i.e. the ampacity) is less when the ambient air
temperature is higher and also when conductors are bundled or
side-by-side.
Overcurrent
Protection
The rating of an overcurrent protection device (fuse or circuit
breaker) should not exceed the ampacity of the conductor it is
intended to protect. The absolute maximum rating permitted by
the NEC for an overcurrent protector is the next larger standard
rating above the ampacity.
Overcurrent protectors may be sized smaller than this maximum
rating. In general, however, protectors should be rated as high as
allowable to avoid nuisance tripping due to high load conditions
or inrush during start-up.
General
Guidelines
The peak current drain (List 2) is used to size the circuit
protection for each individual load. The fuse or circuit breaker
must also protect the wire connecting to it in accordance with
NEC and local code regulations.
Fuses Load fuses are not provided with the fuse panels that are
supplied with the ECS power plant. The individual fuse size
should be 150% of the List 2 current drain for the load that the
fuse is protecting.
Circuit Breakers All circuit breakers supplied with the ECS power plant can be
loaded up to 100% of their rating only if the job engineer can
determine that the user load has no short term peaks greater than
150% of its rating and not exceeding 10 milliseconds in duration.
If the characteristics of the load cannot be determined, apply a
factor of 125% instead of 100%.
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