Description
2.4 Standards and guidelines
3VA molded case circuit breakers with UL and IEC certification
54 Manual, 01/2019, L1V30435333-01
Safety clearances (for IEC applications)
During a short-circuit interruption, high temperatures, ionized gases and high pressures
occur in and above the arcing chambers of the molded case circuit breaker. For this reason,
defined minimum clearances must be adhered to during installation between the molded
case circuit breakers and the mounting plates, conductor bars and other protection systems
placed in the immediate vicinity. This safety area was successfully confirmed with the help of
tests on test setups according to IEC 60947-2 (perforated grid cage).
Safety clearances are required to:
● allow pressure distribution
● prevent fire or damage caused by any diffused ionized gases
● prevent a flashover to grounded parts
● prevent arcing or short-circuit currents to live sections.
The following safety clearances apply to 3VA molded case circuit breakers with UL and IEC
approval:
Molded case circuit breaker without additional insulation measures or with short terminal cover
Molded case circuit breaker with additional insulation measures, phase barrier or long terminal
cover
A Minimum clearance between molded case circuit breaker and current paths (uninsulated and
grounded metal), see tables below
B
Minimum clearance between molded case circuit breaker and side walls left / right (uninsulated
and grounded metal), see tables below
C
Minimum clearance between two horizontally installed molded case circuit breakers, see tables
below;
applicable to fixed-mounted and plug-in versions (see chapter
Plug-in and draw-out technology
(Page 221))
D Minimum clearance between molded case circuit breaker and panel door
E Minimum clearance between live parts of connection system and grounded mounting plate
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