PDBFS303 datasheet(20/23 Pages) COOPER

20 / 23 page

(2) UL508A has provisions to raise the rating of power

distribution blocks by the use of current-limiting

overcurrent protective devices such as current-limiting

fuses (i.e. class J, T, RK1, etc.) in the feeder portion of the

circuit.

(3) If the SCCR rating for a power distribution block, terminal

block or multi-lug connector is not established by (1) or (2)

above, then the SCCR is the default 10kA per UL508A,

Supplement SB, Table SB4.1.

For more in depth application material on SCCR see

Industrial Control Panel section of publication SPD or

Advanced Guide To Understanding Assembly Short-Circuit

Current Rating.

SCCR for Multi-Lug Connector (Power Distribution

Lug) Switch and Circuit Breaker

Switches or circuit breakers with multi-lug connectors for

conductor terminations serve a very similar wire management

function as power distribution blocks. However, it cannot be

assumed that when a multi-lug connector is installed on a

circuit breaker or switch, that the SCCR of the multi-lug

connector is the same as the interrupting rating of the

protective device. Multi-lug connectors are covered under UL

Standard 486 A/B. Much like a power distribution block,

multi-lug connectors are components for distributing tap

conductors to power loads and are not an integral part of the

overcurrent protective device operation. Therefore, the

multi-lug connector must be evaluated in a short-circuit test

with the specific overcurrent protective device and listed with

a specific combination SCCR. It is important to note, most

switches and circuit breakers are not short-circuit tested with

multi-lug connectors. If a multi-lug connector on a circuit

breaker or switch does not have a combination SCCR with

the specific overcurrent protective device used, then it is to

be treated in the same manner as an unmarked power

distribution block, which means the SCCR is the default 10kA

(UL508A, Supplement SB). To repeat, unless the switch or

circuit breaker with a multi-lug connector is specifically

marked with a short-circuit current rating, the actual short-

circuit current rating is 10,000 amperes (or less, if the

interrupting rating of the circuit breaker or fuse is less than

10,000 amperes). The use of a listed and tested combination

SCCR will ensure that a higher rating is achieved for the

product and aid in achieving a higher overall SCCR for the

industrial control panel.

PDB Spacing Requirements for Equipment:

Depending upon the specific application and the standard to

which the equipment is being designed, there are certain

PDBs that can meet these spacing requirements, some with a

high SCCR. The following details the spacing requirements at

600V based upon the equipment standards.

Industrial Control Panels (UL508A):

UL508A contains three important requirements to consider

when applying power distribution blocks.

• Spacing of 1˝ through air, 2˝ over surface (301 to 600V) is

required when used in a feeder circuit (that’s everything

ahead of or on the line side of the final branch circuit

overcurrent protective device).

• An assumed short-circuit current rating of 10kA for power

distribution and terminal blocks not marked with a higher

short-circuit current rating, per UL508A Table SB4.1.

• Conductor ampacity requirements based on conductor

terminal temperature ratings and UL508A conductor

ampacities

The following details the requirements regarding the use of

power distribution blocks in industrial control panels.

Use of Power Distribution Blocks in Industrial Control

Panel Feeder Circuits (600V & below)

• A Listed PDB (UL1953) can be used “as is” since it meets

the 2˝ and 1˝ spacing requirements for feeder circuits in

UL508A section 10.2 (see Table 10.2) & 28.2.4.

• A Recognized Terminal Block (UL1059) can only be used if

it meets the spacing requirements in UL508A sections 10.2

(see Table 10.2) & 28.2.1 and it is suitable for field wiring

(use Group A, C or D of UL 1059).

– Use Group A: Service — including dead-front switch

boards, panelboards, service equipment, and the like.

– Use Group B: Commercial appliances, including

business equipment, electronic data processing

equipment, and the like.

– Use Group C: Industrial, general.

– Use Group D: Industrial, devices having limited ratings.

Such as where the load on any single circuit of the

terminal block does not exceed 15 amperes at 51 to

150 volts, 10 amperes at 151 to 300 volts, 5 amperes at

301 to 600 volts, or the maximum ampere rating,

whichever is less.

Listed PDBs have adequate spacing for feeder

circuit applications but most recognized terminal

blocks don’t have the spacing required

for use in feeder circuits

Spacing between

live parts of

live parts and

UL Standard

opposite polarity

grounded parts

or enclosure

@600V

508A Feeder

Circuits

508A Branch

Circuits

1995 HVAC

Through air

Over surface

@600V

1˝

2˝

1˝

3⁄8˝

1⁄2˝

3⁄8˝

1⁄2˝

Note: Refer to Specific UL standards for complete spacing details.

Application Notes

1011

SB-BU09622

Page 20 of 23

Data Sheet 1049

PDBFS303 Datasheet(PDF) 20 Page - Cooper Bussmann, Inc.

PDBFS303 Datasheet(HTML) 20 Page - Cooper Bussmann, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Datasheet Download

Link URL