Blocks and Holders
Fuse Blocks
General Information
4. Determine if NEC, CSA, UL, or other requirements
are applicable
If fuse blocks will be installed in equipment to be submitted for agency
approval, the requirements should be obtained from the approving
agency in advance of fuse and fuse block selection.
5. Select the type of wire termination
A choice of three types of wire termination is available:
a) Screw* — for use with spade lugs or ring terminals.
b) Screw with Pressure Plate* — for use with solid or stranded wire
without terminal. Recommended where vibration will be a factor.
c) Box Lug — the most durable. For use with all types of solid wire and
Class B and Class C stranded wire. Not for use with welding cable or
other rope-stranded conductors.
*
1
/
4
” Quick Connect terminals rated for up to 20A are
available on the Midget and Class CC fuse blocks.
Fuse Block Selection
The following guidelines should help simplify the selection of proper
fuse blocks:
Screw
with
Pressure
Plate
(P)
Screw
(S)
Box
Lug
(C)
1. Determine the system voltage
Since fuses are selected on the basis of system voltage, fuse blocks are
selected to match the voltage rating of the fuse.
6. Decide on the number of poles in each block
2. Determine the design short-circuit current
Available and/or design short-circuit current is an important
consideration when determining the class of fuse and fuse blocks to
use. If available short-circuit current cannot be determined, or if it will
vary with equipment location, select fuses with a 200,000 ampere
interrupting rating (A.I.R.) and mating fuse blocks with a withstand rating
of 200,000 amperes for maximum safety.
Class H fuse blocks will accept Class H or K5 fuses (which have an
interrupting rating of up to 50,000 amperes) and Class R fuses (which
have a 200,000 A.I.R.). To prevent the possibility of inserting a fuse
with the incorrect interrupting rating, the use of Class R fuse blocks is
recommended for use with Class R fuses. Use Class H fuse blocks with
Class H or K5 fuses. These fuse blocks are dimensionally the same, but
the Class R fuse blocks incorporate a rejection feature which allows only
Class R fuses to be inserted.
The number of poles for each set of fuses is determined by the
characteristics of the circuit. The option to gang individual fuse blocks
into long strips will be determined by the available space and by the
type of wire being used.
Blocks and Holders
7. Determine if fuse clips need to be reinforced
Fuse clips may have a tendency to lose some of their tension over a
period of time. This may be prevented by specifying reinforced fuse
clips. Reinforced clips are standard on certain fuse blocks (see individual
product pages).
Ordering Information
The Littelfuse fuse block part number consists of 6 or 7 components, as
shown below and in the individual fuse block data tables.
3. Determine the type and ampere rating of the fuse to be used
In addition to voltage and interrupting rating as discussed above, the
fuse ampere rating, opening characteristics (fast acting or time-delay)
and size are other important considerations in fuse selection. Once the
fuse type is selected, the mating fuse block can be chosen. Fuse blocks
are available in 30, 60, 100, 200, 400 and 600 amp ratings, and may be
used with a fuse rated at the corresponding amperage rating or below.
For example, a fuse block rated at 30 amperes may be used with a fuse
rated from 0 to 30 amperes.
For all Class R, H, J, T and 15, 20
& 60A Class G Fuse Blocks
© 2005 Littelfuse
•
POWR-GARD
™
Products Catalog
For all Class CC, Midget and 30A
Class G Fuse Blocks
111
www.littelfuse.com
Blocks and Holders
Class T Fuse Blocks
300 and 600 Volt
Features/Benefits
Bases are molded phenolic. To provide a low resistance connection and
long-range reliability, steel reinforcing springs are supplied as standard.
Larger blocks employ an integral heat sink for maximum heat dissipation.
Specifications
Voltage Ratings:
Ampere Ratings:
Approvals:
300 Volts AC
600 Volts AC
0 – 600 amperes
UL Listed (File No. E14721)
CSA Certified (File No. LR73091)
Recommended Fuses
JLLN (300V) and JLLS (600V) series fuses
300 and 600 volt fuse blocks are designed for use with miniaturized Class T
fuses. Class T fuses are very fast acting, current-limiting, and approximately
one-third the size of electrically comparable Class RK1 fuses.
Class T 300V
Amp
Rating
30
60
No. of
Poles
2
3
2
3
4
1
2
3
1
1
1
Catalog
Number
LT30030-2
LT30030-3
LT30060-2
LT30060-3
LT30060-4
LT30100-1
LT30100-2
LT30100-3
LT30200-1
LT30400-1
LT30600-1
Connector Type
(Add Suffix Shown)
Screw Box Lug
Class T 600V
Maximum
Wire Size
S = #10 CU
C = #2 CU
C = #2 CU-AL
60
#2 ⁄0 CU-AL
100
250 MCM CU-AL
(2) 250 MCM CU-AL
(2) 500 MCM CU-AL
200
400
600
Amp
Rating
30
No. of
Poles
1
2
3
1
2
3
1
2
3
1
1
1
Catalog
Number
LT60030-1
LT60030-2
LT60030-3
LT60060-1
LT60060-2
LT60060-3
LT60100-1
LT60100-2
LT60100-3
LT60200-1
LT60400-1
LT60600-1
Connector Type
(Add Suffix Shown)
Screw Box Lug
Maximum
Wire Size
S = #10 CU
C = #2 CU-AL
Blocks and Holders
100
200
400
600
CR
CR
CR
CR
CR
C
C
C
C
C
C
SR
SR
SR
Note: Reinforcing springs standard on all 300 volt Class T fuse blocks up to 100
amperes. 300 volt Class T blocks 200 amperes and larger have stud mountings.
CR
CR
CR
CR
CR
CR
C
C
C
C
C
C
C = #2 CU-AL
#2 ⁄0 CU-AL
250 MCM CU-AL
(2) 250 MCM CU-AL
(2) 500 MCM CU-AL
Note: Reinforcing springs standard on all 600 volt Class T fuse blocks up to 60
amperes. 600 volt Class T blocks 100 amperes and larger have stud mountings.
1.19"
[30.2]
LT30030
[30.2]
1.19
1.13"
[28.6]
0.218" [5.54] THRU
0.39" [9.91] C'BORE
x 0.44" [9.91] DP.
2.88
[73.0]
[73.0]
2.88"
2.25"
[57.2]
2.25
[57.2]
[7.9]
.31
1.13
[28.6]
2.38
[60.3]
[7.9]
.31"
1.13"
[28.6]
0.62"
[15.9]
3.50"
[88.9]
1.12"
[28.5]
2 POLE
3 POLE
120
www.littelfuse.com
© 2005 Littelfuse
•
POWR-GARD
™
Products Catalog
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