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Maintenance
5.3 Replace Internal String Fuse
M42/36/28U 120 and 122 models both have a wiring box provisioned with two
independent internal string combiners, each associated with one of the two
MPPT inputs.
The combiners utilize standard 10 mm x 38 mm PV combiner fuses and associated
fuse holders. Because of the TL design, all strings are floating with respect to
ground, and two fuses are required per string input connected in series with
the positive and negative string leads.
Any 10mm x 38mm Listed PV fuse can be utilized for replacement purposes.
The specifications of the required fuse and the fuse brand utilized at the factory
are listed below.
Rated current
Rated voltage
Operating Class
Fuse Type
Fuse holders do not have load break capability!
Before opening any combiner fuse holder in -120 or -122 models be sure both
DC switches are in the OFF position
15 A
UL Listed
1000 V
UL Listing Category
Solar PV
Typical Mfr
10x38 ferrule
Mfr P/N
Table 5-2: Combiner Fuse Specification
CAUTION – Shock/Fire hazard
76
UL248-19/UL2579
JFGA
Littelfuse
OSPF015
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