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I am trying to understand which fuses to use to protect an NFC 3-Phase Control Relay (RMNF22TB30).

The installation guide describes that a 1A CC/gG fuse for each phase is needed.

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I would like to use a DIN terminal fuse block like this one with a 5x20 mm fuse.

It doesn't specify exactly that it is a CC or gG fuse but has it the characteristics to comply with manufacture requirements?

It comply with the UL 248-14

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2 Answers 2

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If the spec is asking for CC/gG look into a fuseholder like the CHCC3DIU from Eaton. You can use class CC 1A fuses from Littelfuse (CCMR series) or similar fuses from different brands. The fuse holders are quite a bit larger than what you are currently looking at but it meets the requirements.

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Due to its small size a 5x20 mm fuse has a limited breaking capacity that reduces quickly with voltage.

The datasheet you linked showed this fuse has a breaking capacity of 10 kA at 125 V falling to 1.5 kA at 250 V.

A Littelfuse CC/CD fuse has a breaking capacity of 200 kA at 600 V.

So a 5x20 mm fuse is not adequate for use on a 208-480 V 3 phase supply and you should use the specified fuses (or better).

(Using a fuse in the neutral line, if used, seems odd though this does depend on your national wiring regulations.)

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