super lag fuse

caveJuly 16, 2009

I bought a lincoln 225/125 welder and the book said to use 50amp fuses to feed the receptacle. What are the fuses for?

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brickeyee

The fuses are to protect the wiring feeding the receptacle if a short circuit occurs.

The welder contains its own protection to prevent damage to the welder.

    Bookmark   July 16, 2009 at 12:44PM
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cave

I thought welders did have protection built in but, the manufactor's direction said to have the plug coming from a super lag fuse box

    Bookmark   July 18, 2009 at 9:10AM
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brickeyee

"the manufactor's direction said to have the plug coming from a super lag fuse box"

That does not mean there is no protection in the unit.

    Bookmark   July 18, 2009 at 11:42AM
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cave

If I have the plug coming from a super lag fuse box, what feeds the fuse box, the breaker??

    Bookmark   July 18, 2009 at 2:44PM
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brickeyee

"If I have the plug coming from a super lag fuse box, what feeds the fuse box, the breaker??"

A breaker in the main panel.

The manufacturer may be specifying a particular overcurrent method since testing was only performed with that type.

For may years central air condensers required fuses is the outside disconnect to comply with the manufacturers requirements. Many units are not rated to operate from HACR rated circuit breakers and the disconnect at the condenser is only that, a disconnect with no overcurrent devices of any type.

The breaker and branch wiring are still sized in accordance with article 630, and then any manufacturer required devices are added.

The use of "super lag" fuses is likely based on the large surge currents welders develop when starting an arc, and the voltage surges that can occur if the device has an emergency shutdown and the magnetic field in the transformer suddenly collapses.

    Bookmark   July 18, 2009 at 4:13PM
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