Harley

Harley
Harley likes to help out, especially with digging.

Tuesday, September 10, 2013

Replacing a fusible safety switch in a horse trailer


This fusible safety switch is out of a Sidekick horse trailer.  It contains a 20A fuse designed to protect the wiring inside the trailer and provide a shut off.  


120V power is supplied to the trailer through a male plug mounted on the forward side of the trailer, aft of the gooseneck hitch. 


The old safety switch was located in the tack room and saw a lot of moisture. The safety switch was so bad that it was tripping circuit breakers when plugged in, and it looked awful.


The replacement safety switch had different mounting locations.  The new switch had to be relocated to a position such that its mounting fasteners would clear the power inlet box.  The old corroded fasteners were discarded and replaced with stainless steel button head screws.  These are more convenient because an assistant can hold the screw head with an allen wrench while the nuts are tightened.  The original holes were closed with shorter stainless fasteners.  I used Permatex form-a-gasket around the holes, and turned the button heads inward to reduce interference behind the new box.  


It was necessary to replace the entrance line to have enough length so as to have no splices.  


I added shrink tubing to the new entrance line for extra protection at the bulkhead penetration. 


Knock out plugs were provided at different locations around the edges of the electrical box.  The openings were easily made with gentle blows to a screw driver; the screw driver was directed to the side of the knockout farthest from the solid, un-punched portion of the knockout.  The solid part acted as a hinge and then broke away with a little bending back and forth.  The knockouts were punched most of the way through in concentric rings so that they could be opened up to different sizes to accommodate the overall size of wires that needed to fit through the openings.  Cable connectors were installed before pulling the wires though, and then tightened to secure the wires to the box and protect the wires at the box knockout hole penetrations.


The wire bundles were stripped back to just clear the cable connectors when entering the box.  I like to start with a small cut keeping between conductors to reduce the risk of nicking insulation.  


When the cut is long enough to fold the insulation back away from the cut and grasp it with needle nose pliers, the old-fashioned sardine can opening commenced.


Twisting the pliers over and over tears the insulation with little effort.  With some wires, the insulation can simply be pulled to expose the desired length of conductors.  The loose outer insulation was cut, paper insulation wrap cut away, and conductor ends stripped.


The line to the duplex outlet was replaced to leave enough wire length to have no splices inside the box.


Needle nose pliers provided a handy tool to bend the wire ends into loops suitable for screwing down at the outlet.  The 10 AWG wire was stiff and difficult to form, but this was a same-size replacement.


The pliers were used to wrestle the looped ends under the screw heads, taking care not to damage needed insulation during the struggle. The loops were placed with the open ends wrapping around the screw stems in a clockwise direction so that the loops would tend to close as the screws were tightened. 


The needle nose was used to tighten the wire under the screw heads by holding the wires firmly against the stems of the screws while rotating the pliers clockwise, thus bending the loose ends of the loops to conform to the curvature of the screw stems.  The goal is to get close to a complete circle of copper under the screw heads before tightening.  This provides a flat surface for the screw heads and maximizes the desired under-head contact with the conductors.


Replacement wires were left longer than the originals to ease future removal of the outlet.  


Three cable clamps were bolted in to complete the installation.  ~Chuck

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