View single post by Frank McCormack
 Posted: Wed Jul 29th, 2020 01:54 am
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Frank McCormack


Joined: Mon Jan 13th, 2020
Location: SAINT LOUIS, Missouri USA
Combining the old with the new is a good idea in my book.  The fans are pretty well isolated when they windings and switches don't fail as originally designed.  And then that darned age thing comes into play.  A winding insulation fails and allows the wire to touch the metal case of the fan and it becomes energized.  An unsuspecting person touches the fan and becomes the path to ground and yowch!  or worse.  The simple fix for this is to unplug, flip the plug over and plug it back in which changes the fan case to neutral (ground). I can tell you stories of old refrigerators that I fixed from biting someone with this method.

For fans that I plan to use at a minimum I like to use a polarized 2 prong plug and add a 4A fuse to the hot side before the switch.  The hot side is the smaller prong on the plug, the neutral is the bigger one. I'm bigger about those fans being safe first. 

The 3 prong old looking plug that alex shows above with the extra ground is a fantastic idea.  The idea of the ground is to provide a path for an electrical failure like I outlined above and force the circuit breaker to trip.  I like to add a fuse to prevent a failure of an 80 year old fan from causing a fire.  The broke fuse is a clear indication to look for a problem.  You still have to connect the hot to the same side of the plug and the switch. 

GFCIs are great to prevent shock.  They sense if the difference between the hot and neutral is greater than 5 milliamps like when you touch a live appliance and become a path for the hot to ground.  My house is old and doesn't have the 3rd ground wire.  But the national electrical code allows you to replace any outlet with a GFCI to give you the ability to plug in a 3 wire plug and be safe.  I'm putting together a power feed board for fan testing which will include a GFCI.  However, GFCIs don't stop a fan from letting out the smoke if a winding shorts so I would still recommend a fuse even with the GFCI.