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Front and Rear of an Old Style Ceiling Electrical Pancake Box for Knob and Tube Wiring

Replace Old Ceiling Pancake Box

Dear Mr. Electrician:  Should I replace old ceiling pancake box for a new ceiling light fixture installation?  After removing the existing light fixture canopy cover, I found that there isn't a standard ceiling electrical junction box.  Instead, there is a black round disc (about 3 inches in diameter) with a 1-inch long screw-type rod sticking out of it.  The wires are around it.  This is incompatible with the new light fixture I want to install.  What do I do? Answer: The best thing to do is replace old ceiling pancake box.  However, sometimes that is more trouble than it is worth.  Below are photos and old pancake box situations that I have come across. NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate I earn from qualifying purchases. I suspect that the round disc is actually an old black enameled metal pancake box.  It's approximately the diameter and thickness of a hockey puck and made out of metal. Table of Contents: Enameled Ceiling Pancake Box Replacement of Old Style Pancake Box Photos of Website Visitor Pancake boxes Sometimes an old gas pipe protrudes from the middle of this pancake box instead of a fixture stud.  A setscrew tightens the box to the gas pipe. WHAT IS AN ENAMELED CEILING PANCAKE BOX? That was how old houses that originally had gas lighting were converted over to electric lighting.  The pancake box was mounted onto an existing disconnected gas pipe.  The cables were attached to the pancake box, and splices were made.  An additional fitting, such as a 3/8" x 1/8" hickey was threaded onto the gas pipe to support the light fixture which was made for this type of installation. You can see an example of a gas pipe protruding from a ceiling below. The canopy of the old-style ceiling light fixture acted as the junction box for the spliced wires.  When calculating box fill for the maximum number of wires allowed, you can include the cubic inch capacity of the light fixture canopy according to article 314.16(A) in the National Electrical Code. On very rare occasions, I have found that the gas pipes were still connected to the main gas line after I removed an old light fixture or the cap on the gas pipe, so proceed with caution. I got a call to install a new light fixture.  The above photo was what I found when I arrived.  The fan bracket was screwed to the ceiling independently using long sheet metal screws driven into the wood joist.  The remains of the cut old ceiling fan wires protruded down. CLICK HERE To See Old Work Ceiling Fan Electrical Boxes on Amazon Other old pancake boxes were mounted directly onto ceiling joists using wood screws.  Instead of an opening for a gas pipe, they would have a built-in fixture stud for attaching a light fixture.  The fixture stud had the same size thread as a gas pipe of the same diameter. Around the pancake box is four holes, each with a setscrew or clamp, which engages the cable,...