Dear Mr. Electrician: I want to replace old ceiling pancake box for a ceiling light fixture. 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) which has a 1 inch long screw type rod sticking out of it. The wires are around it. This is not compatible with the new light fixture that I want to install. What do I do?
Answer: You need to replace old ceiling pancake box. 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. NOTE: Some text links below go to applicable products on Amazon and EBay.
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.
REPLACE OLD CEILING PANCAKE BOX
That was how old houses that originally had gas lighting converted over to electric lighting. The pancake box was mounted on to 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.
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 ceiling wood joist. The remains of the cut ceiling fan wires protruded down.
Other types of old pancake boxes were mounted directly onto ceiling joists using wood screws. Instead of an opening for a gas pipe, they would have their own fixture stud for attaching a light fixture to. The fixture stud had the same size thread as a gas pipe of the same diameter.
Around the pancake box are four holes, each with a setscrew or clamp which engages the cable, preventing it from being pulled out, and provides electrical continuity for the equipment ground for the armored cable.
The wiring is most likely armored cable (BX). However ungrounded non-metallic cable (The Type Before Romex), or knob and tube type wiring is possible as well.
Beware if the gas pipe has a cap on it. Usually the caps are removed when the gas line is taken out of service. However, until you can verify that the gas line is dead you should not remove the cap.
In a situation where the original wiring insulation has degraded, the best thing would be to install new wiring. However that not only could be expensive, but damaging as well. Walls and ceilings may need to be cut open to re-route or remove old dried and brittle cables and install new wiring.
As you can see above most of the old insulation broke off as I moved the wires. Note that I identified the conductors with colored electrical tape. This was a normal wiring set up for a ceiling light controlled by a wall switch. Here the power entered into the pancake and a two wire cable was run down to the switch. See my post on light switch wiring diagrams for more information.
REPLACEMENT OF OLD STYLE CEILING PANCAKE BOX
Turn off the power. You will need to remove the old pancake junction box. Do it carefully so as to not damage the existing wiring. Often, wiring from that era of home construction now has dry, brittle insulation on it. Any disturbance to the wires could cause the insulation to break off.
Make sure that you identify each conductor in the box before you take apart the splices. The color coding is almost gone on these wires. The wires are likely to be soldered and taped. The insulation on the wires will break off as you separate the conductors. Get a roll of white and a roll of black electrical tape. You may also need rolls of red and blue electrical tape.
It doesn’t show it above, but I was able to strip about 2″ of steel armor off of each cable using BX cutting pliers. I held the cable with Channellock pliers and slowly nipped away at the steel armor using the BX cutters. That gave me enough room to find some good insulation to work back from with new electrical tape.
On some jobs the gas pipe will be a hindrance to installing a new modern round or octagonal ceiling electrical box. Also it is quite likely that there is a piece of wood supporting the gas pipe or the pipe may be attached to the side of a ceiling joist.
Sometimes a pipe wrench can be put on the gas pipe to unscrew it from the elbow. An internal pipe wrench might be needed. Other options are cutting it out with a multi-function oscillating tool or a reciprocating saw, or relocating the ceiling box. Relocating may not be an option due to the lengths of the existing wires.
Once all obstacles have been removed and the existing cables have been identified and taped, a new electrical box can be installed. A new pancake box can be used or sometimes an old work ceiling fan brace and box can be fitted through the existing hole. A side mount type fan box is also available if the joist is right there. Try to get the deeper round electrical boxes as they have more room for wires.
If you are planning to install a ceiling fan, then you must install an electrical box rated for ceiling fans. Ceiling fan boxes are available in pancake depth.
A duplex BX connector was used to attach the cables above to the pancake box. I had to clean up the opening in the ceiling with my multi-tool due to pieces of wood lath and plaster embedded with the old pancake.
Use the proper cable connectors and anti-short bushings for the cables and bring them into the back of the box. Trim the sharp edge of the BX cable using BX cutters or diagonal pliers. Then insert the anti-short bushing inside of the armor to protect the wire from being cut by the metal armor.
In this case it may be best to put the cable connectors on the ends of the cables with the locknuts removed. Tape the ends of the wires together. As you push the box into the ceiling, pull the cables through each connector.
Tighten the locknuts by hitting them with a screwdriver driven by a hammer after the box is secured to the ceiling or bracket. The BX cable metal armor is the grounding conductor, so it needs to be a tight connection.
The box above is ready for a standard light fixture installation. Number 10 x 1.5″ sheet metal screws were used to secured the pancake box to the ceiling joist. The box is grounded through the correct use of the cable connector and the BX armor. A grounding pigtail was added using number 14 wire and a 10/32 green ground screw. The wire with red is the switch leg (LOAD) which gets connected to the black wire on the light fixture.
The white wire with green (The LINE to the switch) was partially covered in black tape before getting connected to the black hot wire with green (LINE). When a white wire is used for something other than a neutral, it must be re-identified. I use colored electrical tape. Some other electricians use a permanent marker pen to change the wire color.
The other white wire (Neutral), gets connected directly to the white wire on the light fixture. The green tape was used for my own purposes in identifying the wires as I worked on this repair. The green tape was removed before I made the final connections to the light fixture. Green is only to be used for identifying a grounding wire.
In the above box you can see that two knockouts have not been punched out.
OLD CEILING PANCAKE BOXES FROM VISITORS
A visitor to my blog sent me the above photo of a pancake box with live electrical wires still in use. The house is from 1930. His dilemma was how to remove the box. There are no screw holes in the back of the box, but there is a metal bar that passes through (See yellow circle).
I surmised that the metal bar is a support bracket that is either attached directly between two ceiling joists, or screwed to wood lath. The box is held firmly onto the bracket by the center screw. If that is the case, then some plaster would need to be removed in order to remove the bracket.
I suggested possibly cutting the bracket with an oscillating multi-tool so that an old work fan box and brace could be installed. However, with a house that old it is quite possible that the plaster would be damaged during the cutting process.
The insulation on the wires is in good condition, but I recommended taping each wire with the appropriately colored electrical tape to keep the insulation intact. White tape on the three neutral conductors. Black tape on the four hot wires. Red tape on the switch leg.
The cable in the upper left section of the pancake box is the one that goes down to the wall switch. The white wire from this cable is connected to the three black hot conductors. The black wire which brings the power back from the switch is by itself. These wires should also be re-identified at the switch with red and black electrical tape.
A white wire can be used as a hot conductor, but it must have its color changed to something other than white, gray, or green. Electrical tape or a permanent ink marker are two common methods for changing the color of wires. Unfortunately the re-identification of the white wire does not always occur as evidenced in the above picture.
Another visitor to MrElectrician.TV sent me the photo below of what he found when he lowered the canopy cover on an existing light fixture in his 1906 home.
The house from the above photo was originally piped for gas lighting. At some point in its history electrical wiring was installed. Normally in a gas to electricity retrofit, a pancake electrical box would slide over the gas pipe and a set screw would lock it in place. The new BX wiring would have terminated in the pancake box.
The ceiling light fixtures from that era mounted differently than the light fixtures of today in order to accommodate the gas pipes. I surmise that at some point someone wanted a new modern light fixture and found it would not mount onto the old pancake box or gas pipe. So the pancake box was removed and the bracket that normally mounts on an electrical box was screwed directly to the ceiling.
This is the wrong way. The wires are not protected in an electrical box and the grounding continuity through the BX armor is lost.
I suggested that the homeowner install an adjustable ceiling fan brace and box that would retrofit inside of the existing hole in the ceiling. However the problem is that old gas pipe protruding from the ceiling. It appears that someone already tried to remove it without much success.
I have been in this situation myself and can attest that it can be almost impossible to unscrew the pipe from its base. In those instances I had to use a reciprocating saw to cut it out. The saw works well with the correct blade in cutting out the pipe, but it can also do some damage to the ceiling in the process.
Another vistor to MrElectrician.TV sent me the below photo with a question: “I am replacing an old chandelier in the living room of my pre-1915 apartment. After removing the old fixture I discovered that it was hanging from a hickey attached to a threaded pipe in the center of the non-load-bearing pancake box. The ceilings are concrete.
My question is whether it is safe to hang the new fixture from the center pipe using a hickey, or whether it would be necessary to bring in an electrician to replace the box with a newer one designed to support the weight of the new fixture using a strap?
The old fixture weighed 26 lbs, and the new one will weigh 55 lbs.”
My response: “I don’t think I can give you a definite answer one way of another, but I can share my thoughts.
Given that there are electrical conduits with wires in that electrical box, I don’t think that there was gas lighting there originally. Normally a retrofitted gas pipe would have cables that were fished over to the gas pipe and a box with a set screw or locknut would be installed over the pipe.
That pipe that is protruding is either part of the electrical box or was added as an accessory during the original installation for the purpose of light fixture hanging.
Since the entire conduit and box assembly is embedded in concrete, a replacement of the box will be challenging and would require repair to the ceiling.
I would try pulling on the pipe using your own body weight to get a feel of the strength of the pipe. My guess is that it is pretty solid.
Depending on the type of bracket that is furnished with the new light fixture, you may be able to provide additional support by screwing the bracket directly to the concrete using 1/4″ plastic anchors with #12 sheet metal screws, in addition to using the pipe as a support. I am assuming that the concrete is in good solid condition.
If the hickey is too big for the new light fixture canopy you can also use locknuts on the pipe, though they can be difficult to find locally.”
“In 1915 the standard mount for a ceiling light fixture was with a pipe and hickey. No screw hole tabs on electrical ceiling boxes were available then. I don’t know exactly when the change occurred, but am guessing before WW2 based on other old wiring that I have seen.
Also back then the ceiling boxes were shallow and did not have allowances for the number of wires because the light fixture canopy had a lot of room. The electrical code still allows the cubic inch capacity of the canopy to be included when calculating box fill.
The original wires that were installed in the conduit were cloth covered. Having the conduits in place made it very easy to replace the old wires with the plastic insulated ones that you now have when the apartment was rennovated.
Many years ago I had to replace cloth covered wires in conduit installed around the same time as yours. When I pulled the old wires out the insulation came off inside the conduit. I had to repeatedly push a fish tape in and pull out pieces of insulation before I could pull new wires in.
The conduits are most likely helping to support the box given that you can push up on the center pipe, but are not able to pull down.
You could try drilling and tapping two holes in the back of the box and use longer screws to attach the light fixture. However with the weight of the new light fixture I would use bigger screws then the standard 8/32.
Under normal conditions I would replace a standard ceiling box with a fan rated ceiling box in order to support a light fixture that weighed over 50 pounds.”
On the center stud of the above pancake box is a brass screw-on cap. I forget how it was used, but I think it had to do with hanging light fixtures.
For more information on switch wiring, see my post on light switch wiring diagrams here.
The National Electrical Code accepts the use of pancake ceiling boxes even though they do not have a lot of cubic inch capacity. They are permitted because the code allows the cubic inch capacity of the light fixture canopy to be included in the total calculation of box fill. See article 314.16(A).
Generally speaking, for each #14 wire two cubic inches is required. For #12 wire it is 2.25 cubic inches. Each internal wire clamp counts as one wire. Read article 314.16 for all of the details.
My post on repairing a loose ceiling electrical box may be helpful.
Also my post on installing a ceiling fan electrical box is good to read.