Installing an old-work electrical box in an existing ceiling (C) Daniel FriedmanPlastic Electrical Box Repairs
How to fix or replace a broken plastic ceiling or wall electrical box; causes of plastic electrical box failure, falling from ceilings or walls

  • PLASTIC ELECTRICAL BOX REPAIR - CONTENTS: how to replace a broken plastic electrical box in a ceiling: or wall; how to use an old work box to replace a damaged or loose electrical box that supports a ceiling-hung light fixture; ceiling light box repair.
  • POST a QUESTION or READ FAQs about fixing a loose ceiling light fixture traced to a broken electrical box whose supports snapped off.
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Repair a broken plastic electrical box mounted in a ceiling or wall

This article describes how to repair a ceiling light fixture electrical box that was falling out of the ceiling, beginning with an explanation of how and why broken plastic electrical box swing clamp supports allowed the electrical box to fall from the ceiling leaving the light fixture hanging by its electrical wires.

In the second part of this article, "Ceiling Light Fixture Installation" we use an "old work" electrical box to replace the damaged box, secure the new box and re-mount the light fixture safely. We discuss the requirement for secure mounting of ceiling electrical boxes for fans and lights and we give step by step details for installing a replacement electrical box, insulating around it, connecting the ceiling light wires, and then testing and completing the installation.

The electrical box repair or replacement procedures described in this article series describes step by step repairs for both metal and plastic electrical boxes used in building electrical wiring systems.

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How to fix a loose, broken or damaged plastic electrical box falling out of place

Ceiling light fixture suspended from a plastic electrical box (C) Daniel Friedman Carlon old workbox, round, 18 cubic inch blue plastic with metalground connector (C) Daniel Friedman

Cause of Ceiling Light Fixture Support Box Failure

The bathroom ceiling light shown above was found one morning hanging by its electrical wires: the plastic electrical box from which the light fixture was suspended was itself falling out of the ceiling - a dangerous situation risking fire or shock, more-so for a light fixture suspended over a bathroom sink. What happened?

Watch out: The round Carlon B618R electrical box used for the original light installation was a Carlon 4 1/4" diameter electrical box that is specifically indicated by the manufacturer as not for fixture support in the ceiling. The concern is that the weight of a light fixture may pull the swing clips through the drywall or cause it to break, or the weight or movement of a heavy light fixture or ceiling fan may cause the swing clips themselves to break. A falling light fixture or fan can kill someone or could start a building fire.

Old work plastic electrical box swing clamp broken (C) Daniel FriedmanBut this light fixture installation failed for a different reason: the swing clamps were tightened using a high-speed and powerful battery-operated drill mounted with a phillips bit to speed the fixture installation. The swing clamp screws were so over-tightened against the drywall ceiling that all three of them cracked and two broke off completely.

A closer inspection of the original blue plastic electrical box to which the light fixture had been mounted discovered that two of the three plastic clips or "ears" intended to connect the electrical box to the ceiling drywall had snapped off.

This allowed the box to loosen and ultimately to fall from the ceiling where it remained hanging by its wires. Below you can see one of the broken-off swing clamp remains. The swing clamp was broken by over-tightening of the clamp screw.


Why was an Old Work Electrical Box Used in New Construction?

First, why was this type of "old work" electrical box used in the first place, rather than installing an electrical box securely fastened to the ceiling framing? After all the light fixture had been installed during new construction. An "old work" electrical box is designed to be installed neatly through a finished wall or ceiling.

Normally a "new work" plastic electrical box installed during new construction is either nailed to the building framing (shown below) or if it needs to be spaced away from a stud or joist in a wall or ceiling it may be supported by a bracket that is in turn nailed to the building framing.

Plastic electrical box nailed to wall stud in new construction (C) Daniel Friedman Plastic electrical box installed for ceiling light (C) Daniel Friedman

But when the electrician is asked to leave a wire exposed for future installation of an electrical box whose precise location has not been determined, say for a ceiling light fixture over a bath sink that has not yet been installed, she may leave the wire protruding through a ceiling or wall and may plan on later re-locating the wire precisely using an old work retrofit type electrical box.

The installer used a Carlon B618R round plastic 18-inch electrical box (shown earlier on this page) that is specifically not recommended for carrying a ceiling light fixture. But had the box mounting screws not been over-tightened to break the swing clamps, this installation may nevertheless have worked for decades without a mechanical failure. Still, why was this box even selected?

That's what happened in this building, as we illustrate below.

Installing Wiring for Ceiling Light Fixture Whose Exact Final Location is Not Known

These photographs illustrate the sequence of construction and history of the wiring of the bathroom ceiling light fixture discussed beginning at PLASTIC ELECTRICAL BOX REPAIR. At below left you can see that a bathroom has been roughed-in, a shower pan is in place, and the electrical wiring rough-in is in place.

Electrical wiring rough-in for a bathroom (C) Daniel Friedman Bath ceiling light fixture wiring rough-in (C) Daniel Friedman

At above right we see that the bath ceiling light wiring for a light over the sink was left dangling through the ceiling with no electrical box (red arrow) because the exact location for the bath light fixture had not been determined.

Watch out: This was not the best practice: it would have been a better, more correct, and safer installation to have installed a ceiling light fixture box well-secured to the ceiling joists. If the ceiling light fixture needed to be suspended from an electrical box that could not be nailed or screwed directly to the side of a ceiling joist or truss a supporting bar can be installed between the joists, allowing the box to be centered between them.

If possible an old-work electrical box can be secured directly to wood framing (below left, using a Madison Electric Products Smart Box as example), or if the exact light support location does not permit that direct connection one could use an old-work fan bar hanger that includes a deep 4-inch octagon box (below left - Racon fan box support). Fan support and ceiling light support bars and boxes are provided with both steel and plastic electrical boxes attached directly to framing or mounted from a telescoping support arm that itself can be fit up through a ceiling or wall opening.

Old work electrical box for mounting to framing - Madison Electric Products Smart Box Old work ceiling fan or light support bracket from Racon

Every construction project experiences sequencing problems and the pressure (and sometimes mistakes) of decisions made under the urgency of arriving contractors who, if not permitted to work on schedule, will throw an entire construction project off course. What's needed is careful attention to the solution of each of the snafus left behind.

The insulation contractor arrived to spray insulation - leaving the wire exposed and dangling.

Electrical wiring in bath ceiling (C) Daniel Friedman Spray foam insulation installation in ceiligings & walls (C) Daniel Friedman

In this particular home the builder had left electrical wires poking through the ceiling while waiting for the homeowner to decide exactly what fixture was to be installed and exactly what sink was to be installed below: the owners wanted to center the light fixture properly over the sink, so the electrical box location was left as a later project.

After framing, rough-in, electrical rough-in (above left), and insulation (above right) were all complete, the drywall contractor arrived to install ceiling and wall drywall, leaving the electrical wire for the bath sink light dangling through a small hole in the ceiling drywall (yellow circle in our photo at below left).

Electrical wire rough-in protrudes through bathroom ceiling with no electrical box to support the light fixture (C) Daniel Friedman Bath ceiling light after new installation (C) Daniel Friedman

Clips on the old work box rotate out over the drywall and then pinch the box to the drywall as the three mounting screws are tightened. This permits installing an electrical box without ripping open a larger hole in the ceiling as might be needed to secure a new work electrical box to the building structure, and it permits mounting of an electrical box in a location where framing is not close by.

Above at left you can see the yellow electrical wires for the ceiling light hanging from the bath ceiling (in the yellow circle). Why are there two wire sets? One brings power to the light fixture and the other provides wiring to the wall switch for the light.

At above right is the bath ceiling light fixture newly-installed using an old work electrical box.

Why Did the Supporting Swing Clips of the Plastic Old Work Electrical Box Fail?

Old work plastic electrical box swing clamp broken (C) Daniel Friedman

Well they didn't spontaneously fail, that's for sure. The electrical box support clips were broken by a heavy hand during installation.

How did I know that the swing clamps had been broken by the screwing operation?

When I removed and inspected this component it was obvious that the swing clamp body had been screwed all the way down tightly against the plastic stop at the end of its travel.

The stop has a thickness of about 1/4" - an amount certainly less than the 1/2" drywall that the swing clamp was expected to grab.

Some electrical work writers recommend and many electricians use a power-screwdriver to speed their work.

As some electrical box or device mounting screws are quite long, hand-turning these screws is tedious, particularly when working overhead such as at a ceiling light fixture.

Using a power screw driver or electric drill to install swing clamp old work electrical boxes can break them (C) Daniel Friedman

But running a high-power battery-operated screwdriver at full tilt when zipping in the old work electrical box mounting screws is asking for trouble.

That's because as the old work mounting box ears contact the drywall (and the installer should stop turning the screws) the drill keeps zooming along, cracking or breaking these parts. In this particular case the old work electrical box was damaged during original installation but the box didn't actually fall through the ceiling until months later after contractor, drywaller, and electrician were long gone.

[OK so I sort-of faked the photo at left: this illustration of using a DeWalt battery operated drill to tighten the swing clamp screws on an old-work retrofit plastic electrical box was made during a later repair step when I was killing time waiting for my foam insulation to harden. But the point is, if you use a high-torque powerful tool like this without setting the torque to a suitably low level you will probably break the swing clamps and if you're lucky the electrical box will fall out now before you're called back to replace it a year from now. ]

The blue plastic box at below left is a new-work electrical box with nails intended for driving into a wall stud or ceiling joist, while at below right is an old work electrical box intended for retrofit box installation through a drywall or plaster ceiling or wall.

Also see this ZIP BOX for another example of an old work retrofit electrical box in a rectangular style.

The rectangular box at below left has screw receivers only at the box corners: not a location where a metallic repair clip will fit.

The round plastic old work electrical box at below right, produced by Carlon provides 18 cubic inches of wiring space and enjoys a wide surface-mounting flange (orange arrow). That flange is not a surface over which the G-clip would fit unless the box itself were modified by cutting away portions of its material.The recessed location of the screw receiving opening on this round box leaves us doubtful that a repair clip repair is possible for these electrical boxes.

Rectangular blue plastic electrical box (C) Daniel Friedman Platic electrical box used for retrofit or add-on applications (C) Daniel Friedman

These round plastic electrical boxes do sport a nice feature if you are worried about piercing an electrical wire while using a make-shift repair screw. The red arrow in the photos show that the device mounting screw receiver on these plastic boxes is manufactured with a deep rib running the full depth of the box. At no point would a wire inside the electrical box be exposed to damage from the fixture mounting screw, as the screw passes through the hole above the red arrow tip continues inside of the raised rib.

Watch out: do not rely on old work boxes with minimal support (just drywall, for example) to carry heavier fixtures or ones subject to vibration or movement such as a ceiling fan. Such installations are unsafe.

Watch out: we have found no code approval nor listing agency listings or approvals for any electrical box repair methods, hardware or approaches. Check with your local electrical inspector about the acceptability of your repair approach. Electrical box replacement rather than screw or screw receiver repairs will be required in some situations such as ceiling boxes carrying weight as well as by local electrical code inspectors.

The Falling of the Light Fixture and Subsequent Calling of the Light Fixture Repair Brigade

The bathroom was beautiful and the electrical work seemed just fine too, until a year later the building occupants noticed that the light seemed a bit closer to the sink. A closer inspection showed that the light fixture was inching its way out of the ceiling along with the round blue electrical box to which it was attached.

For repair procedures for a loose or falling ceiling light fixture due to electrical box damage

Article Series Contents


Continue reading at CEILING LIGHT FIXTURE INSTALLATION - separate article continuing the article above, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



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