Gilles' Outlet

October 20, 2008

Repairing a dangerous electric junction box

Filed under: Electrical — Gilles @ 3:25 am

While removing a recessed medicine cabinet, a dangerous junction box is discovered. The dangerous box is removed, a new box is installed and re-wired.


Skill Level: 2~3 (Basic ~ Moderate)

Time Taken: About 1 hour

While remodeling houses, it is not uncommon to find work which was not properly done. Today’s article describes gross violations of the National Electric Code (NEC) resulting in a fire hazard. The junction box is replaced and re-wired to comply with appropriate building codes.

After pulling the medicine cabinet, I used my digital camera to take a picture of what was in the stud bay, just out of curiosity. Well, I was not disappointed. There was a metal junction box lurking in the wall. On this picture, you can see at least the following NEC violations:


  • 314.29 – Junction Boxes shall be accessible without damaging the building finish
    • –>This box is concealed behind drywall.
  • 312.5 – Use of proper fittings to ensure wires are secured properly
    • –> No clamps are used to secure wires.
  • 314.16 – Volume of junction boxes
    • –> This box is way to small for 8 14/2 wires. This is a fire hazard.


Left: I turned the power off at the main panel and verified that all wires were no longer energized. Remember that you sometimes must trip more than one breaker (up to six in fact) to completely de-energize the whole house. Always double check that the wires you intend to work on are no longer energized.


Right: I used a pry bar to loosen the top nail of the box. It was much more difficult that it looks like. I had to be gentle enough not to damage wires, yet apply enough force to remove the nail.

Eventually, the top nail gave way and I was able to pry the bottom nail. The box was freed from the framing.

Left: This is a 34 cu (cubic inches) remodel junction box. It can contain up to 17 conductor equivalent 14 gauge wires. NEC article 314.16 describe how to calculate minimal volume of a box.

In this situation, there are 8 14/2 wires in the box, no device and no internal clamp. So we have 2 (hot + neutral) * 8 (there are 8 NM wires in the box) + 1 (all ground wires in a box count for one conductor equivalent). The box needs to accommodate 17 conductor equivalent. For 14 gauge wires, a conductor equivalent requires 2 cubic inches. The box must be at least 2 * 17 = 34 cubic inches.

Right: I decided the location of the new box and marked the opening with a pencil.

Left: I progressively cut the drywall for the new box. This revealed more of the dangerous J-Box. It is obviously very crowded.

Right: Another detail of the J-Box. It is difficult to see on the picture, but there is another NEC violation:


  • 314.4 – All metal boxes shall be grounded
    • –> The box itself was not grounded.

Left: I finished cutting the hole with a drywall saw.


Right: Detail of wires entering the box. They are not clamped as required by code but the jacket of the top NM wire has been slightly damaged by the sharp edge of the box. This is a fire hazard. If the metal box cuts the insulation and reaches a wire, this can cause a spark and start a fire.

At this point, I marked all wires and made sure I recorded all connections on a piece of paper. I unwired all connections. Wires were not even twisted properly. This was another fire hazard.

I pulled wires in the new box and secured the remodel box to the wall. Plastic boxes like these have built-in clamps which secure wires at the box.

Damaged wires were replaced. It was now a matter of making the connections according to the notes I wrote in the previous step.

Making a connection is easy: twist wires with a Lineman’s pliers so both wires are twisted tight against each other and cap the twist with an appropriately sized nut (I used yellow nuts which handles two 14 gauge wires according to the manufacturer).

After finishing the wiring, I carefully pushed all wires in the box. I tired to arrange the as neatly as I could to facilitate identification of circuits. Later on, the box will be capped with a 2-gang blank wall plate to conceal wires yet allow for easy access if needed.


This work was clearly not performed by a licensed electrician, not permitted and not inspected. This "do it yourself specials" exposed occupants of this house to fire hazards. When doing any kind of work on any building, always consult your local building department, professional(s) and respect all local and national building codes.

DISCLAIMER: Procedures demonstrated in this article may or may not meet code in your area. Consider this article for entertainment purposes only. I cannot be held responsible for anything that may happen when trying to duplicate anything shown here. Before attempting to perform any work on any building, always consult a licensed professional.

Tools Used:

  • Hammer
  • Drywall Saw
  • Flat Screwdriver
  • Pry bar
  • Lineman’s pliers
  • Impact Driver

Materials Used:

  • 14/2 wire (to replace damaged wires) 
  • Yellow Wire Nut (accommodates two 14 gauge wires) 
  • 34 cubic inches remodel plastic junction box
  • Two-Gang blank wall plate (not show in article)


October 19, 2008

Replacing a Furnace Filter – Adding an Air Filter Return Grille

Filed under: HVAC — Gilles @ 6:14 am

A furnace filter is replaced. During this process, it becomes obvious that the filter is poorly installed. An air return filter grille is added to correct the problem.


Skill Level: 2 (Basic)

Time Taken: About 25 minutes

Forced Air Furnaces have a blower which takes air from the living space, warms it and pushes it through ducts to all rooms. It is important to make sure air blown in the system is free of dust, particles, allergens because:


  • You are breathing this air – dust, particles, allergens … can cause lung irritations or other respiratory diseases,
  • When dust in the air comes in contact of impellers in the blower, they tend to stick to it. This builds up a coat of dust on internal elements of the blower and causes the motor of the blower to have to work harder to pump air. This can lead to premature stress of the motor.

In this article, the filter is poorly held in the furnace and cannot effectively perform its function. We clean the dust accumulated on the blower’s motor and provide a better way to hold the filter.

When I tried to change the filter on the furnace, I could not find a "filter box" (a drawer like device where furnace filters are held). I had a hunch that the filter would be inside the furnace.


Just to be sure, I shut down the power at the furnace.

Left: I unscrewed the cover of the furnace and sat it aside.


Right: I inspected the furnace and noticed that the blower compartment was located at the bottom, hidden behind a protective panel. The panel was held by a few sheet metal screws. I removed them using a simple screwdriver.

Left: There was the filter – held by duct tape. Actually, the glue on the duct tape dried and the filter was pretty much floating freely at the bottom of the blower compartment. This is bad because when the blower starts, the flow of air causes the filter to be sucked tight at the bottom of the cylinder (the blower fan). This leaves large gaps around the filter where air can get through and bypass filtration.


Right: There were signs of dust and particles collecting on the blower. They are clearly visible on the back of the blower’s electric motor.

Left: I pulled the filter out. It is very dirty.


Right: Using a 5HP shop vacuum cleaner, I cleaned the blower as well as I could. I could not access the impellers in the fan assembly so I did not clean these. I was able to touch a few impellers with my finger and observed that some fine dust already started to collect on them.

I could have removed the complete blower assembly, pulled the motor’s arbor and cleaned the fan perfectly. This would have taken at least a few hours and I did not have this kind of time. 

However, it was now obvious I had to find a better way to hold the filter in place. I put the furnace back together and turned the power back on.

Left: All forced air furnaces have an air return grille: this is essentially where air is sucked in the system. This simple grille hides the duct work and prevents items to be sucked in by mistake.

In this installation, the air return grille is easily accessible, making it the perfect candidate to hold an air filter.


Right: This is a new Air Return Filter Grille purchased online. It is an air return grille which can hold a standard 1” thick filter. It offers a removable face which allows for easy filter replacement.

When ordering air return grilles (with filter or not), the width of the duct opening comes first and then the height. In my case, the duct opening is 14” wide by 20” tall so I ordered a 14 x 20. It is easy to forget this and order the wrong part.

Left: Using my impact driver, I removed the four screws holding the old grille in position.


Right: I slid the new grille in position and secured it to the framing at four corners using 2” coarse thread drywall screws.

Left: In order to prevent unfiltered air to enter the system, I applied metal foil tape to seal any gaps between the edges of the air return grille and the duct. I made sure all the duct work to the furnace was properly sealed as well.

While it is impractical to make ductwork perfectly air tight, sealing with metal foil tape is, in practice, pretty effective.


Right: The standard 14×20 1” furnace filter slides in the opening. The removable grille cover gets installed above and secured to the frame.

The brown mark at the top left of the filter is a paper tear I caused when I took the filter out of its packaging. It does not affect its effectiveness.

Tools Used:

  • Impact Driver
  • Screw Driver
  • Shop Vacuum Cleaner 
  • Utility Knife

Materials Used:

  • Air Return Filter Grille 14 x 20 
  • 2” Coarse Drywall Screws (4)
  • 14×20 1” furnace filter
  • Foil tape

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