Monday, January 6, 2020

Nailing Up Electrical Boxes

   Choose the correct box.   

The first step to nailing up electrical boxes, for new residential wiring, is to choose the correct box. Electrical boxes come in various styles, materials, sizes and shapes. It is easy to become overwhelmed with choices. Here are just 6 different styles of boxes, with different material and volume sizes but all of which are the same shape, in this case; a single gang  (made for one device receptacle or switch)

When nailing up boxes to install new wiring you would only need the first box at the left, the single gang nail on box. Preferably a 20 cubic inch deep, tan fiberglass one gang nail on box, but this 18 ci blue plastic nail on box will do.

CARLON 1-Gang Nonmetallic Switch and Outlet Box
Nail on
CARLON 1-Gang Old Work Switch And Outlet Box
Raco 18 Cu. In. Old Work Electrical BoxGampak 1-Gang Aluminum Electrical Box
Metal Remodel         Outdoor   .
CARLON1-Gang Nonmetallic Switch and Outlet Box
Raco 13.0 Cu. In. Handy Electrical Box
Handy box

                                                                                                                           These photos are from 

The 2nd and 3rd boxes are called "remodel", "old work" or "retrofit"  boxes. They are used after sheet rock, paneling or other wall covering is set in place. They are inserted into a cut out hole in sheet rock or cabinetry. The outdoor box is used in wet locations and requires a weather proof plate to cover the devices. The shallow box with its small 8 cubic inch volume is often in violation of the code requirements for "Box Fill" but can be used as a junction box. The "handy box" lives up to its name when you need an indoor, surface mounted, device box. 

When choosing a box, you have to consider;
        ? The code requirements (volume and fire rating)
        ? Your own preferences and
        ? And, which item is on hand when you need it.
It may not be the box you prefer but if it will pass code and there is no time to go shopping then use it.

▃  ▅  █  Size
The NEC (National Electrical Code) limits the number of wires that are allowed in a box. The limits are based on the size of the box, the size and number of wires and if there is a device in the box. ( a junction box has no device and is allowed more wires) Determine your box size by calculating "box fill" in the NEC book. For single gang boxes a good standard size is 20 cubic inches which will allow 3 x 12/2 with ground cables and a device or 4 x 14/2 wg cables and a device. Look inside the box to find the label identifying its size.  4 x 12/2 wg cables with a device are not allowed in a 18 cubic inch box.
  A 4 inch square box with a single gang mud ring can give you over 22 cubic inches of volume and yet fit in a shallow 2 inch wall depth where a standard 20 cubic inch box will not. 

? ? ? Shapes
Device boxes come in 1, 2, 3, 4, 5 and 6 gangs and possibly more through special order. 
Do not exceed more than a 4 gang switch box because the plates can be difficult to find. Instead of putting 5 switches at a door, try to divide the switches into two separate boxes a 3 gang and a 2 gang.  Better yet move or eliminate one of the switches. Some people go overboard on switches. If they were allowed to design the switches in their car they might have one for the front left parking light and another for the front right parking light and a 3rd and 4th for the back left and right. Yikes! How about just one switch to turn on all 4 parking lights.

? ▓ █ Material
Plastic and fiberglass are the most common, make sure they have a 2 hour fire rating stamped in the box.
A 2 gang Nail on box From Ebay

A 4S nail on box From ebay

The box on the left is a standard 2 gang nail on box. It is the correct box to use for 2 switches. Notice the 4 screw holes that are used to mount the switches. 

The box on the right is missing the 4 mounting holes. This is a 4 inch square nail on box (or 4 square or 4S) that requires a plaster ring to be attached to it before the switches can be mounted.

Here is a 2 gang (<left) and single gang (right>) plaster ring or mud ring that must be mounted to the 4 square box. A 4 square box with mud ring is good to use when the wall is shallow 2x2 but the cost of both is nearly double the cost of a standard nail on box. Use the standard nail on box on 2x4 and deeper wall studs.

   Use the Correct Height and Height Method                                                      

Does the height, that is marked on a stud, go on the bottom, center or top of the box? The answer depends on your company policy.    Recommended height method  is to mount the;
        > bottom of rectangular device boxes on the mark and the 
        > center of round light boxes on the mark. 
If you are new to an electrical company, make sure you and everyone else on the team is using the same height and height method. 44 inches to the bottom of the box will set the box 4 inches higher than 44" to the top of the box. Not only do companies use different height methods, they use different heights.  The recommended height is the height specified by architectural blueprints or 44 inches to the bottom of device boxes for switches, kitchen counter outlets and garages. 
   Recommended height for low room receptacles is 12 inches to the bottom of the box.

   Use the correct Depth                                                                                       

   Depth marks on the side of the box should be tight against the stud to set the box at the correct depth for the standard 1/2 inch sheet rock. If you know the depth will be greater than 1/2 inch,  as with a double layer of 1/2 inch sheet rock on a fire wall, then you can pull the box out farther like the center photo below. If you are unsure of the sheet rock depth keep in mind that it is better to be too far in the wall than sticking out of the wall. You can always use longer screws when the box is too too far in the wall but it is harder to fix a box that is too far out. You will have to cut the box nails, push the box in and remount the box with screws or grind off the protruding edge with a stone wheel on a battery drill.

?Wrong depth on bottom. This
box is not plumb, it was nailed
right on top but not the bottom
?Wrong depth. Notice the depth
marks on the side of the box are
not tight against the stud. This box
is sticking through the sheet rock.
?Correct depth, level and
plumb This box is not sticking
out past the sheet rock

Watch for Crooked Studs                                                                           
  This is an over head view looking down on a 3 gang switch box with a piece of sheet rock added below it to give you an idea of how the box will set in the finished wall. A crooked stud, like the one shown,  can cause your box to stick out past the sheet rock. This error can happen even if you nail your box at the correct depth to the crooked stud.
   If your box looks like this "Worst" photo> 
you will have to fix it.
    You can;
  1) Straighten the stud. Use your hammer to hit the stud at the base until it turns your box straight.
  2) Nail the box flush with stud, move it deeper into the wall before nailing it in place.
  3) Try the next stud in the same pocket. If the left stud is warped try the right stud.

   The box labeled "Better" does not need to be fixed but it might require some longer 6/32 screws to attach the switches on the right side that is sunk into the wall.

   The "Best" photo shows how your box should sit just slightly into the sheet rock.
   If you messed up and didn't notice that your box is sticking out until after the sheet rock is finished you can try to fix it by;
  1) Wedge a sheet rock screw in between the stud and the box at the top and bottom corners.
  2) Push the protruding side into the wall with a box support (also called 'F' Strap or battleship shown below)
  3) Cut the box nails, push the box in and remount the box with screws.
  4) Grind off the protruding edge with a stone wheel on a battery drill.
Two "F" shaped box supports
used with retrofit boxes.

   3 ways to mount a box in a narrow space                    

Here are some techniques for mounting boxes in a space too narrow to swing a hammer;
    1) Use a front mount box.
    2) Mount the standard box with screws.
    3) The lineman smash.

1) Use a front mount box.
This front mount box can be screwed or stapled to the front of the stud as shown. Unfortunately this specially designed box is twice the cost of a standard box and not always around when you need it.

If you don't have a front mount box try mounting a standard box with screws.

2) Mount the box with screws.
  With a fiberglass box be sure to set the screw in the reinforced area, that little corner space where the nail was, as shown in this photo.
   Pull the nails out of the box and screw the box to the stud with sheet rock screws as shown. Be careful not to crack the box. Plastic boxes work better with screw mounting.

3) The Lineman Smash.

Use your hammer to swing clear of the studs and hit your lineman's pliers as your lineman sinks the nail into the stud. Keep the tip of your lineman tight against the nail while hitting the "no pivot" side of your lineman with your hammer. 

If your hammer hits this circle shaped pivot, you will damage your tool. Hit the other side with your hammer, the side without the pivot or the side where the pivot's circle does not spin.

   Mounting a box on 2 inch Wood       

If you have to mount a box on the 2 inch side of a 2x4 stud or on the 2 inch edge of an I beam and the nails miss the wood you can;

   1) Use a front mount box
   2) Mount the box with screws
   3) Flip the nails
   4) Add a block of wood

   1) Use a front mount box  We already talked about the front mount above.
   2) Mount the box with screws. This will work with a plastic box but it is not recommended to screw mount a fiberglass box on 2" wood because the screws will be set forward in an area that is not reinforced. This will cause the box to crack around the screws unless the box is plastic. If all you have is a fiberglass box try to flip the nails.

  3) Flip the Nails.

The photo at the right shows a single gang box with nails flipped and mounted to a ceiling I beam. This box can now be used for a smoke detector. Here is how to flip the nails;

The left box in each photo shows how the nails are set from the factory. Each box on the right has the nails removed and inserted backwards allowing the box to be nailed to the 2 inch edge of a stud or I-beam.

4) Add A Board

There is usually a scrap block of 2x4 laying around on a newly framed house. Find one or cut one about a foot long and nail it to the 2 inch edge. This will create a 4 inch edge that will allow you to nail your box

  How to mount a box in a 2" deep wall  

Framing Carpenters like to turn wall studs on their side when framing over a concrete wall. They do this to allow their anchor to pass through the stud and into the concrete. This creates a wall that is 2 inches deep and will not allow a standard, 4 inch deep nail on box to fit. When this happens you can use a 4S box pronounced "Four" and the letter "S" which stands for 4 inch by 4 inch square. The 4S box has a standard depth of 2 inches, just right for your shallow wall. You will need a "mud ring" or "plaster ring" to attach to the face of the 4S box. Mud rings come in various depths but 1/2 deep is standard. They also come in various openings; single gang for one receptacle, 2 gang for 2 receptacles or round for a light. ← This photo shows a plastic 4S box with a plastic 1/2 inch deep single gang mud ring. The mud ring is attached to the box with 2 screws. One at the top right and one at the bottom left. The wire enters the box through a black plastic grommet that was inserted into a 1/2 inch hole.

   A Few Other Key points    

Plastic boxes twist. ?  
Some plastic boxes twist and warp out of alignment making it difficult to mount a switch or receptacle correctly. When using plastic boxes check to see if everything looks straight after you nail it in place, especially with the bigger 2 gang or 3 gang boxes.

Stay away from edges.
Keep your ceiling boxes away from edges, like the edge of a slanted ceiling to a level ceiling.
This photo is looking up at the ceiling inside a 2nd floor closet. The roof slants the ceiling down on the left. The light is mounted on the level side to the right of the edge in the ceiling.
Notice how difficult it would be to mount this large light if the box was mounted too close to this sloped edge.

Special gasket box for cold climates

This photo shows a single gang nail on box with an attached gasket. Some northern regions require these boxes on insulated walls and ceilings.

7 common "Nailing Up Boxes" mistakes by apprentice electricians

1) Choose the wrong box. If the box will be used for a ceiling fan then the box has to be fan rated.
2) Mount at the wrong height. Instead of measuring off the floor, they might measure off the sole plate which is 1½ inches higher than the floor. Or they set the box with the height mark at the wrong position; top of box, center of box or bottom of box. Each company has a different method.
3) Nail box up so that after sheet rock is installed the box is sticking out through the wall.
4) Nail plastic boxes too hard causing the box to twist so that a 2 gang box looks more round than square.
5) Mount larger 3 and 4 gang boxes so that they are not level.
6) Mount too close to corners.
A bath vanity receptacle 1 inch from the corner will not be accessible if a 2 inch framed mirror is mounted.
7) Mount too close to doors, windows and cabinets. Wide trim around doors and windows will cover half a device box.

  Boxes for Lights.                                                                                               

Here are some boxes used for lights and ceiling fans. Because fans are heavy and tend to wobble they require a box specifically designed and "rated" for ceiling fans.  Heavy chandeliers and lightweight fixtures are permitted to be mounted to fan rated boxes, but fans are not permitted to be mounted to light boxes.