Blueprint Drawings & Wiring Diagrams. for branch circuits

Transcription

1 Blueprint Drawings & Wiring Diagrams for branch circuits

2 Blueprint Symbols Wiring Diagram Symbols 2

3 Table of Contents Single Pole Switching p Three-way Switching p Four-way Switching p Two Pole Switching p Three Pole Switching p Receptacles p.37 Switched Receptacles p Multiwire Branch Circuits p Ground Fault Protection p Switches in Series p Switches in Parallel p

4 Introduction The intent of this booklet is as a learning tool, and a field reference manual. It has been set up so the reader can see typical blueprint drawings alongside a corresponding wiring diagram. Although no one book could ever contain all the wiring possibilities, this book should expose the reader to typical wiring arrangements, and make clear the wiring for portions of a complete blueprint drawing. This book will refer to important code topics such as conductor identification, required outlets, and ground fault protection, but the focus of the information is on the wiring of devices in specific configurations. It is not to be used as a code reference. The wiring starts out very simple, and slowly adds more complex elements. Ultimately the reader will be able to use the series and parallel switch connections as a springboard to learning the concepts for motor controls. The Author 4

5 The Single Pole Switch The single pole switch is the simplest of all switches. A conductor from the source is terminated under one screw (called the line side of the switch), and another conductor goes out from the other screw (the load side) to the device being fed. When the switch is in the off position, there is a gap in the circuit path at the switch, and the switch is considered open. When the switch is in the on position, there is a complete path through the switch and the switch is considered closed. 5

6 Single Pole Switch switch) In these introductory schematics we see a simple single pole switch at a doorway, controlling one light in the center of the room. A 2-wire feed enters the box with the switch, the neutral is spliced through and continues onto the load. The hot wire from the feed is landed on the line side of the switch, and on the load side is the switch leg, which carries the switched power out to the light. 6

7 Single Pole Switch light) Here we have a very similar set-up to the previous page, with one small change. In this case the 2-wire feed enters the system at the light. NEC Art (c)(2) requires the white wire in a cable assembly for switch loops be used as the feed to the switch. The source neutral enters the box containing the light and splices directly onto the neutral for the light. The hot wire from the feed splices onto the white of the 2-wire down to the switch, and the black switch leg returns as switched power to the light. 7

8 switch light 1 light 2 8

9 Single Pole Switch Controlling Multiple Lights On the opposite page we see three similar wiring configurations. In all three cases there is a single pole switch controlling two lights. The only difference is where the feed enters the system. In the top diagram the 2-wire feed is at the switch, and the neutral carries through the circuit providing a return path for both lights. The hot leg is switched and 2-wires carry switched feeds to each of the lights. These lights are wired in parallel. In the middle diagram the feed is at the first light. The hot leg is spliced onto the white wire to bring constant power to the switch, and the switch leg returns to light 1 on the black wire. There is also a 2- wire to carry switched power to light 2. These lights are also in parallel. It is important to remember your "box fill calculations when bringing multiple cables into a box. For box fill requirements refer to NEC Art Lastly, we see the 2-wire feed at the second light. What makes this configuration different is in order to carry a neutral from light 2 to light 1, a constant feed on its way to the switch, and a switch leg (red) between the lights, it is necessary to use a 3-wire between the 2 lights. Notice that these lights are still in parallel, with the constant power (black) in the same cable assembly. 9

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11 The Night Light In some branch circuit applications (primarily commercial & industrial) the design requires that a light source be unswitched or constantly on. We call these fixtures night lights. They are primarily used for lighting areas for security or safety (lobbies, stairways, etc.). More often than not, certain fixtures in a bank of switched lights are chosen to remain on at all times. As a result it offers the opportunity to the installer to bring the feed into the circuit at multiple points. On the opposite page are some sample diagrams to show how the reader how to make connections for a night light. It is a general practice to bring a 2-wire feed to a switch and loop to all the lights with a 3-wire, and a 2-wire between the last 2 lights (top diagram). The installer can bring the feed into the system anywhere, as long as all the considerations are made for box fill, and ensuring there are enough conductors from box to box (constant feed, switched feed, and a neutral). As always, the feed to the switch goes down on white, back on black. 11

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13 The Three-way Switch The three-way switch can most simply be described as an A or B selector switch. A feed is brought to the switch and landed on the pivot. This position is usually noted by a different colored screw and is sometimes called the common. The other two screws make contact with the feed depending on the position of the switch. Remember both loads can never be on at the same time or off at the same time, it is always one or the other. You may see this configuration in a photographer s darkroom, where you either want the normal bright light for general work, or the dark red light for photographic development. From the switch you can go out to your loads with separate 2- wires, or from one load with a 3-wire, and onto the second load with a 2-wire. 13

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15 Using Three-way Switches to Control Lights from Two Locations. The most common use for the three-way switch in branch circuit wiring is when it is used in pairs to control lighting from 2 different locations. A feed enters the three-way system, and lands on the pivot. The two other screws, which are called travelers in three-way switching, carry conductors to another three-way switch, and land on its traveler screws. The end pivot goes directly to the load as a switch leg. This configuration allows the user to turn the light on or off from either location. In the top wiring diagram on the opposite page, the reader can see that in its original configuration the power enters the circuit at the right. The neutral is spliced through directly to the load. The hot leg lands on the pivot, carries through the black traveler, and goes out on the right pivot directly to the load. If either switch is changed to make a connection with the red traveler, it will interrupt continuity from the hot leg to the load and the light will go off. Then if either of the switches are changed the light will go back on. As a rule, we always run a 3-wire between switches for a simple three-way system. 15

16 In this configuration the 2-wire feed enters the system at another switch. The neutral is spliced and goes out to the light. The feed splices onto the white wire (by code, just like a single pole switch) and the red and black return to the original box. Then a switched black goes out to the light. As always, ensure you have enough room in your boxes for the necessary conductors. 16

17 Here we see the feed at the light. The neutral lands directly at the light, and the hot leg goes down on white into the three-way system. The red & black travelers run between the switches and the last black pivot carries the switched feed up to the light. As in all three-way installations, there are 3-wire connections between the switches. 17

18 It is also possible to bring the 2-wire feed in at the light, and run a separate 3-wire down to each one of the three-way switches. Here the neutral goes directly to the light, and the hot leg goes down on white. The black and red travelers splice onto the white and red travelers to the second switch, allowing the black to function as the switch leg for the light. The biggest concern in this case is overloading the light box. These are commonly called dead-end three-ways. 18

19 The Four-way Switch The four-way switch is unique in that it is only used in conjunction with three-way switches to allow the designer and user to control lights from more than 2 locations. Its function is to swap the position of the travelers. The 4 terminals on a four-way switch are typically divided into 2 pairs, commonly labeled input and output. A pair of travelers coming into a box are landed on the input screws, and the outgoing pair are landed on the output screws. Generally the input & output screws are different colors to insure that the installer does not confuse their purpose. In one position of the switch, there will be continuity from color-to-color. When the switch is flipped, the continuity swaps to the opposite traveler. Like the three-way switch, the connection must be one or the other. In the following diagrams, the reader will be able to see the various ways a four-way switch can be integrated into a multi-location switching arrangement. 19

20 Four-way Switching end three-way) 20

21 Four-way Switching four-way) 21

22 Four-way Switching middle three-way) 22

23 Four-way Switching light) 23

24 Dead End Three-ways & Four-way Note the use of the 4-wire for the four-way (2 travelers out, 2 travelers back) 24

25 Switching From More Than 3 Locations It is possible to control a load from many locations, just by connecting additional four-way switches at any point between the three-way switches. In the diagram below, we can see by adding additional four-way switches between the three-way switches, we can now control the light from 5 locations. As always, we have a 2-wire feed, and a 2-wire switch leg, with 3-wire jumpers between the three-ways & four-ways. Additional four-ways simply create more locations for the user to swap the travelers, Even if a user wanted to control a light from 50 locations, the installer would still use only 2 three-ways at each end, with the balance of the middle locations being four-way switches. 25

26 Providing Multiple Location Switching and Constant Feed (NEC Acceptable) Here we see a typical post light configuration. As a means for remote lighting, a post light is installed some distance from a building. The lamp can be controlled from both the building and at the post, and a constantly fed receptacle is energized regardless of the positions of the three-way switches. Note the use of 4 conductors between the building and post light: one hot leg (spliced at the first box to feed the 3-ways & onto the receptacle), one neutral (for the light and the receptacle), and two travelers. One 2-wire jumper carries the switch leg and a neutral up to the light, and another 2-wire carries a constant feed and a neutral to the receptacle. 26

27 Providing Multiple Location Switching and Constant Feed (NEC Violation) This is an arrangement a wireman may only see in a very old house or by observing the work of a cheater. Here the same overall effect is achieved, using only a 3-wire jumper between the building and the post light. In this case the hot and neutral are landed on both traveler screws at both switches, and then onto the receptacle. The pivots are run up to the light in a 2-wire. When the pivots (shown as the 2 reds up to the light) are both grounded (through the neutral) or both hot, the light will be off. If one pivot is hot and the other grounded, the light will be on. This is absolutely a violation of NEC Art by energizing the screw shell of the lampholder. It is included in this text only as a reference, and not for instruction! 27

28 The Two Pole Switch The two pole switch works exactly the same as 2 single pole switches controlled with 1 handle. In the diagram below, we see 2 conductors (red & black) landing on the line side of the switch. The conductors out to the device being controlled are landed on the load side of the switch. When the handle is moved to the open position, the red and black circuits are opened simultaneously. Whenever the handle of the switch is closed, contact is made across both the red and the black conductor simultaneously. It should be noted that a two pole switch may not be used as a four-way switch, or vice-versa. 28

29 Two Pole Switch Controlling a Single-phase, Two Pole Motor switch) Note the double arrow on the 2-wire feed, indicating two hot legs to the motor, and a 2-wire switch leg out to the motor. This implies that there is no neutral supplied to the load. If cable is run, NEC Art (c)(1) requires that when the white wire is used as an ungrounded conductor, it must be permanently remarked a color other than white, grey or green. Typically, colored marking tape is used to identify the white wire as a hot leg. 29

30 Two Pole Switch Controlling a Single-phase, Two Pole Motor motor, one 4-wire) When the feed is brought to the motor location, two conductors must be brought to the switch as a feed, and two conductors must be brought back as switch legs. This may require the use of a 4-wire cable (with the white wire remarked where possible). This is why in most situations the feed is brought directly to the motor. 30

31 Two Pole Switch Controlling a Single-phase, Two Pole Motor motor, two 2-wires) If 4-wire cable is not available, an installer may opt to use two 2-wire cables. As always, the white wire is remarked. 31

32 Two Pole Switch Controlling 2 Single Phase Circuits There may be a situation in which an installer may be required to control 2 single phase circuits simultaneously. In the example below, a large dining hall contains six 600 watt chandeliers. Since this is too much of a load for one 20 amp circuit, it is necessary to split the load into two 20 amp circuits. The customer may wish to control all six lights from one switch, and this is a situation easily resolved with a two pole switch. Notice the double arrow on the 3-wire homerun. This indicates 2 hot legs sharing a neutral. This is called a multiwire branch circuit. 32

33 In the above diagram, we can see the 3-wire homerun entering the switch box, and the 2 hot legs landing on the line side of the two pole switch. The neutral tails off and goes out to each of the 2-wire lighting circuits. Both conductors off the load side of the switch go off separately, each to one of the 2-wire lighting circuits as a switch leg. With the two-pole switch, the user can simultaneously control both circuits. 33

34 The Three Pole Switch Rarely seen in residential applications, the three pole switch is primarily used for controlling three phase loads. Similar to the single pole switch and the two pole switch, its function is to simultaneously open or close 3 conductors. It is identical in design and purpose to a 3-phase, unfused disconnect switch, however for in the 15, 20 and 30 Amp sizes, the switch is small enough to fit on a standard single device yolk. 34

35 Three Pole Switch Controlling a Three Phase Motor switch) Here is a homerun marked with three arrows on a threewire cable, indicating this is a straight three phase circuit, meaning there are 3 hot legs and no neutral. With 3 wires in and 3 wires out, the installer should plan the box sizing accordingly. As with the single phase, two pole motor, when a white wire is used a hot leg, it must be remarked at every termination point. 35

36 Three Pole Switch Controlling 3 Single Phase Loads This configuration is nearly identical to the twopole switch controlling 2 single phase circuits. Here we have a 4-wire homerun from a 3-phase system, with 3 hot legs and a neutral. Each hot leg is simultaneously switched and the neutral is spliced, sending three 2-wire feeds out to each one of the lights. This is also an example of a multiwire branch circuit. Three hot legs may share a neutral only when they are on three different phases of a three phase system. 36

37 Wiring Receptacles On 1 Circuit In this simple diagram, one 2-wire feed enters the circuit and feeds all the receptacles. In all cases the hot leg is tailed off and lands on the brass terminal. The white neutral is tailed off and lands on the silver terminal. This is commonly called a branch circuit with a dedicated homerun, because the neutral is not being used by any other circuit. 37

38 switch receptacle 38

39 Switched Receptacles Here we introduce the idea of switched receptacles. NEC Art mandates areas that require switched lighting outlets. In addition to lighting fixtures, a switched wall receptacle (with the intent of controlling a cord-connected lamp) satisfies these requirements. In the top diagram, a 2-wire feed enters the circuit at the switch. The neutral is spliced through at the switch and carries through to each receptacle. the remaining two wires are a constant feed (black) and a switched feed (red). It is a common practice to run a 3-wire between all the receptacles to give the installer the option of having the outlet be switched or constantly hot. In the lower diagram, the feed enters the system at the last receptacle. Again this installer has elected to run all 3-wires between the receptacles, though only one is switched. At the switched receptacle the reader can see that the constant feed is spliced onto the white as a switch feed and returns with the switch leg on the black. It should also be noted that the tabs connecting the screws on the sides of a receptacle can be removed, making the top and bottom electrically separate. See NEC Art (b). 39

40 Multiwire Branch Circuits (alternating circuits in one room with 3-wire) As the reader may recall, multiwire branch circuits are simply when 2 or 3 hot legs share a neutral. In some situations, an installer may wish to feed a work room or other large space with more than one circuit. It is a common practice to alternate the receptacles. In this configuration, a 3-wire homerun feeds the circuit and a 3-wire is looped from outlet to outlet. This gives the installer the option of what circuit the receptacle will be fed by at the time of installation, and makes it very easy for the user to make changes in the future. Some installers may wish to avoid splices by landing their conductors on the screws of the receptacles, however, NEC Art (b) requires that the grounded conductor (neutral) of a multiwire branch circuit be tailed-off before being landed on a device. 40

41 Multiwire Branch Circuits (alternating circuits in one room with 2-wire) 3-wire cable is naturally more expensive than 2-wire cable. Another option for having a room with alternating circuits is to bring a 3-wire homerun to one of the receptacles, and feeding the rest of the room with two 2-wire loops. The advantage to the installer and the customer is a less expensive job with the same desired effect. However, with a 2-wire loops there can be no simple changes to the circuit in the future. 41

42 Multiwire Branch Circuits (split for different rooms) Multiwire branch circuits can also feed multiple rooms. It allows the installer to run fewer homerun cables back to the panel, and still provide the necessary circuits to an area. Once again, NEC Art (b) states that the continuity of a grounded (neutral) conductor in a multiwire branch circuit cannot depend on a device where the removal of the device would interrupt the continuity of the conductor. In this case, in the box containing the homerun, the white wire must be tailedoff before hitting the outlet. In all other outlets, the installer has the option of landing both the ins and outs on the screw terminals of the receptacle. 42

43 The GFI Receptacle The ground fault interrupting (GFI) receptacle is designed to protect the user from stray voltage. It is fed by landing a hot wire and a neutral on the line terminals. The user can plug a device into either of the two receptacles, and has the option feeding out on the load terminals to feed other receptacles with a ground fault protected feed. The GFI simultaneously measures the current through the load side hot leg and neutral. If there is a difference of more than 5 milliamps, or if the TEST button is pressed, the GFI trips and interrupts power to all the loads. Once the fault has been identified and cleared, the RESET button can be pressed to return power to the loads of the GFI. 43

44 Bathroom Receptacle Protected By GFI Receptacle NEC Art (d) requires a receptacle adjacent to each bathroom basin in a dwelling. Art (a)(1) takes the next step of requiring bathroom receptacles to be ground fault protected. In this example a 2-wire feed is landed on the line terminals of a GFI. Power will flow to the receptacles on the face as long as the circuit is clear of ground faults. If there is a fault, the circuit will immediately open. 44

45 Bathroom Receptacle Protected By GFI Circuit Breaker Another method to protect a circuit from ground faults is to feed the entire circuit from a GFI circuit breaker. A GFI breaker works on the same principle of measuring a circuit for an imbalance to detect leakage current, and interrupts power to the circuit in the presence of a ground fault. The GFI breaker has two terminal screws, one for the hot leg, and also one for the circuit neutral. It is important to note that GFI breakers cannot be used with multiwire branch circuits, because the circuit needs a dedicated neutral for each hot leg in order to detect an imbalance. GFI breakers are also very expensive, and must be reset at the panel. For these reasons, they are only used in situations where it is not practical or possible to use GFI receptacles. 45

46 Kitchen Receptacles (One 3-wire homerun) NEC Art (b)(3) requires two small appliance branch circuits for a dwelling kitchen. In addition, Art (a)(6) mandates countertop receptacles be ground fault protected. In this configuration, usually seen in renovations, an existing 3-wire multiwire branch circuit is feeding the countertop receptacles. Since the circuits are sharing the neutral, ground fault protection can be established by installing GFI receptacles at every locations. This system meets NEC standards, and if there is a temporary ground fault, only the receptacle with the fault will trip, leaving the rest of the circuit energized. The only disadvantage is the high cost of GFI receptacles. 46

47 Kitchen Receptacles (Two 2-wire homeruns with GFI breakers) In a situation where the installer has elected to use individual 2-wire homeruns, it is possible to use GFI breakers to protect all the countertop receptacles. This is a means to provide ground fault protection to receptacles with old, frail wiring, or installed in boxes too small to accommodate a GFI receptacle. However, it should be noted that GFI breakers are very expensive, and must be reset at the panel. 47

48 Kitchen Receptacles (Two 2-wire homeruns with GFI receptacles) It is also possible to provide ground fault protection to 2-wire circuits by installing one GFI receptacle at the beginning of each circuit. This method avoids the use of costly GFI breakers, and allows the user to reset a tripped circuit from within the room. 48

49 Kitchen Receptacles (One 3-wire homerun with GFI receptacles) Most popular for new installations, this wiring configuration takes advantage of installing one 3-wire homerun to feed the countertop receptacles, and uses one GFI receptacle per circuit. It should be noted that the neutral is shared by the circuits on the line side of the GFI receptacles, but each of the protected loads have their own dedicated neutral. 49

50 The Faceless GFI The faceless GFI is an inline ground fault protective device for a branch circuit. It functions exactly like a GFI receptacle, in that it is fed on the line side, while measuring and protecting the load side. It also has both the test and reset buttons. The difference is it does not have the 2 receptacles on its face, and the only protected output is on the load terminals. It is often seen in the vicinity of a Jacuzzi or bubbler tub. NEC Art (a)(3) clearly states that receptacles feeding a spa or hot tub must be ground fault protected. More often than not these pump motors are on their own dedicated circuit. If a GFI breaker is installed, and there is a temporary fault opening the circuit, the user is forced to go to the panel to reset the breaker. 50

51 In these diagrams we can see a 2-wire homerun feeding the load side of a faceless GFI in the room. Without the receptacles, the circuit is still dedicated to the tub and cannot feed any other loads. From there the circuit jumps another 2-wire out to feed a standard receptacle in the base of the tub. This allow the user to cord-andplug connect the pump motor to the circuit. With this configuration, in the event of a temporary ground fault, the user can reset the circuit without leaving the room or accessing the tub base and motor. The faceless GFI is often mounted above the room s lighting switches and must be at least 5 feet from the inside wall of the tub, as per NEC Art (c). This device can also be used to protect the lights above a tub or shower from a ground fault. 51

52 Single Pole Switches in Series switch) There are special situations that will require an installer to connect multiple single pole switches in series. Local building codes often require that a means of disconnecting the home heating source must be located at every entrance of a home s basement. Therefore our circuit logic dictates that any of the above switches can turn the motor off, and prevent the other locations from turning the motor on. This is accomplished by connecting the single pole switches in series. In this particular example, the reader can see an oil burner motor connected to a daisy chain of 3 single pole switches. 52

53 The cutoff switches are left in the ON position as long as the burner is functioning correctly. If there is a problem, and any of the switches are moved to the OFF position, or opened, the circuit will no longer be continuous and the motor will not run. More switches can be flipped, but the motor will not work unless all the switches are in the closed position. These switches are functioning as stop switches because their job is to stop the burner motor when it is necessary. The rule is: stop switches are normally closed and wired in series. In this diagram you can see the neutral is spliced through the switches to the motor, and the hot leg is switched at every location in series. 53

54 Single Pole Switches in Series motor) The feed can also be located at the motor with the daisy chain of switches located remotely. As always, it is necessary for the feed to go down on white, back on black. The neutral goes directly to the load. 54

55 Single Pole Switches in Series motor, separate switch loops) Sometimes it is necessary to add switches in series, or run individual switch loops to multiple locations. As long as there is only path for current to flow, the switches will function as stops and are considered in series. 55

56 Single Pole Switches in Parallel switch) Here we see a case where 3 bathrooms share a common exhaust fan motor. Rather than 3 separate switched fans, the designer has opted to use one fan with one ducted vent in each of the three bathrooms. The control logic dictates that the three single pole switches are normally in the OFF or open position. If any of the three rooms needs exhaust, a switch will be flipped ON (or moved to the open position). It is also necessary that while one room is calling for the motor to be on, that none of the other rooms can turn the fan off. This is accomplished by connecting single pole switches in parallel. In this particular example, the reader can see an exhaust fan motor connected to a daisy chain of 3 single pole switches. 56

57 As with the single pole switches in series (feed at the switch), the neutral is spliced through at each location and carries on to the motor. The difference here is that in order to provide parallel paths the wireman must install 3-wire jumpers between each location, similar to 3-way switching. At the end of the switches, a 2-wire jumper carries a neutral and the switch leg up to the motor. These switches are considered start switches because their job is to start the exhaust fan from any of the 3 locations whenever it is necessary. The rule is: start switches are normally open and wired in parallel. 57

58 Single Pole Switches in Parallel motor) The feed can also be located at the motor with the daisy chain of switches located remotely. As always, it is necessary for the feed to go down on white, back on black (and red). The neutral goes directly to the load. It is still necessary to install the 3-wire jumpers between the switches to provide parallel paths. 58

59 Single Pole Switches in Parallel motor, separate switch loops) Sometimes it is necessary to add switches in parallel, or run individual switch loops to multiple locations. As long as there are parallel paths for current to flow, the switches will function as starts and are considered in parallel. 59

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