What is Conduit Wiring? Types, Advantages & Applications
Table of Contents
Installation means the act of installing something. Connecting two things or recombining two things in such a specific configuration or sequence that a complete system builds as a result of their joining or conjugation, is called installation. Electrical installation means the provision of corresponding supply to electrical appliances or instruments and their induction together with the safety circuits. The electrical installation provides a safe source for connecting electrical appliances of a consumer with electrical supply through over current and earth leakage protection. It consists of all cables, pertinent safety components, and control gear. In short, fixing different types of circuits and electrical equipment on a panel, recombination of electrical components with an incomplete system for making a complete system thereof, installation of electrical wiring in a precise or correct fashion either temporarily or permanently, installation of protective gadgets, installation of service lines on a one floor or multi-floor buildings, installation of motors, installation of load and earthing system are all included in electrical installation. In fact, the electrical installation consists of a complete system of all types of electrical wiring and its associated electrical components or instruments, protection, testing, signal communication circuits, and entire instruments related to the electrical control, installed in residential and commercial buildings, industrial units, factories, and refineries, etc.
The following wiring systems or methods are used:
- Cleat Wiring System
- Batten Wiring System
- Casing Capping Wiring System
- Conduit Wiring System
Conduit wiring may further be classified into the following two types
(i). Surface Conduit Wiring
(ii). Concealed Conduit wiring
Conduit Wiring System
The system of wiring in which all wires or cables from supply to load are passed through iron or PVC pipes is called a conduit wiring system. The objective behind passing wires through the pipes is to safeguard it against unpleasant consequences of weather conditions, physical breakdown, fire dangers, and atmospheric effects. It has to be kept in mind while passing cables through the pipes that that its insulation does not get damaged. This type of wiring system is most widely used as compared to the rest of the wiring systems.
Types of Conduit Wiring
- Surface Conduit Wiring
- Concealed Conduit Wiring
Surface Conduit Wiring
If conduits are installed on the surface of a roof or wall, it is called conduit wiring. For this type of wiring, the first holes are made on the wall surface in a straight line at equal distances. Then rowel plugs are fixed into these holes and saddles are installed above these rowel plugs through screws. After this, conduits are installed above it. The size of the conduit used in this type of wiring depends on the number of wires going to be passed through it. Moreover, the size of conduit which is used in wiring, and fittings will also be used of the same size.
In figure 1.7,
has been illustrated. This type of wiring is done away from gas, water, and steam pipes. This type of wiring is extremely suitable for houses, factories, and industries.
Concealed Conduit Wiring
If PVC conduit is concealed by means of carving grooves on the wall, and then plaster is done above it, this type of wiring is called concealed conduit wiring. As this type of wiring is not visible from outside, only switches and lamp holders are visible, therefore it is known as concealed conduit wiring. In other words, wiring carried out inside a pipe within a wall is called concealed wiring. In the concealed type wiring, grooves are formed on the wall, pipe fitted in it, and then covered with plaster. Only junction box spots remain visible, wherefrom wiring can be looked after and repaired. Conduit pipes are tightly fixed onto the walls through hooks prior to being plastid. Prior to putting concrete on a roof during a linter, PVC conduit pipes are spread all over the roof, whereas prior to doing plaster on the building walls, grooves are dug onto the walls, and then conduit pipes are fixed in these grooves. It is then plastid. After the plaster has been completed on roofs and walls, wires are inserted into these fitted conduits with the help of steel wires. As conduits are not visible in this type of wiring, therefore it remains protected against fire, water, moisture, and other weather conditions. In the concealed wiring system, all switchboards are also fitted on walls and flush-type switches and sockets are used in this type of wiring. This type of wiring is commonly used in houses, offices, bungalows, and all other modern buildings, etc.
Types of Conduit
The following two types of conduits are used in the conduit wiring system according to their structure.
(1). Metallic Conduit
(2). Non- Metallic Conduit
Metal conduits or pipes are fabricated from steel. These conduits are durable and also costly. Therefore, these are used only in high–standard construction. Technically, a number of merits have been observed in steel conduits e.g., at the time of fixing a conduit if there is a need to bend it, it can easily be done without any sort of breaking or rupture in pipes. Further, no cracks or hiatus occur in it. There are two types of metal conduit with respect to gauge.
(i). Light Steel Sheet Conduit (Class A Conduit) or Low Gauge Conduit
(ii). Heavy Steel Sheet Conduit (Class B Conduit) or Heavy Gauge Conduit
(i). Light Gauge Steel Conduit (Class A Conduit)
Light steel sheets or class A conduits are such steel pipes that have no grooves or narrow stripes on them (i.e., they can be used without forming any kind of grooves or stripes). Therefore, their knots or joints are closer or adjacent which can be fortified through welding or breezing. As such pipes are manufactured from light steel, therefore such pipes cannot be twisted or bent extensively. These types of pipes are relatively cheaper compared to heavy gauge steel pipes. These are available in a diameter of 13 millimeters to 50 millimeters and they can be applied in mediocre-type buildings for a 250 volts supply. Light-sheet quality conduits are never used in power wiring.
(ii). Heavy Gauge Steel Conduit (Class B Conduit)
The heavy-gauge steel conduit (class B conduit) is uniformly designed with a neat and clean interior structure. Thus, the danger of wires cutting or erosion does not exist at the time of inserting wires into the pipes. The heavy gauge conduit cannot be used without making narrow strips or grooves on it and all joints are stiffened by means of tightening narrow strips at the ends of pipes. As a result of combining together through narrow strips, the electric continuation of such pipes remains stable. (Remember that if wires insulation gets damaged or weakens due to any reason, the flow of leakage current continues within the steel pipes and an electric shock can be felt by touching any part of switchboards or pipes. In order to eliminate this danger, entire conduit wiring and annexed accessories are properly connected together and earthed on two spots, so that leakage current shifts to earth and no electric shock can be felt upon touching it). In order to use these conduits within a wall a blackish color, for use on surfaces inside the room a black color, and for exterior use, galvanizing is done. In size, these conduits are available up to 63 mm in diameter. The heavy gauge conduits can protect wires in a better manner. They can be bent or turned at any angle without any danger of breaking down or bursting. Wires can easily be injected into it without any sort of damage to the wires. They view quite seemly to eyes. They have no danger of being by fire etc. They are durable and robustly built, as a result, they can easily sustain any sort of jerks, etc. They also do not have any sort of weather impacts on them; therefore, such pipes are vastly used in top–quality construction. However, they have just one defect i.e. they are costly.
PVC conduits are abundantly used nowadays as a non–metallic conduits, because PVC pipes are quite flexible, and they can be twisted or bent quite easily. A hard PVC pipe can be bent according to ones’ needs by means of providing heat to it through fire. The sizes of PVC pipes are also similar to metallic pipes and these pipes are available in coils. Whereas the length of every pipe ranges from 3 meters to 10 feet. As non–metallic pipes are being fabricated from insulator material, therefore the biggest issue in it is the electric continuity of the earth. That’s why they are not earthed. As such, a separate earth system has to be devised for the purpose. Heavy gauge pipes are prepared in PVC form also, which are used in places where the probability of external pressure or concussion on wiring exists. As PVC pipes pose considerable resistance against acidic vapors and moisture etc., therefore it is commonly used for a single-phase system.
Normally, pipes are available for conduit wiring in 13, 16.2, 18.75, 20, 25-, 37-, 50- and 63-mm diameter (or ½, 5/8, ¾, 1, 1.25, 1.5, 2 and 2.5 inches)
Types and Number of Wires Used in Conduit
Mostly VRI and PVC wires are used as conduit wiring, which is suitable for low and medium voltage grades. Where ever the risks of moisture, humidity, external shocks, and contusion are high, tough rubber sheathed PVC wires are used. Flexible wires should not be used in conduits, because the risk of damage to their insulation or even breaking down of insulation exists at the time of putting wires into the conduits.
As the maximum number of wires which can be adjusted in a conduit depends on conduit size, wires sizes, wires insulation, wires’ current capacity, weather conditions, etc., therefore cables manufacturing companies issue tables regarding the number of wires to be injected into a conduit. It should be bear in mind while inserting wires into a conduit that wires could be pulled easily in the conduit. And at the same time, they could be moved easily when there is a need to repair it. Remember that the collective size of wires to be inserted into pipes should not exceed 40% of the interior pipe size. In table 1.1, the number of cables in a specific type of conduit has been reflected according to the cable sizes.
Table 1.1 – the number of cables in a conduit
|Number of Cables in a Conduit||Cable Size|
|25 cm (1”)||20 cm (3/4”)||15 cm (3/8”)||Decimal System||English System|
|16||10||6||1 / 1.13||1 / .044|
|13||8||5||3 / 1.38||3 / .029|
|10||6||4||3 / 1.78||3 / .036|
|10||6||4||7 / 0.85||7 / .029|
|7||4||3||7 / 1.00||7 / .036|
|5||3||2||7 / 1.04||7 / .044|
In a conduit wiring system, different types of accessories or materials are used for the purpose of joining pipes, which are known as fittings. For example, elbow, junction box, union, socket, nipple, cross joint junction, clip, saddle, grips, inspection band, inspection T, etc. Bending of a conduit when required, is also included in it.
There are two types of conduit fitting. Surface and concealed. Surface fitting is done for the purpose of wiring which is mostly carried out in factories, workshops, go-downs, hospitals, and other commercial organizations. Its advantage is that wiring can be inspected as and when required. On the contrary, concealed fitting is used for concealed wiring, which is mostly carried out in homes, offices, shops, hotels etc. As conduit is installed in a concealed manner in this type of wiring, therefore this type of wiring normally presents a very beautiful appearance. However, its inspection is relatively difficult whenever required.
The accessories which are utilized in order to tightly install a surface conduit on walls are called conduit fixings. For this purpose, different types of clips and saddles are used. The distance of saddle with the conduit is retained at approx. 3 feet and, in every fitting, their distance is maintained 4 inches. Saddles are installed on rowel plugs or wooden dowel pins with the help of rust-free round-headed screws. Saddles can be found in different sizes and shapes according to needs e.g., spacer bar saddle, distance saddle, multiple saddle and girder clip, etc.
Precautions in Surface Conduit Wiring
- Conduit should be selected according to the number of wires and sizes in such a way that a reasonable space is available after inserting the wires.
- Conduit fittings must always be installed on walls according to conduits weight
- Rowel plugs or dowel pins are planted at a reasonable distance according to the sizes and weight of pipes
- An earth wire of an appropriate size should also be run along pipes and it should be earthed at reasonable distances by combining with conduits. Moreover, all junction boxes, iron-clad switches, and distribution boards, etc. should also be properly earthed.
- Conduits should be kept apart from water and gas pipes
- Wires should not be penetrated through the conduit in excess of the required numbers
- Wires of opposite polarity must essentially be passed through metal pipes so that a substantial voltage drop does not occur as a result of AD current
- Pipes should reach inside up to the metal boards and bushes should be installed on their heads or ends
- PVC pipes must not be used in places where the danger of mechanical disruption or wear and tear persists
- After grafting grooves or narrow strips on metal pipes, its edges should adequately be smoothened through a sandpaper
- A separate saddle and clamp should be used for each pipe and if most of the conduits are in parallel, multiple saddles should be used for the purpose. Only one saddle should never be used for all pipes,
- All bends on pipes should be in a rounded form so that wires insulation is not scratched at the time of dragging wires
- The number of 90-degree bends between adjacent boxes should not exceed 4
- At the time of bending a conduit, it should be filled with sand, due to which, it does not skid from the twisted spot
- Metal conduit should be bent by means of heating it through a yellow lamp
- Only girder clamps should be applied while fixing conduits along guarders and beams
- At the time of dragging wires into conduits, it must be ensured that no twists or winds occur in wires and wires should be drawn perfectly straight.
- An inspection T and bend and box should be used in a long conduit
- Conduits less than 16 mm in size should never be used
- Conduit pipes should internally be clean and dry and externally should be painted in order to get protected from rust. They should always be installed through a heavy gauge saddle
Surface wiring has under – mentioned advantages;
- Alterations or additions are possible in this system according to future needs
- Its revamping, repairing, and maintenance is quite easy
- In case wiring is performed in an expert manner, it seems relatively good-looking
- In the case of PVC conduit, this wiring remains protected from rust as well as fire
- This type of wiring can also be used in places prone to weather as well as chemical impacts
- As a result of proper earthing of metal conduit, no danger of an electric shock exists in this type of wiring
- It has a long life
- It is a reliable and popular method for wiring purposes
- Most of the accessories used in this type of wiring, can be reused as required
- It tends to be less attractive as compared to the concealed wiring
- It requires significant labor and skilled technicians
- As dust and cobwebs etc. form on conduit, therefore they require occasional cleaning or dusting
- They are not protected against mechanical shocks and as a result of such blows, there always remains a risk of conduit getting uprooted
- If earthing has not properly been done, then in the case of metal conduit, the risk of an electric shock lingers on
- A significant amount of time is required for the purpose of installing this type of wiring
- It is comparatively expensive due to the large application of accessories e.g., elbows and Ts, etc.
- It is difficult to trace out fault and repair it quickly. Repair work involves a lot of time-consuming
- If a metal conduit has been used in wiring, it becomes imperative to get it earthed, which obviously involves extra costs
- During the wiring process, the straightness of the conduit is always kept in mind for beautification purposes
Precautions in Concealed Conduit Wiring
The precautionary measures being employed for concealed conduit wiring are nearly similar to those being adopted for surface wiring, however following some precautions are specifically associated with concealed wiring, which must necessarily be kept into mind;
- On a concrete roof, conduit must be spread before the roof is being concreted
- At the time of putting conduits on a concrete roof, pipes of different points should be combined directly, and bends should be avoided as far as possible.
- Mouths of conduits should properly be covered with some paper, so that cement does not freeze on it during plaster
- Pipe must essentially end up within the box
- Every metal box must duly be earthed
- Wires should be passed through conduits prior to fittings
- For making connections in a concealed wiring, the looping in the method should be adopted (i.e., every wire which reaches a certain point may be joined with that point and then without cutting, bend it towards another point). Though more wire is consumed under this method, however wires are neither cut nor any kind of bend is put on them.
- As moisture infiltrates into pipes during watering of the plaster, therefore a cotton cloth must be passed through the pipes prior to the inserting of wires into the pipes, so as to clean up the moisture
- Metal conduits being used on walls and ceilings must properly be painted so as to protect them against rust etc.
- It is common that junction boxes to move down from the wall surface as a result of plaster. For this purpose, a special type of paint must be used in order to bring the junction box’s surface equal to the wall surface, so that wiring does not seem obnoxious.
- All boxes should vertically and horizontally be absolutely straight. In the case of the crooked or curved boxes, wiring presents an unpleasant look
- If metal conduits have not been used for installing wires on an iron box, then the box should be earthed separately
- For the purpose of installing metal pipes on a metal junction box, only an even and smooth brass bush should be used.
- While passing wires through a conduit, wires must be dragged in such a fashion that their insulation does not damage
- A wooden ladder should be used instead of an iron staircase while doing electric work
- A protective glass or spectacle must be used while grafting a groove, so that cement or sand particles do not enter the eyes
- At the time of dragging wires into the conduit, wires reels or drums must rotate freely so that wires could enter into pipes perfectly straight.
- The number of cables going to be passed through a conduit should be such that enough space or capacity remains available even after the existence of these wires.
Advantages of Concealed wiring
- This wiring seems pretty attractive due to the fact that the conduit is buried with the walls.
- It is protected against all sorts of weather as well as chemical effects
- It is quite enduring as a result of being protected against mechanical shocks
- It remains protected against fire eruption
- As the straightness of wiring is not cared about in this type of wiring, therefore the usage of elbows and Ts, etc., is relatively less. As such, it is less time consuming and also less costly
- There is no danger of conduits getting uprooted
- It is one of the safest wiring systems
- It is most popular as well as reliable as compared to the rest of the wiring methods
- There is no menace of electric shocks or accidents
- There is no need to earth it due to the application of PVC pipe.
Disadvantages of Concealed wiring
- Once the wiring has been completed, additions or alterations in wiring become difficult
- It is more costly as compared to other types of wiring
- It is difficult to find out the defect and remove it
- As a result of making grooves in the wall, there is an imminent danger of the building getting unstable and weak
- Extra hard work is required for making grooves apart from being time-consuming
Uses of Conduit Wiring
As a result of being protected against setting on fire, getting rusty, safeguarded against mechanical shocks, free from chemical and weather conditions, being beautiful, enduring, and safest, the conduit wiring system is the only wiring system, which is being considered the most popular despite being expensive and it is widely used in the following places;
(i). Places where extreme dirt and dust exist or where cotton wool work is performed e.g., textile mills, sawmills, flour mills, etc.
(ii). Places and areas having moisture e.g., cold storage, etc.
(iii). Workshops etc.
(iv). All such places, where the danger of fire breaking persists e.g., oil mills, varnish factories, ammunition companies, etc.
(v). Places where important documents are preserved e.g., record rooms, courts, etc.
(vi). Ordinary residential and public buildings, where beautification is given foremost attention
(vii). In large houses, bungalows, commercial buildings, offices, etc.
(viii). In cinema houses, railway stations and hospitals, etc.
(ix). Parks, recreation spots, where safety is being given paramount importance
(x). In mosques and other places of worship e.g., churches, synagogues, temples, etc. due to their attractiveness and durability
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