Q: Why should every wire joint be inside a junction box?

A joint is the weakest point of any wiring run — it’s where strands loosen, oxidise and heat up. A junction box does three jobs for that weak point. It contains the heat and any sparking if the joint deteriorates, keeping it away from concealed woodwork and insulation. It keeps the joint accessible, so it can be inspected or remade without breaking a wall — a taped joint buried in plaster is invisible until it fails. And it protects the joint mechanically, from tugging, dust, moisture and pests. Outdoors, the box needs to be a weatherproof one with proper cable entries, especially through the monsoon. A twist of insulation tape hidden in a conduit is the classic shortcut behind flickering lights, warm switchboards, and worse.

Q: Why must cable armour be earthed?

The steel armour on a cable isn’t only mechanical protection — it’s a safety conductor. If the cable is damaged and a live conductor touches the armour, the armour has to carry that fault current back to earth so the protective device trips quickly. That only happens if the armour is solidly earthed, normally through the cable gland at each end, which clamps the armour wires and bonds them to the earthed gland plate or enclosure. Unearthed armour does the opposite of protecting: under a fault it can sit at a dangerous voltage along the whole cable run, waiting for someone to touch it. This is why gland selection and proper fitting deserve far more attention than they usually get on site — the gland is part of the earthing system, not just a cable clamp.

Question 1

Why does my MCB keep tripping?

Accepted Answer

An MCB trips to protect the circuit, so a repeat trip is telling you something, not misbehaving. The three usual causes are overload, a short circuit and, if it is actually the RCCB tripping, an earth leak. Overload is the common one at home: too many heavy appliances, an iron and a geyser and a microwave, on a circuit sized for less, so the wire would overheat and the breaker cuts in. A short circuit trips instantly and hard, often with a flash, and points to a damaged cable or a faulty appliance.
Unplug things and reset once. If it holds, you were overloading it. If it trips with nothing on, or trips the moment one appliance is plugged in, stop resetting and call an electrician: you have a fault in the wiring or that appliance, and repeated resetting only risks the very fire the breaker is trying to prevent.

Question 2

What is the difference between heat-shrink and cold-shrink cable terminations?

Accepted Answer

Both seal and insulate the end of a cable where it meets a joint or termination; they differ in how they grip. A heat-shrink termination uses tubes and boots that shrink down tight when you play a gas torch over them, so it needs an open flame on site and a steady hand to heat evenly without scorching.
A cold-shrink termination is a pre-stretched rubber sleeve held open on a removable plastic spiral. You slide it into place and pull the spiral out; the rubber contracts onto the cable on its own, no flame needed. Cold-shrink is quicker, safer in areas where you cannot use a torch, and more forgiving of a rushed installer. Heat-shrink is cheaper and copes with a wider size range per kit. Both work well when fitted to the maker&#8217;s instructions on a clean, correctly prepared cable.

Question 3

Why are single-core cables laid in trefoil formation?

Accepted Answer

Because three single-core cables each throw off a magnetic field, and how you arrange them decides whether those fields fight or cancel. Clip the three phases together in a symmetrical triangle, which is what trefoil means, and the fields very nearly cancel outside the group. That keeps induced currents and stray heating low in cable glands, armour and nearby steelwork, and it keeps the three phase impedances equal so the load shares evenly.
Lay them flat and touching instead and the field is unbalanced and the impedances unequal. Spaced-flat is sometimes used deliberately to get more air and better cooling around each cable on a heavily loaded tray, but then you re-check the current rating. Either way, cleat single-cores firmly, because a short-circuit throws them apart hard.

Question 4

How deep should an underground power cable be buried?

Accepted Answer

Deep enough that the next person to dig finds soil, not your cable. IS 1255, the Indian code for laying power cables up to 33 kV, measures depth from ground level to the top of the cable and raises it with voltage: roughly 0.75 m for LV up to 1.1 kV, about 0.9 m for 3.3 to 11 kV, and about 1.05 m for 22 to 33 kV. Under roads and crossings, go deeper and pull the cable through a pipe or duct.
Depth alone is not enough. Bed the cable in about 75 mm of clean sand, cover it with another 75 mm, lay bricks or protective tiles over that, and run marker tape at the surface. Use an armoured cable for direct burial and earth the armour.

Question 5

What is the minimum bending radius for a power cable?

Accepted Answer

It is the tightest curve the cable will take without hidden damage, and it is quoted as a multiple of the cable&#8217;s overall diameter, written as a number times D. Bend tighter than that and the insulation thins on the outside of the bend while the screen wrinkles inside, and the cable can fail there months later even though it tested fine.
As a rough guide, in line with IEC 60502-1, LV multicore cables sit around 12 &times; D, single-core LV around 15 &times; D, and screened MV and HV cables from 15 up to 20 &times; D. The diameter is the whole cable, armour and all, not the conductor. During pulling keep it gentler still and use rollers. The number printed on the drum always overrides any rule of thumb.

Question 6

Why should every wire joint be inside a junction box?

Accepted Answer

A joint is the weakest point of any wiring run — it&#8217;s where strands loosen, oxidise and heat up. A junction box does three jobs for that weak point. It contains the heat and any sparking if the joint deteriorates, keeping it away from concealed woodwork and insulation. It keeps the joint accessible, so it can be inspected or remade without breaking a wall — a taped joint buried in plaster is invisible until it fails. And it protects the joint mechanically, from tugging, dust, moisture and pests. Outdoors, the box needs to be a weatherproof one with proper cable entries, especially through the monsoon. A twist of insulation tape hidden in a conduit is the classic shortcut behind flickering lights, warm switchboards, and worse.

Question 7

Can I join two different wire sizes on the same circuit?

Accepted Answer

Avoid it. The breaker or fuse protecting a circuit is chosen to protect the wire size the circuit was designed with. If a thinner wire is added downstream — a common shortcut when extending a point — that thinner section can overheat under a load the breaker considers perfectly normal, because the breaker is still guarding the fatter wire. The thin stretch becomes the unprotected weak link, usually buried in a wall or above a false ceiling. If you&#8217;re extending a circuit, continue with the same size and grade of wire, make the joint properly inside an accessible junction box, and if the new load is heavier than the circuit was planned for, run a new circuit from the distribution board instead. It costs a little more once, and removes the risk permanently.

Question 8

What is a cable jointing kit?

Accepted Answer

A jointing kit contains everything needed to join two lengths of power cable so the joint performs like the cable itself: connectors or ferrules for the conductors, insulating layers (usually heat-shrink or cold-shrink), and materials to restore the screen, armour continuity and outer sheath. Joints exist because cable comes in finite drum lengths, and because repairs happen. They&#8217;re also the most common weak point in a buried run — a joint made in a hurry, in a wet pit, by an untrained hand, is where many cable faults begin. Good practice is simple to state: use a kit matched to the exact cable construction and voltage, follow the kit instructions to the letter, and keep the work dry. Where a route can be supplied in one drum length, no joint is the best joint.

Question 9

Why must cable armour be earthed?

Accepted Answer

The steel armour on a cable isn&#8217;t only mechanical protection — it&#8217;s a safety conductor. If the cable is damaged and a live conductor touches the armour, the armour has to carry that fault current back to earth so the protective device trips quickly. That only happens if the armour is solidly earthed, normally through the cable gland at each end, which clamps the armour wires and bonds them to the earthed gland plate or enclosure. Unearthed armour does the opposite of protecting: under a fault it can sit at a dangerous voltage along the whole cable run, waiting for someone to touch it. This is why gland selection and proper fitting deserve far more attention than they usually get on site — the gland is part of the earthing system, not just a cable clamp.

Question 10

What is water blocking in an underground cable?

Accepted Answer

Water blocking is a construction feature that stops moisture travelling along the inside of a cable. Swellable tapes or yarns are placed under the sheath, and sometimes within the conductor; the moment water reaches them they swell into a gel and seal the path. It matters because a small nick in the outer sheath of a buried cable lets water in, and without blocking, that water can migrate metres along the core and sit against the insulation, degrading it slowly until the cable fails somewhere far from the original damage — which also makes the fault harder to locate and repair. For cables that will spend their lives underground, in ducts that flood, or in high water-table areas, it&#8217;s a feature worth specifying at enquiry stage, not after laying.

Question 11

Should stranded wire ends be crimped with ferrules before terminating?

Accepted Answer

For stranded and flexible conductors going into a screw terminal, yes, and it&#8217;s worth insisting on.
A bare stranded end under a screw gets crushed unevenly. Some strands take the clamping force, others splay out sideways and carry nothing. The effective contact area shrinks, resistance rises at that point, and the joint warms up under load. Warm joints loosen, and loose joints get warmer. That cycle is behind a good share of the terminals that end up discoloured inside distribution boards.
A ferrule gathers every strand into a solid cylinder that the screw can clamp properly, and it stops stray strands wandering across to the next terminal. Use the right size for the conductor, crimp with a proper ferrule tool rather than pliers, and don&#8217;t tin the end with solder instead, because solder creeps under pressure and the joint slackens over time.

Question 12

How many spare cores should a control cable have?

Accepted Answer

Set the figure in the specification rather than leaving it to site, because a contractor asked to decide will choose zero.
The good news is that standard core counts do much of the work for you. Control cables are made at 2, 3, 4, 5, 6, 7, 10, 12, 19, 27, 37, 44, 52 and 61 cores, not at every number in between. Need eight cores and you&#8217;re buying a ten anyway, so the spares arrive free. The outside diameter barely moves either: on the 1.5 mm&#178; construction, going from 7 to 10 cores takes the cable from 14.5 mm to 18.0 mm.
Terminate the spares onto the terminal block at both ends and mark them on the drawing. A spare coiled inside a gland box is a spare nobody will find. See the core-count planning guide and the control cable range up to 61 core.

Question 13

What is a drain wire in a screened cable?

Accepted Answer

It&#8217;s a bare or tinned copper wire laid in continuous contact with the foil screen, running the full length of the cable. Foil is thin and awkward to clamp under a terminal, so the drain wire gives you something you can actually terminate. Whatever the screen intercepts travels down the drain wire to earth.
It&#8217;s tinned to slow galvanic corrosion between the copper and the aluminium in the foil, which would otherwise raise the contact resistance over time and quietly degrade the screen.
Two rules decide whether it works. Earth the drain wire at one end only, because earthing both ends creates a loop that carries current between two earth points and injects noise rather than removing it. And keep the untwisted, unscreened tail at the termination as short as you can. A screen that stops 200 mm short of the terminal has a 200 mm aerial on the end of it.

Question 14

Do I need individually screened instrumentation cable, or is an overall screen enough?

Accepted Answer

It depends on whether the pairs inside the cable can interfere with each other, not just on outside noise.
A collective screen, written CAM, is one overall screen wrapped around all the pairs. It protects the bundle from the plant around it. That&#8217;s usually sufficient when every pair in the cable carries the same kind of signal, or when the signals are digital and switched.
Individual screens on every pair plus a collective screen, written IAM/CAM or ICAT, also stops one pair talking to its neighbours. That matters when a single multipair carries several low-level analogue signals from different loops with different earth references, which is the normal situation on process plant.
If the run is analogue and shared, specify individual screens. APAR&#8217;s instrumentation cables are made in both configurations.

Question 15

What does 1P, 2P or 12P mean on an instrumentation cable?

Accepted Answer

The number is the pair count and the P stands for pair. A 12P cable carries twelve twisted pairs, so twenty-four conductors in total. You&#8217;ll also see T for triad, as in 2T, which means two sets of three twisted cores, normally used for three-wire RTDs.
Pairs are twisted rather than laid up loose for a reason. A pair running past a noisy power cable picks up induced voltage on both conductors roughly equally, and because the twist keeps swapping their positions, most of that noise cancels out at the receiving instrument.
Order by signal count, not conductor count. Each 4-20 mA loop needs one pair. Our instrumentation cable selection guide covers pair count alongside the screening and armour choices, and the screened instrumentation cable range shows what&#8217;s available.

Question 16

What is the difference between LSH and LSZH cable sheathing?

Accepted Answer

Both are fire-performance sheaths, but they are not the same claim. LSH (low smoke and halogen) means reduced smoke and reduced halogen content — the material may still be PVC-based. LSZH (low smoke zero halogen, also written LSOH or FR-LSZH) means the compound contains no halogens at all, so a fire produces no corrosive halogen acid gas. Zero-halogen grades are the stricter choice for enclosed public spaces and equipment rooms. On house wire the same split appears as FR-LSH (PVC-based) versus HFFR (halogen-free) — our guide to choosing the wire grade covers it.

Question 17

What is the difference between a covered conductor and an insulated cable?

Accepted Answer

A covered conductor has an XLPE covering bonded over an overhead line conductor — enough insulation to survive touching a branch or another phase, but not rated as full insulation, so it is still treated as a live overhead line. A cable is fully insulated and screened for its voltage and can be buried or ducted. The covering is what removes the majority of overhead-line faults: clashing in wind, vegetation contact, birds and animals. APAR covered conductors span 11 kV to 132 kV — see the MVCC selection guide.

Question 18

Can fibre optic cable survive a fire?

Accepted Answer

Standard fibre cable cannot — but fire-rated constructions can, and the distinction is measured. APAR&#8217;s Fireoproof range includes an indoor dielectric construction that keeps the circuit alive for 180 minutes at 850°C, and outside-plant designs rated 120 minutes at 750°C, tested to IEC 60331-25. They also limit smoke (IEC 61034) and acid gas (IEC 60754), which is why they are specified for metros, tunnels, airports and emergency systems where the communication link must outlive the fire. See fire resistant fibre cables.

Question 19

What is ADSS fibre optic cable?

Accepted Answer

ADSS stands for All-Dielectric Self-Supporting: an aerial fibre cable with no metal in it at all, strong enough to span between poles without a support wire. Because it is fully dielectric it can be strung safely alongside power lines — the usual route for utility fibre. APAR&#8217;s AerioFib ADSS range runs from 1F to 432F for short, medium and long spans, with an anti-tracking sheath option for high-tension corridors. Where a metallic messenger is acceptable, Fig-8 cable carries an integrated support wire instead. See ADSS and Fig 8 cables.

Question 20

What temperature can a solar cable operate at?

Accepted Answer

APAR&#8217;s e-beam cross-linked XLPO solar cable is rated for 120°C continuous operation across an ambient range of −40°C to +120°C, with a short-circuit limit of 250°C for 5 seconds. That headroom matters on a rooftop, where cable in conduit behind a panel routinely sees far more than the air temperature. The cable is certified to BS EN 50618:2014, IEC 62930:2017 and UL 4703, rated 1.5 kV DC (maximum 1.8 kV), with a service life expectation of more than 25 years.

Question 21

Why are solar cable conductors tinned?

Accepted Answer

A solar DC cable spends 25 years or more outdoors, and its fine class-5 copper strands would slowly oxidise. A thin tin coating on each strand blocks that corrosion, keeps terminations reliable, and preserves the conductor over the cable&#8217;s life. The trade-off is honest and tiny: tinned conductor resistance sits about 2% above the bare-copper maximum — which is why a genuine solar cable datasheet shows, for example, 8.21 Ω/km at 2.5 sq mm instead of the bare-copper 7.98. See APAR solar cables.

Question 22

How much current can a 95 sq mm copper XLPE cable carry?

Accepted Answer

For a single-core 1100 V XLPE copper cable to IS 7098 Part 1: about 260 A laid direct in the ground at 30°C, and 303 A in air at 40°C. Those figures assume standard conditions — deeper laying, hotter ground or grouped cables all reduce them, which is what derating factors are for. The full table from 4 to 1000 sq mm, with aluminium equivalents, is on our current-rating chart.

Question 23

Why does a cable&#8217;s current rating change with how it is installed?

Accepted Answer

Because the rating is really a heat-removal budget. The same 1100 V copper XLPE cable is rated differently laid direct in the ground, pulled into a duct, or clipped in air — and the pattern reverses with size. A 4 sq mm cable carries 47 A in the ground but 41 A in 40°C air, while a 400 sq mm carries 537 A in the ground and 737 A in air: small cables shed heat well into soil, but for large cables the soil&#8217;s thermal resistance becomes the bottleneck and free air wins. Always size against the rating for your actual installation method — our LV XLPE current-rating chart lists all three.

Question 24

How does a concentric cable prevent electricity theft?

Accepted Answer

In a concentric service cable the phase conductor runs down the centre and the neutral is laid as a complete layer of wires around it. Tapping the phase means first cutting through the energised neutral layer — difficult to do, and easy for the utility to detect. It is the standard construction for house-service connections where pilferage is a problem. Two arrangements exist: CNE, where the concentric layer is combined neutral and earth, and SNE, where neutral and earth are separate wire sets in the same layer. See concentric anti-theft cables.

Question 25

What is a control cable and how is it different from a power cable?

Accepted Answer

A control cable carries signals and switching commands rather than bulk power — between control panels, switchgear, relays and instruments in power stations and substations. The conductors are small (typically 1.5 or 2.5 sq mm) but numerous: APAR&#8217;s XLPE control cables run from 2 up to 61 cores in a single cable at 600/1000 V, each routine-tested at 4 kV. A power cable is the opposite: few cores, large cross-sections. See control cables up to 61 core.

Question 26

When should I choose armoured over unarmoured cable?

Accepted Answer

Choose armoured wherever the route offers no mechanical protection: direct burial in the ground, outdoor runs at risk of impact, and industrial areas with traffic or rodents. Unarmoured is appropriate indoors, in conduit or duct, and on protected trays. One detail worth knowing: single-core cables use non-magnetic aluminium armour (steel around a single core would heat up from induced currents), while multicore cables use galvanised steel. Our cable armouring guide covers the designations.

Question 27

What is the difference between 90°C and 105°C XLPE cable?

Accepted Answer

Conventional XLPE is rated for a maximum continuous conductor temperature of 90°C. High-ampacity XLPE uses an insulation suitable for 105°C. The 15°C difference matters because a cable&#8217;s current rating is set by the gap between ambient temperature and the conductor limit — widening that gap lets the same cross-section carry up to 15% more current. The benefit is largest exactly where ambient is hottest: at a 50°C ambient a 90°C cable is derated to about 89% of its catalogue rating, while a 105°C cable keeps its margin. See high ampacity XLPE cables.

Question 28

What house wire should I use for a new home in India?

Accepted Answer

For a home being wired today, a sensible specification is:

Grade: HR-FR-LSH or HFFR, from a BIS-certified manufacturer
Lighting circuits: 1.5 sq mm
General power points: 2.5 sq mm
Geyser, small AC: 4 sq mm
Large AC, EV charger: 6 sq mm

Two points worth planning for. First, size against the load you will actually have, not the one you have today — EV chargers, inverter ACs and induction cooking all arrived after most Indian homes were wired. Second, use the correct current column from the datasheet: a wire in conduit carries less than the same wire clipped to a surface.
Slightly oversizing key circuits now is far cheaper than rewiring later.
For a new home, Anushakti Fire Protekt HFFR or Anushakti HR-FR-LSH are the grades to look at. Size each circuit with the wire calculator.

Question 29

Is more expensive house wire always better?

Accepted Answer

No — but unusually cheap wire is almost always worse.
Price differences usually come from three places: the insulation grade (HFFR costs more than FR), the amount and purity of copper, and brand positioning. The first two are real engineering differences; the third is not.
The way to tell them apart is conductor resistance in Ω/km. Two wires both marked 2.5 sq mm should both meet the IS 694 maximum. A wire that misses it has less copper than its marking implies — the most common way cost is quietly removed.
Compare within the same grade, check the resistance figure, and confirm the certification. Then price is a fair comparison.
APAR publishes conductor resistance for every size — see any house wire specification.

Question 30

How can I tell if a house wire is genuinely ISI-marked?

Accepted Answer

Check the wire itself, not the packaging. On a genuine product the following is printed continuously along the insulation:

Manufacturer and product name
Size in sq mm and voltage grade (1100 V)
The applicable standard (for example IS 694 or IS 17048)
The ISI mark with a BIS licence number in the format CM/L-XXXXXXX

Printing on the insulation is far harder to counterfeit than a sticker or a printed drum label, which is exactly why reputable manufacturers do it. If the licence number appears only on the packaging, treat that as a warning sign.
Every APAR wire carries its grade, size, voltage, standard and BIS licence number printed along the insulation.

Question 31

Does IS 17048 apply to my house wire?

Accepted Answer

It applies if the wire is HFFR (halogen-free flame retardant). IS 17048:2018 is the Indian Standard for halogen-free flame retardant cables up to 1100 V, and BIS certification under it is mandatory for such cable sold in India.
If your wire is a standard PVC grade — FR or FR-LSH — the applicable standard is IS 694:2010, which covers PVC-insulated cables up to 1100 V.
The two are not interchangeable. If a wire is marketed as HFFR, ask which standard it is certified to; a genuine HFFR product should reference IS 17048.
APAR&#8217;s HFFR house wire is Anushakti Fire Protekt EBXL HFFR (XZ).

Question 32

What oxygen index should a safe house wire have?

Accepted Answer

Look for 29% or higher. A strong HFFR compound reaches 31% or above.
The oxygen index is the minimum oxygen concentration needed for the insulation to keep burning. Normal air is about 21% oxygen — so any material with an index above 21% cannot sustain a flame in open air once the ignition source is removed. It self-extinguishes.
The higher the number, the harder the wire is to keep alight. It is the single clearest indicator of flame-retardant performance, and any serious manufacturer publishes it.
For reference, APAR Anushakti Fire Protekt publishes an oxygen index of &ge; 31%.

Question 33

Is HFFR wire worth the extra cost over FR-LSH?

Accepted Answer

In most cases yes, because the difference across a whole house is small relative to what it protects.
Wiring is typically 1–2% of the cost of building a house. Moving the whole installation up a fire-safety grade usually adds a few thousand rupees — against a rewiring job later costing lakhs, since it means breaking and re-finishing walls.
It is most clearly worth it where evacuation is slow or crowded: high-rise apartments with enclosed stairwells, homes with elderly residents or young children, basements with no natural ventilation, and buildings with a single exit route.
For a detached house with multiple exits, FR-LSH or HR-FR-LSH is a reasonable specification.
Compare the grades directly: Shakti FR-LSH against Anushakti Fire Protekt HFFR.

Question 34

Which is the safest house wire for an Indian home?

Accepted Answer

Judged on measured fire performance, HFFR (halogen-free flame retardant) is the highest common domestic grade. It resists flame, produces little smoke, and releases essentially no halogen gas when burning.
That matters because most fire deaths are caused by smoke and toxic gas rather than flame. Ordinary PVC insulation releases hydrogen chloride when it burns — poisonous to breathe and corrosive to equipment.
Genuine HFFR wire is certified under IS 17048:2018, where BIS certification is mandatory. Ask for the halogen figure: 0.5% or below indicates genuinely halogen-free, while &#8220;low halogen&#8221; means reduced but still present.
APAR&#8217;s halogen-free grade, Anushakti Fire Protekt EBXL HFFR, publishes an oxygen index of &ge; 31%, smoke density &le; 10% and acid gas &le; 0.5%.

Question 35

Which is the best house wire in India?

Accepted Answer

There is no single answer, because &#8220;best&#8221; depends on what you are wiring and the grade you need. A more useful approach is to judge any wire against six things:

Conductor — electrolytic-grade (99.97%) annealed copper, with published resistance in Ω/km
Insulation grade — FR, FR-LSH, HR-FR-LSH or HFFR
Standard — IS 694:2010 for PVC grades, IS 17048:2018 for genuine HFFR
Fire-performance data — oxygen index, temperature index, smoke density, halogen content
ISI mark and BIS licence number printed along the wire, not just on the drum
Current rating for your actual installation method

Any manufacturer worth buying from publishes all six. For a new Indian home, an HR-FR-LSH or HFFR wire from a BIS-certified maker, correctly sized, is a sound specification.
APAR publishes all six for every wire in its range — see the Anushakti Fire Protekt EBXL HFFR specification as an example.

Question 36

What is the shelf life of electrical wire?

Accepted Answer

Unused wire that is stored well has a very long shelf life. The copper conductor itself does not deteriorate, and modern insulation — especially HR-FR-LSH and cross-linked (XLPE-type) compounds — stays sound for many years in the coil. In practice, quality wire kept properly will still be perfectly good long after purchase.
What shortens its life is poor storage. Direct sunlight and UV, high heat, damp or humidity, contact with oils and chemicals, and crushing or sharp bends can all harden, discolour or crack the insulation. Keep coils in a cool, dry, shaded place, off the floor, away from chemicals, and don&#8217;t stack heavy loads on them. Inspect older stock for brittle or cracked insulation before use and discard anything doubtful.
Installed wiring is a different story. Under continuous load, current warms the conductor and the insulation slowly ages from that heat over decades — which is why home wiring is typically reviewed for replacement after about 25–30 years, sooner if it shows warning signs like warm switches, a burning smell or frequent tripping.

Question 37

Is thicker wire always better?

Accepted Answer

Not quite — the goal is the correctly-sized wire for the load, not simply the thickest one available. Wire is chosen so it can comfortably carry the circuit&#8217;s current, with allowance for how hot the surroundings are and how many cables run together (derating). A conductor that is too thin runs hot, wastes energy as heat and is genuinely dangerous, so under-sizing is never acceptable.
Going one size thicker than the minimum is often a good idea on long runs, because a larger conductor has less resistance and therefore less voltage drop, so appliances at the far end get their full voltage. That is a real benefit.
But endlessly oversizing every circuit has downsides: it costs more, thick cable is stiff and awkward to terminate neatly in switches and boards, and beyond the size the load needs you gain very little. Just as important, the MCB must match the cable — fitting a bigger breaker to a thin wire to &#8220;stop tripping&#8221; removes the very protection that keeps the wire safe. The right answer is to size each circuit to its appliance and run length, step up a size for long runs, and match the MCB to the cable.

Question 38

Can I mix copper and aluminium in the same circuit?

Accepted Answer

It is best avoided, and for new work you should not do it. Copper and aluminium behave differently where they meet: they expand and contract at different rates with heat, and aluminium quickly forms a hard, insulating oxide layer on its surface. A plain copper-to-aluminium joint therefore tends to loosen and develop resistance over time, which makes it heat up — a well-documented cause of connection failures and electrical fires.
If the two metals genuinely must be joined (for example, connecting to an existing aluminium service), it has to be done properly: with bi-metallic connectors or Al–Cu rated lugs designed for the purpose, treated with an anti-oxidant compound, and torqued correctly by a qualified electrician. Ordinary twist joints or a single lug crushing both metals are not acceptable.
For a fresh installation, keep the whole circuit in a single metal. Copper is the usual choice for home wiring because of its higher conductivity, better flexibility and easier, more reliable terminations; aluminium is generally reserved for larger, cost-sensitive fixed runs sized up to compensate for its lower conductivity.

Question 39

How much wire do I need for a 2 or 3 BHK home?

Accepted Answer

The exact quantity depends on your floor plan, the number of light and socket points and the wiring layout, but the following gives a sound planning estimate. House wire is sold in 90-metre coils, and you generally use three sizes: 1.5 sq mm for lighting, 2.5 sq mm for general sockets, and 4 sq mm for heavy appliances such as ACs and geysers.
For a typical 2 BHK, budget around 3 coils each of 1.5 and 2.5 sq mm, plus one or two coils of 4 sq mm. For a 3 BHK, allow roughly 4–5 coils each of the lighting and socket sizes and about two coils of 4 sq mm. Add a heavier size (6 sq mm or more) for the incoming mains run.
Always add a margin for wastage, offcuts and future points — running short mid-job is far costlier than a spare coil. For an accurate bill of quantities, let your electrician count the actual points and runs from the wiring diagram. Our home-wire estimator breaks this down by size.

Question 40

Can the same circuit power both an AC and a geyser?

Accepted Answer

No — an air-conditioner and a geyser should each sit on their own dedicated circuit, never a shared one. Both are among the heaviest loads in a home: a 1.5-ton AC draws roughly 1.5–1.8 kW and a geyser 2–3 kW, so together they can pull well over 20 A.
Put them on one circuit and you invite trouble. The shared cable and MCB can be overloaded whenever both run at once, causing nuisance tripping at best and, at worst, an overheated cable — a genuine fire risk. Sharing also causes a noticeable voltage drop, so the AC or geyser underperforms, and it makes fault-finding harder because one tripped breaker kills two appliances.
The correct approach is a separate circuit for each high-load appliance, wired in a size that matches its current (commonly 4 sq mm copper for a 1.5-ton AC or a geyser) and protected by its own correctly-rated MCB. Lighting and general sockets stay on their own circuits. This keeps every appliance safe, avoids nuisance trips, and makes the distribution board easy to understand. If your home currently runs an AC and geyser off one line, ask a licensed electrician to split them.

Question 41

How do I calculate the total electrical load for my home?

Accepted Answer

Sizing your wiring, main switch and even your sanctioned supply all begin with knowing your total connected load — the sum of the wattage of every light and appliance in the home. But because you never switch everything on at the same moment, the figure your wiring actually has to handle is the maximum demand, which is smaller.
Step 1 — Add up the wattages
List every appliance with its rated power in watts (it is printed on the nameplate). Lights and fans are small (10–75 W each); the big loads are the microwave (~1.5 kW), air-conditioner (~1.5–1.8 kW for a 1.5-ton unit), geyser (2–3 kW) and an EV charger (3.3–7.4 kW). Add them all to get the connected load.
Step 2 — Apply a diversity factor
Multiply the total by a diversity factor of roughly 0.6–0.8 to reflect that only some loads run together. For example, a 9 kW connected load at 0.7 gives a realistic maximum demand of about 6.3 kW.
Step 3 — Convert watts to amps
On a single-phase 230 V supply, current (A) = watts ÷ 230. A 6.3 kW demand is therefore about 27 A, which points to a 6 sq mm copper main and a suitably rated main switch and MCB. On a three-phase supply the load is spread across the phases, so divide accordingly.
Give heavy appliances (AC, geyser, EV charger) their own dedicated circuits, keep lighting and general sockets separate, and have a licensed electrician confirm the final sizing for your layout. Our load-calculation guide works through a full example.

Question 42

What is a Uninyvin cable?

Accepted Answer

A Uninyvin cable is a specialised single-core flexible wire built for demanding, mission-critical wiring — with a heritage in aircraft applications. It pairs an annealed tinned-copper conductor with heat-resistant (105 °C) HR-PVC insulation, often with a glass-fibre braid, for high reliability where ordinary wire would fail.
It suits high-temperature and heavy-duty installations. See APAR&#8217;s Tarang Shakti Uninyvin cable, part of the communication cables range.

Question 43

How do I choose a speaker cable?

Accepted Answer

A speaker cable carries the audio signal from an amplifier to loudspeakers. The keys to good sound are conductor quality and the right thickness: high-purity copper lowers resistance, and a thicker conductor (lower gauge) is better for longer runs or higher power, giving distortion-free, attenuation-free sound.
Look for bright-annealed, electrolytic-grade copper and quality insulation. APAR&#8217;s Tarang Shakti Speaker Cable uses electrolytic-grade copper with transparent FR-PVC insulation for clear, high-fidelity audio.

Question 44

What is a CATV (cable-TV) cable?

Accepted Answer

A CATV cable carries cable-television and broadband signals. It is a coaxial cable — a central conductor surrounded by a dielectric, shielding and an outer sheath — engineered for low signal loss and anti-interference performance so the picture stays crisp over long distribution runs.
APAR&#8217;s Tarang Shakti CATV cable is built for high signal quality and low loss. Browse all communication cables.

Question 45

Which cable do CCTV cameras need?

Accepted Answer

Most analog CCTV cameras use a coaxial cable, commonly an RG-59 &#8216;3+1&#8217; type — a coaxial core for the video signal plus three power cores in one cable, so a single run carries both video and power to the camera.
Good CCTV cable uses annealed tinned-copper conductors and proper shielding for clear, distortion-free video over distance — see what a coaxial cable is. (IP cameras instead use LAN cable.)
APAR&#8217;s Tarang Shakti CCTV cable is a purpose-built RG-59 3+1 surveillance cable.

Question 46

What is a LAN cable, and what&#8217;s the difference between Cat5e and Cat6?

Accepted Answer

A LAN (Ethernet) cable connects computers, routers and devices for wired networking and internet. Inside are four twisted pairs of copper wires; the twisting and construction control interference and signal quality.
Cat5e supports gigabit speeds and is fine for most homes and offices. Cat6 has tighter construction (often with a separator) for higher bandwidth, lower error rates and better performance over longer runs or for heavier data — a good future-proofing choice. See what communication cables are used for.
APAR&#8217;s Tarang Shakti LAN cable is available in Cat5e and Cat6 with four twisted copper pairs for fast, low-error connectivity.

Question 47

Copper vs aluminium multicore cable — which should I choose?

Accepted Answer

It is the same trade-off as for any copper vs aluminium conductor. Copper multicore (APAR Shakti / Mahashakti) is more conductive and compact — ideal for most appliance, motor and control wiring. Aluminium multicore (APAR AlumShakti) is lighter and more economical, a smart alternative for cost-sensitive power distribution and larger runs.
Aluminium needs a larger size for the same current, so size to the metal you choose. Browse all multicore cables or contact APAR.

Question 48

What is XLPO insulation?

Accepted Answer

XLPO stands for Cross-Linked Polyolefin. Like XLPE, the polymer chains are cross-linked into a thermoset, so the insulation resists heat, won&#8217;t melt or drip, and lasts longer than ordinary PVC — but XLPO compounds are also formulated to be low-smoke and halogen-free for better fire safety.
It is used where both durability and fire performance matter. APAR&#8217;s Mahashakti Round and Mahashakti Flat multicore cables use a specially developed XLPO compound.

Question 49

Which cable is best for a submersible pump?

Accepted Answer

Submersible pumps need a cable built for the worst conditions — underwater, underground, in mud and constant wet. The standard choice is a flat multicore cable: its slim profile runs neatly down the bore alongside the pipe, and the construction resists water and abrasion.
APAR&#8217;s Shakti Flat Multicore (copper) and AlumShakti Flat Multicore (aluminium, economical) are engineered for submersible pump motors. Size the cable to the motor and depth, and have an electrician confirm — see how to choose the right cable.

Question 50

What is the difference between round and flat multicore cable?

Accepted Answer

Both bundle several insulated cores together; the difference is the shape. Round multicore is the general-purpose form for appliances, motors and control wiring. Flat multicore has a slim profile designed mainly for submersible pumps and tight installations, where it sits neatly along a pipe.
See single-core vs multi-core for the basics. APAR offers both in several ranges — round (Mahashakti, Shakti, AlumShakti) and flat (Mahashakti, Shakti, AlumShakti). Browse all multicore cables.

Question 51

What is an eco-friendly (green) house wire?

Accepted Answer

An eco-friendly or &#8216;green&#8217; house wire is made with safer, more sustainable materials — typically lead-free, RoHS-compliant insulation that is also low-smoke and halogen-free. In a fire it releases far less toxic gas, and over its life it avoids the hazardous additives of ordinary PVC.
Green wiring also tends to last longer and run more efficiently (less energy lost as heat), so you replace less and waste less. APAR&#8217;s Green Wire (HR-FR-LSH PVC) is built around exactly this — eco-friendly, lead-free, fire-safe.

Question 52

What is the difference between FR-LSH and FR-PVC wire?

Accepted Answer

Both are flame-retardant house wires. FR-PVC resists the spread of flame on standard PVC insulation — reliable and economical. FR-LSH adds low smoke and low halogen, so in a fire it emits far less smoke and toxic gas.
If fire safety and clearer escape routes matter (homes with children/elderly, crowded buildings), FR-LSH is the better pick; FR-PVC suits budget-sensitive general wiring. See the full FR / FR-LS / HR-FR-LSH ladder.
Compare APAR Shakti FR-LSH and Shakti FR-PVC.

Question 53

What is HR-FR-PVC wire, and how is it different from HR-FR-LSH?

Accepted Answer

HR-FR-PVC is a Heat-Resistant, Flame-Retardant PVC house wire. It adds heat resistance (around 105 °C) and flame retardance to standard PVC insulation — a strong, well-priced safety grade for homes and buildings.
The difference from HR-FR-LSH is the &#8216;LSH&#8217; part: HR-FR-LSH also gives off low smoke and low/zero halogen in a fire, while HR-FR-PVC focuses on heat and flame resistance. For maximum fire safety choose HR-FR-LSH; for a robust, economical heat-resistant wire, HR-FR-PVC is excellent.
APAR Anushakti HR-FR-PVC is e-beam built for durability; compare with Anushakti HR-FR-LSH.

Question 54

What does &#8216;50% more current-carrying capacity&#8217; mean?

Accepted Answer

It means the wire can safely carry significantly more current than an ordinary PVC wire of the same conductor size. The reason is the insulation: e-beam cross-linked insulation tolerates higher temperatures, and a higher temperature rating directly raises a cable&#8217;s current-carrying capacity (ampacity).
In practice this gives you more headroom for heavy modern loads, cooler-running circuits and a longer life — or the option of a neater installation. APAR Anushakti HR-FR-LSH offers up to 50% more current-carrying capacity, and the e-beam Fire Protekt range up to 100% more.
Always still size to the load and have a licensed electrician confirm — see how to choose the right cable.

Question 55

What is self-extinguishing wire?

Accepted Answer

A self-extinguishing (flame-retardant) wire is one whose insulation stops burning on its own once the source of flame is removed, instead of continuing to burn and spread fire along the cable. It resists ignition and does not propagate flame.
This is the core idea behind FR, FR-LS and HR-FR-LSH grades. It is different from fire-resistant cable, which keeps a circuit alive during a fire. Premium house wires combine self-extinguishing behaviour with low smoke and zero halogen.
APAR Anushakti HR-FR-LSH and Fire Protekt wires are self-extinguishing and low-smoke.

Question 56

What temperature can HR-FR-LSH house wire handle?

Accepted Answer

HR-FR-LSH stands for Heat-Resistant, Flame-Retardant, Low Smoke & Halogen — and the &#8216;HR&#8217; is the key here. Ordinary PVC house wire is rated for roughly 70 °C continuous; an HR-FR-LSH wire tolerates noticeably higher continuous operating temperatures (around 105 °C), and withstands the brief, intense heat of a short circuit far better.
That heat headroom matters for today&#8217;s homes, where air-conditioners, geysers and dense circuits run hot. It also links to capacity: a higher temperature rating lets the same conductor carry more current safely — see ampacity.
APAR Anushakti HR-FR-LSH achieves this with e-beam cross-linked insulation; the premium Fire Protekt range goes higher still. Confirm exact ratings on the product datasheet.

Question 57

What certifications make a house wire fire-safe?

Accepted Answer

For a house wire, fire safety is proven by testing to recognised standards. Look first for the ISI mark against IS 694, then for fire-performance test compliance: flame retardance (IEC 60332 / IS 10810), smoke density (IEC 61034) and halogen acid-gas emission (IEC 60754) for low-smoke, halogen-free grades.
Premium fire-safe wiring such as APAR Anushakti Fire Protekt (EBXL HFFR) combines these with e-beam durability. You can review APAR&#8217;s certifications and approvals for reference.

Question 58

What is dielectric strength in a cable?

Accepted Answer

Dielectric strength is the maximum electric field a cable&#8217;s insulation can withstand before it breaks down and lets current leak through. Higher dielectric strength means the insulation is a better, safer barrier — it can handle higher voltages and surges without failing.
Along with high insulation resistance, it is a core measure of insulation quality. Premium insulation such as XLPE and the e-beam cross-linked compound in APAR Anushakti Fire Protekt offers excellent dielectric strength for reliable, long-life performance.

Question 59

What is short-circuit protection in house wiring?

Accepted Answer

A short circuit is when live and neutral (or earth) accidentally touch, causing a huge surge of current. Protection comes from two things working together: the MCB that trips and cuts power instantly, and wire whose insulation can withstand the brief, intense heat of a fault without melting or igniting.
This is where the quality of the wire counts. Melt-resistant, e-beam cross-linked insulation such as APAR Anushakti Fire Protekt tolerates very high short-circuit temperatures, reducing fire risk during a fault. Always pair correctly-sized wire with a correctly-rated MCB — see how to choose the right cable.

Question 60

Does e-beam (electron-beam) wire melt? What is melt-resistant wire?

Accepted Answer

Ordinary thermoplastic insulation softens and can melt or drip as it gets hot. Electron-beam cross-linked insulation is different: the e-beam bonds the polymer chains into a thermoset structure that holds its shape at high temperature and will not melt or drip — which is why it is called melt-resistant.
This matters for safety and reliability: the wire keeps insulating even under overload or fire conditions, resists short circuits and lasts far longer. APAR&#8217;s Anushakti Fire Protekt uses this e-beam technology for melt-resistant, long-life performance.
Related: XLPE insulation and HR-FR-LSH.

Question 61

What is EBXL HFFR wire?

Accepted Answer

EBXL HFFR describes a premium fire-safe house wire. EBXL means Electron-Beam Cross-Linked — the insulation is hardened by an electron beam rather than by chemicals or heat — and HFFR means Halogen-Free Flame Retardant, so in a fire it resists flame while giving off no halogen gas and very little smoke.
Together this delivers a wire that is heat-resistant, melt-resistant, long-lasting and far safer in a fire than ordinary PVC. APAR&#8217;s Anushakti Fire Protekt (EBXL HFFR) is built this way, with up to 100% more current-carrying capacity and a service life measured in decades.
See also low-smoke zero-halogen (LSZH) cable and e-beam cross-linking.

Question 62

What wiring does a home EV charger need?

Accepted Answer

A home EV charger draws a high, sustained current, so it needs its own dedicated circuit sized to the charger — not a shared socket. A typical home AC (&#8216;Level 2&#8217;-style) charger runs on a dedicated higher-current circuit with its own correctly-rated MCB and an RCCB for shock protection.
Because charging runs for hours at high load, the cable must be correctly sized for the current and run length (see ampacity), with proper earthing. An outdoor or garage charge point also needs weather-suitable wiring. For the charging cable itself, see what cables an EV charging setup needs.
Always have an EV circuit designed and installed by a qualified electrician using quality house wires and cables. Contact APAR to discuss suitable cable.

Question 63

How do I wire a new home to be smart-home and future-ready?

Accepted Answer

Future-ready wiring plans for the loads of the next decade, not just today. The essentials: a distribution board with spare capacity and MCBs for more circuits; dedicated, correctly-sized circuits for heavy modern loads (AC, geyser, kitchen, and an EV charger); and plenty of well-placed power and data/LAN points.
Run good-quality, fire-safe HR-FR-LSH wire throughout (it is far cheaper to do this during construction than to rewire later), add conduits with pull-strings for future cabling, and ensure solid earthing and surge protection for sensitive smart devices.
Plan the layout with a qualified electrician, and choose durable house wires and cables plus communication cables so the home is ready for automation, fast networking and EVs.

Question 64

Can better house wire actually lower my electricity bill?

Accepted Answer

To a small but real degree, yes. Higher-quality wire uses high-purity copper with lower conductor resistance, so less energy is lost as heat as current flows. Over years of use across a whole home, that reduced loss can translate into modest energy savings — and cooler-running wire also lasts longer and is safer.
The effect is greatest on circuits that carry heavy loads for long periods, such as air-conditioners and geysers, and where wires are correctly sized rather than undersized. It is not a dramatic saving, but it is a genuine bonus on top of the main benefits of safety and durability.
Look for pure electrolytic copper and energy-saving claims backed by real certifications. APAR markets low-conductor-resistance, energy-saving house wires for exactly this reason.

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