Take care of your house electrical DB before it’s too late.

Perhaps we all have experience of damages of expansive household appliances like ACs, Refrigerator, TV, Washing machine, Microwave, Fan, light etc. due to abnormally high voltage or lightening strike. Unfortunately there could be few cases of loss of property, even human life as well.

And most of the cases it’s found that, incorrect/ absence of requisite house electrical distribution board (popularly known as house DB) and poor workmanship/termination are the main root causes.

Hence, please ensure that your house is out of it.

Have a proper DB

First of all, check that, you have a modern electrical DB (i.e. Distribution Board) in your home. An indicative snap of such DB is furnished below for your ready reference.

If your house is old one or due to any other reason you don’t have this kind of DB, it’s highly recommended to get one asap.

Now you check, whether you have single phase connection or 3 phase connection. You can check it from your monthly electric bill issued by electric service provider. Though in India, it’s varies state to state, but in general, power more that 4 KW supplied as 3 phase, otherwise single phase only. Needless to mention, single phase supply comparatively more simple, requires fewer accessories, exposed to lesser issues/risk that 3 phase supply.

Upto 4 KW -> Single Phase supply -> Voltage 230 +/- 5% (+ not preferred)

Above 4 KW -> 3 Phase supply -> Voltage 415 +/- 5% (+ not preferred) [440 V  for industry]

DB shall have right accessories

MCB or Isolator?

The first thing, we have to check in the DB is whether the given main incoming circuit breaker is MCB (miniature circuit breaker) or just mere Isolator? The main difference between Isolator and MCB is where the former acts mere an On/Off switch, the later, along with On/Off operation, trips due to ‘over load’ (above rated ampere) & ‘short circuit’.

Over load means over current (i.e. ampere), not over voltage. Short circuit means when phase and neutral gets connected before load (here electrical fixtures/appliances). Please note MCB doesn’t give protection from over/under voltage.

An interesting fact is, Isolator & MCB both looks alike. It’s difficult for commoners to decipher the difference. The trick here is, check the circuit symbol, printed on its body. The symbol of MCB & Isolator furnished below.

Another interesting fact is, Isolator is also printed a rated ampere. But please note, it’s not for ‘safety trip’, but mere guidance to use it within that rated current circuit. Be careful.

It’s obvious that, MCB is costlier than Isolator. Say for example a TPN 63A Type-C Isolator of reputed manufacturer priced Rs 760/-, whereas MCB of same rating & type is Rs 1320/- (both the prices are without GST). Hence, just for mere pittance, suggest not to compromise with safety of life/property/expansive gadgets.  

Next, we have to check that, whether there is a main incoming MCB of appropriate type and rating or not? For 3 phase supply it would be TPN (i.e. 3 phase + neutral) MCB. For general house hold the type of MCB should be ‘C’ type with required ampere rating. As a commoner, we can check the ‘type’ but may not the ‘ampere rating’, which is the expertise of an electrical engineer/licensed electrician.   

Different types of MCBs with their area of usages and response time furnished below for reference.

Tripping performance of installed main or other MCBs should be checked periodically.

RCCB is a must

A Residual Current Circuit Breaker (RCCB) is essentially a current sensing device used to protect a low voltage circuit in case of a fault. It contains a switch device that switches off whenever a fault occurs in the connected circuit.

Often people get confused between ELCB & RCCB. ELCB (earth leakage circuit breaker) is the old name and often refers to voltage operated devices that are no longer available and it is advised you replace them if you find one. RCCB or RCD is the new name that specifies current operated (hence the new name to distinguish from voltage operated).

As name depicts, for single phase there will be single RCCB and for 3 phase, one for each phase. 

Tripping performance of installed RCCB should be checked periodically.

Checking of Earthing

Perhaps we are aware that, the connection between electrical appliances and devices with the earth plate or electrode through a thick wire of low resistance to provide safety is known as ‘Earthing’ or Grounding.

It’s tested that in general human body withstand only 30mA (milli-ampere) current beyond which it’s fatal. Earthing system makes the equipment electrically shock free and gives you a safe place to stay.

Apart from human life it,-

1. protects your electric equipment or devices.
2. provides a safe path for lighting and short circuit currents and saves the building from structural damage.
3. Voltage Stabilization: In an electrical distribution system, Earth is the omnipresent conductive surface, which makes it a universal standard for all-electric systems.
4. Over Voltage Protection which happens at the time of lighting and unintentional contact with high voltage lines.

Earth value and continuity of earthing cable shall be checked periodically.

For normal household, earthing (voltage) value (between earth pit conductor to neutral mains supply 220 V AC 50 Hz) shall be less than 2 Ω (Ohm).

This test can be done in two parts. One with the Electrician test lamp followed by measurement.

Defective earthing can also raise voltage, damage expensive appliances…….threat human life. You can check whether the RCCB is working or not, easily by pressing the Test push button on it – one for each phase – for 3 phase connection – to check your earthing.

Over voltage is directly linked to improper earthing and will lead to failure of insulation of appliances in which the current exceeds 1.73 times the one designed for any standard insulation of appliances.

If earthing is defective, the current builds up at appliance and ultimately has telling effect in the form of appliance insulation rupture resulting in MCB tripping that part of the circuit after damage is done.

The problem still remains. Whichever other appliances have an inbuilt voltage absorber like, refrigerator, some inverter AC will survive but if not precautionary checked, will result in further weakening of insulation and after millions of fatigue cycles, it will fail but at a much later date.

Periodical Testing

Please check values of phase to phase, phase to neutral, earth resistance in of your home electrical system prior to start dwelling.

For 3 phase supply it will be between,-

R-Y       : < 415 V,        R-B : < 415 V,              Y-B : < 415 V

R-N      : < 230 V,        Y-N : < 230 V,              B-N : < 230 V

Earthing value shall < 2 Ω (Ohm), preferably < 1 Ω (Ohm).

Periodical testing shall be done in house/apartment DB as well as in meter room also.

Is your Neutral floating?

Now another dangerous incident/accident may happen due to floating or loose connection of neutral wire. If 3 phase supply is there in your house/apartment or in your building/tower, this could happen. Neutral in the wiring associated with a flat (in rising mains or inside flat) becomes loose or open due to bad workmanship/wrong termination. Even poor crimping, loose terminations and sulphate deposits cause the issue.

In such case, due to a loose neutral, 230 V can rise upto even 440 V and such sustained over voltage can burn connected loads like ACs, Fridge, Fans etc. even could threat human life.

Revered readers may go through the following interesting explanation by SLDs (single line diagrams), which requires mere brush-up of our standard-X physical science knowledge.  

Case-1 : The standard SLD

All Ok. Voltage between each phase and neutral is 230V and between respective phases are 400 V. If 230 V changes then 400 V will also change simultaneously.

Case-2 : When neutral of a particular phase gets disconnected from rest.

The particular phase, which could be a) inside a house/flat, b) inside a building/tower/block or c) in locality/housing society etc. will not get electric supply.

Case-3 : When neutral gets disconnected between any two phase lines

As shown in above illustration, neutral got disconnected between Y & R phase lines. In this case internal circuit voltage between these two phases will rise to 400 V in place of 230 V Resistive loads of these two phases with become in series connection and  depending upon load resistance of each phase, this soaring voltage will get apportioned with differential voltage (shown below).

These differential voltages could be higher than standard 230 V and cause damage to appliances as well as life threat.  

Case-4 : When neutral gets disconnected at the beginning.

Effect will be same as Case-3. All loads will be in series (sometimes in parallel as well). Voltage in any phase line will depend on electrical loads in the same phase as well as other phases.

This phenomenon of loose neutral of 3 phase 4 wire system could happen,-

a) individual apartment/flat level (where internal connection is 3 phase),

b) building/tower/block level (where 3 phases came inside, but individual apartments are of single phase connection),

c) locality/housing society level (where main power is of 3 phase but individual building/tower/block given single phase connections).

That means, where you could be, there is hardly any escape from probability of neutral fault.

Protection from Over/under Voltage

Interesting fact is, in general there is no over/under voltage protector being used in our domestic DB. Even though voltage fluctuation in many area/states in India is considerably high, we are not very concerned about the issue.

Few of us, install expansive voltage stabilizer for single or multiple gadgets, spending huge.

But as a commoners, we could at least use some suitable over/under voltage protector for our house. This we could do by using plug-in type high/low voltage cutouts……easily available in local market or e_market costing Rs 1000+, for expansive gadgets (e.g. ACs, TV, Refrigerator etc.)……one for each.

Otherwise, prior to main MCB, we could use smart automatic over/under voltage (with adjustable setting, LED display) protector.

This kind of devices are available in e_market now-a-days. They claim following features,-

• Over voltage Protection for Complete Home Or Specific Device, Voltage Display Range 145 – 300V
• Under voltage protection 210V-145V (adjustable) (default: 170V)
• Over voltage protection 230V-300V (adjustable) (default: 270)
• Over current protection 1A-63A (adjustable) (default: 40A)
• Reconnect time (delay on time): 3s-300s (default: 30s)

To know more about similar product, interested readers may click https://www.amazon.in/dp/B07C3NNT62/ref=cm_sw_r_wa_api_i_eB8VDbAHC3CZQ

Solutions

We have to follow few simple steps,-

1. Get checked your house DB and wiring system by a competent electrical engineer/licensed electrician.
2. Please check values of phase to phase, phase to neutral, earth resistance in of your home electrical system prior to start dwelling.
3. Ensure that RCCB & Main MCB (not Isolator) of right ‘Type & Rating’, are there in your DB.
4. Thoroughly check all terminations/joints etc for quality of workmanship and rectify/replace any defects / defective devices. This should include all electrical installations including MCBs, RCCBs, Isolators, Fuses etc. inside flats, in rising mains, common passages as well as Diesel Gen interlocks, Electricals of Lifts etc. Adequate Earthing of flats and test of RCCBs should be carried out and findings recorded.
5. Install an over/under voltage protector in your DB.
6. Appropriate Lightening arrestor system should be there in your building or in your locality covering each building.
7. Asking electric service provider to regulate their ‘Tap switch’ in their PSS (i.e. package sub-station), and right set distributed voltage rating.

Conclusion

Generally we do many types of insurances….e.g. Life insurance, House/Property insurance……..even now-a-days insurances (some times in the form of AMC) of expansive home appliances/gadgets etc. Needless to mention ……all these are passive in nature. Let’s spend a pittance and act on active part of it following the proverb “prevention is better than cure”. Even, as we know, when it’s related with damages or loss of life………it’s irrecoverable. Let’s be wise……act wise. 

Author : Avijit Datta

Disclaimer : Images sourced from internet and used for visual indication only.

P.S. In case of any further query or consultation……eMail/whatsAPP.