Some house lights start blinking when another section is turned off

[Wrichik Basu]

This is kind-of a sequel to my two other threads, but not exactly related to them.

We re-did a portion of our house wiring to accommodate a new 20A outlet. Also shelled out a few more bucks to replace the in-house fuses with MCBs. The circuit looks like this currently:

​

Note that the two pairs of wires from the downstairs MCB to the MCB panel inside the house have been newly installed and not existing lines.

Here's what happens: As you can see, the hall bathroom is connected to the $4~\mathrm{mm}^2$ wires separately through an SP MCB and do not pass through the isolator. However, if I switch off the isolator, the lights in the bathroom (including the geyser outlet) start blinking (dimly lit → off → dimly lit). We do not have a geyser; I verified the blinking in the geyser outlet with a 40W incandescent bulb. This line should remain unaffected by the isolator. If I switch off their MCB, they stop blinking.

On the other hand, if I switch off the MCB for the hall (the second MCB that connects to the isolator) with the isolator still turned off, the lights connected to that hall circuit start flickering at a low brightness (dimly lit → off → dimly lit).

Now I have called the electricians — the same guys who installed the new wires and the outlet — tomorrow, but would be grateful if anyone can make an educated guess on what is happening. Electricians here aren't exactly qualified (as in, they do not need a licence to work), so some opinion from the experienced people here is appreciated. I have a multimeter, so can do further tests as long as I don't have to open the MCB panel (can't do that because we don't have ladders).

I am also going to ask them to interchange the kitchen with the hall bathroom line, as the kitchen refrigerator outlet can handle 20A, and we do not have plans of installing a geyser in the near future.

Edit: labelled the MCBs

 

[Averagesupernova]

Something is crossed up somewhere. I hate to imagine. Isolation is your friend. What other breakers getting turned off affect this? I am curious what the voltage is when you have the incandescent bulb hooked at the geyser outlet and it blinks.

 

[Tom.G]

There are likely other possibilities, this is the one that comes to mind from your description.

ONE of the wires feeding the Hall Bathroom is not connected to the main incoming power. It is instead connected to something on the right hand side of the drawing.

If I switch off their MCB, they stop blinking.

Unclear.
Which MCB and which 'They'?

Also, what does the Isolator consist of? What is in it?

Cheers,
Tom

 

[Rive]

Exactly because of such cases why it's advisable to have different circuits placed in different tubes/boxes while following the 'natural' topology based on physical/logical placements.

Something is just cross-wired there, I think.

To start with, having that 'Hall bathroom' on the left while having a 'Hall bathroom extra outlet' (was that installed later?) on the right is just asking for trouble and highly suspicious, IMO.

 

[Wrichik Basu]

General note: I have updated the picture and labelled the MCBs to refer to them easily.

Also, what does the Isolator consist of? What is in it?

Just a DP switch that can handle upto 40A.

was that installed later?

The extra outlet in the bathroom was indeed installed after the main house wiring was done. But before we shifted to the apartment. Not sure why they connected it to the drawing room and store room line; probably they thought that if we install a geyser of high capacity, the bathroom line will be drawing nearly ~16A, while there was no heavy load on the drawing room/store room line. How do I know it is connected to the drawing room/store room line? Switching off the MCB D switches off that outlet.

 

[Wrichik Basu]

Something is crossed up somewhere. I hate to imagine. Isolation is your friend. What other breakers getting turned off affect this? I am curious what the voltage is when you have the incandescent bulb hooked at the geyser outlet and it blinks.

Something is just cross-wired there, I think.

ONE of the wires feeding the Hall Bathroom is not connected to the main incoming power. It is instead connected to something on the right hand side of the drawing.

Unclear.
Which MCB and which 'They'?

Here are some new findings and readings that may help.

I am testing in three places:

1. An LED lamp that is connected to the hall MCB.​

2. An LED in the bathroom that is connected in parallel to the geyser.​

3. A 40W incandescent bulb connected to the geyser outlet.​

4. A multiplug socket, with an LED indicator, connected to the extra outlet in the bathroom.​

If I turn off only the isolator, with all the MCBs under it (MCB D to G) switched on and the geyser outlet switch (not MCB A) off, the bathroom LED lamp starts blinking: dimly lit → off. The LED indicator connected to the extra outlet starts blinking too. Now if I switch off the MCB for the hall (MCB E), the hall LED starts blinking: dimly lit → off, while the bathroom LED goes brightly lit → off. Can't measure any voltage at this stage, obviously.

Once I turn on the switch to the geyser outlet with the incandescent bulb connected to it, the bathroom LED stops blinking; the hall LED glows continuously but dimly. The incandescent bulb doesn't glow, though. PD across it was fluctuating a lot — it was 5V at one point, then 22.3V, then something else. The interesting part is, the LED indicator in the extra outlet is now steadily on at full brightness. On measuring in that outlet, I found PE and neutral was ~220V; same for PE to live. Live to neutral was 4.86V, so ~5V. So somehow the entire lines are getting interchanged?! That's concerning, to be honest.

 

[Rive]

LED lamps are notorious troublemakers during such debugging. You may get better results by replacing (some of them) with (low power) incandescent ones.

Just in case I would make the electricians re-hook that 'extra outlet' to its rightful circuit and remove any wiring which is going there from the other domain.

Once I turn on the switch to the geyser outlet with the incandescent bulb connected to it, the bathroom LED stops blinking; the hall LED glows continuously but dimly.

Sounds like a low current bypass (like a switch indicator?) between mis-wired lamp circuits?
But honestly, this is just guessing. Somebody will need to check that whole circuit wire by wire anyway.

 

[Averagesupernova]

Concentrate on the geyser circuit with the incandescent. That's the low hanging fruit. If the incandescent can light it indicates a significant path to be able to source the current needed to light an incandescent.
-

Just in case I would make the electricians re-hook that 'extra outlet' to its rightful circuit and remove any wiring which is going there from the other domain.

The 'rightful circuit' is very subjective. Just because it does not make sense to someone doesn't mean it's wrong.
-
Like I said, start with the low hanging fruit. If anyone is unable to find a problem like this starting out with the geyser outlet with the incandescent then they need to keep their fingers out of there and let someone look at it who can handle it.

 

[Wrichik Basu]

PF is a clean place, and I would rather not use any expletives; so I would just say that the house wiring is really messed up. And these guys messed it up more.

Here's what happened: In the past, before this re-wiring job, we had only one pair of 2.5mm² wires coming up to the fuse panel from downstairs. The air conditioner was wired directly to the live wire coming from downstairs, and the rest of the house was connected via a DP MCB. There was no separate neutral from the air conditioner or the hall bathroom geyser. I was not aware that there were no separate neutral wires from the air conditioner or geyser outlet.

These guys installed two pairs of wires, as mentioned in the OP. But they joined the two neutrals at the isolator, making the new wiring diagram something like this:

​

So as soon as I switched off the isolator, neutral was disconnected from the entire house except the treadmill outlet, while three places still had the live switched on. This resulted in a "phase reversal" as they call it: for the entire house, the neutral line was now carrying the live. Which explains why I was seeing a 230V PD between earth and neutral after switching off the isolator. They are asking me why I am switching off the isolator. I mean, you installed it so that we can switch it off later, right? Their solution: turn off MCBs A to C first, then turn off the isolator.

I am frustrated at this point. Interchanging live and neutral in costly appliances is just the dumbest thing to do. And they were pretty much aware that this would happen. Just never felt it necessary to let me know.

 

[Averagesupernova]

In the USA ANY neutral would never be interrupted in a case like this. Only the hot. It sounds like you still have a path back to neutral in some way since you had an incandescent bulb lighting when it should not have been. Or at least a partial path. I would work on finding this.

 

[Wrichik Basu]

In the USA ANY neutral would never be interrupted in a case like this. Only the hot. It sounds like you still have a path back to neutral in some way since you had an incandescent bulb lighting when it should not have been. Or at least a partial path. I would work on finding this.

The incandescent bulb blinked only once. It never lit up after that one time, irrespective of whatever combination I set the MCBs in during further testing.

 

[Averagesupernova]

Left in the condition you described you still have an unsafe installation. Turning off the isolator puts voltage on everything due to feeding through the breakers and loads that are not interrupted by the isolator.

 

[Wrichik Basu]

Left in the condition you described you still have an unsafe installation. Turning off the isolator puts voltage on everything due to feeding through the breakers and loads that are not interrupted by the isolator.

Yes, true. We are going to re-wire things.

 

[Wrichik Basu]

From what it seems (I tested yesterday a bit), the air conditioner and the treadmill outlets both have their live and neutral wires directly connected to the pair of 4mm² wires. The bathroom and geyser section is the only one that is connected to the 4mm² live, but uses the existing house wires as neutral, and hence, its neutral is connected to the isolator. The circuit is approximately like this:

To be honest, I am still not sure why live and neutral are getting interchanged when I switch off the isolator.

Anyway, what I have decided is to call the guys and ask them to connect the geyser live to the 6mm² wires, so it will be in sync with the rest of the house. I'll also ask them to shift the geyser to a 10A MCB and the kitchen to a 16A MCB because we don't have a geyser and don't need to draw 16A from that section, while the kitchen section could definitely use another 10A for small kitchen appliances like toaster and mixer grinder (clarification: doesn't include microwave), along with the existing 6A-rated refrigerator. The kitchen wires are already 2.5mm² wires, so it shouldn't be an issue to draw 16A.

 

[Averagesupernova]

Is there a good reason the neutral is interrupted in your country?

 

[Wrichik Basu]

Is there a good reason the neutral is interrupted in your country?

None that I know of, to be exact. It's customary to keep the house circuits (includes lights, fans and 6A outlets) on a DP isolator before passing into separate SP MCBs for each room. Larger loads like air conditioners and microwaves are directly powered via an SP MCB from the main MCB.

 

[Wrichik Basu]

I was wondering if I could add a 15kVA servo stabilizer for the entire house.

Even though I live in a metropolitan city, we do have sudden voltage fluctuations, as well as constant low voltage in the summer due to every house running an air conditioner. Part of this happens because people use more load without obtaining a green signal from the company. I had to buy one rated 5kVA for my treadmill — the seller recommended it as the motor and motor controller are sensitive to fluctuations. And to be honest, this is precisely what I was looking for. The stabilizers that we have currently for the air conditioner and refrigerator are relay-based and have a single tap in the transformer. Which means that if supply goes down to 200V, it will output 220V. But if it goes down to 180 or 170V (which does happen once in a while), it will output 200 or 190V. Which is outside the range of rated voltage for appliances. They don't have any support for higher voltages, either; they just turn themselves off to save the appliance. A servo stabilizer gets rid of each of those issues. Buying separate servo stabilizers for each appliance makes no sense — these are costly, and if I can get one that serves the entire house, I will be happy to pay a bit more and get that.

I had a word with the servo stabilizer seller; he said that 10kVA supports up to 7.5kVA, so 15kVA should be enough for my entire house, including the current air conditioner and any future loads up to the sanctioned maximum load. The wiring is what I have to plan.

I was thinking of feeding the two 4mm² and 6mm² wires coming from the MCB downstairs directly to the servo stabilizer. Then separating the output into two parts. In this situation, I will not be able to separate the loads from the 4mm² and 6mm² wires.

Any better idea anyone? Or any advice regarding this idea of adding the stabilizer? I want a single solution for the entire house, if possible.