Voltage drops when turning on equipment

[Roeland]

Hello, we recently rented this 3floor old house in Bangkok and are expierencing some problems with the electrical system. 

The problems occur when we turn on some demanding equipment like the AC, Water pump or the hot shower. 

 

I've measured the voltage with my multimeter and under normal circumstances its around 223 Volt but when turning on the AC it drops 189 Volts and stays that way.

The hot shower is the worst as it makes the voltage drop to 150V. (lights just stop burning)

 

What could be the cause of all this? 

 

 

 

 

[Forkinhades]

Undersized cables.
Xy will be here shortly to give a more detailed answer, and solution.

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[Roeland]

This is my fuse box. Wiring is really a mess.

I've seem to have 1 phase black/grey coming in with the black attached to the earth 

 

 

 

 

[Forkinhades]

At least you have an Safety Cut.
The main cables coming in look undersized. How far away from the meter are you?
Most probable though is that the cables from the Tx are undersized as well.
More pictures will help.
There are undetvoltage accessories that you can install. Depends on budget.

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[Roeland]

Yeah, the safety cut was a nice suprise althought one kabel seems to be connected right after the main switch.

We are renting this place so im searching for a cheap solution. 

 

Thanks for the help

 

[Crossy]

What size is your meter? It should say on the plate, 5(15), 15(45) are the common ones.

 

Are you measuring those voltages at the main breaker?

 

[Roeland]

Meter is a regular 15(45) 

I've measured both at the main breaker and at the socket (same result)

[Forkinhades]

How many meters from meter to Distribution Box?

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[Roeland]

 

9 minutes ago, Forkinhades said:

How many meters from meter to Distribution Box?

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About 8 meter. 

[Forkinhades]

That's ok then. Can you follow the wires upstream of your meter to the transformer? Not that you can do much about it mind.

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[Crossy]

I think we're looking at a PEA problem, it's worth talking to them and showing the issue.

 

They've provided a 45A supply which can't even support a meagre aircon and water heater.

[RichCor]

...where do the MAINS wires from the meter apparently get changed from BLACK/BLACK to GREY/WHITE ???

 

Anything else occurring between the meter and the first breaker?

[Crossy]

Nice spot @RichCor

[Forkinhades]

Can you visibly see the whole cable route ? Any joins ? Could have a high resistance join. Cables could have been decreased.

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[RichCor]

I'm thinking corrosion or loose joint at a transition connection.

 

I guess watching the sparklers at night isn't everyone's night-time hobby.

 

EDIT:  

 

If there is a join where the Black/Black wires are transitioned to Grey/White then this is the primary spot to look for a highly resistive poor connection causing your voltage issue.

 

CAUTION as this is a MAINS cable connection directly from the meter, directly from the overhead transformer without benefit of any breaker or Safe-T-Cut to protect anyone getting near a resistive join. 

[Moonlover]

Undersized cables is usually the cause of this problem. This a common problem in old buildings throughout the developing nations. They were wired up when all the occupants had was lighting, a few fans and an old valve radio. The wiring is simply not up to the modern loads that we impose on it.

 

You are having quite a large voltage drop and that means that energy is being dissipated somewhere. That energy will be going in the form of heat in the undersize cables.

 

That can cause fires and often does so. I would advice caution here.

 

Professional help is strongly advised. 

 

 

[Roeland]

Alright, I'll take a look tomorrow morning. I'm not going to mess with anything above the main breaker. 

 

The thing that makes no sense is that Grey is live and Black is Neutral. The white cable connected to the Black cable (above the main breaker) goes to a screw which is connected to the earth rod. 

I loosened the white cable on the screw side and could see some light sparks forming. When I turned the power back on with the white cable not connected I was very surprised.

Not only was the power not working but the white cable was actually a live one now. 

 

 

[RichCor]

59 minutes ago, Roeland said:

 

The thing that makes no sense is that Grey is live and Black is Neutral. The white cable connected to the Black cable (above the main breaker) goes to a screw which is connected to the earth rod. 

 

I loosened the white cable on the screw side and could see some light sparks forming. When I turned the power back on with the white cable not connected I was very surprised.

Not only was the power not working but the white cable was actually a live one now. 

 

This cable appears to be a required MEN (Multiple Earth Neutral) Bridge Connection upstream of the Safe-T-Cut breaker.

 

 

 

Extreme caution should be exercised around this connection if your MAINS Connection is operating in a FAIL MODE (Neutral partially or fully disconnected).  With the MEN bridge in place your Earth Ground is acting as the alternate Neutral Return to the transformer.

 

Most likely your MAINS Neutral has a major issue (corrosion or partial connection) somewhere between the meter and the CU.  Since this failure is occurring upstream of your Safe-T-Cut it isn't being triggered.

 

But a poor Neutral (and possible a matching poor Live connection) will likely to be the cause of your voltage loss.

 

Still, a bad, and very potentially lethally dangerous, situation. 

[Roeland]

A well its time to find a "professional" then any ideas on where to find one?

 

[Crossy]

Ask around your area if anyone knows a decent sparks, show him the issue (the voltage dip) and hope he has an idea what's going on.

 

I think @RichCor is on the right track with there being a bad neutral connection.

 

When you removed the MEN link did the house lights actually work? The fact that your neutral became live suggests a very high resistance or completely open neutral somewhere.

[Roeland]

Update: I think I may found the problem: 

Unbelievable that I missed it. It seems to be broken off and badly connected.

 

Girlfriend just told me PEA is closed at 3:00 so I guess I have to wait till monday .  

 

 

 

[Roeland]

[Jdietz]

I wouldn't point any closer than that, preferably much further away...

 

[bankruatsteve]

Holy crap.  All those wires that look like they've been fried probably have.  Are those burn marks on the ceiling?  You need to show this to your landlord and politely suggest that if he/she doesn't want the house to burn down all the bad looking stuff should be replaced.  Probably not a big expense.

[elgordo38]

On 4/21/2017 at 3:44 PM, Roeland said:

Update: I think I may found the problem: 

Unbelievable that I missed it. It seems to be broken off and badly connected.

 

Girlfriend just told me PEA is closed at 3:00 so I guess I have to wait till monday .  

 

 

 

From the looks of some of that wiring a rewiring job may in order for your safety. 

[Formaleins]

What really surprises me from your photos is that it looks like you are able to run your Safe_T_Cut on the 5mA setting! I am amazed - or is the Safe-T-Cut bypassed by any chance?

 

I would be grateful if you could pass on the contact details for your electrician, he obviously had an eye for beauty when he wired up that little lot, very aesthetically pleasing with just a hint of danger.

[RichCor]

On 4/20/2017 at 5:14 PM, Crossy said:

I think we're looking at a PEA problem, it's worth talking to them and showing the issue.

 

On 4/21/2017 at 3:44 PM, Roeland said:

Update: I think I may found the problem: 

Unbelievable that I missed it. It seems to be broken off and badly connected.
 

[ Thai-style_finger_pointing.jpg ]

Girlfriend just told me PEA is closed at 3:00 so I guess I have to wait till monday .  

 

It's been a week now. Wondering if the OP can provide a happy update?

[crutchy26]

There are a few 'joins'. Usually they are just twisted together. Add corrosion & time: they turn out to be 'hot-spots' which will reduce your main at a wall outlet. If the voltage drop is BEFORE the meter, you have bigger issues. 

[sandyf]

On 4/20/2017 at 6:29 PM, Moonlover said:

Undersized cables is usually the cause of this problem. This a common problem in old buildings throughout the developing nations. They were wired up when all the occupants had was lighting, a few fans and an old valve radio. The wiring is simply not up to the modern loads that we impose on it.

 

You are having quite a large voltage drop and that means that energy is being dissipated somewhere. That energy will be going in the form of heat in the undersize cables.

 

That can cause fires and often does so. I would advice caution here.

 

Professional help is strongly advised. 

 

 

Not only the developing world. 

Team Lotus used to operate out of an old building in East Anglia and I made an oven for them to dry off body shells. Shortly after it was installed Colin Chapman rung me up, very irate and said his office had been turned into a disco. exactly the same problem , as the heaters turned on the lights went dim. The building was out in the sticks so nothing could be done about the wiring. I changed the controller from fast cycle to phase angle, didn't get rid of the problem but it became hardly noticeable.

You are quite right about the energy being dissipated in the cables but if it is over some distance it is of little consequence. The real problem is a short length of undersized cable or a bad connection where the heat can be intense and lead to burning.

[Moonlover]

1 hour ago, sandyf said:

You are quite right about the energy being dissipated in the cables but if it is over some distance it is of little consequence. The real problem is a short length of undersized cable or a bad connection where the heat can be intense and lead to burning.

And looking at the final photos that he sent, that's exactly what he found. I hope he's got that mess sorted.

 

I was chatting with a pal last night who oversees bespoke house building work. He was telling me how difficult it is to try and get the electricians to put in a ring main for the sockets.

 

He said they just cannot understand why they have to put two cables to each outlet. .'One is enough. It's always worked ok'.

 

Ways to go!