Abnormal voltages in power outlets, reason?
Recently our LED TV stopped working and when the service tech came for repairs he checked the voltage of the wall outlet with a multimeter. It showed it to be somewhere around 240V. Then he checked a few others in other rooms and they all showed different readings like 210V and one room had 250V ! Our region has a 220V supply. So is this variation abnormal and can it damage appliances? What is the normal range for mains voltages? And most importantly, what could be the reason for this abnormality in voltages all over our house? Can it be fixed? It is an older house but the wiring was laid afresh during renovations.
Thanks!
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This is a certain sign of an open neutral in the system. You need a service on the system to locate and repair the problem. A qualified professional electrician would verify at the main power panel that the voltages are correct and then try to locate where the open neutral is in the system. The usual cause of this is a bad connection in the neutral wire in the convenience outlets where the neutral is shared by 2 receptacle circuits. This is usually in the first outlet location in the circuits. The neutral may have been connected on the device instead of using a wire nut and a pigtail. The power then tries to return through the other leg of the circuit and the high voltage is developed. This will continue to destroy all electronic devices installed on the system and may also destroy refrigerators and cooking devices. This is what will and does happen in North America. If you are not in North America then you need to get a qualified professional electrician to do the work.
I think Ken's answer is the closest of what you got so far. HOWEVER!
Any normal circuit (in the US) will be 120 volts. That means a single hot line and a single neutral line and likely a safety ground line. The ONLY way to get 240 volts is to have two hot lines. That is to say in NORMAL circumstances. But it is possible that you've lost some of your neutral lines.
If one circuit feeds a lamp and the neutral line goes open, it will have 120 volts (with a slight drop due to resistance). If that neutral is tied into another neutral AND the neutral lines are not making it back to the panel then you CAN find 240 volts on an outlet. And any appliance rated for 120 volts will suffer the consequences.
I'll draw a picture to help you understand better.
To address the question of other "ODD" voltages, it all goes back to the same cause - open neutral line somewhere. Depending on what is plugged in and what type of load they provide they can, and most likely reduce, but in some cases increase they can increase the voltage.
This is my area of expertise, so you can have faith in what I say. I'm an electrical / electronics engineer with 30 years experience. But to explain all the possibilities that could be plaguing your electrical system would be cumbersome. So the best (and right) thing to do is to call a professional out to fix the problem.
Here's that drawing>>> http://www.flickr.com/photos/85188010@N05/96652053...
Hope this helps.
'av'a g'day mate.
'')
voltage fluctuations are quite normal.
all appliances are designed for the supply voltage +- 10% so that should not be a problem especially for electronic things like LCD TV or computer power supply.
the usually start working at around 100 volts up to the maximum input voltage.
Can you ask your supplier to check the suppl(ies) where they enter the house?
In multiphase supplies you can get voltage variation between phases, particularly when the neutral is flaky.
Only certain units need 200 volts and most of the house needs 110 volts. which makes me think that somebody been fooling around with the main fuse or circuit box. and wired things wrong.
Sounds like you lost your ground/neutral.