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Posted By Topic: House voltage

Mng112
Jun 01 2017 19:07

I have a problem that under load the voltage drops, the voltage is pretty low sitting around 230v to 234v, when you turn on some load the voltage drops down to below 220v sometimes causing lights to flicker, I wonder if it a loose neutral in meter or further back?
   

Sarmajor
Jun 01 2017 20:24

As most meter neutrals are shunt neutrals it is unlikely that this is the cause of the problem.
It is more likely that there is a loose or degraded connection in the mains if you are measuring the voltage fluctuations at the main switch.
You will be able to eliminate internal wiring connections by testing as close to the point of supply as you can get. This will most likely be the switch in the meter box. If there are still excessive voltage fluctuations under load there then the problem is back further in the mains from the street or connections between the switch in the meter box and the transformer terminals.
Likely candidates are the supply fuse terminations or the neutral connections. If it is an overhead supply then the point of entry box if any is also a possibility.

220 volts is a bit lower than I would expect in a correctly designed installation in good order.

If you are not an electrician then you should engage a competent one to investigate further.
An earth loop impedance tester will be of some help in diagnosing this fault.
   

Mng112
Jun 01 2017 21:09

I am an electrician and have measured the voltage at main switch in the board and from the line going into the meter and the earth of the meter box. The street has had overhead lines taken out and main is now via underground with no boundary box at gate
   

AlecK
Jun 01 2017 22:17

Do some loop impedance tests - the high current is good for showing up poor connections. Good test one side of 9whatever), bad test the other, indicates a poor connection to that item
   

SaintAlan
Jun 02 2017 17:10

I think an old-style analogue meter is better for finding these faults than a digital; the needle fluctuates with the supply variations and is easy to see.
If the problem is seen on the incomer to the mainswitch then the supply company should be contacted. Line taps in overhead wires sometimes loosen and cause high resistance joints.
   

gregmcc
Jun 02 2017 17:29

you could also measure the current in the main earth, if you saw a rise in current with the flickering lights it would indicate a loose main neutral connection somewhere, if there was no change then it would be a loose phase connection