Hi
I was wondering if anyone could explain "how to test for a neutral" in a way that a first year apprentice would understand. My boss says it is really simple when you know how, but it is really difficult to explain.
Any help would be appreciated.
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Hi
I was wondering if anyone could explain "how to test for a neutral" in a way that a first year apprentice would understand. My boss says it is really simple when you know how, but it is really difficult to explain.
Any help would be appreciated.
We assume that you have a voltage measuring meter of some sort and know how to use it.
If working at a single phase control panel of some sort firstly check that you have voltage at the incoming power supply.
You would normally do this by placing one voltage probe on the earth and the other on the 'live'; this should show, in the UK, 230 volts.
Now move the probe from the earth and place it on the neutral terminal, you should also have 230v.
If you have a suspect component which is fed by 230v then with the power turned on place the probe on the live side and the other on the main neutral terminal; you should have your 230v still.
Now move the probe from the main neutral and put it on the neutral of the item being tested. If the voltage is zero or much less than 230v then it would indicate a break in the neutral wire back to the main terminal.
This can often be due to a wire coming loose in a connector somewhere.
If the item being tested is a coil, such as a contactor or relay then with power on and a faulty neutral from it you will be able to measure 230v at the live terminal and the neutral terminal with one meter probe connected to the main neutral. This is because there isn't a complete circuit so the live power is not being used.
Hope this helps.
Brian that is a good explination, the final test after you have carried out the above is to check continuity between the earth and Neutral as at the transformer this will be the star point.
It is called the MEN - Main Earth Neutral.
You could try what has been suggested or you could disconnect the circuit from the origin, link out the neutral and earth the test for continuity between the two, just make sure you use a tester that can place a good current load on the circuit, i.e. 25 plus amps
Hi Guys
Thanks for the replies, I think I am going to have to practice this one some old kit just to get some confidence, a bit nervous about if i touch something I am not suppose to with a probe and the machine goes BANG.
Thanks for your advice though, i am going to read it over and over until it sinks in.
As long as you do not touch more than one thing at a time with your test probe then all should be well.
Extra care when checking PCBs but normal electrical terminals are sort of safe. ;)
Your Boss is right!Quote:
Originally Posted by ChrisCrick
I like to explain electrics to newbys by using your sink at home.
Here goes
Object to wash a plate (moter, contactor, relay etc)
You turn on your tap (live, the tap is the switch)
The water rushes over the plate (power use)
The water falls down the drain (neutral)
If you notice the sink overflow (Earth) and the drain are connect under neath the sink (so it can be said that the earth and neutral at some point are the same)
If you put the plug in the drain (broken neutral) flow of water will stop (the sink fills) Imagine the sink now is a fully sealed. The sink will be at the same pressure as the tap (Voltage, or we should say potential difference) If sealed sinks leaks it goes dowm the overflow (earth fault).
Easier to say than write!!!!!!!;)
Quote:
Originally Posted by mad fridgie
LOL, i like it!!!