I am handling the supply in a locomotive coach and have noticed that the neutral and earth wires have been accidentally flipped,inside the appliance(hot case) is there a problem from the safety point of view?
Electronic – In any electrical equipment having single ph 230 v ac supply ,if neutral and earth wire exchanged then what will be the consequence
earthneutralpower supplywiring
Related Solutions
Be careful! Death is easy to come by in such situations!
You need to say what you are testing with.
You need to say what you are measuring relative to.
If any equipment works when plugged in the pump is faulty or unsuitable for testing with.
If nothing works then something is broken.
If P & N are connected correctly and shorted the a fuse or equivalent will blow.
Measuring a floating conductor with a high impedance input meter may show high voltages due to capacitive coupling.
Make a test unit: Mains voltage light bulb with two probes.
Test PN PE NE
If PE and NE light N is connected to P.
If PE lights and NE doesn't and PN doesn't then P OK but N O/C.
If no light from any = major problems.
If no light as above, connect a long lead to outside ground. If any light from P/N/E to outside ground = problems.
You need to establish what voltages are genuinely present that can provide power - not just an O/C meter reading. Draw a diagram and show what does and doesn't light light bulb.Meter alone can fool you if unloaded.
When a fault occurs in an un-earthed metal cased device the case becomes live. When you touch it you form a circuit. Now you'd think that current couldn't flow through solid wood, etc. Well, that would be the case for DC, but not for AC. You see, you form part of a capacitor. You're basically one plate of a capacitor, the ground being the other. The floor, your boots, etc, form the dielectric insulator between the two.
The capacitor would block any DC current, but it allows the AC to flow quite happily. The equivalent circuit would be:
simulate this circuit – Schematic created using CircuitLab
The resistance of your body, and the resistance of the ground both limit the amount of current, but it only takes a tiny amount to kill you.
Now with the case grounded, and typically this involves a wire connecting the ground direct back to the ground point, which is also connected to neutral, and a fault occurs, the current will flow straight down the earth wire back to the neutral. This is a much much lower resistance connection than any human could provide, so considerably more current flows. This results in the fuse blowing isolating the circuit.
Also, if the fuse were not to blow for whatever reason (too high a rating?) the low resistance path would effectively short out the human reducing the current available to shock you to an absolutely minuscule amount.
Best Answer
There is a problem.
Generally the neutral and earth are connected at source. On fixed installations (e.g., your house) this may be the local transformer or at your meter-box, depending on local regulations. On your coach the generator / alternator most likely has its neutral connected to the chassis. The advantage of this is that we no longer need to fuse the neutral line as a short circuit between it and chassis will not cause high current to flow. On the other hand, a short from live to earth will cause a high current to flow and it will be detected when the fuse blows.
simulate this circuit – Schematic created using CircuitLab
Figure 1. Properly wired system.
Consider what happens in a correctly wired system.
simulate this circuit
Figure 2. Swapped N and E on LAMP2.
Things get much more interesting and dangerous once we start mixing up N and E. In the example shown in Figure 2 all appears well to the user and even the electrician doing a voltage test.
simulate this circuit
Figure 3. Broken neutral - live equipment case.
Figure 3 shows one potential scenario.
It's best to keep neutrals and earths properly connected.
See my answer to Why don't we use neutral wire for to ground devices and earth wire for closing the circuit? for answers to a similar question.