Grounding of electric appliances

[hk blues]

3 hours ago, Dave Hounddriver said:

I have a Smart TV upstairs ( @sonjack2847 has the same model and may be able to confirm).  That TV does not work if the plug is put in backwards.  It is 2 prong and both are the same size, but if I plug it in one way the TV does not work and if I turn the plug around then it works.

Kevin, does yours do the same?  Maybe mine is an anomaly.

I asked because I often get a little spark when I plug something in, but not every time so I assumed It might be due to the polarity being wrong.  However, everything still works.

[Jollygoodfellow]

11 minutes ago, hk blues said:

I asked because I often get a little spark when I plug something in, but not every time so I assumed It might be due to the polarity being wrong.  However, everything still works.

Probably because most power points dont have an on/off switch so the live current is suddenly touching something which is the prong causing it to spark. My guess. 

[KurtVD]

10 hours ago, Dave Hounddriver said:

I totally agree.  I was just pointing out that one anomaly, the HiSense Smart TV, which reacts to being plugged in "backward" by not powering up.  It could be a wiring problem on my specific TV set.

EDIT:  Checking it further.  The plug coming from the tv is 2 prong but one prong is larger than the other.  This is how the problem became an issue.  It seems my wall outlet has the wires reversed so I had to use an adaptor with 2 "same size" prongs to plug in the tv with the opposite polarity so it would work.  Anyone with correctly wired household current would not notice it but it DOES make a difference which way it is plugged in.  Wonder how many other appliances are built that way.

Take a look at the male plugs and see which ones have one side larger than the other. 

It would seem that those must be plugged into the correct polarity.  I must have got lucky with my Inverter fridge.  It has that type of plug too.  That socket must be wired correctly.

Hmmm...somebody correct me if I’m wrong , but AC (alternative current) means that there is no left or right polarity, but that the polarity is constantly switched between the two poles. This is why there is usually a frequency indicated with the voltage (like 220V, 50Hz) , 50Hz meaning that the polarity is switched 50 times per second. I’m no electrician, but that’s how I understand AC works.  DC is different, for example your 12V system in your car: connect something the wrong way (anything, the battery or even just the wires for the smallest lightbulb), and you will blow a fuse at the very least, or worse. 

[Capa]

5 hours ago, KurtVD said:

Hmmm...somebody correct me if I’m wrong , but AC (alternative current) means that there is no left or right polarity, but that the polarity is constantly switched between the two poles. This is why there is usually a frequency indicated with the voltage (like 220V, 50Hz) , 50Hz meaning that the polarity is switched 50 times per second.

Alternating current (AC) has electron flow in both directions, alternating between forward and backward. It also has changes in polarity. This appears on an oscilloscope as a sine wave that repeats itself 60 times per second in the PI. This frequency is unusual, as most countries that use 220-240 VAC use 50 Hz (50 times per second. This is the LINE or HOT conductor (usually the black wire). Putting your hand on this wire will shock or even kill you!  The NEUTRAL line (usually the white conductor) can be handled all day with no ill effects, since it is nearly at ground potential. I hope this helps!

[Capa]

15 hours ago, Jollygoodfellow said:

Probably because most power points dont have an on/off switch so the live current is suddenly touching something which is the prong causing it to spark. My guess. 

That is correct, but not the whole story. Suddenly touching live current appears to be a dead short for a few milliseconds until hysteresis from either transformer windings, or more commonly these days, from a bridge rectifier sets in.

[sonjack2847]

21 hours ago, Dave Hounddriver said:

I have a Smart TV upstairs ( @sonjack2847 has the same model and may be able to confirm).  That TV does not work if the plug is put in backwards.  It is 2 prong and both are the same size, but if I plug it in one way the TV does not work and if I turn the plug around then it works.

Kevin, does yours do the same?  Maybe mine is an anomaly.

I think you must remember that you have an inverter and stuff before the power goes to the tv.Mine works whichever way I plug it in.I suspect it is down to polarity.

[Gary D]

8 hours ago, Capa said:

Alternating current (AC) has electron flow in both directions, alternating between forward and backward. It also has changes in polarity. This appears on an oscilloscope as a sine wave that repeats itself 60 times per second in the PI. This frequency is unusual, as most countries that use 220-240 VAC use 50 Hz (50 times per second. This is the LINE or HOT conductor (usually the black wire). Putting your hand on this wire will shock or even kill you!  The NEUTRAL line (usually the white conductor) can be handled all day with no ill effects, since it is nearly at ground potential. I hope this helps!

You do need to take into consideration that the person who wired the house probably only had one reel of cable of whatever colour that came to hand so both wires could be the same colour and the wiring orientation completely random.

[Capa]

34 minutes ago, Gary D said:

You do need to take into consideration that the person who wired the house probably only had one reel of cable of whatever colour that came to hand so both wires could be the same colour and the wiring orientation completely random.

So true! Example: I have an outlet that the previous owner of my house added on the surface, 2-wire. Since most things I plug in have 3 prongs, I am in the process of replacing it with a 3-wire outlet, and will add the green ground wire. When I opened it up, both HOT and NEUTRAL wires are red! I thought about replacing them with the proper color coded wires, but no, that will not benefit anyone once it is buttoned up. So all I did was check it with a DMM and put a big black mark on the HOT wire, just for my reference. (As you face the outlet, HOT is on the right side, and NEUTRAL is on the left.)

[hk blues]

2 hours ago, Capa said:

So true! Example: I have an outlet that the previous owner of my house added on the surface, 2-wire. Since most things I plug in have 3 prongs, I am in the process of replacing it with a 3-wire outlet, and will add the green ground wire. When I opened it up, both HOT and NEUTRAL wires are red! I thought about replacing them with the proper color coded wires, but no, that will not benefit anyone once it is buttoned up. So all I did was check it with a DMM and put a big black mark on the HOT wire, just for my reference. (As you face the outlet, HOT is on the right side, and NEUTRAL is on the left.)

My house was build by one of the biggest developers here in the Philippines, yet the wiring colours varies - red/green/yellow/black are all used and without any consistency or logic. Probably not a big deal but can make tracing wires a challenge. I mistakenly thought that the wire gauge were colour coded.

[Capa]

50 minutes ago, hk blues said:

My house was build by one of the biggest developers here in the Philippines, yet the wiring colours varies - red/green/yellow/black are all used and without any consistency or logic. Probably not a big deal but can make tracing wires a challenge. I mistakenly thought that the wire gauge were colour coded.

There is a Philippine Electrical Code that spells out what the color coding is, and I imagine it is similar to US code and the colors are supposed to be those I mentioned before. Obviously it is not followed! A big deal? Only when things have to be opened up for service or repair. In that case just be hyper-aware that it is an unsafe condition to not know which color is the HOT wire (220V)!