question about polarity

[skip34]

Hi

This is Skip - trying to restore a rusty IGT s+ machine.

I began assembly of the wiring components when I found that after the power comes in to the line filter,  the output appears connections give reverse polarity.
From the the original picture (prior to disassembly) at the output of the line filter the white wire is connected to the right hand lug (in foreground) while the black wire is connected to the left lug closest to the back of the machine. This yields reverse polarity when testing with a circuit tester. The reverse polarity flows to the convenience outlet and through the  power switch. This leads me to believe that reverse polarity flows through the entire machine.

I could easily solve the problem by swapping  the black and white wires , but as the wires exit the harness to get to the line filter, the length of each are such that it seems that this reverse polarity was purposeful i.e. I would hav to remove numerous binding straps  to free the white wire nough the get to the back (left) lug.

The picture below is shows the line filter as it was before disassembly.

Is the machine supposed to have reverse polarity?

Thanks,
Skip

[Foster]

How are the Line Filter outputs labeled?

I would either swap the outputs from the line filter or at the convenience outlet.
The rest of the 120VAC in the machine (Fluorescent lights and hopper) should be isolated AC
Means you can still get shocked but not as dangerous.

[skip34]

I think I will change the wiring at the line filter.

Right now, because the Hot (black) wire is on the left (or back) lug of the line filter, It also makes all ground connections hot. This will cause all metallic parts of the cabinet to be energized. This can cause a shock when touching the metallic parts if standing on a ground potential - like a damp concrete floor.

This is reminiscent of the days before polarized , 3 prong plugs, when plugs and receptacles were all 2 prong. Everything worked but if you felt a shock when touching the refrigerator door of a lamp body, you just reversed the plug in the outlet to eliminate the condition.

Skip

[Foster]

The neutral is not connected to the chassis.
The S+ can be used on 220/240.
There is 2 primary windings rated for 120V. they are wired in parallel for 120VAC and wired in series for 240V
There is also a secondary winding that outputs 120V (that way they dont have to worry about the hopper and lights being changed to 220/240 versions in another country)

[Jim]

there is no reverse polarity when it comes to AC.  Alternating current is just that, it swings both ways.  how did you determine that you had reverse polarity?  if you put the meter leads on the output of the filter you should measure 115vac, if you reverse the leads you will still read 115vac.

the black and white are the 115vac, the green wire is the machine ground. that is the same potential as the ground terminal on your wall outlet. the white wire (neutral) should go to the black bus bar(terminal bar or lug) located in front of the SSR (solid state relay), all the other devices that use 115vac in the machine will have the white wire plugged into that terminal block. the black wire should go to the on/off switch, fuse, then to the terminal for the black wires.  

Jim

[poppo]

there is no reverse polarity when it comes to AC.

He may have used the wrong term. But having neutral and hot reversed is often called that.

Always best to check the outlet first for an open ground. Also, sometimes people will break off the ground lug on the cord or power strip. If the ground is good, then the chassis should never be hot.

[skip34]

If I power up the line filter and measure voltage between the two lugs I get 120 volts no matter which lead is on which lug. If I measure the right lug to the green ground wire comung from the line filter, I get 120vac. If I measure between the left lug and ground, I get 0 vac. If I then switch the meter to measure continuity and measure between the the left lug and the green ground wire, I get straight continuity. (with power not applied - I get no continuity.)

Just as if you measure resistance between between the ground connection on a standard 3 prong receptacle and the left (larger) opening on that receptacle you will get straight continuity. Dont try it between the ground and right (small) opening - you will blow up the meter.

I discovered reverse polarity by plugging a circuit tester into the convenience outlet.  The lights on the tester indicated "Hot/Neutral Reverse" commonly known as reverse polarity. I traced the wires back to the output of the line filter, then tested the line filter and determined that is where the reverse polarity originated.

I realize that AC is AC and the machine won't know the difference. But if somehow the hot(black) wire shorts to the chassis, it won't blow a fuse but will energize the chassis giving the potential for shocks. So  Unless there is some specific and pressing reason the machine is supposed to run off reverse polarity, I am going to change the wiring.-Skip
-Skip


-Skip

[Foster]

I doubt the metal cabinet or chassis can be at 120V potential it is grounded to earth ground by the Ground/3rd Wire in the cord.

I would be careful about swapping wires at the filter. the outlet may have just been reversed not the rest of the machine.

[poppo]

I doubt the metal cabinet or chassis can be at 120V potential it is grounded to earth ground by the Ground/3rd Wire in the cord.

This is why I asked about a possible open ground (or reversal) at the wall outlet or power strip. Since he has a circuit tester, he can check those.  

But he is right that a reversed hot and neutral is not good, and if the ground should open or is open, the chassis can become hot.

However, as you mentioned it is also possible that the service outlet that he is checking is the one that is wired wrong.

But, since the hot and neutral pretty much go straight to the transformer windings (through the power switch) it is unlikely that there would be a problem reversed ot not  However since the convenience outlet is showing a reversal, the cause of that should be determined and fixed. One way to to check would be to measure the voltage from gound to the main fuse (which should be hot). If there is 115vac, then it's just the service plug wired wrong. If it measures 0vac, then it's wrong elsewhere..

[skip34]

I switched the white/black wires at the line filter - everything tests good (polarity wise).

With power on, when testing between the ground connection at the convenience outlet and the 3 fuses, I get voltages of  116, 81, and 122 from top  to bottom. I assume these voltages are correct.

Thanks,
Skip