[Amps] Re: Neutral and ground is in how you use them (was SB-220 on 220V)

[Gary Schafer]

R. Measures wrote:
> 
>>
>>R.Measures wrote:
>>
>>>**  The neutral in the 240V outlet for the amplifier is shared with every 
>>>120V and every 240V circuit in the house because All of the neutrals 
>>>connect to the neutral/ground terminal strip in the breaker-box.  If I am 
>>>fortunate, it is that I know Ohm's law good enough to get by. 
>>>
>>>__  Which is what I do on the 240v outlet for the tetrodes-with-handles 
>>>mains outlet.  //  The imbalance current is c. 85mA-avg in the 
>>>neutral/ground because I utilize one side of the mains-neutral potential  
>>>to power a half-wave rectified, C-filtered 160VDC supply for operating 
>>>the high-speed T/R relays.  Although there are some who would be alarmed 
>>>about the potential-drop in 99' of #6 wire at 85mA, I am not one of them. 
>>> 
>>>
>>
>>Rich, I am sure that you know and understand this stuff but some others 
>>may not.
>>
>>1. The biggest reason for having separate ground and neutral wires is to 
>>insure safety in case the neutral should open (in the case of a common 
>>ground/neutral system like you use.
>>Even your 85 ma that you are running on your common ground/neutral line 
>>can be a hazard. If the ground/neutral line opens anywhere you will have 
>>120 volts at chassis through the transformer primary with enough current 
>>to cause electrocution if you are between chassis and some other ground.
>>
> 
> ** Providing this person was standing in water.
> 

No water necessary. Moderately sweaty palms will more than suffice.


> 
>>In your system it may not be too likely to happen. However in many 
>>wiring installations it can easily happen.
>>
>>One house that I owned years ago (was a brand new house too) had 
>>problems with some of the wiring. Upon further looking I found that just 
>>about every outlet in the house had the wires wrapped around the screw 
>>terminals loosely as you normally would, but the screws were never 
>>turned down! Most of the outlets worked properly as far as I knew. I 
>>would have never known if I had not opened them up and looked at them. 
>>That is unless I had a fire first!
>>Suppose in that house I had a 220 outlet with only 3 wires used as you 
>>do above. I could have very easily had a poor (guaranteed to be poor!) 
>>neutral/ground lead.
>>
>>If your 220 line had it's ground/neutral connection wired like that and 
>>you were using it as a neutral/ground you could very easily have a "hot 
>>chassis". I have also seen "electrician" installations where the lugs in 
>> the breaker panel where not tightened. Wires slipped into hole but 
>>never tightened down. they make a connection but not a reliable one.
>>
>>It is easy to have a poor outlet connection too. Fingers in the plug not 
>>making proper contact. Especially on older / well used outlets.
>>
>>If any of these things happen on your neutral/ground line then you are 
>>sure to have a "hot" chassis because you are asking that line to carry 
>>current that is tied to the chassis.
>>
>>But if you have a separate neutral and ground line then even if you 
>>would have a poor connection on ANY of the lines (even the ground line) 
>>you would not have a "hot" chassis. Unless of course there were multiple 
>>faults.
> 
> 
> **  If the screws are not tightened on the ground and neutral wires, you 
> would.  
> 
>>2. As to "proper to code installation of wires" you may use any color 
>>wire that you wish. Even all black wires. Yes even for ground and 
>>neutral! But each end is supposed to be tagged with proper colored tape 
>>to identify them.
> 
> 
> **  I identify them by size.  #6 is ground/neutral and the #4s are mains. 
>  
> 
> 
>>I do it in my own stuff mainly to be able to identify what I did several 
>>years latter.
>>If you use 3 conductor Romex for a 220 line (black, white and bare)
>>the white wire should be marked with red tape on each end. The main 
>>reason to do so is to tell someone that may be in that circuit doing 
>>repair work that that is a 220 line and not a 120 volt line neutral.
>>
>>3.  A three wire 220 line as above is perfectly fine with the NEC as 
>>long as it is used as "hot, hot' ground and no neutral is involved.
> 
> 
> **  How can neutral be not involved if the not-hot third wire connects to 
> the ground/neutral terminal strip?

The key is that ANY of the wires in the line can become open and NOT 
cause the chassis to be hot.


> 
>>A 3 wire 220 line is fine for most of the amplifiers provided there is 
>>no 120 volt / neutral requirement.
> 
> 
> **  I have been using one half of the amplifier's 240vct, 20A circuit to 
> power my 120v radio and soldering iron for the past 28-years.  

Not the best idea.


> 
>>4.  I saw someone post earlier that "ground wires and neutral wires were 
>>intermingled on the lugs in the breaker panel". Even though the two buss 
>>bars are tied together in the panel the proper way (to NEC code) is to 
>>connect all the neutral wires to the neutral buss bar and all the ground 
>>wires to the ground buss bar and not intermingle them.
> 
> 
> **  In my General Electric Co. box there is one common strip for all of 
> the neutral and ground wires

It must be a VERY old box.

> 
> 
>>There is good reason for it. 
> 
> 
> **  Apparently, GE did not think so.

They do now!  You can't buy one that doesn't have two separate busses.

> 
> 
>>Though they may be electrically the same, 
>>it is much easier to identify which is which when looking in the crowded 
>>panel to try and identify a wire. Also if you have an external main 
>>breaker or this panel happens to be a sub panel the ground and neutral 
>>would NOT be the same at that point.
>>
>>5.  Yes inspectors do (should) look for properly identified (proper 
>>color) wires. You may know what they are on your own work but the next 
>>guy that comes along may not know where they are supposed to go unless 
>>they are the standard color codes.
>>
> 
> **  I trust my DMM more than I trust a color.
> 
> cheers, Gary 
> 

73
Gary  K4FMX