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

[Gary Schafer]

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.

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.

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 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.

A 3 wire 220 line is fine for most of the amplifiers provided there is 
no 120 volt / neutral requirement.

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.
There is good reason for it. 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.

73
Gary  K4FMX