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
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