Although, I am a VK, , I am also an A class Electrician here, and here
is how
The SAA wiring rules relates to this matter for best safety, inline;
On 6/5/21 10:01 am, MU 4CX250B wrote:
Hi Jeff and Jim,
I happily defer to your greater knowledge of electrical codes, about
which I know very little. I also understand that amateur equipment
powered off 240VAC should have four conductor power cords and internal
circuitry that separates chassis ground from Neutral. In that
circumstance, AC imbalance currents then return safely through the
neutral wire, while no load current flows into the ground connection.
No question that is the ideal setup, to which we should all aspire.
Only L2 and L2 with ground is required. Neutral is not required, in what
is a ,
simple AC path provided across L1 and L2 with no current imbalance issue
toi concern us in this application.
The neutral if present should be connected to a terminal in the amp for
connection to 120v devices, fan etc,
also fed from L1 or L2. If more than one device share the load using L1
for some and L2 for the other 120v
devices to share load. If the HV primary fails on one of 2 primaries
(open circuit), it would be better that the
whole amp shuts down, so I would not recommend neutral connection to the
center tap if accessible.
If we were dealing with heater banks then yes the neutral would be
beneficial at the primary load centre tap.
Three or 2 phase supplied heater banks use a neutral to allow maximum
possible heater banks to operate,
if one bank open circuits> fails , in a star (3ph star or wye wired) or
centre tap (2ph) connection with neutral
connected to the star point or center tap respectively.
nmeutral should never be connected to ground anywhere else in the system
but at the switchboard 'MEN (main earth neutral)'
connection strip where a neutal and earth terminal block are connected
to gether and a main eath stake connected to the earth
terminal block.
This keeps ground and neutral potential equal. The appliance (which is
the amp here), must have its metal body grounded,
unless double insulated from the exterior touched surface. The groung
connection is purely there for the purpose of keeping
the exterior metal potential minimum and taking the surge currect to
ground , blowing the supply fuse in the case of insulation breakdown
or other short to earth. It is there to save lives. The chassis should
never carry AC supply current otherwise.
Connecting a neutral to chassis compromises this safety in known fault
conditions where the neutral to ground connection removes the safety for the
appliance user exposing that person to potential above ground.
It is a safety issue.
Any old amp should be updated and rewired to match modern standards,
otherwise you are playing Russian roulette with peoples lives.
vk4tux
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