[Amps] What to do about 'Neutral' in HB amp?

[Adrian]

It is interesting to see the various opinions on Neutral and electrical 
safety.

In Australia we have world best regulation on Electrical standards and I 
am an A class licenced Electrician.

Here we have a MEN (Main Earth Neutral) connection at the switchboard. 
Power circuit are also RCD protected

with a 30mA trip when the 240v single phase neutral current does not 
match the active (red/brown)current.

Neutral (black) is designed to carry load current in single phase 
appliances and out of balance current in 3 phase appliance's like a

eg; large building HWS system, where if i2 of 3 star connected, 3 
elements (1 per phase ) open circuit, there is still a return path for 
the last

  element. Here L1, L2 & L3 are 120 deg apart providing 440v between L1 
and L2 and L3, and 240v to neutral for any Lx.


There you have a centre tapped (neutral point) transformer supply with 
L1, L2 180 deg apart on each end phase, giving twice the phase to 
neutral voltage.

Here neutral is never connected to chassis on an appliance, and the 
appliance when metal chassis, is mandatory connected with a dedicated

  ground/earth green/yellow wire, that is designed to only carry fault 
current and never operational current. If you connect a neutral to the 
chassis,

and the earth wire return fails, or there is no earth for whatever bad 
reason, then you have full active voltage on the chassis waiting

  to use you as a conductor to get back to ground/neutral potential. 
There if you have a 220v appliance on L1/L2, you should also be

  using a earth wire , not neutral to connect the chassis. It seems like 
some American homes are not wired properly providing earth

wiring to all outlets to get it right, getting consumers to use neutral 
instead. This is riskier on 110v gear than 220v (which contain current 
to L1 & L2), as the chassis is

  in the return path already. Any volt drop between there and the swbrd 
ground connection will be seen on the chassis.

When the neutral breaks/opens you get the full effect of the electrical 
shock. All appliances here, as well as the wall outlet must be switched 
in the active.


At least you should install a sw/brd RCD (residual current device ) aka 
ELCB to trip the active, if you do get

on the end of a live chassis.

An ELCB or RCD induction core uses the active/neutral emf that should 
cancel each other out, to trip the active if there

is a slight 30mA induced imbalance to then save lives as someone 
touching the chassis will trip it superfast before an electric shock is 
even felt usually.

They are compulsory here on all power circuits. Every install has 
paperwork submitted and inspected by the regulation authority.


vk4tux