Our safety regulators have insisted that power cord safety ground/earth go
first to the metal chassis, with rare exceptions. Exception, the majority of
chassis is plastic, with internal metal structures to tie it all together.
Only the screw heads are exposed and tied to some of the internal metal chassis.
A complex system of wires, washers, terminals, etc. were needed to ensure it
was all one complex earth grounded structure.
I AM NOT a safety engineer, but I do know a few !
- Bill
On Monday, September 23, 2019, 07:42:11 PM EDT, Pete Perkins
<[email protected]> wrote:
This is a great discussion. It took some work to get most of
the world to use a solid, direct earth/ground connection in cabinets and
equipment. CSA published detailed connection diagrams and pushed direct
connection into many product standards with good results. The struggle has
been since the modularization of components and units has come into play. This
raises questions as to how to interconnect everything together in a way that
preserves the integrity of the earthing/grounding connection when it is a
principle safeguard against electric shock. As an OF (= Old Fellow, in polite
company) I prefer that the earth/ground wire be tied to the mechanical
structure of the cabinet or equipment first then carried to the distribution
components. It is very difficult to destroy the integrity of this earthing
first philosophy. There are many scenarios where the quick install/quick
connect terminal block can be disconnected from the earthed rail and leave the
cabinet/equipment without the needed earthing/grounding connection. Let’s keep
the focus on providing the highest integrity protection scheme in place (and
common practice).
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 1067
Albany, Ore 97321-0413
503/452-1201
IEEE Life Fellow
[email protected]
Entropy ain’t what it used to be
From: John Woodgate <[email protected]>
Sent: Monday, September 23, 2019 4:19 AM
To: [email protected]
Subject: Re: [PSES] Grounding of metal cabinet
The question is how the cabinet is earthed if the PE wire goes to a terminal
block. If a wire comes out of the terminal block to a stud on the cabinet,
that is less reliable than a solid connection. I suggest you take the advice.
It doesn't apply if the 'terminal block' is not an insulating block with metal
inserts but a metal block firmly attached to the cabinet.
Best wishesJohn Woodgate OOO-Own Opinions OnlyJ M Woodgate and Associates
www.woodjohn.ukRayleigh, Essex UK
On 2019-09-23 11:33, Amund Westin wrote:
A flexible 1-phase AC cable is entering a metal cabinet and the PE-wire is
directly connected to an Earth terminal block (green/yellow).
Some years ago, a safety engineer told me that the earth wire should first be
connected to a ground stud inside the cabinet via a lug terminal climp and
fastened with a nut. From the stud, a green/yellow wire should connect to the
Earth terminal block.
I thought it’s OK to go directly to the Earth terminal block, right? …
BR
Amund Westin
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