On Tue, 21 Mar 2017 17:41:37 -0400, wrote:

`On Tue, 21 Mar 2017 17:24:54 -0400, wrote:

On Tue, 21 Mar 2017 09:14:32 -0700 (PDT), Tom Horne
wrote:

John

Many electric stoves were built, tested and listed by a recognized electrical testing laboratory, sold, and installed with connection blocks which were listed for both copper and aluminum conductors. The reason that the lugs are seldom used for connections of cables is the requirements for ease of servicing and cleaning in many residential codes which in turn dictate the use of cord and plug connections for kitchen ranges. In those areas where such residential codes are not adopted it is very common to see the cable connected directly to the range. With built in counter cook tops and ovens it is rare to see cord and plug connections used because of the increased cost of the additional parts and the additional labor that would be required for installation. As long as the connections are listed and or labeled for both Copper & Aluminum conductors there is no issue.


Built in and "stand alone" are totally different - a built-in doesn't
get moved
One of the factors which led to a lot of direct connection of Aluminum conductors to ranges was an exception in prior editions of the National Electric Code (NEC) in the USA which permitted the range's non current carrying conductive parts; such as the frame and metal case; to be bonded to the neutral of the supply circuit in lieu of requiring a separate equipment grounding conductor provided that the circuit originated in the Service Equipment. Since the neutral would only carry a rather small current during normal operation it was thought that the voltage drop would be low enough to avoid any hazardous difference of potential between the range and adjacent grounded surfaces such as refrigerators, metal sinks, other electrical appliances, and so forth. This exception may have originated during world war two as a materials conservation measure. Experience with it showed that although problems were quite rare any high resistance connection or open in the neutral to the Ranges
and
Clothes Driers installed under this exception created an extremely dangerous condition. As a result the exception now applies only to extensions of the original circuits and the installation of replacement appliances. Thousands of these installations will be around for decades.
Here in Ontario "range plugs" and "drier plugs" have been required for
at least 45 years.It is in my 1969 copy of the ontario electrical code
in the 1969 ontario supplement section 26 subsection 106.This became a
CODE REQUIREMENT in 1969 in Ontario. I am not sure if it became a code
requirement Canada wide at that time or not. ( I remember quite a few
details frim that time period as I worked with/for my Dad who was an
electrician in Ontario during those years, before starting my
apprenticeship as an auto mechanic)- and I have both 1966 and 1969
code books, all these years later - - - This is about the same time
aluminum wiring became popular and problems with aa-1350 wire started
to surface. Requiring a plug-in "cord connected" installation reduced
problems caused by flexing 1350 aluminaum conductors.

I bet those range and dryer plugs were 3 prong on 1969. It was 1996
when the NEC finally decided the war was over and eliminated using the
neutral as the ground.

You are correct. I believe Ontario started requiring 4 wire plugs in
the early '90s but I'm not sure, as I was out of the electrical bus by
that time and my Dad had retired. by 1990.
It was not actually because of any particular body count, it was just
to standardize grounding practices.
The ironic thing was, if these were wired with Romex, it usually
included a ground along with the 3 insulated conductors since 3 wire
without ground was not really very common. The ONLY 2 wire w/g that
was allowed was SE cable and only if it was coming from the main panel
with the main bonding jumper (no subs)
The typical installation was the white neutral going to the grounded
terminal on the receptacle and the grounding conductor went to the box
so conversion to the 4 conductor plug is trivial. Some idiots just cut
the ground off.
Correct - virtually all stove and drier cable was 3 wire plus ground
- although there WAS some 2 wire plus ground used since there was no
neutral required on a strictly 240 volt appliance. It was the 120 volt
clocks and lights that screwed things up, requiring a neutral.
European 240 volt appliances did not require the neutral because the
controls ran off a transformer connected to the 240 volt power.