| Ben Miller wrote:
|>> I stand by my statement because I believe that inability to safely wire a
|>> multi wire branch circuit indicates a lack of understanding of basic
|>> electrical principals needed for the competent installation of electrical
|> I agree. Unfortunately, homeowners don't know what they don't understand!
|> I recently did some work at my house adding and rearranging circuits, and
|> found a couple of shared neutrals in unexpected places. The end result is
|> correct due to a lot of tracing and verifying, but I wonder what would have
|> happened if someone without that knowledge had done it. If the circuits are
|> lightly loaded there might be no problem for a long time, until a new load
|> is plugged in.
|> Ben Miller
| My position is that it is not feasible to idiot proof the world. Anyone
| who engages in work involving something that can kill and does so
| without a full understanding of the necessary physical principles and
| safety precautions is a Darwin award candidate.
| The logical extension of the no multiwire branch circuit position is
| that there should never be two separate circuits in any box, all device
| connections should be by pigtail, neutral and grounding connections
| should be made up with irreversible crimps, the main breaker for every
| home should be located in the meter enclosure and shunt tripped open by
| anyone opening the homes lighting and appliance panel cover, and so on.
| It is not the job of government to protect people from themselves.
| Any attempt to write idiot proof building codes inevitably imposes
| burdens on the rest of us that would be a totally unwarranted intrusion
| into our lives.
IMHO, your position on this is absurd.
I'm opposed to having multiwire branch circuits in my house, and in most
other areas I influence decisions for, based on the principle that if there
is a single wire open failure, it should cause the circuit to stop working
for reasons of safety. This is not about "not understanding" it. This is
in fact about understanding the reality of a work in which things can fail
despite our best efforts. But practice is to assume that some unexpected
failure may take place, and to design to minimize the impact of failures,
with special emphasis on those that can result in damage beyond what will
fail, especially if this could involve injury or death to animals or people.
If there is no need for a 3-wire circuit, why have one? To save a few
dollars on wire cost?
I'm not proposing to eliminate multiwire circuits from the code for the
sake of preventing others from the risks I see in it. But I would support
such a code change as a means to force appliance manufacturers that now
use a 3-wire circuit to make them work on a 2-wire circuit. If they were
to make versions that worked on 2-wire circuits with no code change to get
that to happen, then I would see no need to support any such code change.
My objective is only to have the choice to make all my circuits be 2-wire
only to the maximum extent possible. And yes, I am indeed looking for a
circuit that can sense a radical imbalance in voltage between phases on a
single phase service and shunt trip the main off in that case. Actually,
simply independently checking for out of range voltage on both phases may
be all I need.
Europeans surely know there is no fundamental need for things like clothes
dryers and electric stoves to have both 120 and 240 volts. They can run
them from 240 volts alone. Certain sub-circuits in these appliances that
in American models would use 120 volts could be made to use 240 volts as
is already done in Europe. They can be made to work safely on line-to-line
and thus work safely in both locations, even if the supply is L-N as it
would be in Europe. The tumbler motor in the dryer can be rewrired to run
2 windings in series instead of parallel. Electronics running on lower DC
voltages can use switch mode power supplies that can select the voltage or
be autoranging. Lights can be powered from the DC power (and will even
be more reliable as a side effect of the thicker low voltage filament).
I do agree that idiot proofing the building codes is a misdirection. But
to the extent that more restrictive codes in the direction of being safer
results in the necessary materials, procedures, equipment, and appliances
that are compatible with the safer methods being more readily available at
a lower cost, then I do see a general benefit from such restrictions. If
safe practices are done by only 1% then the market is to small for things
that are needed for those safe practices. But if we can make such safe
practices be carried out by a much larger percentage of the market, such
as 95%, then these things will be there for those of us that act safe not
to comply with code, but to actually be safe.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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