Date: Fri, 30 Dec 2011 23:12:43 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: (F) The importance of a good ground (LVC)-an important home
wiring lesson here!
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For any home equipment the case or outside ground is for safety only. Unlike
a vehicle the case being grounded is never required for operation.
In your home there are two very important grounding type conductors. The
green, sometimes un-insulated, or third prong conductor is known as the
grounding conductor. This is a safety ground only and shall not be part of a
normal current carrying circuit. The other is known as the "neutral". It is
usually white although in some types of circuits could be gray. This also
referred to a "grounded" conductor. At the service entrance or main panel
for most of the branch circuits the grounded, (neutral), and grounding,
(green or bare) are connected together. Here, with the proper connection to
the service ground rod is the only place these conductors shall be tied
together. Why? Because if the grounding conductors carry normal currents,
than there will be a voltage drop across that conductor. So now if you turn
on the sink faucet and touch that metal part of the wall switch cover or
screw that voltage drop (potential) will now want to travel through you
through the water pipes. As little as 70 mA across the heart and you may be
a goner.
Now let's go a little bit further. Many tools and appliances are known as
"double insulated". These eliminate the risk. Now for 3 wire tools the
ground is the safety. As part of the plan the switch on the tool has to
disconnect the "hot" or ungrounded conductor. As such when we make extension
cords or boxes or do our own house wiring the order of the black and white
wire does matter. Light sockets shall always have the neutral, white,
grounded conductor on the outer shell, hot or black for the center terminal,
and this is the leg the switch must be on. This is why most 2 prong
appliances have those polarized plugs that only fit one way.
So now find how that board is really designed to work and if that is a case
or an equipment ground and what else is wrong.
And that repairman is not as good as he should be.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Evan Mac Donald
Sent: Friday, December 30, 2011 4:07 PM
To: vanagon@GERRY.VANAGON.COM
Subject: (F) The importance of a good ground (LVC)
Earlier this winter, my home's furnace started acting up. I live in
Michigan, so that is a big deal at this time of year. I took my trusty
mutlimeter down to the unco-operative unit, and could not figure out what
was wrong. The pieces all tested out good, but would not work as an
assembly. Thinking it was beyond my knowledge base, we called in an expert.
He came down, looked, poked, prodded, and generally reccommended that we
look at replacing it. The repairs would be at least $400, and possibly as
much as $900.
Hmm. Time to think. I tried some simple fixes, but it really didn't seem to
make much difference. Same symptoms.
Then, one time I was down at the furnace, and held the brain out, tight
against its mount screws. Perfect function! I pulled the brain off, and
removed the cover, and found the mounting screws had vibrated thier way
through the solder that provided the ground to the frame of the furnace.
Even with the screws fully tightened, the ground was inconsistant.
I added an internal star washer, to take up some of the space, and cut into
the remaining solder. No issues since.
Two morals here -
Don't always trust a shop
It's the ground, stupid!
I should have seen that from the start....
Evan Mac Donald
"...in the absence of facts, myth rushes in, the kudzu of history."
-Stacy Schiff
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