Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[SteveRF]

Charles Sullivan,
Well, you almost have it straight.
Power goes off, relay "opens", power bumps
back on and relay closes and causes a ground
fault from neutral to earth ground.  This ver
minor fault causes a Gnd/Neu sensing GFI to
break thus leaving my pump safe until I
manually reset.  Keep in mind that this mod
does not in any way involve rewiring
anything.  I constructed a simple 3-wire plug
in module, protected in an approved inclosure
which simply plugs into any GFI protected
circuit receptacle.  In my case, it was the
receptacle serving the pump motor.  Bottom
line is that this method is very safe in that
the tripping current differential is only
about 4-7ma and can be plugged into the
existing protected circuit.  If one has the
ability to wire receptacles correctly,
understand Hot, Neutral, Ground and white to
bright and black to brass...then it is safe
and may very well save my pump from starting
a fire.
SteveRF

[roger1818]

SteveRF:  It may be “safe” when used in a
controlled environment, but I doubt if it
would receive CSA or UL approval since you
are relying on the GFI outlet to be wired
correctly.  Also, I think GFI outlets are
designed to only be tripped occasionally.
The increase in number of trips may cause
it to fail prematurely.  I would certainly
test the GFI after each power failure.

I am curious why you decided to use this
approach rather than having the relay
interrupt the circuit?

[roger1818]

I just re-read your description and if the
relay is closed when the power is on then
you are operating with a continuous ground
fault and if a real ground fault were to
occur, the GFI may not trip.  Am I missing
something?

[Bill H]

SteveRF:
Have to agree that this is not a good plan.
Besides the other potential problems below,
if the GFI does not work properly (which can
happen), you have purposely created a ground
fault. In this case, add a defribrillator to
your tool kit. Suggest you return to the
relay idea (or something like it).

[Charles Sullivan]

The fact remains that you are using the GFI
in an unapproved manner which most likely
violates code.  And if anything "goes wrong"
which can in any way be attributed to your
scheme, your insurance company will void your
homeowner policy and deny coverage.

[SteveRF]

WOW..So many opinions...Thats good.  If I
have better options then I may change it.

Roger H.  It was my error in description:  I
meant the relay was pulled in or energized
during operation thus eliminating the Neutral
to Ground fault.  During a power failure the
fault causing contacts are closed.  I agree
with you about testing the GFI device after
each power failure: That is exactly what my
device will do.. same as pushing the "test"
button on the GFI.

Bill H.  I understand your thinking but that
is the purpose of the GFI device, to detect
an imbalance of as little as 7ma current flow
between the Hot, Neutral/Ground or the same
between Neutral and Ground. Mine tripped at
about 4ma.  Basically, it is doing the same
thing an overheated pump might do but way
before burning up the pump or my home.

Another saving grace here is that this is an
isolated circuit, running from the breaker
panel outside directly to a small pumphouse
and terminating in a protected GFI device.

Charles, As far as using in an unapproved
manner, you may be correct but I am
essentially doing the same as pressing the
"test" button on the GFI device and causing a
momentary short.  Except, the test button
shorts the Hot and Neutral through a 15k
resistor and I am using the neutral and
Ground sensing circuit, which is much safer.

Bill, I will order the Defib today..smile...

and now...
I actually do appreciate all the thoughts,
ideas and warnings... If I see one single
glitch I will unplug and report my device as
a failure.

Regards,
SteveRF

[dave w]

Hey Steve!
I'm not going to weigh in on the propriety
of using the GFI to disable the pump, but
you said something that makes me think I do
not understand how a GFI works.

"Except, the test button  shorts the Hot and
Neutral through a 15k  resistor "

I thought a GFI tripped if there was a
differential between the current going out
the hot and current back through the
neutral. If not equal, the difference is
getting to ground through something or
someone, creating the trip.

If your GFI test switch shorts hot to
neutral through a 15K resistor, then the GFI
must also be looking for "small" currents
traveling the normal path?

[SteveRF]

Dave W.,
The GFI that I have creates a current
differential between the HOT and Neutral
through a 15K resistor when pressing the TEST
button to simulate exactly what you said, a
momentary differece in current flow in the
Hot and Neutral. ( I should not have used the
word "short") When this condition is detected
then a trip is initiated...So you are
absolutely correct !  Most GFI's also sense a
difference between Neutral and Ground and
trip if more than (I think..7ma).. and you
are correct it can detect a very small
differential current flow.  The one I am
using will actually trip between 2-4ma.  I
hear some motors will actually cause GFI's to
trip when starting and can cause lots of
heartaches when using GFI's ... thank
goodness mine does not do that. I believe I
took the safe approach by using a Neutral to
Ground trip simulation.  I read more every
day and I have also noted that most experts
suggest that you test often.  I will
definitely do that !  I just decided that I
did not want to rely on the 12amp relay
carrying the pump load and decided to use it
to create a safe momentary fault condition
that would trip the GFI.
Considering that we use GFI's to protect our
lives, using it this way to protect a pump
made sense to me.

Thanks for your input and thoughts...
Everytime someone mentions something it makes
be check and double check this setup.
Obviously, I was going to use a X10 appliance
module at first but decided against that
route after some suggestions from the forum.
Many Thanks !
SteveRF

[steven r]

How has this arrangement worked for you?