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Strange, Possibly GFCI, Failure ??

J

Jim Thompson

Jan 1, 1970
0
Scenario:

Intermatic (motor-driven clock) timer fed from GFCI into 12VAC
lawn-lighting transformer

When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

Manually "pushing" timer thru turn-on point, lights come on just fine,
with transformer "thumping" from surge, output voltage is correct.

Timer runs just fine on another outlet

Is it conceivable that GFCI is resistive unless loaded heavily?

How would you test?

...Jim Thompson
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Jim Thompson
Is it conceivable that GFCI is resistive unless loaded heavily?

Maybe the contacts don't 'wet' on low load current.
How would you test?

Put a lamp in parallel with the transformer primary.
 
S

Spehro Pefhany

Jan 1, 1970
0
Scenario:

Intermatic (motor-driven clock) timer fed from GFCI into 12VAC
lawn-lighting transformer

When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

Manually "pushing" timer thru turn-on point, lights come on just fine,
with transformer "thumping" from surge, output voltage is correct.

Timer runs just fine on another outlet

Is it conceivable that GFCI is resistive unless loaded heavily?

I don't think so. They are pretty much wire and contacts all the way
through- and I don't think the sensing coil adds enough inductance to
bother things with a single turn primary. Maybe its just very marginal
and perhaps is on the other half of the 120. Have you measured the
voltage at the outlets?
How would you test?

...Jim Thompson

Our fancy Loran one got its timer fouled up (I think the #$(*#$
earwigs got into it) so I put an inexpensive Noma electronic timer
ahead of it, and it's been working fine since, and switching some high
voltage exterior lights at the same time. It uses a dirt-cheap 5A
relay inside, so it will eventually fail, even at 2 operations per
day, but that's no big deal.


Best regards,
Spehro Pefhany
 
J

Joerg

Jan 1, 1970
0
Hello Jim,
When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

That's odd. As Spehro said GFCI are pretty "digital" devices. Either the
internal relay is on or off. If half on it would go bzzzzt.

Could it be that the timer is in a slightly different mechanical
position between the two outlets? If it's one of those black hardware
store editions with a lid over them they have plastic gears. Our
experience so far: After a few years they make faint but weird grinding
noises, after another year they work only when Mars and Venus are in
perfect constellation, a few months later they are toastissimo.

Listen to the timer closely. If the gear noises are a very faint and
regular hash it may be ok. If it sounds like a pulsating grind it's on
the verge of seizing.

Regards, Joerg
 
B

Bob Noble

Jan 1, 1970
0
Sure it is conceivable, but not likely.
More likely that a wire feeding the system has a bad connection that is
sucking all your voltage when you increase the current draw, such as would
happen when the motor is pressured to turn the switch on.
My experience with GFI's is they either work or they don't.
Many times I find that people don't tighten the wires to them very well.
But even then, they either work or they don't.
 
J

James T. White

Jan 1, 1970
0
Jim Thompson said:
Scenario:

Intermatic (motor-driven clock) timer fed from GFCI into 12VAC
lawn-lighting transformer

When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

Manually "pushing" timer thru turn-on point, lights come on just fine,
with transformer "thumping" from surge, output voltage is correct.

Timer runs just fine on another outlet

Is it conceivable that GFCI is resistive unless loaded heavily?

How would you test?

Jim,

First, use your DVM to confirm your suspicion that the voltage drops at the
motor when the load goes up just before it trips on. If it doesn't, then the
timer has a problem as others have suggested.

If it does, then backtrack to the GFCI and check the voltage from the output
screw to neutral to see if it is there. If not, then you've got a loose wire at
the output of the GFCI or somewhere downstream toward the timer.

If you see the voltage drop at the output screw of the GFCI, then assuming you
are using an outlet GFCI, check from the input screw to neutral to see if the
voltage drop is also at the input. If it is there too, then your problem is at
the input connection to the GFCI or upstream toward the breaker panel. If you
are using a breaker style GFCI or the voltage drop isn't at both sides of the
outlet style GFCI, then the GFCI is likely at fault.

HTH
 
Jim said:
Scenario:

Intermatic (motor-driven clock) timer fed from GFCI into 12VAC
lawn-lighting transformer

When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

Manually "pushing" timer thru turn-on point, lights come on just fine,
with transformer "thumping" from surge, output voltage is correct.

Timer runs just fine on another outlet

Is it conceivable that GFCI is resistive unless loaded heavily?

How would you test?

Wait until it's stalled and connect a jumper (or two, as needed) across
the GFCI.
(If you don't like the taste of electric juice, wear rubber gloves.)
 
R

RoyalHeart

Jan 1, 1970
0
Jim said:
Scenario:

Intermatic (motor-driven clock) timer fed from GFCI into 12VAC
lawn-lighting transformer

When timer reaches turn-on point it appears that voltage drops enough
that timer stops turning, so lights don't turn on.

Manually "pushing" timer thru turn-on point, lights come on just fine,
with transformer "thumping" from surge, output voltage is correct.

Timer runs just fine on another outlet

Is it conceivable that GFCI is resistive unless loaded heavily?

How would you test?

...Jim Thompson


Jim, just for comparison, I have a LV landscape lighting system as well.
It also uses an Intermatic (Motor-driven) timer/transformer pack. The
pack is plugged into a GFCI outlet, via an nextesion cord, on a circuit
dedicated to yard outlets.

The timer/transformer pack is the only utilization device on that brach
circuit, and the timer operates just fine.

From this, it is possible that the timer may be defective, or that a
bad connection exists at the GFCI contacts or screw terminals, as others
have suggested.

Hope this helps.

Thomas
 
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