GFCI circuit for pool lights trip when turned OFF ???

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ritelec

ritelec

Senior Member
Location
Jersey
cadpoint said:
If you took off all the devices, use a meggar on some wires.
Click to expand...

Some wires in the circuit are existing. Some are new.
I don't have a megger, but if I did or can get one, If the wires are fine, Would not the inductive kick back cause the breaker to trip any way?

If there is a damaged wire, would not, should not it trip with no loads or the A lamp installed?

gar.. sounds good, but I don't think they want additional lights coming on with the in the pool pool lights. Especially, A light in the panel... :- )

Thank you for the calculator links eHunter.... why did you pick 2.7k ??? just wondering.
And I can see the calculations.......but how or why did in the calculation of 5 w's jump to 25 w for the suggested resistor?

Rich
 
E

eHunter

Senior Member
Location
North Texas & Georgia
ritelec said:
Some wires in the circuit are existing. Some are new.
I don't have a megger, but if I did or can get one, If the wires are fine, Would not the inductive kick back cause the breaker to trip any way?

If there is a damaged wire, would not, should not it trip with no loads or the A lamp installed?

gar.. sounds good, but I don't think they want additional lights coming on with the in the pool pool lights. Especially, A light in the panel... :- )

Thank you for the calculator links eHunter.... why did you pick 2.7k ??? just wondering.
And I can see the calculations.......but how or why did in the calculation of 5 w's jump to 25 w for the suggested resistor?

Rich
Click to expand...

You are welcome.

I picked 2.7K because it it a common resistor size that would have a relatively low current draw and produce minimal heat.
Wherever you place/mount the resistor, you will need to be cognizant that the resistor will get hot when energized.
However, I did have difficulty locating a 2.7K 25W unit, but I did find a close value of 3.0K that is readily available. See Below...

The power(W) handling capacity of a resistor should always be at least 2x the calculated power dissipation for longevity.
Your situation has the added element of the transformer inductive kick that is of an undetrmined peak voltage, current and duration, so a SWAG from exprience ~5x the calculated power dissipation was used to be safe and assure the long term life of the resistor.

Voltage (E) = 120 Volts
Current (I) = 0.04 Amps
Resistance (R) = 3000 Ohm
Power (P) = 4.8 Watts

Voltage (E) of 120 known
Standard Resistance (R) of 3.0K Ohm is selected
I = E/R = 120/3000 = 0.04
P = E*I = 120 * 0.04 = 4.8

Digikey Link for 3.0K 25W wirewound resistor:
http://www.digikey.com/product-detail/en/TMC0253K000FE02/TMC25-3.0K-ND/269955

Digikey 2.5K-3.5K 25W search:
http://www.digikey.com/scripts/dkse...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
 
ritelec

ritelec

Senior Member
Location
Jersey
Thank you for clarifying, the links and the education.
MUCH appreciated !!!

I'll let you know how it turns out.
I'm also in touch with the pool installer that supplied all the equipment for this install, so I'll let you know the lighting manufactures thoughts on this.


Interesting stuff.
Thanks again,
Rich
 
ritelec

ritelec

Senior Member
Location
Jersey
Varistor varistor everywhere..lol

Varistor varistor everywhere..lol

Hi all.

I finally installed them.
Put one at the most problematic xformer (i would think). Held better but still tripped on off.
Installed two more. one at each of the other two transformers..
All good.
But now the gfci breaker is tripping when turning the lights on.

I put another one in the feed of the circuit. It held better but still trips.
I put one in each of the travelers. held better but still tripped.

I put the light bulb in again, all worked fine.

Please bare with me.

The switching for these lights (3 xformers) are switched from three points.
A 3 way in the house (power to and two travelers) A 3 way outside (return and two travelers).
These travelers meet in a control panel. I had a previous post which it was suggested I could use a 4 pole contactor as a 4 way switch operated from a relay in that panel....which I did.

So..

After the bulb held.
I removed the added varistors from the supply and the travelers.

I removed the bulb and got the trip on the "on".

Sometimes on off on once or twice, some times five or fifteen times.....

3 ways would be in any position and it would trip......

But I've somewhat discovered the switches hold when cycled most of the time if not all of the time.

Most trips would occur with the contactor being switched on and off and on.

If I take a screw driver and manually push the contactor in and out, the circuit holds. I push it in and out 50 times and it holds.

There's is a relay controlling that contactors coil. If I energize the coil to close the contactor (not sure right now if it also does
it with coil is deenergized...pretty sure its only when energized and pulls in), it trips. Sometimes after one time (and breaker may sometimes trip when
resetting) some times after 5 or 10 times (and breaker may sometimes trip when resetting).

The gfci circuit (travelers) goes threw the contactor. The control for the relay and coil of the contactor are a different circuit and different neutral.

As stated, I can manually push the contactor on and off all day with no trip. When using the coil to pull it in it trips.....maybe after a few cycles but it trips.

Any thoughts???

Thank you
 
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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
130806-2326 EDT

Did you put an MOV directly across the coil of the contactor? Try a capacitor, 1.0 mfd in series with a 10 ohms resistor, in parallel with the MOV and coil at the contactor coil.

Your description seems to imply the contactor coil is a major problem.

Personally I would rip out the whole mess and use a GE RR series relay or relays. This would be a much simpler system to troubleshoot for transients.

I would never use 3-way or 4-way switching in the first place. Associated with one RR relay I can have as many switch points as I want. Any switch has up for on and down for off. I control my main kitchen lights from 5 locations with simple 35 V DC 3 wire control signals. The garage from 3 locations, breezeway from 3, and the side hall to the breezeway from 3, etc.

The coils in the RR relay will not generate any significant transients.

.
 
ritelec

ritelec

Senior Member
Location
Jersey
Thanks gar

Yes. I was going varistor crazy so I tryed one across the
coil. It still tripped the circuit when energized so I removed
it.
As mentioned. The GFCI lighting circuit and control circuit
are different circuits with seperated neutrals (the circs are
also on different phases if that makes a difference)
Why would the load of the non GFCI coil circuit be picked
up from the GFCI lighting circuit?
I will look I to the suggestion of the RR and what it's about
 
G

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
130807-0842 EDT

ritelec:

I think some bench testing of individual items in a simple circuit would be useful.

The only GFCI that I have done much experimenting with is the Leviton 7899. I found this to be relatively immune to the transients I could generate. I could not cause false trips of the 7899 with my transient generation when on the input side of the 7899, but I could rarely cause trips when the transient generator was on the output side of the 7899.

I produced the best transients with an AB Bul. 709 Size 2 catalog 709COD starter. This is a 50 year old model. Not a terribly large physical coil, 120 V. My other good generator is an 8 ft Slimline with magnetic ballast and no input RFI filter. The transient generated is random in character because of the uncontrolled turn off point. Rapidly cycling the generator produces some good transients in a short time. Wiggling a two prong plug in an outlet is a useful switch.

If you are not using an 7899 in the application, then I suggest you try one for comparison. On the bench have your test circuit consist of the GFCI under test provided with constant 120 V input and possibly 6 ft of #18 from an outlet to the GFCI input. Wire another outlet to the output terminals of the GFCI and bolt this outlet down. This outlet will become your rapid switch for the load type being tested. Separately test the transformer or power supply (whatever it is), and the contactor. See if this experiment will cause tripping.

I went looking in old threads for where I described my test on the Leviton 7899, but I did not find the one I was looking for. Two that I did find were:

See the comments by ELA and me at:
http://forums.mikeholt.com/showthread.php?t=119387&page=2&highlight=gfci+leviton+transient+load

Potential problem with long trace to SCR gate:
http://forums.mikeholt.com/showthread.php?t=132154&highlight=gfci+leviton+transient+load

The internal construction of the Leviton 7899 can be seen on my website at:
http://beta-a2.com/GFCI.html

.
 
P

Phil Corso

Senior Member
Location
Boca Raton, Fl, USA
Ritelec...

Try the following:

1) Connect one of the GFI-fitted receptacles drectly to a source CB using a 3-wire extension cord!

2) Plug in one of the pool-light xfrmr's and energize it from the source CB!

3) If above is OK, then connect 2nd pool-light xfmr to same GFI-fitted receptical!

4) If above is OK, then connect 3rd pool-light xfmr to same GFI-fitted receptical!

Let us know results!

Regards, Phil Corso

ps: what is approx length of your 3-way control circuit?
 
ritelec

ritelec

Senior Member
Location
Jersey
Thanks guys......

I'll look into maybe installing the gfi receptacle to feed the circuit.
Right now it's on a murray gfci breaker.
The intermatic panel also accepts seimens, square d (hom) and one other man. I can't remember.

As mentioned.....
It was tripping when turning the lights off from either 3 way switch or the 4 pole contactor. Never tripped when turning on.

I installed the mov's at each transformer, it doesn't trip when turning off at any location, doesn't trip when turning on from the two 3 way toggle
switches, doesn't trip if I push the contactor in............But Trips if I energize the contactor.

thank you
Rich
 
P

Phil Corso

Senior Member
Location
Boca Raton, Fl, USA
Little Bill...

Thanks for clarity! Reduces problem complexity somewhat! But, still interested in distance between source and xfrmr receptacle location(s)?

Phil
 
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Phil Corso

Senior Member
Location
Boca Raton, Fl, USA
Ritelec...

I believe the phenomenon leading to false-tripping of the GFI-fitted CB is related to Ferroresonance.

A relatively simple test can prove or disprove it! Observe the voltage on the secondary of the pool-light xfmr with a scope! I suggest first with the lamp ckt disconnected!

Phil
 
S

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Little Bill said:
That right there is your problem. 3-ways and GFCIs don't work well when in different states, especially in north eastern states!:lol:

Also a huge voltage drop when ran that far!:angel:
Click to expand...

Besides that, conductors are run that far to us Northerners even the misplaced ones.:slaphead: Sorry, I just couldn't resist.
 
G

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
130808-1452 EDT

Phil Corso:

So you are referencing a simple LRC resonant circuit. How does it being resonant present a problem vs an LR circuit?

Suppose you have an LRC series circuit with R internal to L, and we view a pair of terminals that are the capacitor in parallel with a series combination of L and R. Apply a voltage to these two terminals, and fully charge the inductor with energy (let it reach steady state). The capacitor has a charge such that its voltage is +V volts, and the inductor has a current +V/R.

Open the switch that is supplying current to this circuit. The current to the inductor must instantaneously remain the same. Thus, no change at the instant the supply switch is opened because the capacitor is of the same voltage as was the source. Before and just after the energy source is removed the voltage across the inductor is 0 V, all the voltage drop is across the resistor.

Energy is being lost in the resistor and the size of the resistor will determine whether the capacitor voltage simply decays away, or there is a damped sine wave starting at the initial voltage across the capacitor. The peak voltage on the capacitor as the sine wave develops will depend upon the ability of the capacitor to store energy compared to the inductor. The smaller the capacitor with the inductor held constant the larger is the voltage across the capacitor. But this will never be greater than if the capacitor was not present. In fact a solution to large peak voltage generation is to make the capacitor larger.

I see no reason to modify the word resonant with ferro unless there there is some aspect of its hysteresis loop that is of importance.

.
 
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