weird power problem

[Bigglez]

It's probably a GFCI. It has the letters GFCI on it (in incredibly tiny lettering). The lighting is in both a bedroom (commandeered as my office) and a bathroom.

Greetings Philba,

Okay, that makes sense. A bathroom would require a
CGFI, the installation has one in the breaker panel.

DO NOT remove the CGFI, unless you upgrade the
outlets in the bathroom to include CGFI protection.

It seems to be invariant whether there is a load or not. I made sure all the lights were on and powered up the computer - the breaker tripped. I then reset the breaker, turned all the lights off and powered up the PC - the breaker tripped. The info from the breaker is pretty much what I posted earlier (Type HOM, Series 1, labeled as 20A).

Of the top of my head I would think the two
circuits are sharing a neutral and/or a ground.

The CGFI is looking for an unbalance in current
between the L and N of the downstream branch.
The most obvious error condition is that current
is flowing to ground due to a short or leakage.

If by chance your branch circuit has an open
neutral or ground it will trip the CGFI. As others
have explained the use of a split-phase 120V
branch might result in one side influencing the
other.

There's nothing wrong with experimenting by
substituting the offending breaker (for a non-
CGFI version).

Comments Welcome!

Peter

[jollyrgr]

I was thinking ARC FAULT as well, hence the bedroom comment. I put in a ceiling fan with light kit at my brother's house. He has these arc fault breakers installed. When we were doing the install he went to the basement and I talked to him on a walkie talkie until he got the right breaker. (Thus I did not know he had these.) We installed the fan.

First time testing the light kit didn't work right. But I had already hooked up the wall switches for both the fan and light kit. So I turned off the wall switches and pulled the fan down to the INSTALL hook position and checked the wiring. The closet light was on the same circuit and when I disconnected the HOT for both the fan and light kit nothing happened. When I disconnected the neutrals the closet light went out. Note, these were JUST on the same circuit and not running to the same wall switches. Possibly I touched the neutral bare wire when I was disconnecting it. Well get everything hooked back up and test again. Still no light. But with the light in the ON position I turned on the fan and the breaker pops! Hmmm. Check wiring, no problems. Have my brother reset breaker with both switches off. Turn on fan, works just fine. Turn off fan, turn on light, no light! Tap lightbulb closet light flickers. Hmmm again. Start to remove bulb and closet light goes out, breaker trips. Try lightbulb in work light on another circuit. Turns out the brand new lightbulb had a bad filament. Every time it "sparked" the ARC breaker was acting goofy. New bulb, no more tripped breaker.

My thought was there is a bad lightbulb somewhere in the ARC circuit. When the bulb "flickered" due to the surge draw from the computer starting up it tripped the breaker.

For grins, do you have a power strip with surge on the computer? How about trying something a bit different on this circuit, like something with a sparking (BRUSH) motor? Blenders, vacuums, drills, etc. will do nice. Do these on the "computers" circuit cause that breaker to trip? Maybe there is HASH getting back to the ARC breaker. If you have a UPS, can you see if that helps cut down the tripped breaker.

Here is an idea, is the breaker for the computer outlet on the same PHASE as the ARC breaker? Breakers 1 and 3 are on OPPOSITE phases (how you get 220V). Breakers 1 and 5 are on the same phase. If so, simply flip flop breakers around. But be careful! If you have more than one ARC breaker if you flip the computer room breaker so that it lands on the phase of another arc breaker, you'd only move the problem. My guess is that the electrician put multiple arc breakers side by side. It may take some creative shuffling to fix if this works.

[haklesup]

OK, not AFCI (the color of the button may be just a misconception as I said I wasn't sure)

Of the top of my head I would think the two
circuits are sharing a neutral and/or a ground.

I thought of this hence my comment about 3 wire cable and opposite phasing but in practice you have to connect both the hot and neutral to the GFCI in the breaker box making it virtually impossible to use anything on the another branch using the same neutral without tripping the breaker (I assume the electrician that put it in was happy with his work)

More and more it sounds like you may have a bad power supply on your PC. Well, if it were tripping the breaker on the same branch I might say it has a big surge. but you said it was an adjascent branch. Again, I suggest the easy experiment of changing phases for one of these branches.

ANother thought. If ground and neutral come together at a point before the breaker box, you could have odd behavior of GFCI. It would test normal with a circuit tester but some current could return to neutral through the ground conductor thereby off balancing the current in the GFCI. Again, how this would influence an adjascent branch, I would need a wiring diagram of your house to guess further.

I once heard a 4th hand story about a guy whose lights flickered when he turned his TV on and off. Turned out the TV was sitting on the lamp cord pinching it off and making it go open.

[Bigglez]

Of the top of my head I would think the two circuits are sharing a neutral and/or a ground.

I thought of this hence my comment about 3 wire cable and opposite phasing but in practice you have to connect both the hot and neutral to the GFCI in the breaker box making it virtually impossible to use anything on the another branch using the same neutral without tripping the breaker.....

Greetings hacklesup,

For the GFCI to operate it must measure the load
current in both the L and N wires, so the device has
four terminals. In the case of the breaker version
it has three terminals and a pig-tail wire. Either way
the neutral on the load side of a GFCI is dedicated.

If the OP has a wiring error or rework that was done
incorrectly, it is possible that neutral current on the
suspect circuit (powering the PC) is fed in to the
victim circuit (lights and bathroom outlets on the
GFCI protected circuit), causing the trip.

A highly reliable test (but somewhat hard to do)
would be to isolate the suspect and victim wires
at the panel (or sub panel), remove all light bulbs
and unplug all appliances, on those two branch
circuits and measure the resistance from conductor
to conductor.

My hunch is that a path will be found linking the
two branches in an illogical but practical way,
such as accidental or deliberate contact inside
a J-box.

Comments Welcome!

Peter

[Robert Reed]

A split circuit breaker is easy to identify. It will be housed in one enclosure and have two manual / trip levers on it. These levers are smaller than single circuit breakers.They also MUST trip together for a fault in either circuit. I don't understand how a panel mounted GFI breaker could work for a split circuit since the whole idea is only to measure one circuits differential current, that being the L & N leads. Most are set to trip at 5 ma differentilal regardless of load current, and which is exactly what their test button accomplishes - introduces differential. The only practical GFI for split circuit as I see it is outlet mounted only. So it seems you have a single circuit run with GFI protection in your panel.
We could beat this subject to death, but a simple test of an extension cord - computer to another circuit run's outlet or a quick swap of panel breakers ( without even removing from the panel) as has been mentioned, would at least eliminate the breaker question. Either problem found or continue from there.

[Bigglez]

They also MUST trip together for a fault in either circuit.

Greetings Robert,

Can you cite a reference for this claim? I was told that
240V (L1,L2) loads require the two handles to be locked
together, but replacement breakers with two independent
120V circuits do not require the handles locked (as they
will trip independently if either is overloaded).

Comments Welcome!

Peter

[Robert Reed]

Hello Peter
Not sure I understand your question as I thought it was clear as I stated. It really isn't a claim as it is local code as well as national in our area. In a split circuit, one circuit cannot be disabled manually or tripped electrically without out actually taking down both circuits and done strictly for safety reasons.
I am not a proffesional electrician so I do not keep up with code changes on a daily basis, but when confronted with a large job at hand, I do pick up a copy of the local code at our Dept. of Building. This usally occurs every 5 years for me. What I am referring to in the above was my last big project (wiring a new home I had built) about 8 yrs. ago. If something in reference to that has changed since then - it should not have- as it makes a lot of sense to do it in that manner.
I was a little hesitant to post this as I mentioned, we are beating this subject to death in ' what if's ' and we should be awaiting a replie as to Philba's latest findings before continuing further.

[Bigglez]

Greetings Robert,

Not sure I understand your question as I thought it was clear as I stated.

Well it may have been clear to everyone except me...

In a split circuit, one circuit cannot be disabled manually or tripped electrically without out actually taking down both circuits and done strictly for safety reasons.

I think my stumbling block is the nomenclature. To me
a 'split circuit' breaker is one with two circuits in a single unit,
designed to increase the capacity of an existing panel that
is full. The new breaker is one half the width of the two being
replaced. It has two handles, and controls two circuits.

On a second reading of your post I think you are describing
a "double pole" breaker with two locked handles and designed
to power a 240V load from L1, L2 and no neutral. OR, with
unlocked handles to power two separate 120V branch circuits.

Philba was confrunted by a GCFI breaker with a yellow
handle or reset button that others thought might be the
newer AFCI (Arc Fault Circuit Interrupter).

Correct?

I was a little hesitant to post this as I mentioned, we are beating this subject to death in ' what if's ' and we should be awaiting a replie as to Philba's latest findings before continuing further.

Agreed. Although we have hi-jacked the thread this is
an important topic. Every used home I've bought has the
legacy of previous owners or their hired help. I'm a
little surprised more homes don't go up in flames!

We inherited some dumb work from the previous owner,
including pairing two (unrelated) 120V branches to
power a 240V pool pump, insulating new wiring splices
with duct tape, an open neutral that burned through a
number 0000 cable in the meter raceway, strapping
N and G to get three prong outlets to work, etc. etc.

Comments Welcome!

Peter

[Robert Reed]

Hello Peter
All my 240 volt breakers are double pole and operate manually with a single handle. Physically they look identical to the 120volt breakers except that they are twice as wide. The"split circuit" breaker I was referring to carrys two runs that share a common neutral.The width is the same as a standard 120Volt breaker. Each hot line is fed fom opposing bus bars and the intended flow is from bus to bus and bypassing the common neutral if each run is carrying equal load. If not the the differential flows through neural and thereby maintains correct 120Volts to each circuit. With any combined load of 0 to 40 amps, the neutral current can never exceed 20 amps just as its max capacity was designed for. Maybe my terminology ("split circuit") is wrong here, but since thats what the local electricians refer to as being, I always called it the same. One of the circuits I installed in this fashion was at the advice of the plumber advising that the dishwasher and disposal be wired in that fashion,so that they would trip off together if trouble occurred in either (tied together waterwise). Seemed a little extreme but I guess a scenario could be contrived where it would be worthwhile.
As to previous home owners sloppy and hidden electrical work, it doesn't stop there. One of the commercial marinas where I did ship/shore radio work had the worst electrical system I ever saw in my life. It's pole wiring consisted of anything the owner could get his hands on such as romex for a hundred feet then crimped to # 18 machine wiring for 200 feet and after that God knows what, maybe even vaccuum cleaner cord. as to grounds - what grounds? a 2 ft. pole stuck in the earth at each dropdown.No continuous ground carried on the overhead pole run. In one area I was doing work, I calculated a 2 volt drop for every amp that was pulled off the line. Lots and lots of burned out refridgerator compressor motors on startups!.And this was a commecial installation. To this day, I don't know how he ever got away with it. I guess the moral is, be it residential or commercial - Let The Buyer Beware!

[Bigglez]

Greetings Robert,

All my 240 volt breakers are double pole and operate manually with a single handle. Physically they look identical to the 120volt breakers except that they are twice as wide. The"split circuit" breaker I was referring to carrys two runs that share a common neutral.The width is the same as a standard 120Volt breaker. Each hot line is fed fom opposing bus bars and the intended flow is from bus to bus and bypassing the common neutral if each run is carrying equal load....

An excellent description, thank you! I think I've sorted
out where I was going wrong. Here's a summary,
if there are no further questions we can give this
thread back to Philba.

Split-Breaker
Either a double pole breaker with one or two
handles, as you described, providing two circuits,
one on each line (L1, L2). Can be strapped to
have only one handle (240V service or "split
loads" described below. Or, operated without a
handle strap for two independent 120V loads.

-OR-
A replacement breaker with single body width
that has two sections and two handles, and
can have two 120V loads that are on the
same phase (L1 OR L2). Can't provide 240V.

Split-Circuit
A wiring scheme using three conductors plus
ground for a common Neutral and two lines
(L1, L2). Popular to save wire as "3W+G" wire
can be run.

Split-Receptacle
A normal 120V duplex with the strap
removed to provide two independent 120V
loads on two separate circuits, with a common
Neutral (N). Popular with Dishwasher and
Disposal hook ups in kitchens.

These are my words from two sources:
An NEC guide book by Ray Mullin, and
An on-line forum for Code questions run
by Mike Holt.

Comments Welcome!

Peter

[evahle]

Hi Robert! You know, you don't have to keep positioning yourself in this forum. We all know that you are a professional. You don't have to keep proving it. I have held an electrical license and knew some time ago that you knew what you were talking about. There is no since in responding to someone who needs to get the last word in and wants to argue. It sounds a lot like someone else that was kicked off the forum earlier.

In any case, everything you've said, I completely understand and agree with. Like you said, we hope some testing gets done before continuing this thread.

I will not respond to any argumentitive, disrepectful, quote from the book posts! I hope you do the same.

Thanks Robert.

evahle

[philba]

First, a comment on forum decorum. So far, this thread has been fine. Sure there was a mild disagreement but overall, it seemed to be ok to me.

Now, on to the original topic. I had to wait until today while my family was out of the house but I powered down the panel and switched the offending breaker with an adjacent non-GFI type. Thus, the GFCI circuit is on the other leg of the 240VAC service. I'm happy to report that the problem (er, symptom) went away. Also, the breaker I swapped into the old position has no problems (doesn't trip when I power up the offending PC). I tested this 10 times just to make sure.

Thanks for all the help!
Phil

[bodgy]

Just out of interest, I beleive what I call an RCD (Residual Current Detector) is what you call a GFCI.

That being so, the normal retail and wholseale ones for that matter trip at 15 - 20mA unbalance.

The rarer and more useful and expensive type trip at 10mA unbalance.

I find it strange that in the UK and here in Australia, with all the hoo ha about it being illegal for people to touch anything connected + 50vac, and that 10-15mA is enough to kill a person, that the lowere rated RCD's aren't the ones mandated to be available. Of course the 20mA ones work because they disconnect so fast, but still.......


Colin

[cdenk]

Flickering indicates a loose connection, and it could be dirty (damaged) contacts on the breaker. How old is the house, what type wiring does it have, and I'm thinking in the USA standard wiring. If any of the wires are aluminum (and this is a major safety issue!!!) preferably change them to copper, if not possible (money or tearing walls apart - but there have been ore than a few houses burndt to the ground) clean EVERY wire end, coat with the proper anti corrosion and reterminate. Follow all wires from breaker box, bare to ground (green screw), white is neutral (nickel plated screw)- gets grounded at only one point in house, black or red (brass screw) are hot. Only exception would be 3 or 4 way switch where white might be hot, but should have a wrap of black tape near each end, often overlooked. Many devices (outlets and switches) have push-in terminals, don't use them, wrap clockwise around screw and tighten securely, exception is where wire is inserted into a hole and screw tightened to clamp the wire.

1:Is it: Non-metallic (Romex) cable with 3 or 4 wires contanined in a plastic sheath. Check the ends of the cable (and there likely will be splices in other boxes) for corrosion and loose wire nuts.

2: Is it "Knob and tube" - (pre 1960's) individual wires are ran through the house, when parallel to the wood framing, a porcelin (sp) round insulator with a nail through the middle and wire wrapped around, and when going through the wood, a porcelin tube with the wire in the middle. Splices are made wherever in wall or ceiling by skinning insulation for an inch, wrapping branch wire around soldering and taping. My dad was a building inspector back then, and he required looking at the solder before, and after taping.

3: Conduit with wires inside, not common on houses, but usually require commercial/industrial. Wires can get skinned when pulling in, and may take awile to surface as a short or intemittent.

Safety is "Job ONE" when working by hot circuits, always one hand behind back, so if happen to touch hot, the current doesn't go through heart. Always 2 separate DRY things between you and possible grounds, like dry shoes and a piece of dry plywood. Of course where possible turn off and test that it's off first.

Even a cheap multimeter can show much. A long piece of wire clipped one end ohm meter other end (dead circuit) should be less than a few ohms roughly, certainly less than 10 ohms. One end of wire grounded, or neutral other end with AC voltmeter should show your normal voltage at breaker panel less a volt or 2, except heavy loads might be a little more, or else the wire is undersized. Check wire sizes and breaker ratings. Typical are #14 wire = 15 amp, #12 = 20 amp, and #10 = 30 amp. These are maximum breakre rating for wire size. Buy a foot or 2 of each size wire, both solid and stranded from your electrical supply, hardware or home center as samples. You could take a micrometer to measure, but generally just a bending with the fingers will tell the difference.

Lastly, take the computer and move it to another circuit, could even be a temporary outlet directly at the breakers. Plug something else that draws a healthy amount of current, say a 100 watt light bulb briefly and see what happens.

[philba]

I'm not sure but I think the standard USA GFCI trips at 20 mA.

As for the questions about the wiring, the house is 80+ years old but the wiring is from 2001/2002. Nothing but copper wires. Every circuit is grounded. Except for AFCIs on bedroom circuits, I believe it is fully up to the current code. It was fully code compliant in early 2002.

I'm calling it good and moving on. thanks all for helping out. I learned a little along the way.

Phil