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Square D breakers very sensitive - Head scratcher!

szuba
13 years ago

I have a newly wired studio with a new 125A Square D service entrance panel. 6 individual circuits are wired with 20A breakers for some large draw equipment. Trouble is the 20A breakers keep tripping... A lot. They never used to at all.

This issue seems to be specific to my new place and these Square D breakers.

I had the same set-up in the previous studio ( built in 1993) which worked perfectly. Typically this equipment works fine on standard 15A circuits (outside the studio, which we regularly do). Occasionally 15A breakers will trip so in the previous studio we installed the 20A breakers on dedicated circuits and eliminated tripping.

Now, the exact equipment on the new Square D panel is constantly tripping the 20A breakers. Curious?

When I take the equipment anywhere outside the studio it works fine (downtown offices, my 3 year old new home, even an older unit in my condo, etc) .

My equipment is about 15 years old and in very good condition. There are countless identical units in regular operation throughout the city (Toronto) and thousands in North America. The equipment was manufactured in USA and is known for it's exceptional performance and reliability.

Here's what I've tested:

1) 80% of the tripping happens within moments of the units being turned on.

2) Each of the new dedicated circuits are wired correctly in conduit (20A T-slot outlets) and test ok for polarity, continuity etc. The voltage reading (DMM) at the panel and outlets is almost exactly 120V.

3) Units work perfectly when plugged into the 15A outlet on the stove (even at 100% load). This stove outlet uses it's own built-in 15A breaker beside the outlet (like a power bar) and a regular 40A Square D at the panel. The electrician says 'those built-in breakers aren't real breakers' which has me scratching my head. It's a brand new Whirlpool stove.

4) 2 of 4 units were sent out to an authorized service technician who says the units are perfect with no unusual tripping in his shop. He has never heard of this issue in his 20+ years of business. If he applies a 100% load, he gets tripping on a 15A circuit breaker (power bar) after 30 seconds of continuous 100% load. This is normal and expected. He uses a 20A circuit for testing with a power bar so the power bar breaker trips first. On his 20A circuit the breaker never trips even at 100% load. He's in the building right across the street from me.

5) A brand new unit was brought in from a dealer with the same results.

6) Swapped out the 20A breakers to 30A in the Square D panel and the same thing happens. The 30A trips on start-up with the regularity as the 20A.

The builder says "20A breakers are as specified, the wiring is correct, therefore it's your problem. I sort of understand where he's at, but I still can't use my stuff in my brand new studio and need a solution.

Here are some questions:

1) Are Square D breakers generally known as 'sensitive?'

2) Have Square D breakers undergone a design change recently which may explain this NEW problem of comparable hyper-sensitivity?

3) Are there known issues of counterfeit Square D breakers? My builder has used some very low quality materials and trades on other areas of construction so a bargain panel wouldn't be out of character.

4) Are there different breakers for this panel with different operating characteristics? Maybe 3rd party manufacturers? I can't believe we have never encountered Square D breakers in my 20 years before this so there is something different here (fishy maybe?).

5) Are there older models of Square D breakers that would fit the panel and work like every other breaker in the city.

6) Another thought was to install a different sub-panel beside the main Square D which would service just the 20A circuits. We would test the brand/breakers to death before choosing the replacement. The expense would be mine and I have already paid large to 'upgrade' my hydro service to 125A and 20A circuits. Plus, the condo board may need to be involved for approvals which sounds like a nightmare based on other issues we have seen so this would be a last resort.

Any help or insight here is really appreciated.

Thanks!

Comments (16)

  • wayne440
    13 years ago
    last modified: 6 years ago

    Square D makes a breaker for high in-rush applications...

    Here is a link that might be useful: High mag breaker

  • wayne440
    13 years ago
    last modified: 6 years ago

    Also a Google search on "counterfeit Square D breakers" will yield many pages of information...

    Here is a link that might be useful: ID counterfeit breakers

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  • itsunclebill
    13 years ago
    last modified: 6 years ago

    The type of equipment we're discussing is important. Also of interest is if the circuits were wired with a shared neutral, also called a multiwire branch circuit.

    Does the "equipment" trip the breakers when only one "equipment" is powered up and only one circuit is used?

    Details needed in quantity to help.

  • pharkus
    13 years ago
    last modified: 6 years ago

    I get the impression that he's talking about audio/video equipment.

    That said, I haven't encountered any problems like that myself - and I use SquareD almost exclusively (Homeline breakers will fit almost anything). As someone in another post put it, they are "the cadillac of circuit breakers" :P

    The comment about a "design change" in SquareD breakers inspires me to wonder if maybe they're AFCI breakers or GFCI breakers, and are thus tripping due to some non-overload reason.

    I've seen a LOT of situations in audio/video setups that could conceivably piss off a GFCI, and I don't know much about AFCIs...

  • bus_driver
    13 years ago
    last modified: 6 years ago

    Phaskus correctly notes that SqD makes Homeline breakers. That is correct. But the Homeline is their "competitive" line, not an exceptionally good breaker in my opinion. I prefer their QO line. At one time, I considered that no better breaker than the QO was available. Cutler Hammer "CH" series is excellent equipment. About the problem that prompted this post, lots more diagnosis is in order. Check voltage and amperage at both the panel and the equipment while it is in use. Verify that the breakers are genuine SqD.

  • brickeyee
    13 years ago
    last modified: 6 years ago

    Put a peak reading clamp on ammeter on the circuit and measure the actual peak current.
    Most higher end audio equipment tends to have a rather large inrush current to charge up the DC power supply filter capacitors.
    These large electrolytic capacitors become 'leaky' with age, even more so if they are subject to high temperatures (even 'normal' operating temperatures can be considered high in this case).

    Without an actual measurement you are simply playing games since breakers have a significant tolerance range for tripping, especially on short term overloads.
    Do a search for 'inverse time breaker' and you can find the curves.

  • billhart
    13 years ago
    last modified: 6 years ago

    The wire probably isn't rated for 30A breakers, so get those 20's back in there.

    The fact that 30A breakers also trip just as often indicates that it isn't current load. Investigate the GFCI/AFCI idea. Tell us what kind of equipment this is. Does it switch on and off internal loads at about the time the breaker trips? Maybe the switching noise fools an AFCI.

    Find one of those DANGEROUS "ground cheater" 3-prong to 2-prong adapters, make sure you are not going to touch both the equipment and anything else that could be grounded, and that the equipment is not going to see any other ground path, and see if the equipment trips the breaker through the adapter. That will tell whether a GFCI (also the less sensitive similar part of an AFCI) is causing the trip due to leakage onto its chassis.

    Can you put some other benign but heavy load on the breakers and see if they trip? Try some space heaters up to 100% capacity.

  • davidandkasie
    13 years ago
    last modified: 6 years ago

    our recording studio and mobile sounds equipment have never had this problem on 20A circuits either. i am thinking you have AFCI/GFCI breakers and they don't like something your equipment is doing.

    have a DIFFERENT sparky come in and check the wiring. one thing it have seen numerous times is that equipment will pass ground continuity from one to another via the cables. if some of your outlets are not wired properly this can cause voltage on the grounds and trip out GFCI breakers. when it does work do you hear any ground hums in the speakers? if so then you definitely have issues. as pointed out above, a 3wire to 2 wire cheater works great to isolate these since it ignore the ground, but if the problem is ground/neutral reversed it will likely still act the same way. and yes, i have seen that myself at a couple places.

    if they used shared neutrals and GFCI breakers, i think the breakers need to be 2 pole to work properly.

  • szuba
    Original Author
    13 years ago
    last modified: 6 years ago

    Thanks for the excellent responses. Currently I can answer these questions.

    1) Initially the service entrance voltage was 140 - 141V. Way too high. A transformer supplying power to our unit was changed and readings are now correct. Oddly, at 141V the tripping was just as frequent. I would have thought higher voltage would have lowered the Amps drawn, and there would have been less frequent tripping. Can this high voltage (for a couple of months during construction) have caused the breakers to become prone to tripping?

    Voltage is now correct at both ends of the run.

    No run is longer than 75 feet or so from the main panel.

    2) I kept the nature of the equipment back as it might cloud the issue a bit. Yes there is an inrush as this is studio flash equipment. That being said, there is no problem using this gear anywhere else in the city (I have been). Even the 15A on the stove is fine, but even a 30A SqD trips repeatedly.

    The units plug in with standard 16GA cords. I have changed the cords to 15' 14GA heavy-duty high-visibility (orange and black) cords mostly for visibility.

    The equipment repair technician says a transformer charges capacitors and only basic switches and so-on are between the line-in and the transformer. No capacitors directly connected to the line-in.

    There is a 'slow' setting (or gentle) on the unit for situations where the units must work on non-dedicated circuits that already have significant loads on them. This 'slow' setting trips as often as the normal setting.

    Again, they work everywhere else (on normal setting), even the stove outlet.

    3) Counterfeit: I compared a breaker to the photos in the article. #C is not identical. Most of my tab is exposed, not 1/2 as pictured otherwise they match.

    4) Multi-wire branch: I think so, 1 Neutral for 2 circuits. A single unit can trip a breaker or several units at the same time can trip 1 or more breakers in no particular pattern. My previous set-up was 12GA 3-wire BX cables with 2-20A sharing 1 neutral with no issues.

    5) The breakers are QO type HACR 20A.

    6) An ammeter was put on the units. There is a very brief peak over 20A. It measures between 28 to just over 30A. There was some talk about this brief peak measurement being unreliable for an exact figure. A cheaper meter read anywhere from 20A-38A. A better quality Fluke was typically under 25A. The 30A SqD trips with the same frequency as 20A so simply swapping to 30A (even in the short term) isn't an option.

    Thanks for your knowledgeable responses and effort to help with this.

    Tom

  • davidandkasie
    13 years ago
    last modified: 6 years ago

    tyr turnign off 1 breaker of a shared neutral circuit and see if the equipment on the other breaker still trips it out. if so, then the shared neutral is nto the problem. if not, then it likely is.

  • hexus
    13 years ago
    last modified: 6 years ago

    little story on the whole homeline thing....

    I used to use homeline, and had nothing but problems with them. Constant nuisance tripping all the time. I like the QO series but find it a little expensive.
    I went to one of those open house free lunch things that the supply houses put on every once in awhile. There was a square D rep there at the time. I asked him point blank what the deal was with their homeline breakers. After I asked several electricians around me overheard and said they've had the same problems also.
    The square D rep swore up and down that the homeline breakers are the exact same as the QO's minus the little red flag that comes up when the breaker trips. He said the only difference is the boot of the breaker and the little red flag. He promised us they are manufactured and produced the exact same as the QO line.
    Long story short I have since switched to Seimens and not looked back.

  • gil_shultzhome_com
    13 years ago
    last modified: 6 years ago

    From what I see you have arc fault breakers (AFCI). The electronic flash units have a switch mode power supply which will put hash on the AC line if not up to snuff with filters etc. Since yours is many years old the filters were probably not required. My suggestion is to go to regular or GFCI 20A breakers.

  • pharkus
    13 years ago
    last modified: 6 years ago

    Whelp

    I'll bet that a camera flash will almost definitely piss off an AFCI! Since their entire mode of operation is to charge up a big capacitor and then INTENTIONALLY create an arc!

    I can certainly imagine ways to isolate the arc and its tell-tale waveform from the AC line - but no xenon flasher I've ever seen has done so (I have little experience with photographic studio equipment, but the strobe lights we sometimes use at concerts are very similar circuitry, just with an automatic repeating trigger instead of a camera-synchronized one.)

    ---

    I don't know about the electronics used in AFCIs, but I do know that overvoltage won't permanently increase the sensitivity of normal circuit breakers. I would expect the same deal - that if the overvoltage doesn't DESTROY the breaker, it won't affect it at all.

    ---

    Out of curiosity (a long time ago - if I did it since this post I'd send some pictures) I chiseled open both a QO and a homeline. They are, in fact, "identical minus the red flag" - If I remember correctly, the piece that the red flag would attach to was actually inside the homeline too, it just wasn't red.

    When I get back to my normal base of operations, I'll repeat the experiment and photograph the innards.

    My comment above was that I use SqD for everything. Given the choice, ie if I'm installing the panel, it's QO - but I use homeline breakers in every existing panel they fit.

    Is QO better? Got me. I tend to believe it's not since, as I said, their internal workings are the same. I just like them - personal thing. My preference for using homeline over original equipment is based on perceived quality - the local hardware store sells exclusively "Murray", so there are a LOT of said panels in use. Original Murray breakers have the operating feel of rotted pancakes. They also seem to get hot and make a lot of noise, given heavy loads. I know very well that the heat and noise are within their engineered operating parameters, I just don't like it, personally.

  • szuba
    Original Author
    13 years ago
    last modified: 6 years ago

    Thanks everyone for your thoughts and experiences.

    After many calls to Schneider I connected with an engineer who conformed an earlier post by wayne440 (Thanks Wayne) I should try the QO-HM series of breakers. HM= High Magnetic and are intended to better tolerate the high inrush of inductive loads like mine.

    He said he was aware of instances of nuisance tripping on refrigerators, microwaves and such even on individual circuits using standard QO breakers.

    The breakers in question are NOT GFCI or anything other than plain/simple breakers labelled QO. I have learned QO is for quick-open.

    The flash units (or 'packs' as we call them) don't use switching power supplies with any filters. They connect a transformer directly to the AC cord via a heavy duty switch.

    The 'arc' or flash is isolated from the AC-line so it doesn't see the 'arc' or 'short-circuit' if you will.

    Thanks
    Tom

  • pharkus
    13 years ago
    last modified: 6 years ago

    Just for the record, since I look like an idiot right now :) ...

    Most of the strobes we use simply have the AC line rectified and sent through a big resistor to a capacitor. When that cap's voltage reaches a certain point, it triggers the flash/strobe tube through a trigger transformer. The arc inside said tube continues until the cap is sufficiently discharged by it, then the cycle repeats. The cap and tube are never disconnected from the resistor/rectifier/ac line.

    I don't have a problem believing they're not all this way - since I myself can think of any number of ways to isolate the arc from the line, but in the ones I have, it isn't.

  • brickeyee
    13 years ago
    last modified: 6 years ago

    "The flash units (or 'packs' as we call them) don't use switching power supplies with any filters. They connect a transformer directly to the AC cord via a heavy duty switch."

    Any type of flash unit uses a switching power supply to step up the line voltage to the thousands of volts required to operate the flash tube.

    In single camera flashes you can hear the wine of the coil as the high voltage capacitor is charged up through a step up transformer to a few thousand volts.

    A trigger pulse of a few thousand is then placed on the tubes trigger input to initiate the arc.
    The trigger node is normally the one in the middle of the tube since a lower voltage can then be used to start the main discharge from end to end on the tube.

    Depending on the design of the DC supply in the equipment you end up with a nasty current waveform at turn on.
    The transformer often saturates briefly since the uncharged load capacitors on the transformers secondary appear initially as a dead short.
    After a few cycles of the AC power line there is enough stored charge to pull the transformer out of saturation at the peaks of the voltage.
    The higher current draw continues until the capacitors are fully charged, and then the charging current appears as small sections of a sine wave when the transformer secondary rises in voltage enough to put charge on the capacitors.

    Any decent peak reading meter can measure the surge on 60 Hz equipment, though it can take a few on-off tries to get an absolute peak.
    The peak will depend on the instantaneous voltage when the power switch is closed.
    Near a zero crossing of the 60 Hz voltage the peak will not be as large as closing the switch at the peak voltage (about 170 V for 120 VRMS).

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