Anotherpower.com Forum
Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: birdhouse on April 30, 2012, 12:25:00 pm
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hello-
last weekend i was at my ranch, and finally purchsed a standard issue cheap coffee maker to get away from burning propane via a perculator.
plugged in the coffee maker (900w on label) and the inverter tripped. the inverter is a xantrex prosine 1800w with surge of i think 2800w on a 24v bank. bank voltage never dropped below 24.8 while coffee maker was on.
so, i turned off the stereo and coffee maker, reset the inverter, then turned back on just the coffee maker. no other loads on the inverter. it finished the pot.
so the next morning, NO other loads on the inverter, and it tripped out about three quarters the way through the brewing.
what gives? later the same day, i had my pancake 2.0hp air compressor running, and without thinking, i cut a 2x6 with my 10" hitachi chop saw (1520w) and even both of them running in tandem didn't trip out my inverter, yet a 900w coffe maker will??
i'm very confused!
adam
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Adam;
Maybe the long extension cord trick will work?
Some loads are funny on start up but it sounds like your issue is different since it runs awhile before it kicks out.
I would suggest all the "regular" stuff to check like good, solid connections on all the battery connections. Check the drop across the battery to inverter cables to be sure you are not losing power in the cabling. I am not familiar with how new coffee machines work but if it has some kind of switching power supply feeding the heater it could draw huge spikes.
Might check the actual load of the maker with a watts up or other method as it is running. Maybe check it on a grid or generator supply so it doesn't lose the data when the inverter resets. If possible. Could even be a faulty machine that would work fine on the grid but overloads the inverter?
The only thing that is going to help much is some logical testing. One of my 32" CRT televisions makes my Outback beep an overload error when it switches on and the degaussing coil activates. It keeps running but apparently that load is huge for a short time and it literally pegs the 150 amp ammeter on the battery to inverter cable which indicates a 3600 watt load on a 2500 watt inverter or nearly 1.5X its rating.
Good luck with it.
Tom
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tom-
i didn't have any time to put meters on things while i was up there. too busy building another deck with RE. i'll post about that tonight.
the inverter is connected to the bank with 3/0 copper with anti-ox and solid copper connectors (6') and has a 150 a fuse that has never blown. the AC side of things is all #10 hard wired to the inverter and branches off to various locations. the coffee maker was plugged into an outlet ~110' from the inverter (still #10), and on a 15' #14 extension cord.
i'm guessing my air compressor draws ~800w min. while running, and my chopsaw, which doesn't have a soft start feature draws WELL over 1200w when your first pull the trigger. (induction motor)... and my inverter did that just fine, so, i'm guessing there aren't issues with the wiring connections.
I am not familiar with how new coffee machines work but if it has some kind of switching power supply feeding the heater it could draw huge spikes.
i think this might be the case. either that, or my wiring is too stout, and maybe the coffee machine on a 100' #16 cord would do it?? i've read about putting capacitors across the AC hot and neutral, much like a motor start capacitor. is it actually that simple, given the correctly sized/rated capacitor is used?
i'd be more than willing to drop $150 on capacitors if that might solve these finnicky issues. i just don't know how to find and or install them. (help!)
i'm already thinking about getting an outback 3500 vented jobby, but even then, the same capacitor rig could be used with the new inverter.
thanks for any info!
adam
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Wondering if the Prosine has fault protection? Maybe it's not draw but fault? Does seem odd that
you can load it up even more with no problems. Probably off base, good luck with it.
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Wondering if the Prosine has fault protection?
there probably should be some GFCI's in place, but there aren't. not even breakers on the AC output. just hardwired straight to the inverter.
heck, that inverter will even run my miller-matic 135 MIG welder if the dials on the welder aren't cranked.
adam
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Adam,
It almost sounds like a problem with the coffee maker. Any chance you can try a different one?
Kevin
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Inverter related but not coffee machine.
A few weeks ago an acquaintance locked his keys in his car. After trying many other methods the decision was taken to drill out the lock on the rear door.
I produced one Hilti drill, one inverter and a 12 volt battery. It all worked as required except that the adjustable speed Hilti drill had to have the switch handle pulled on to full power before the inverter was turned on.
The inverter does not like adjustable speed equipment, but was quite happy powering the drill. The rear door eventually opened in the usual way.
David in HK
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The inverter does not like adjustable speed equipment, but was quite happy powering the drill.
that makes me think. also, the inverter has been sitting doing nothing all night, then a 900w load put on it all a sudden. does an inverter like to be warmed up first? seems counter intuitive to me as the cooler the inverter is, the better it could perform???
i've read similar things to what you've stated. maybe a few 100w light bulbs running first and left on while the coffee maker brews might do it?? seems stupid, but might work??
seems inverters don't like to be ramped up too quickly?? but if they're already working they handle it fine??
my inverter will start all sorts of thing in the early AM when it has sit hour hours at idle, i reallly don't get why it has a fit with the coffee maker!
oz, or ross, where are you to explain this to me, and to explain how to use caps to lessen this issue!!!!! >:( just joking, but i'd love your input!
adam
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Do you have just an all cheapo Hot Plate.. (single burner /coil).. see how that behaves.
Just a thought.
Rover
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its a standard cheap $25 12 cup coffee machine made by "mr coffee"...
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Huh...
I have the same set up. 24 volt 1800 watt prosine and mr. coffee maker and it works just fine.
Maybe its the long wire run? The inverter puts out clean power so it must be after it. Or maybe
just low on power first thing in the morning.
I placed some solar panels facing more to the east just for getting the morning sun to charge faster
for coffee in the morning.
I put a motor start cap across the input terminals on a heart inverter once, it wasn't charging.
The tech guys there sold me one for $25. It worked but the real issue was turning up the throttle
of the genny to get the volts and frequency more in the ball park for the inverter.
I'm sure it's not the inverter. All the weird tricks were for modified sine wave inverters. Unless your
dealing with noise or reception problems then some of those old techniques help.
Good luck with it.
Mike
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oz, or ross, where are you to explain this to me, and to explain how to use caps to lessen this issue!!!!! >:( just joking, but i'd love your input!
A decent capacitor right across the DC INPUT lines will help provide some of the extra surge current the inverter needs to deliver high output bursts.
Most decent inverters operate at very high frequencies internally, and to them even one AC cycle is a "long time". As you say, the longer they're running the hotter they get, which is generally a bad thing. (unless it's stupid cold of course!)
Capacitors on the AC side won't do anything to help with peak loads directly - however if your peak load is a largely inductive load (like a motor), then a correctly-sized capacitor on the AC side may help correct the power-factor sufficiently that the inverter will manage the starting current. This won't be the case with your coffee pot, I'm sure.
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The following is an extract from my inverter instructions:-
Current Draw of Equipment
Most electrical tools, appliances and audio/video equipment have a label indicating the power consumption in amps or watts. Check to ensure that the power consumption of the item you will be using at 230 Vac is below 1.43 Amps for the INV33O.
Resistive loads are easiest (or the Inverter to drive, through larger resistive loads such as heaters and cookers would require more wattage than is available from these inverters,
Inductive loads, such as TV’s and stereos (devices with a coil or a transformer in it) may require more current to operate than a resistive load of the same wattage reading.
Televisions may require several times their wattage reading to ‘start up’.
This condition may require repeated ON/OFF switching of the inverter in order to get them started.
Experimentation is the only means of determining whether the inverter can handle the surges required to start up a particular load.
NOTE: The inverter will not operate mug appliances designed to produce heat, such as hair dryers, irons, heaters etc. The current draw of these items is beyond the capacity of this unit.
My be of some help or interest.
David in HK
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Take the coffee maker back and ask for a replacement.
It maybe that unit has a poor electrical connection.
That would be worth a try.
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Are you sure the inverter is shutting down/tripping from overload or ground fault? Really sounds to me like something is funky in the coffee maker causing a ground fault shutdown. If you have a generator handy quick wire up a GFCI outlet and plug that coffee maker into it and see if it trips the GFCI. Doing it with the inverter won't work because the ProSine has built-in GFCI protection via auto-shutdown if it detects a fault.
I'll bet a crisp new dollar bill it kicks out the GFCI outlet on the generator, and the problem is in the heating coil that heats the water for brewing.
We've had a couple of those cheap coffee makers go up in smoke with a POP SIZZLE FIZZ, then the breaker kicks out, because that brewing heating element got a short in it.
Edit: I just went out to the shop to see what brand the last one was that blew up. It's a Mr. Coffee 12 cup with computers in it. I saved it to steal the hot plate out of it because that's still good. My wife went to several different stores looking for a coffee maker that don't have computers in it. They all told her that they all got computers now. But she found a Sunbeam one at Farm & Fleet that just has a on/off switch and no computers.
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Chris
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interesting thoughts chris!
the mr coffee 12 cupper i was having problems with just has an on off switch also. no clock, or timer ect.
the ProSine has built-in GFCI protection via auto-shutdown if it detects a fault.
i don't know if that is true. they make the prosine 1800 either set up for hard wiring, or with a standard GFCI outlet on the front. why would they use a GFCI if the inverter already has that protection built in? the screen on my unit just says "system shutdown"nwhile beeping. the same message comes up when i overload it from welding too much with the dials maxed.
you could very well be right about the coffee maker shorting. even very short (duration) shorts could create spikes large enough to overload the inverter.
i won't be back up to my place for two weeks, but i'll try the GFCI on a genset trick, and also watch the inverters screen while coffee is being brewed!
i should really get a kill-a-watt meter too!
adam
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Does the coffee maker have a two or three prong plug?
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watt-
two prong
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Well that kinda wrecks the GFI possibility.
I am guessing either a short, or its some sort of strange setup that has a large capacitor for one reason or another.
Maybe to stop the clicks when it kicks in and out. I remember hearing this in the radio at my grandpas all the time when the coffee pot heater turned on and off via the chincy bi-metal thermostat.
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Well that kinda wrecks the GFI possibility.
Not necessarily. Most appliances have two prong plugs and they can still have a ground fault which will trip GFCI protection on a grounded neutral system.
All single phase residential power in the US and Canada uses grounded neutral, and most all inverters that are UL Listed for use in the US and Canada have it as well.
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Chris
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Kinda unlikely to be tripping it even with possibility.
I would bet it sits on plastic feet, with no path to ground to trip it.
I might be missing something though, since I'm not there to see.
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i don't know if that is true. they make the prosine 1800 either set up for hard wiring, or with a standard GFCI outlet on the front. why would they use a GFCI if the inverter already has that protection built in?
Because if it's a UL458 compliant inverter, with the inverter used as the service (bonded neutral) it has to have auto-shutdown on ground fault. The model with the built-in GFCI plug does not have a bonded neutral because it's designed for RV or marine use, which requires a floating neutral. The hard-wire model with the relay in it has a bonded neutral.
I looked at those inverters for our RV, but went with an AIMS 3 kW instead because the Prosine didn't have quite enough power to run some of the stuff in our RV.
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Chris
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I would bet it sits on plastic feet, with no path to ground to trip it.
You don't always need a path to ground to cause nuisance tripping on GFCI. All it takes is a case or frame to hot conductor fault, or certain resistive heating loads to cause nuisance tripping when there is no real ground fault problem at all. Nine times out of 10, if you take a 100-150 foot cord, wrap it in a coil and plug it in to a GFCI outlet, and try to run something with it it, it will trip it.
That's why I think there's something wrong in the coffee maker. There's obviously nothing wrong with the inverter.
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Chris
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watt-
two prong
Do you happen to have a gfci in any other location fed by the mains? Maybe you could plug it in to the house before you return it. Would trip if there is a problem....
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I thought adam was off-grid with this setup and that's why I suggested trying that with the generator and a GFCI outlet wired up to it. Just to get a second opinion from another GFCI on that coffee maker. If it's like the Made in China Mr. Coffee units we've had, I'm not impressed with how long they last, or how well they're made.
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Chris
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Can get Mr Coffee's with just a switch at Family Dollar for $10.
I bought 3 or 4 one day... "Pause & Serve"? On the 1st 2 or 3, the pots were not high enough to push the plunger up to let the coffee out. Overflowed the basket, vinegar (cleaning cycle) all over everywhere.
The one that worked worked fine.
The one it replaced was a higher end coffee maker brand.
Would not heat up.
Thermal fuse was shot. Naturally, no numbers on it. Ordered one direct from the company (cost more than the $10 machine). Replacement had numbers on it.
Thermal fuse blew again in 2 days.
Up to RatShak to get another one for $1 this time. Worked 1 or 2 pots. Back to RatShak. Repeat repeatedly.
Cycled fine, like it should? Not sure if the thermostat or the element was the problem.
After replacing the fuse too many times, and too many dozen $1.50 cups of coffee from the gas station,
went with the Family Dollar $10 Mr Coffee as a temporary solution and had 0 problems with it for a long time, but the woman I'm married to decided she wanted one with a timer.
G-
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I thought adam was off-grid with this setup and that's why I suggested trying that with the generator and a GFCI outlet wired up to it. Just to get a second opinion from another GFCI on that coffee maker. If it's like the Made in China Mr. Coffee units we've had, I'm not impressed with how long they last, or how well they're made.
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Chris
You may be right Chris, I took his first post to mean he stays somewhere besides his ranch he had visited that weekend.
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I have the same cheap Mr Coffee 12 cup maker, no electronics just a switch. Even my cheap chinese 1kW inverter (aims I think) would run it. My Trace 2512 thinks nothing of it at all, even the fridge or whatever can kick on while it's brewing.
So I don't know what is going on but it does seem odd. It should work no problem.
Jonathan
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but the woman I'm married to decided she wanted one with a timer.
LOL! Your Spousal Unit wants one with a timer, my Spousal Unit went to like 7 different stores to find one without a timer.
The one we had with a computer in it would make the coffee fine for in the morning. But we usually don't drink it all for breakfast and there's some left for dinner. But the problem with it was that it would shut the heating plate off after awhile and the coffee was cold so we had to microwave it to heat it up for dinner.
With just an on/off switch WE got control of when that confounded thing gets turned off, and our coffee is hot when we come in for dinner and want a grab a cup :P
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Chris
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i think there is something fishy going on with that coffee maker.
yes, my vaca spot is off grid, but i live, for the most part, on grid in portland, OR.
after reading all this, i'm convinced that the coffee maker would probably run fine on a 20A grid circuit. it may produce shorts up to 4000-5000w, but for VERY short times. i'd bet a grid 20A circuit would hold that just fine. i'm continually amazed in old commercial buildings where i purposefully short the hot and neutral with an old junk screwdriver, and how many sparks fly before the breaker finally flips! (gloves, and sunglasses on for these jobbies)!
but with an offgrid setup, my surge is maxed at 2900w, and i don't think it goes past that by even 100w.
in conclusion: i think chinese coffee makers are built to abuse 20A grid circuits, but not off grid inverters. i may be able to buy 15 of the identical coffee maker, and have 2 or three that work just fine with my inverter, but all the others may not.
i plan on buying a completely different brand/style next time up, and returning the one i bought the first time on my drive back home.
and yes, the coffee maker was far from ground. sitting on a wooden bench, on it's plastic feet. basically a non-issue.
adam
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There's obviously nothing wrong with the inverter.
if it will run an air compressor while cutting a 2x6 on my chop saw, i'd like to hope that's the case!
adam
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if it will run an air compressor while cutting a 2x6 on my chop saw, i'd like to hope that's the case!
Adam, your description of what else you run with the inverter, with no problems at all, made me decide that. There is nothing inherently "weird" about coffee makers that should cause any big current spikes to trip out the inverter. I have run many, many coffee makers on inverters and have never yet seen a properly functioning coffee maker that even small inverters will not power.
That leaves a ground fault problem in the coffee maker, by process of elimination. Based on what I've seen blow up in those, my best guess is an intermittent short from hot to frame, or hot to neutral in the brewing heating element. Like you say, plugged in to a true 20 amp circuit, the thing would probably function OK - for awhile. It depends on what the problem is in it. I'll bet you could find the problem by taking it apart and ohming it out to find the leak. But to my way of thinking, the thing is defective and should be replaced by the store where you bought it from.
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Chris
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if it will run an air compressor while cutting a 2x6 on my chop saw, i'd like to hope that's the case!
Adam, your description of what else you run with the inverter, with no problems at all, made me decide that. There is nothing inherently "weird" about coffee makers that should cause any big current spikes to trip out the inverter. I have run many, many coffee makers on inverters and have never yet seen a properly functioning coffee maker that even small inverters will not power.
That leaves a ground fault problem in the coffee maker, by process of elimination. Based on what I've seen blow up in those, my best guess is an intermittent short from hot to frame, or hot to neutral in the brewing heating element. Like you say, plugged in to a true 20 amp circuit, the thing would probably function OK - for awhile. It depends on what the problem is in it. I'll bet you could find the problem by taking it apart and ohming it out to find the leak. But to my way of thinking, the thing is defective and should be replaced by the store where you bought it from.
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Chris
It's just odd for a gfci to trip due to a 2 prong plug device which didn't have some of the fault current returning to say an earth ground by way of water contact. My understanding is a gfci monitors the current leaving one terminal and returning on the other. If a difference of ~6mA is monitored out but not returned, the gfci is tripped. With 3 prong plugs, if that ~6mA is returned on the earth ground plug, the gfci is tripped.
I did read where the maker alone plugged in worked fine ( for a while anyway ). This could be a combination of multiple device current leaks but not one of the items alone is enough to trip his gfci.
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My understanding is a gfci monitors the current leaving one terminal and returning on the other. If a difference of ~6mA is monitored out but not returned, the gfci is tripped.
It measures the current differential on the hot and neutral. There is no real "return" like DC because the hot and neutral alternate 60 times/second (or 50 if you live overseas).
But GFCI is not foolproof. Wiring two of them on one circuit will cause one to trip even though there's not a ground fault. Neutral is bonded to ground at the service entrance (or inverter). So with a polarized two-prong plug on an appliance - you still have a grounded neutral. But if you touch neutral to ground anywhere else in the system, even though they are bonded, it will trip a GFCI. The reason is because in a situation where the load side neutral is grounded and a ground fault also occurs, a parallel path through the GFCI for the ground fault current could exist. The portion of the ground fault current returning on the neutral conductor will not be sensed as differential current. This has the effect of desensitizing the GFCI. So the UL standard requires that GFCIs trip with a 6mA ground fault even when the neutral and ground are connected. To meet the requirement, GFCIs trip when the load side neutral and equipment grounding conductors are joined, even if there is no ground fault.
So there's several things that could be wrong in that coffee maker, causing the inverter to spit out. But it all points to a problem in the device, and not the inverter. The inverter is doing what it's supposed to do.
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Chris
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chris-
i fully agree with your thoughs on GFCI's and the defunk coffee maker. worst part is, now i have to buy a new one next weekend to be able to make coffee, then return the old one on the way home. two trips to the same store for the same issue... >:(
maybe i'll try a different model! hopefully it work the way it's supposed to work!
adam
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My understanding is a gfci monitors the current leaving one terminal and returning on the other. If a difference of ~6mA is monitored out but not returned, the gfci is tripped.
It measures the current differential on the hot and neutral. There is no real "return" like DC because the hot and neutral alternate 60 times/second (or 50 if you live overseas).
But GFCI is not foolproof. Wiring two of them on one circuit will cause one to trip even though there's not a ground fault. Neutral is bonded to ground at the service entrance (or inverter). So with a polarized two-prong plug on an appliance - you still have a grounded neutral. But if you touch neutral to ground anywhere else in the system, even though they are bonded, it will trip a GFCI. The reason is because in a situation where the load side neutral is grounded and a ground fault also occurs, a parallel path through the GFCI for the ground fault current could exist. The portion of the ground fault current returning on the neutral conductor will not be sensed as differential current. This has the effect of desensitizing the GFCI. So the UL standard requires that GFCIs trip with a 6mA ground fault even when the neutral and ground are connected. To meet the requirement, GFCIs trip when the load side neutral and equipment grounding conductors are joined, even if there is no ground fault.
So there's several things that could be wrong in that coffee maker, causing the inverter to spit out. But it all points to a problem in the device, and not the inverter. The inverter is doing what it's supposed to do.
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Chris
So, where is that current going that is missing to cause the gfci to trip? It's not going through the counter top or the plastic case of the device. With a two prong device, there is clearly not a return path to ground. If it's a very simple coffee maker, it will have a heating element for the pot warmer, a coil for heat tube up to the coffee grounds, some kind of heat limiting device and a switch to turn if off and on. Also, a neutral with alternating current is nothing more than a " bond " to help protect from a voltage potential. What if: " the sock, where the coffee maker is plugged in, is wired with the taller prong ( neutral ) ' hot ' and the smaller of the two prongs ( hot ) wired with the ' neutral '?" The coffee maker will work fine and honestly just as if plugged into a properly wired plug. Will the coffee maker still trip a gfci? Sure it will if there is a current differential or a return on the earth ground conductor to the inverter in a certain amount of time. He is dealing with alternating current, from one prong back to the other and so forth and so on. Does the gfci trip while the current is flowing from the ' hot ' leg or does it trip when the current is flowing from the ' neutral ' leg?
Here is a statement similar to the training I have had regarding these devices.
GFCI Limitations
The use of GFCI devices is obviously not a substitute for using good common sense. If you have your hairdryer, toaster or other electrical apparatus powered through GFCI receptacles or GFCI-protected extension cord, this doesn’t mean you can do dangerous things. It is possible to have an AC-operated tool or other device powered through a GFCI and still get electrocuted. GFCI’s only operate when they sense a ground fault (short through to ground). If the operator puts himself between the hot wire and neutral without any current flowing to the earth, the GFCI will not open the circuit. As a rule, DO NOT use any AC-powered tool while you are standing in water. NEVER use any electrical tool if you or the tools are wet.
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chris-
i fully agree with your thoughs on GFCI's and the defunk coffee maker. worst part is, now i have to buy a new one next weekend to be able to make coffee, then return the old one on the way home. two trips to the same store for the same issue... >:(
maybe i'll try a different model! hopefully it work the way it's supposed to work!
adam
I certainly hope you can make it through your next RE project with a pot of coffee by getting that coffee maker replaced. ;D However, if the next maker doesn't cause the gfci to trip, I hope it wasn't due to a different underlying cause.
Good luck and best wishes.
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Watt,
That is exactly as iIunderstand it , and always have. Previously they were a core balanced relay, where the incoming current had to balance the outgoing current. If any current found a way to circumvent this circuit, it unbalanced the circuit and a fault was sensed.
They can only then find a way out of the active-neutral circuit,if the electrons can find some other/alternative way home... can only be via an earth fault.
Neutral and ground bonded at the switchboard, and separately distributed thereafter. A 2 pin appliance sitting on a plastic tray cannot trip any remotely decent leakage detector... and no current can leak out of the circuit.
If you step up to the tray and grab the 2 pin appliance with any part live or leaking, then the core/relay will trip.
A three pin appliance can trip on it's own, as there is now an earth point in that frame of reference on the plastic tray. The track to ground then can be as small as spider web across the active to earth at any point, mixed with moisture and dust.... or you grab the active bits.....
It cannot trip without an earth return of some kind as I understand it.
............oztules
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Watt,
That is exactly as iIunderstand it , and always have. Previously they were a core balanced relay, where the incoming current had to balance the outgoing current. If any current found a way to circumvent this circuit, it unbalanced the circuit and a fault was sensed.
They can only then find a way out of the active-neutral circuit,if the electrons can find some other/alternative way home... can only be via an earth fault.
Neutral and ground bonded at the switchboard, and separately distributed thereafter. A 2 pin appliance sitting on a plastic tray cannot trip any remotely decent leakage detector... and no current can leak out of the circuit.
If you step up to the tray and grab the 2 pin appliance with any part live or leaking, then the core/relay will trip.
A three pin appliance can trip on it's own, as there is now an earth point in that frame of reference on the plastic tray. The track to ground then can be as small as spider web across the active to earth at any point, mixed with moisture and dust.... or you grab the active bits.....
It cannot trip without an earth return of some kind as I understand it.
............oztules
oztules, we use a similar scheme to help protect our folks in the field when we use delta generators. We have master electrician roughnecks ( sarcastic ) which makes testing often necessary. You wouldn't believe how many different ways they can make a light illuminate with 480v. :o
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thanks watt!
The use of GFCI devices is obviously not a substitute for using good common sense. If you have your hairdryer, toaster or other electrical apparatus powered through GFCI receptacles or GFCI-protected extension cord, this doesn’t mean you can do dangerous things. It is possible to have an AC-operated tool or other device powered through a GFCI and still get electrocuted. GFCI’s only operate when they sense a ground fault (short through to ground). If the operator puts himself between the hot wire and neutral without any current flowing to the earth, the GFCI will not open the circuit. As a rule, DO NOT use any AC-powered tool while you are standing in water. NEVER use any electrical tool if you or the tools are wet.
this is what they tell you, but like chris has sated, GFCI's will trip from a multitude of reasons. sometimes they will even trip if you plug in a two pronged device a little crooked where the hot hits before the neutral... even a 20A rated GFCI will trip long before the same circuit 20A breaker trips. being a contractor in the states, all of my power usage outdoors is supposed to be GFCI protected. i tried that for a minute, but the CONSTANT tripping of the GFCI with big draw equipment was a no go. just try running a 3 horse 4 gallon twin stack air compressor on a GFCI, it's not going to happen! i tell my guys that if they get shocked (usually using a circular (double insulated) saw in a downpour) that they should call it a day, or work indoor if its an option. if i had to halt my crew every time a GFCI blew, or repeatedly blew, i wouldn't make any money!
then there's AFCI's, but lets not get started on that!
adam
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Neutral and ground bonded at the switchboard, and separately distributed thereafter. A 2 pin appliance sitting on a plastic tray cannot trip any remotely decent leakage detector... and no current can leak out of the circuit.
forget the ground for now. lets say two pronged stuff:
if the neutral arcs to the hot for a millisecond, doesn't that create an imbalance? to me that makes sense, but you, OZ know WAY more electrickery than i do!!!
adam
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thanks watt!
The use of GFCI devices is obviously not a substitute for using good common sense. If you have your hairdryer, toaster or other electrical apparatus powered through GFCI receptacles or GFCI-protected extension cord, this doesn’t mean you can do dangerous things. It is possible to have an AC-operated tool or other device powered through a GFCI and still get electrocuted. GFCI’s only operate when they sense a ground fault (short through to ground). If the operator puts himself between the hot wire and neutral without any current flowing to the earth, the GFCI will not open the circuit. As a rule, DO NOT use any AC-powered tool while you are standing in water. NEVER use any electrical tool if you or the tools are wet.
this is what they tell you, but like chris has sated, GFCI's will trip from a multitude of reasons. sometimes they will even trip if you plug in a two pronged device a little crooked where the hot hits before the neutral... even a 20A rated GFCI will trip long before the same circuit 20A breaker trips. being a contractor in the states, all of my power usage outdoors is supposed to be GFCI protected. i tried that for a minute, but the CONSTANT tripping of the GFCI with big draw equipment was a no go. just try running a 3 horse 4 gallon twin stack air compressor on a GFCI, it's not going to happen! i tell my guys that if they get shocked (usually using a circular (double insulated) saw in a downpour) that they should call it a day, or work indoor if its an option. if i had to halt my crew every time a GFCI blew, or repeatedly blew, i wouldn't make any money!
then there's AFCI's, but lets not get started on that!
adam
Adam, don't confuse the two different devices. A gfci is not a circuit breaker and is not meant to current limit the circuit. Dual function incorporated devices are available however, in a gfci/breaker package.
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Neutral and ground bonded at the switchboard, and separately distributed thereafter. A 2 pin appliance sitting on a plastic tray cannot trip any remotely decent leakage detector... and no current can leak out of the circuit.
forget the ground for now. lets say two pronged stuff:
if the neutral arcs to the hot for a millisecond, doesn't that create an imbalance? to me that makes sense, but you, OZ know WAY more electrickery than i do!!!
adam
I'm not oz but, I'd like to answer this. An air gap arc is a circuit and you will have current returning in the same amount as supplied. No, that does not mean that circuit is unbalanced. That is also why your welder doesn't trip your gfci. The example you gave regarding plugging in the two prong plug to the ' hot ' before the neutral was contacted, that's not a circuit until both prongs made contact and there was a load.
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i wasn't confusing them. all i'm saying is if your pushing the limits of a 20a breaker and have a GFCI in line with that breaker, in totally dry three pronged situations, with zero ground potential, the 20A GFCI will ALWAYS!!! trip before the breaker does.
GFCI's are finicky! no question... ask any contractor! it's proven!
adam
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i wasn't confusing them. all i'm saying is if your pushing the limits of a 20a breaker and have a GFCI in line with that breaker, in totally dry three pronged situations, with zero ground potential, the 20A GFCI will ALWAYS!!! trip before the breaker does.
GFCI's are finicky! no question... ask any contractor! it's proven!
adam
I agree gfci's are finicky, but 6mA is very small and so is m/s in time. I've searched for days to find faults in the past. One was a 16awg extension cord laying on the ground ( dry ground ) that had gotten wet weeks prior and had a pin hole in the insulation and one ' neutral ' conductor. I tore the pvc jacket off and found the paper like reinforcement damp. I dried the cord where the tiny pin prick was and heat shrink-ed a sealing jacket over it. Then reset the gfci and no more problems. Yes, I know how finicky they can be.
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The example you gave regarding plugging in the two prong plug to the ' hot ' before the neutral was contacted, that's not a circuit until both prongs made contact and there was a load.
i understand what you are saying, and the math makes sense, but in reality, this is not the case. maybe it's because the hot is energized a bit before the neutral completes the circuit, and some inrush current trips the gfci. i don't know.
one thing i do know is that GFCI protected outlets that are down stream from the GFCI (especially WAY down stream) are less prone to being finickky. why, i don't know.
adam
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The example you gave regarding plugging in the two prong plug to the ' hot ' before the neutral was contacted, that's not a circuit until both prongs made contact and there was a load.
i understand what you are saying, and the math makes sense, but in reality, this is not the case. maybe it's because the hot is energized a bit before the neutral completes the circuit, and some inrush current trips the gfci. i don't know.
one thing i do know is that GFCI protected outlets that are down stream from the GFCI (especially WAY down stream) are less prone to being finickky. why, i don't know.
adam
Are you saying you have more than one gfci in one circuit? ( after re-reading, I think you are not saying that at all ) One more point, no argument I promise. You say " maybe it's because the hot is energized a bit before the neutral completes the circuit, and some inrush current trips the gfci." at what part of the cycle are you plugging it in? When the current is ' hot ' to ' neutral ' or ' neutral ' to ' hot '? Or, is the current not changing, at a peak?
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Current in a series circuit is the same through ALL that series circuit.
A core-balance or RCD type device is by its very nature quite sensitive. It has to "counteract" a substantial current in one direction with an almost exact version opposite in another wire. We're talking an imbalance of 0.03% of the full load current here.
My own experiences with "balancing" currents are that a number of conflicting events are at work.
You want multiple turns of the "sense" wire to get enough sensitivity at low currents.
Of course, you need then to have *exactly* the same for the return wire.
Stray magnetic fields from asymmetrical wiring can and do affect things.
Arcing and sparks have a high-frequency component. Transformers generally work far better at high frequencies (assuming the core is up to it), so even minute differences in layout can have far greater effects under these circumstances. Not to mention imperfections in toroidal core construction etc.
Add into the mix capacitive coupling. Long leads laying on the ground, metal-cased equipment, metal benches, metal pipes etc will all capacitively couple to the cables (even short ones). So while there may be no DC path, there *MAY* be just enough stray capacitance to get enough current to trip. Especially when a switch opens and you get a burst of HF noise.
Finally, while most ELCB/RCD/etc are made well and with suitable shielding, there's no guarantee that there won't be at least a little interference left - perhaps just enough to trip the circuit. Some of these things have moderately high gain amplifiers inside you know!
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Are you saying you have more than one gfci in one circuit?
no.
i think ross sums it up nicely with why these devices are so finnicky. although he explains it much better than i can. i can only relate my field experiences with them.
i guess all im getting at is there is NO way EVER with construction equipment, or coffee makers that you can instantainiaously (sp?) pull 20A from a rated 20A GFCI.
basically, though a very good safety precaution, they're little bitche$!
apparently my inverter has one built in, but it seems to be pretty absorbant to various things, or maybe it doesn't have one built in. maybe it just faulted from very short dead shorts??
i don't know... sounds like time to buy a different coffee maker!
adam
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Are you saying you have more than one gfci in one circuit?
no.
i think ross sums it up nicely with why these devices are so finnicky. although he explains it much better than i can. i can only relate my field experiences with them.
i guess all im getting at is there is NO way EVER with construction equipment, or coffee makers that you can instantainiaously (sp?) pull 20A from a rated 20A GFCI.
basically, though a very good safety precaution, they're little bitche$!
apparently my inverter has one built in, but it seems to be pretty absorbant to various things, or maybe it doesn't have one built in. maybe it just faulted from very short dead shorts??
i don't know... sounds like time to buy a different coffee maker!
adam
Go have some coffee. 8)
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actually it's beer time! been planning for my next visit to my ranch... too much 16' stuff to haul. i'm the only one of my ranchmates that can haul 16 footers, yet i've got the smallest truck!!
hauling materials... story of my life...
thanks for the contributions watt!
adam
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actually it's beer time! been planning for my next visit to my ranch... too much 16' stuff to haul. i'm the only one of my ranchmates that can haul 16 footers, yet i've got the smallest truck!!
hauling materials... story of my life...
thanks for the contributions watt!
adam
What are you planning to build this time Adam? Post lots of pics.
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Are you saying you have more than one gfci in one circuit?
no.
i think ross sums it up nicely with why these devices are so finnicky. although he explains it much better than i can. i can only relate my field experiences with them.
i guess all im getting at is there is NO way EVER with construction equipment, or coffee makers that you can instantainiaously (sp?) pull 20A from a rated 20A GFCI.
basically, though a very good safety precaution, they're little bitche$!
apparently my inverter has one built in, but it seems to be pretty absorbant to various things, or maybe it doesn't have one built in. maybe it just faulted from very short dead shorts??
i don't know... sounds like time to buy a different coffee maker!
adam
Adam,
I wanted to share a bit of an experience I had with electrical distribution on a construction site once. This dealt with one 120v gfci and a fairly large 240v compressor. This meter setting on a pole provided that 240v split phase service to the site. On that panel was a gfci 120v circuit with the only load device being a radio/power center type device setting on the ground which happened to be playing Mexican music as loud as can be. While a couple of guys were doing some framing and a bit of chiseling, the compressor would cycle and when the compressor would kick on, the radio would go off and a couple of Mexican guys doing some brick work would go over the panel and cuss like I couldn't understand. Anyway, after a bit of scratching my head I realized the earth ground rod and bonding wire at the pole had a bad connection and the compressor had a fault in the motor. That compressor was setting on the grass but was enough to trip the circuit because some current was being returned to the mains at a nearby power pole and the other through the gfci and ground provided by the equipment ground of the radio. Anyway, I can't comment on your GFCI experience but I bet we all have them for sure. Those guys kept saying the other guys were turds for turning off their radio. I thought it was funny anyway....
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watt-
yea, i hear what you're saying. and for small tools, a GFCI works fine. the one item i own that GFCI's don't play well with is my 3hp campbell housfield(sp?) air compressor. (and that POS coffee maker)
my 5500w generator won't even run it, though it should. so yea, put that beast on a gfci and forget about it ever running.
i love working with mexican guys, because im the unusually nice GC that they never experience. i treat them well, and they do better work because of that.
i'm pretty picky about where my cords run AND their gauge, AND if they hit the ground at connections. i run off homes circuits many times, and im the only one with the clients key, so i try to hammer in correct distribution of electrical needs.
next project isn't another project, but rather finishing my roof deck.
i'll post pictures and probably video too!
adam
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A note on GFCI and how touchy they can be, and this is an easy demonstration. Find a power tool that will run on a GFCI outlet just fine plugged directly into it. Don't matter if it's two prong or three prong.
Now, plug in a 100 to 150 foot cord wrapped in a coil on a cord reel and plug your power tool into the cord and try to run it. Bingo - your GFCI will trip. Unwrap the cord off the reel and stretch it out, and the GFCI will normally not trip.
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Chris
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I have never found this... nor should I wish too.
Thats just too weird .......to contemplate.
I understand you have seen this to comment as you have, but I'm struggling....... just totally amazed ...... yes....amazed.
I have never seen any earth leakage device over here trigger but for leakage reasons (and sometimes I'm it).
My best guess is inductive coupling in the ext cord to ground via the spikes due to the phase switching but gee.....thats my best guess until something better comes along.
lost in space again...............oztules
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Like adam or somebody else said, contractors have known about this for years because many of them carry their extension cords on plastic cord reels. If a contractor shows up at a job site and there's a GFCI plug to power their tools the first thing they say to one of the grunts is, "go find a real power plug". Or if they got a generator in the truck (most do these days) it's "get the generator out".
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Chris
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Ok I just tried this Chris. on any GFCI in my house I could not trip any of them.. BUT just to be sure I tried this at my mothers house and bingo!
I have a bit more spendy of GFCI because of the MSW inverter, that's likely the difference.
As most of you likely know many GFCI wont like MSW at all and either buzz like crazy or trip without even anything plugged in .
One thing did come to mind last night.
Does the birdhouse's inverter have Arc fault protection as well? The thermostat in any cheap coffee pot will trip one of those.
Those things have been worse to me than any GFCI.
Its funny, electricians and politicians make up the code and laws to require these things in homes, but cannot stand then themselves.
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Ok I just tried this Chris. on any GFCI in my house I could not trip any of them.. BUT just to be sure I tried this at my mothers house and bingo!
I have a bit more spendy of GFCI because of the MSW inverter, that's likely the difference.
As most of you likely know many GFCI wont like MSW at all and either buzz like crazy or trip without even anything plugged in .
One thing did come to mind last night.
Does the birdhouse's inverter have Arc fault protection as well? The thermostat in any cheap coffee pot will trip one of those.
Those things have been worse to me than any GFCI.
Its funny, electricians and politicians make up the code and laws to require these things in homes, but cannot stand then themselves.
Wolv, do your mom a favor and find the underlying cause of the gfci fault. She might very well be able to thank you for your troubles some day.
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Yeah the cause is a cheap GFCI nothing more.
There is no measurable amount of power leaking to ground from neutral.
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Does the birdhouse's inverter have Arc fault protection as well?
I don't think so. When I looked at the ProSine for our RV (I bought an AIMS instead because it's 50% bigger) they had two different ones I could get. One had a built-in GFCI plug on it and it was designed for marine/RV with a floating neutral. The other model had a hard wire with a transfer relay in it, and it had a bonded neutral. I don't recall ever seeing anything in the specs about arc fault protection in them.
The ProSine inverters are highly regarded in the RV business - a lot of new RV's come with them factory installed now.
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Chris
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Yeah the cause is a cheap GFCI nothing more.
There is no measurable amount of power leaking to ground from neutral.
Looks like it is time to get her a pricey one. ;)