Inverter GFCI, Microwave & Faulty Power Strip

[oldjohnt]

I had an unusual problem yesterday with my RV's Microwave tripping my PSW Inverters GFCI protection on start up I thought Id share to maybe help someone in the future. (YES batteries full charged voltage open or loaded more then adequate)  

Even though all worked perfect for like a year, while on my 2000/4000 PSW Inverter power as soon as the 1100 Watt microwave started it tripped the Inverters GFCI protection circuit (has tripped notification light and shuts down till reset)  hmmmmmmmmmmm  

I plugged a 1500 watt 2 wire heater and a 1500 watt 2 wire hair dryer into the same outlet and they worked perfect no tripping, yet microwave tripped it instantly on start up 

I tried different of the 3 Inverter outlets/circuits and as expected, no difference ONLY the microwave (no other devices, even higher powered) tripped the GFCI

I plugged the micro direct into a GFCI outlet on my porch, it worked perfect no tripping..

Sooooooo I started unplugging any other devices to see if that helped, everything except micro, still tripped DRATS........

Finally I unplugged a 6 outlet non surge protected standard household metal power strip (had nothing else plugged to it) NOW MICROWAVE DOESNT TRIP GFCI yayyyyyyyyyy    Micro was NOT plugged to that Inverter fed power strip, its located elsewhere for low power electronic devices...

I installed a new 6 outlet power strip now all is back to perfect yayyyyyyyyyyyyyyyyyyyyyyy

That darn metal power strip must have a very minor but yet sufficient ground fault the Inverters GFCI circuitry detected when the micro started causing it to DO ITS JOB and trip...   Standard GFCI for homes etc only requires around 0.005 Amps to trip, Im unsure what the Inverters GFCI trips at, but it was that darn power strip causing the problem, now the micro and all else is well making me a Happy Camper. I like EVERYTHING working and if not Im very upset lol 

Best wishes yall, be safe be happy 

 

John T

Edited July 8, 2021 by oldjohnt

[Bill Joyce]

I had a similar problem many years ago with a power strip, but it was more obvious than yours since the power strip just had to be plugged in to cause a GFCI fault. 

[Kirk W]

43 minutes ago, oldjohnt said:

Micro was NOT plugged to that Inverter fed power strip, its located elsewhere for low power electronic devices...

Now that brings up a nice theoretical problem for you to use to test all of theory classes from your school days! It must have somehow been subject to RF, maybe? Just for fun, use an extension cord to get that problem strip outside of the RV when connected and see if the microwave will still make it trip the GFCI. Maybe tear the strip apart sometime when you have nothing to do and see if you find anything? That sort of thing used to bug me when I knew what was causing a problem but couldn't understand why, but any more I just take the "if it ain't broke, don't fix it" approach to things.  ☺️

[oldjohnt]

1 hour ago, Kirk W said:

Now that brings up a nice theoretical problem for you to use to test all of theory classes from your school days! It must have somehow been subject to RF, maybe? Just for fun, use an extension cord to get that problem strip outside of the RV when connected and see if the microwave will still make it trip the GFCI. Maybe tear the strip apart sometime when you have nothing to do and see if you find anything? That sort of thing used to bug me when I knew what was causing a problem but couldn't understand why, but any more I just take the "if it ain't broke, don't fix it" approach to things

 

Good ideas Kirk, thanks, I still have it and can run some tests in my shop. I plan to carefully disassemble it (can split it in half with no damage to what's inside I think, there's NO surge protection involved) looking for a minor short or burn spots etc.......I too wonder if the microwave tube and any high frequency somehow ????????????? contributed but how in the world it ONLY tripped the Inverters GFCI if it was simply plugged in elsewhere 8 feet away with no cords on any of its 6 outlets???????????

 Hey RF was NOT my area of study, old fashion AC power is about all I remember grrrrrrrrr

Best wishes take care, as you indicate its NOT broke now and don't need fixed but I may play with it   lol

John T

 

Edited July 8, 2021 by oldjohnt

[oldjohnt]

UPDATE

I plug the bad power strip into an Inverter fed outlet in the RV kitchen (NOT where it was before) plug micro into it, Inverter GFCI trips instant micro starts

I plug the micro into a kitchen outlet but plug the strip into the other duplex outlet in kitchen, Inverter GFCI TRIPS instant micro starts.

I plug the micro into a porch GFCI outlet, micro works perfect

I plug the strip into a garage outlet (fed by GFCI Circuit Breaker) and plug grinder or drill press or saw into the strip ALL WORK PERFECT

Found no burns or shorts or bad wires when I split the strip in half.

The inverters GFCI trips ONLY if that power strip is plugged anywhere in the RV into Inverter fed outlets even if NOTHING is plugged into any of its 6 outlets 

Hmmmmmmmmmmmmmm RF Microwave tube related like Kirk mentioned??????? Its has to do with the Inverters GFCI electronics but its above my pay grade and Im done messing with it since the new power strip allows all to work perfect  

Thanks for listening, experiment is over Im tossing it never to know why/how it happens but didn't for a whole past year ??????

John T

[Ray,IN]

Sometimes things just wear out. Hummm, I'll stop at that, too close to home.

[oldjohnt]

20 hours ago, Kirk W said:

Now that brings up a nice theoretical problem for you to use to test all of theory classes from your school days! It must have somehow been subject to RF, maybe?

THANKS IN PART TO KIRKS ENCOURAGEMENT TO EXPERIMENT, I THINK I MAY HAVE DIAGNOSED THE CAUSE !!!!!!

Here's what I believe caused the Inverters GFCI to trip when the microwave started anytime the power strip was present in the Inverters circuit. No warranty, I'm more experienced in AC power engineering then electronics.

NOTE other devices like heater or hair dryer or a drill press or saw plugged to the strip worked fine either in the RV or elsewhere, it was ONLY the microwave in the RV IF STRIP WAS IN THE INVERTERS CIRCUIT ANYWHERE that caused the Inverters GFCI to trip..    

1) Contrary to what I thought earlier, the power strip which only has a lighted on off rocker switch (no other lights or indicators) like most do HOWEVER it did have surge protection as barely legible stamped on the case  and had a small circuit board inside (with I believe an onboard MOV)

2) What a cheap basic surge protector "very basically" does is use a Metal Oxide Varistor (MOV) which shunts out to ground a high voltage spike on the line to prevent electronic equipment damage.

3) What GFCI very basically does is sense any current imbalance/difference in the Hot and Line and if there's more then 0.005 amps difference it trips out. If current (caused by HV line spike from micro starting) flows to ground as the surge protectors MOV does instead of Neutral, that's a "ground fault" as far as GFCI is concerned and senses. NOTE repeated MOV use caused by sufficient energy line spikes over time can eventually render them inaccurate or inoperative. This problem didn't happen before but started recently ............

IT IS MY BELIEF WHEN THE MICRO STARTED IT INDUCED A BRIEF HV SPIKE IN THE LINE,,,,,,,,,THE POWER STRIPS SURGE PROTECTOR SENSED THAT AND SHUNTED THE HV SPIKE TO GROUND,,,,,,,,,,WITH SOME SMALL CURRENT SHUNTED TO GROUND VERSUS NEUTRAL, THE INVERTERS GFCI SENSED THE IMBALANCE AND CORRECTLY TRIPPED AS DESIGNED TO DO........IE the surge protector and the Inverters GFCI BOTH WORKED CORRECTLY 

Soooooooo any of you fine experienced technicians or engineers think this makes sense ??????? Its the reason why I think the GFCI tripped with the power strips surge protection in the Inverter circuit when the micro started.

 Thats my story n Ima stickin to it (for now at least lol)

Best wishes yall

John T Longgggggggggg retired n rusty electrical engineer but still enjoy the subject and love to help anytime I can    

[Kirk W]

Your theory is as good as any, probably better than most. In field service it has long been known that an MOV does age and lower quality(ie.. cheap) ones will weaken more quickly. Faulty fluorescent lights have long been a source of rf related problems in the field. Another factor can also be condustor lengths as they can become antennas if length matches a particular wavelength. In addition to your cheap power strip having aged, it is also true that microwave leakage sometimes increases with age and with the vibrations that an RV microwave is subjected to, that may well have also contributed. 

Some years back my son, the former Army radar tech, attempted to teach me more about rf, antennas, wave guides, and all sorts of other hocus-pocus and my conclusion was that it isn't magic as I once believed, but really it is all voodoo.

[Star Dreamer]

Hmmm, we recently had our microwave trip our inverters circuit breaker, twice now, and come to think of it after reading this post, I recently have a power strip plugged into an outlet on the other side of the kitchen. 

I may have to remove that power strip and see if we do not have that issue any more too.

[Alie&Jim's Carrilite]

I had a power strip that had an overload circuit protector built in, that failed internally, light was still on, button pushed, but wouldn't pass power thru.

[oldjohnt]

 

 

14 hours ago, Star Dreamer said:

Hmmm, we recently had our microwave trip our inverters circuit breaker, twice now, and come to think of it after reading this post, I recently have a power strip plugged into an outlet on the other side of the kitchen. 

I may have to remove that power strip and see if we do not have that issue any more too.

Hey Star Dreamer, The ONLY things I can say for sure now are...

1) The Six Outlet Power strip in question (despite my original post) did indeed have Surge Protection...

2) Anytime it was plugged into any of my Inverters three outlet circuits, even if NOT where or same circuit the microwave was plugged, even if NOTHING was plugged to any of its 6 outlets, when the microwave started my Inverters GFCI tripped

3) For maybe two years prior, this DID NOT HAPPEN (Surge protectors MOV's can fail due to prior faults)  

4) With the micro plugged to a GFCI on my porch it never tripped

5) With a saw or drill press or grinder plugged to the power strip in my garage which has GFCI protection  NO trips   

6) With the old power strip gone and a new non surge power outlet strip installed ALL WORKS PERFECT

 That's why my conclusion was the power strip was at fault WELL DUH and my best guess and theory was the microwave start introduced a line spike causing the power strips surge protector to shunt out the HV spike to the Equipment GroundING Conductor (NOT Neutral) thereby causing an imbalance due to the ground fault it sensed causing the Inverter to trip .............

 Either that or magic or gremlins lol

 Best wishes take care be safe

 John T