Emergency backfeed failed
JoshK
Solar Expert Posts: 232 ✭✭
I'm only looking for troubleshooting advice of what when wrong in the past, I know this is a bad idea and anything added is for educational purposes only...
It's my belief that I can use my 4-prong dryer outlet to power the 2 rails in my breaker box and then only turn on 120v breakers. Never a 240v because the rails will be in phase.
I shut off my main breaker AND all the individual breakers for inital verification. I powered the Left and Right prong on the dryer outlet with the hot wire from the inverter. I connected the neutral to neutral, and then the two green ground wires together. That was all verified with a continuity tester. When I plugged in the inverter, it should have energized the two rails and been ready to flip on one breaker. Instead the inverter immediately went into overload and shut off. Why would that be?
It's my belief that I can use my 4-prong dryer outlet to power the 2 rails in my breaker box and then only turn on 120v breakers. Never a 240v because the rails will be in phase.
I shut off my main breaker AND all the individual breakers for inital verification. I powered the Left and Right prong on the dryer outlet with the hot wire from the inverter. I connected the neutral to neutral, and then the two green ground wires together. That was all verified with a continuity tester. When I plugged in the inverter, it should have energized the two rails and been ready to flip on one breaker. Instead the inverter immediately went into overload and shut off. Why would that be?
Comments
You say backfeed, if you want to back feed you have to have an inverter designed to back feed and sync up to the sine wave of the grid.
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
My thought is that your problem is with your ground pin. Your inverter likely does not support bonding the ground pin to the neutral line which is what happens to those two lines in the breaker box. If your inverter still works, you may be able to get it to operate by not hooking up the ground pin on your back feed jumper.
Yes it does, nothing was harmed in the process.
You just might be a genius, that would have never crossed my mind. I will give it another try soon. Thanks you guys
Need to get "BB" to look at this one. If he does not pick up, I'd recommend you send him a private message to look at this thread.
Mark
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSplitPhaseandMultiWireBranchCircuits.pdf
MSW inverters do not generally like Neutral to Earth grounding on the AC output and having the battery bank grounded to earth ground (more or less, creates a dead short through the inverter).
With the AC Mains turned off, and the all the other branch circuits turned off. Does the inverter work? Then turn on the AC Branch Breaker for the inverter (no other breakers on). Does it still work?
Then turn on one branch circuit breaker at a time (work/not work per circuit).
If this is a PSW/TSW inverter--I am not sure why you are having a problem (in general, TSW inverters are find with a ground referenced neutral on the AC output and Grounded battery bank negative bus).
Hmm... Perhaps you have a polarity problem. Many TSW inverters have a green wire to AC neutral ground bond. If you have the AC inverter Hot/Neutral reversed--The ground bond "neutral" inverter connection and ground bond neutral in the main panel could be reversed and give you a dead short (i.e., Hot from inverter connected to neutral in main panel, and neutral from inverter connected to main panel hot)..
-Bill
Also, for the same reason, if several circuits are run through one conduit the derating according to the number of Current Carrying Conductors (CCCs) may not work out either. That is usually more of a regulatory than a safety problem, unlike the double neutral current which could actually start a fire.
As for the shutdown, does your inverter have a GFCI built in? What happens when you try to power only one of the two panel buses?
Thanks again to Brlux for nailing the issue!
When I was a kid I helped my folks build their house. We could not get a power pole and they would not hook up power till all the final inspections were done. We used a little 2400W sears generator 120V 20A with a 5hp brigs engine to run the place for a year while building it. Once all the electrical was in we used 2 lengths of romex with 120V male plugs at each end, the first was used to plug the gen in to a single receptacle dedicated 20A circuit for the central vac system in the garage and the second cord to jumper between 2 different 120V receptacles on different phases of the panel. It worked surprisingly well running all the lights in the house, plus drills, table saw and whatnot as needed to get the house done.
If you hook such inverter up like the OP did, you would short circuit or overload the inverter between the neutral (60 volts ) and ground since neutral and ground are joint together in the breaker box.
Note: Some inverters will put out 120 volts on one leg and will have a true neutral and ground.
Other inverters may not even have a ground hooked up inside them, like my china inverter that burned up last year after almost 5 years of use.
Here is the first of the videos detailing repair. In the #3 video he says it will not operate his refrigerator which is about 160W running. He has had no problem running the fridge on other 600W inverters.
https://www.youtube.com/watch?v=qG60rPmSqxc
The second issue--In the USA (at least), there are two styles of Dryer plugs. One is a 3 prong (L1 / L2 / Neutral) and the other is a 4 prong (L1 / L2 / Neutral / Safety Ground). If you have a 3 prong, changing over to a 4 prong plug at least gives you a true green wire safety ground (instead of using the plug's neutral as both White wire neutral and as a safety ground). Doing that, at least, allows the idea of separate neutral/ground wires from the genset/inverter to carry through to the house wiring.
NEMA outlet chart:
https://acupwr.com/pages/nema-chart
NEMA 10-30R and 10-30P "3 prong" 120/240 VAC L1/L2/N (N is assumed tied to safety ground "upstream" of outlet at power source)
NEMA 14-30P and 14030P "4 prong" 120/240 VAC + L1/L2/N+Safety Ground
https://www.homedepot.com/p/GE-6-ft-3-Prong-30-Amp-Dryer-Cord-WX09X10004/203497480? (3 prong cord)
https://www.homedepot.com/p/HDX-6-ft-30-Amp-4-Prong-Dryer-Power-Cord-HD-601-004/202532733? (4 prong cord)
I always wondered with 3 prong 120/240 VAC split phase dryer cords are still "legal"... Violates that whole idea of safety grounding the dryer sheet metal--Especially given the dryer is next to water (washing machine and sink).
For example, 4 prong allows you to have the same green wire ground for the generator frame/AC inverter chassis and choose where to do the "neutral to earth ground" bonding. This choice is a bit confusing--In North America, that bonding choice is usually inside the Main panel (neutral bus bar grounded to panel sheet metal/safety ground bus). In larger generators/AC inverters, Neutral to Safety Ground are (usually) tied together by default (around 3,000 Watts or so seems to be the default--But you can find gensets that do not follow that rule).
Functionally, the AC power system works fine either way (panel bond or genset bond, or even bonded in both places). The reason this is not usually done is because NEC (national electric code) does not allow the green wire to carry normal current--Only current if there is a short circuit. And second, the whole issue of GFI (ground fault interrupter) outlets. If you have a GFI outlet on the generator and tie N+G in side the genset/inverter and carry H+N+G to the AC panel which is also N+G bonded--The genset/inverter GFI outlet will usually trip (because N and G are in parallel and sharing current flow--Which looks like a ground fault to the GFI).
After I have typed all of the above... The short answer is "it will work" with the dryer plug (3 or 4 prong). Just a "safety" issue with "suicide" plug on genset/inverter side.
Longer term, if you installed a manual transfer switch or even a simple relay transfer switch--You could have two normal blade plugs--One for genset and one for AC inverter--And not do the "suicide plug" anywhere.,
https://www.solar-electric.com/search/?q=transfer+switch (transfer switches)
Use a manual transfer switch, or a relay type (for example, AC inverter connected to "default/AC mains" input, and genset connected to GEN input--AC inverter connected normally, and switches over to the generator when generator is running).
If you only have one power source at a time on your system... You could use normal "blade plug" on the cabin input, and a normal "socket plug" on the genset/inverter/extension cord and do away with the whole "suicide plug/cord".
If you ever plan on using a 120/240 VAC electric dryer with a larger genset (typically 6 kWatt or larger)--You would want a separate circuit from the genset to the main panel, so you can run the dryer too.
You would only "revisit" the cabin "blade" plug if you added another source of power (bring utility power to the cabin, want backup generator + AC inverter power sources always connected)... Then a transfer switch or suicide plug decision would be needed.
If/when you purchase a new AC inverter--You can look at the more sophisticated models that have a Genset input and their own internal transfer switch... As well as AC Battery charging, Generator Support (AC inverter "shares" heavy loads with small genset--Pretty nifty), or even Grid Tied (hybrid) Inverter if you ever get Grid Power and want to "sell" excess energy back to the utility (GT may or may not be legal with your utility).
-Bill