Having Inverter Issues (Long Post, Sorry)

[BillAdams]

When I bought this coach it had an inverter that was not also a transfer switch (separate charger and inverter) so there was one transfer switch that controlled the switching between shore power and generator and another that controlled the switching between inverter and no power from either shore or generator.  After installing a new charger/inverter combo with integrated transfer switch I was told to remove the 2nd transfer switch as it was no longer necessary.  I wired 2 incoming 30 amp 3 wire A/C connections which are on separate legs and provide 240V between the 2 hots.  To wire this up I put 1 hot in the Hot 1 connection and the other hot in the Hot 2 connection with both neutrals in the neutral connection and the 2 grounds connected to the ground post.  This allows full battery charging plus full pass-through of power on that circuit.  There are 2 outputs and there are 2 120V lines that go into the coach from the inverter.  The output side has connections for 2 hots and 2 neutrals for each line and the grounds are combined into 1 post.  The problem is that after awhile, the inverter fails saying there is an A/C fault that cannot be recovered from and requires repair/replacement.  The manufacturer says that this can only be caused by A/C feedback (sorry for the long story).  The company has been good enough to replace it twice under warranty but it just happened again.  I have not "used" the inverter as I have been parked in the same location for many months but the inverter was "on" in the software despite always having 120V power.  One morning we wake up and it's showing the error.  Nothing happened and nothing changed other than the inverter and the battery charger are now dead.

My first question is, what is A/C feedback and would that be coming from the A/C input side or somehow from the 2 - 120V lines coming out of the inverter that power dedicated plugs inside the coach.  Second, would re-installing a 2nd transfer switch solve this problem?  Again, this transfer switch would keep the 2 lines going into the coach from the inverter isolated from the inverter as long as shore or generator power was available and would only send power to the plugs inside the coach from the inverter if neither shore power or generator power was available.

[kaypsmith]

Bill, is this a 240 volt output inverter, or is it a 120 volt inverter with two connections? The inverter should be labeled either 240 or 120 volts, also how many watts is the inverter? Will answer the first question when I know the specs on the inverter. Also, is there any device in the coach which is a true 240 volt device?

[BillAdams]

This is a 3000 Watt inverter/charger (Kiase).  The output is 120V and the input is 120V but it will take a 50 amp input (2 120V hots) with 240V measured between the 2 hots.  I am not running a standard 50 amp cord to it, however, which would have red, black hots plus neutral and ground.  I am running 2 30 amp connections from my breaker box.  They are on opposite legs of the incoming 50 amp power so I have 2 sets of 12/2 wiring.  Each of which has 1 hot, 1 neutral and 1 ground.  I am connecting 1 hot from each to hot 1 and hot 2, the 2 neutrals to the 1 connection labeled neutral and wiring both grounds to the ground connection.

[manholt]

Bill, I'm not an electronic expert by any means, but my gut feeling is to re install the second transfer switch. 

Carl

[kaypsmith]

Bill, sorry to take so long to get back. AC feedback is a term used meaning that there is a ac entering the dc side of the device, meaning of course that there is probably a neutral side of the ac circuit somehow touching or maybe miswired and making way to the frame of the inverter. With shore power disconnected and generator not running, test for continuity at the two blades of the shore power cord, neutral and ground are the two blades. Continuity can mean any amount of resistance between the two, not just 0 ohms, if this occurs check for bonding al all junction boxes, there should be none, if there is that will be the source of the feedback. If possible please include the model number of the inverter.

[BillAdams]

This is the link to the inverter http://www.kisaepower.com/products/abso-inverter-chargers/abso-inverter-chargers-low-frequency/model-ic-1230150/

IC-1230150 3000 watt sine wave inverter with 150 amp charger.

 

By bonding do you mean that the neutral and ground are somehow touching or jumped?

[BillAdams]

So, with the coach unplugged from the pole but plugged into the coach I do not get any continuity reading of any kind on any lug in any combination.  Checking the port where the cord connects to the coach I also get no continuity reading between any 2 connections.  However, this wiring leads to the Surge Guard surge suppressor and there I get infinity continuity between green and white or touching chassis ground and green as well as chassis ground and neutral (white).  I see that same things at the main transfer switch after the Surge Guard.  Does the Surge Guard bond neutral and ground somehow?

[BillAdams]

I see I am also in the wrong category.  Could someone move me from Electronics to Electrical, please?

Thanks..

[kaypsmith]

There should be absolutely no continuity between green or chassis to neutral. If you are seeing this, then there is a problem. Could be a blown diode within the inverter, or within any circuit breaker box someone may have accidentally placed a ground wire to a neutral bus, there is supposed an additional bus bar everywhere in the coach, this is only supposed to take place at the the CG pedestal. Since your batteries negative are supposed to be grounded to the chassis, if ac gets to the chassis at any point other than the pedestal, it will cause the feedback condition. Sometimes this condition will actually cause that tingling sensation in wet conditions, don't want that to happen. The surge guard is not supposed to bond neutral to ground, as mentioned earlier this should not happen before the campground pedestal, although there may be an electronic circuitry to make this happen in the absence of electrical connection, without schematics of the surge guard it would be hard to tell. One other place that comes to mind, the generator is supposed to be mounted in rubber with no metal touching the bus chassis or not even bonded with a wire, the green (ground) wire on the generator should be attached at the transfer switch ground circuit, I have seen over the years an installer put that wire to neutral which is incorrect. 

[BillAdams]

I do get a tingle from time to time from the stainless body panels.  I have for years and years.  I avoid barefoot on wet soil!!!  I can't even think where to start.  I assume the power cord would go directly to the transfer switch the wires for both hots are black going into the transfer switch so they go somewhere else first.  There are 2 50 amp breakers (confusing) one labeled main and one labeled shore and a 3rd breaker for the Generator.  Could the wiring be reversed between the 2 breaker boxes (red/black reversed as I don't see any way to reverse the large neutral and the bare ground wires).  Is there some way to trace a circuit where input and output are 40 feet apart?  I can start disconnecting wires and see what goes where.

In the meantime, can I assume that this has not been a  problem in the past was the additional transfer switch that prevented any A/C shore/generator power from being active at the same time the inverter was active (although the battery charger would have still be charging while on shore power).

By the way, the inverter powers dedicated lines which are only powered via A/C pass-through of the inverter or with no 120V inverter power.  If the inverter is taken out of the circuit there is no power to these 2 circuits.

[kaypsmith]

It doesn't matter that L1 and L2 (red/black) are inverted in a 240 volt circuit, both are 120 volts to common (neutral), either side will do just fine. The neutral making way to ground after leaving the CG post is still the most likely culprit, by the way if you want to ground the chassis directly to the pedestal by means of a separate wire, simply use a single wire attach it to the chassis and terminate the other end to the round of a standard 120 volt male plug, plug this into the 120 outlet on the pedestal, breaker can be on or off as you are only using the ground anyway. The generator is most often a culprit of this grounding to neutral because many don't realize that it makes a difference, I have even found times that someone put a strap from the generator straight to the chassis. Inside all breaker boxes after entering the coach as mentioned earlier there must be separate ground bus which must not be bonded to neutral in any manner for safety sake, remember that there is an equal load as the appliances on a circuit carried back to ground in a 120 circuit, ie. if you use 5 amps, 5 amps are carried back to ground, enough to cause that tingle when you are standing in a wet condition outside the coach. One other thing that I forgot to mention earlier to test for backfeed to DC, set your digital volt meter to the lowest setting, make sure you are plugged into shore power, and turn on several high amp draw appliances, now hold the test leads to your 12 or 24 volt DC source that powers the inverter, if you read any AC voltage, that is backfeed, it should read no voltage at AC. An analog meter will not show this because there is too little voltage for you to be able to see the movement. Hope this helps, and the chassis to ground has helped several with bus conversions over the years.

[BillAdams]

The inverter is currently dead as a door nail so I am not sure that this will do anything but I will run some appliances that are on the inverter pass through and see if I read any A/C on the D/C circuit.  I am going to have to beg the manufacturer to repair this unit or I am going to have to buy a new one so I want to ensure that whatever I do does not result in another burnt out inverter.  Seriously, the only thing that changed was the removal of a faulty transfer switch (apparently very, very bad advice).  Ever since I did this, the inverter has not lasted more than 6 months.

I do want to find the actual source of this problem so if anyone has any ideas about how I should work my way through the wiring system to find where something went terribly, terribly wrong I am open to any and all suggestions.  While this might not have anything to do with anything, a few years back Prevost did not properly plug in our coach and we ended up with 150+V  (an high as the meter goes) on one leg and 0 V on the other (open ground/neutral?) which burned out many of our 120V appliances.

Thanks in advance to everyone!

[kaypsmith]

That sounds as though 120 applied to either L1 or L2 and 120 applied to common/neutral with the common input into the other leg of the 240 circuit. Everything that was in the on position of the hot leg would have received the full 240, ouch!

[BillAdams]

Yep, they burned up a lot of stuff in the coach when that happened.

[manholt]

Have you been able to isolate anything yet?  Or are you trying to get inverter rebuilt or replaced?  Hate to mention this, but your still going to blow the inverter unless you resolve the ground issue.  I personally would go back to what you had before!

Carl

[BillAdams]

It has been suggested elsewhere that the way I wired the inverter could also cause a feedback issue.  It is designed to accept a 50 amp input (4 wire) but I used 2 30 amp connections (6 wire) on opposite legs so I get the same power effect but I have 2 neutrals in the neutral slot and the hot from 1 leg in Hot 1 and the hot from the other leg in Hot 2.  The 2 ground wires are tied together with a wire nut and a a jumper to the inverter chassis ground connection.  I also changed this when I pulled out the inverter but I suspect it still has nothing to do with why I have continuity between ground and neutral.

So now a question about how to find where this might be happening.  Correct me if I am wrong, but I assume that any circuit in the coach where the neutral and ground somehow have come together would cause this issue throughout the coach.  If that's true, could I disconnect all of the neutral wires from the neutral bar in the main breaker box and test each one until I find what I hope to be one bad circuit?  If I am that lucky, would there be any way to trace that one circuit other can connecting everything back up and see what's not working?  I can't see anyway that the incoming wiring could be wrong as the ground and neutral wires are very different (big fat neutral and solid copper ground) so I am  thinking during one of the remodels someone screwed into a line or broke a line somewhere.

[BillAdams]

Interesting followup. I now have the inverter completely out of the circuit and with the coach plugged into the pedestal but not powered on I have NO neutral to ground continuity issues anywhere (except the generator wires going to the transfer switch all beep no matter what 2 wires you touch!). There is neutral to ground issue at the Surge Guard even though I did not turn on the breaker outside. If I unplug the coach from the pedestal there is no neutral to ground continuity again. I am not sure it means anything, but with the power turned on any everything working there is continuity everywhere with every connection.
So, it appears the coach is actually wired right and after all so I am back to trying to figure out what's blowing up the inverter (this is the 3rd time). If, as the instructions seem to indicate, the coach should have a neutral/ground bond what am I supposed to do? As I mentioned, when A/C power is coming into the coach I do have continuity on neutral and ground.

[kaypsmith]

If no continuity between ground and neutral with coach unplugged from the pedestal, this is correct wiring. The ground and neutral are bonded at the pedestal, which is where that is supposed to happen. This condition will now show continuity all the way back into the coach with shore power plugged up, throwing the breaker at the pedestal will not effect the continuity reading back inside the coach as the breaker only opens the two hots (L1 and L2). Electricity will use the least resistant path to ground in all cases. If there was continuity while unplugged between the two with the inverter in place, then the culprit is the inverter itself. I noticed in the manual that the battery DC wires must not touch the AC wires, this can be another source of backfeed, not their words but mine, this is a known fact.

 

 

 

[BillAdams]

From the manual, the inverter does bond neutral to ground when 120V is NOT present.  The testing I was doing with the inverter not working must be what was causing the coach to show the bonding.

 

The inverter does bond neutral and ground when inverting.

Manual p7:

When the KISAE Inverter-Charger is running in Battery mode, the internal neutral-to-ground
bonding system is enabled. The unit will act as an AC Source and will automatically connect
the AC Output Neutral circuit to safety ground.
When the unit is running in Pass-Through mode, the internal neutral-to-ground bonding
system is disabled. The unit will not act as an AC Source and the AC Output to safety
ground is disconnected inside the unit. Therefore, the AC Input source that is connected to
the Inverter-Charger should have its own neutral-to-ground connection. If not, have an
electrician look into bonding the AC Source’s neutral to ground at your AC Source.
 

[manholt]

Unless, I'm miss reading manual p. 7.  That leads right back to what Kay wrote earlier, your problem is at the post or origin of AC.  Also, have you tried as Kay also suggested, run a single wire from coach back to post as a ground? 

[manholt]

Sorry, that should read single wire plugged in to 120v at post. 

[kaypsmith]

Thanks Carl, the single wire is not to help with inverter issue, it only will help get rid of the AC tingle when touching the metal of the coach while in a wet condition.

[BillAdams]

The problem cannot be at the post as it has happened everywhere, all the time.  This post does have the neutral / ground bond as I could test that with the unit plugged in but not powered up.

I think the consensus is that I was trying to use a fault wiring scenario but trying to create a 50 amp circuit style circuit using 2 3 wire connections.  I will see if I can get the inverter repaired and then run a correct 4 wire line from the existing transfer switch (generator / shore) and see if that keeps the inverter working.  I bought a new transfer switch to go between inverter and the existing transfer switch but I don't think it was ever the source of the problem.

Thanks to all for your input.  Any followup ideas are welcome as well.

[hermanmullins]

Bill,

I am not the one to chime in on this post. My eyes have crossed several time just reading it. However with regards to having the inverter repaired. I had my inverter checked out by National Indoor Storage in Lewisville, TX and it was found to be in tip top shape. They were able to bench test it and would have repaired it if necessary. I believe they have several locations around the country. What I did find when I pulled mine out was a loose ground. Not disconnected just loose. It was where the Grounds for both the Generator and the Shore Power connected together to the Inverter chassis. When I reinstalled the inverter I made sure all connections were tight and have had no issues since. So you might try National Indoors for assistance if there is one close to you.

[blakeloke]

Bill,

I've read, reread and reread this thread several times in hopes of understanding what is going on with your coach and inverter (I'm slow on the uptake).  I'm on first pass going through the owner's manual and have gotten to page 8 that shows electrical flow diagram.

I see that there is a DC overcurrent protective device or fuse.  What I haven't gleaned from the manual yet is if the overcurrent protection is integral to the inverter or is it an auxiliary piece (I'll keep reading).

By any chance are you house batteries connected correctly.  ie: 36vdc instead of 12vdc?  Something simple to check with your Fluke meter.

Blake