Having inverter issues. (Long post)

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.

31 Replies

CA_Traveler
Explorer III
Apr 20, 2017
With dual input the neutral will carry the sum of the hot loads. The load is not likely to be split evenly by the neutrals because of the different impedance of the two wires. And the difference could be enough that one neutral gets overloaded.

I made my suggestions to try and narrow down the problem. But now since the problem may not occur for months I'd do a permanent 3 wire input with the wires large enough to carry the full amps of the two hots - ie the neutral will need to carry all of the amps. And frankly your bench test is meaningless since it can take months to fail in the rig - so it could be the inverter but maybe or maybe not.

And with 2 new and totally known output circuits wait months to see if it fails and if so that would point to a inverter design problem.
MrWizard
Moderator
Apr 20, 2017
Bill
I don't remember
Did you check the balance of loads in the RV
Are the two or more A/C units on different hot legs
What about things . Like the outlet used for hair dryer
Versus the water heater element
Portable electric heaters , are the outlets used on opposing hot legs, not just didn't breakers, but different hot legs, so the load is spread and the neutral does not have too carry a . Large difference
Bill_Satellite
Explorer II
Apr 19, 2017
The problem is that every setup I have tried "works" just fine for a few months. I don't know enough about RV wiring to know what is in phase and what is split phase. With my 50amp coach (50amps of power available on each or 2 separate legs) the only way to send 240V to any device is to supply power from Hot L1 and Hot L2 plus the neutral and ground. If I can get the inverter fixed/replaced I am going to return to the option of tapping into the transfer switch and run a 4 wire (2 hots plus 1 neutral and 1 ground) as the incoming power but I don't believe that this is any different than running 2 3 wire connections to the same ports when that source is the same Hot L1 and Hot L2 with a 2 neutrals and a 2 grounds coming from the same bus bar. It even seems that I could just not connect both neutrals and both grounds in the inverter since they are already connected at the breaker bus bar.
Help!
CA_Traveler
Explorer III
Apr 19, 2017
From the manual for the 150:
Input AC Source from Dual Input:
The dual input has 2 line inputs, 1 neutral and 1 ground. The two 120Vac lines are in phase and must come from the same source.

To be clear this is your intended configuration and not the split phase 120/240V correct? And you are using 2 3 wire connections for this hookup so you have parallel neutrals and parallel grounds. Correct? Are you sure both hots are from the same 120/240V leg?

Skipping for now my safety concerns about this suggested hookup, etc and trying to help find the problem.

Temporary wiring to isolate the problem: Run 3 wires and only 3 wires from the ATS (you asked about this) to the inverter input. Does it now work OK?

If not remove all output wires but leave the 3 wire input. Does it now work OK?

Is so then connect first one output, OK? Disconnect and then connect the other output. OK? And disconnect means remove all 3 output wires.

If OK then perhaps something is misconnected on the outputs. Further connect 2 completely rig independent output circuits and load them. This should be OK and the same as your bench setup.
Bill_Satellite
Explorer II
Apr 19, 2017
Sorry, I missed your post CA Traveler. The inverter has 2 outputs and each goes to its own individual set of wires, 1 for each circuit. The inputs sending 120V to the inverter from shore is designed for either a 3 wire 20-30 amp circuit input (from my breaker box) or 1 4 wire 50 amp (240 out of phase) circuit. I have talked with others that using 2 3-wire inputs should work just the same as the 50 amp 4 wire since both neutrals and grounds are already connected to the same bus bar in the breaker box.
CA_Traveler
Explorer III
Apr 13, 2017
The pedestal CB disconnects only the hot lines. As long as you are plugged in you will have neutral ground bonding back at the service panel.

"This is partly why having L1 connected direct and L2 through the inverter might be causing the trouble because they are not completely isolated."

If this is how it's wired then wire it correctly and see if that resolves the inverter issue.
CA_Traveler
Explorer III
Apr 13, 2017
With the inverter off the neutral ground bond occurs at the CG service panel and all rig circuits are effected. When inverting the internal ATS switches both the neutral and hot outputs to the inverter and bonds the output neutral to ground.
Bill_Satellite
Explorer II
Apr 13, 2017
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.
time2roll
Nomad
Apr 13, 2017
Bill.Satellite wrote:
Time2Roll...tried to quote you but the software won't let me so in response to what you posted about the Kisae.....

I read that some time back but did not understand it. Now it's even more confusing as it seems to say that the inverter A/C input SHOULD have a neutral to ground bond.
Only bonded in the inverter when inverter is supplying 120v power. This bond is made because the inverter is the power source. Same as the utility power bond back at the source(first main panel off the power company transformer).

If the inverter is off or charging the battery there should be no bond made as the power source is off.

Inverter, generator, utility as independent sources are kept separate by the transfer switch. This is partly why having L1 connected direct and L2 through the inverter might be causing the trouble because they are not completely isolated.
CA_Traveler
Explorer III
Apr 13, 2017
In that case you know that the problem is not on the output of those GFCIs. All other circuits and wiring are suspect even the ATS. And this includes GFCI input wiring.

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Having inverter issues. (Long post)

31 Replies

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