Update on Generator issue

[Stan Simpson]

Yesterday, while dry camping, I was running both a/c's and the generator sounded funny, and seemed to have an abnormal load. I shut everything except the a/c that was powered by 120V and the Aladdin screen looked like picture #1, which seems awfully illogical.

I shut off the bedroom a/c (I only have 2 a/c) and the Aladdin screen looked like picture #2.

While switching the Aladdin back and forth, just briefly when I switched from one screen to the electrical screen, a sentence in red came up that said "short detected in gen set leg". It only appeared very briefly, and I was unable to take a picture.
/c
Right now, I'm on 50A shore power in Cheyenne, and the screen looks like picture #3 while both a/c's are running.

Can someone analyze what I'm seeing, and offer some ideas? I can't believe that both a/c's running show all of the amperage being supplied by one leg of the generator.

Thanks in advance,

Stan

[Stan Simpson]

Disregard the third picture above. Its a duplicate. Here is the Aladdin screen with shore power and both a/c's.

Stan

[Edward Buker]

If everything in the coach gets power, then I would say that you have had the breaker in the main panel that runs each air conditioner on the same leg of your AC feed. Go to your breaker panel with the 120V AC powered off from the generator, power post, and inverter. Pull your cover and examine the layout of the power busses that the main breaker feeds. One side of the main breaker feeds half the distribution breakers and the other side feeds the other half. They alternate, that is distribution breakers that are side by side will be on opposite legs of the power feed. Find your two air conditioner breakers and move one of them up or down one position by exchanging it with another breaker. Turn everything back on and check your monitor with both air units running and see if they show up on opposite legs by the current readout.

There is also the possibility that the coach is wired wrong from the factory in some way putting all of the load on one leg, or the monitor system is providing false data. Start with the breaker panel check and check the air conditioner breaker layout. The temporary message of short may come from a current limit that you are exceeding because of your excessive load on one AC leg.

Later Ed

[Edward Buker]

That is quite a mystery. ...The new third screen on shore power indicates that shore power is distributed properly with one air unit on each leg. I missed that the amps went up when you shut down the bedroom AC so my first theory is out and I see no logic in what the monitor is telling you regarding the generator. I would as a minimum go to the transfer switch and with AC off check that the wiring looks right and tighten all of the lugs holding the generator wirings as well as check the others. If you have the capability to give the contacts a blast of air or lightly burnish the contacts in the relays go ahead.  I would also turn the breaker on and off that is on the generator which will reset it and reseat it in case that is playing a role in this. After this, start the generator with both airs on shore power, record the screen with a photo and then watch it when it switches over and see what happens. The voltage might be slightly different but the current should be similar in each leg. I'm not sure which generator you have but there is some chance that the waveform is confusing the monitor logic and the readings will not make sense. You could get hold of a clamp on AC amp probe and test the current flow on each generator leg with both airs running in the transfer switch housing to see if that gives you a different story than your monitor does. That is where I would go next...

Later Ed

[Steve Huber Co-Admin]

I suspect you lost AC1 neutral or ground, probably neutral, between the geni and the transfer switch. That would explain the high amperage reading on AC2. I'd start by checking input at transfer switch. If OK there, check output there.
Steve

[Edward Buker]

Steve,

I think if he lost neutral he would not get a 120V measurement by the monitor. There is just one common neutral or ground coming from the genset. I had some thoughts that one leg of the generator may have failed and that a prior owner might have paralleled the good side at the transfer switch putting all the load on one leg. That seemed far fetched so I did not mention it. I think having an independent voltage and current measurement at the generator input to the transfer switch will define what the generator is actually feeding the coach as well as have a good visual of the contacts in the transfer switch to assure they are closing and clean on both legs. Then you will know for sure what the generator is doing....this is a mystery.

Later Ed

[Stan Simpson]

Thank you Ed and Steve for your responses. I'm hooked to shore power now, and the Aladdin shows amperage on both legs. Logically, the generator is the problem. I did notice a bracket loose on the place where my 50A cord attaches to the surge guard. Perhaps I pulled something loose when I had to use all of the cord to reach the power pedestal on one my stops.

I don't know how to do the things you are suggesting. I'll be home next Monday, and will get with my electrician who should be my go to guy instead of an Onan shop. Do you agree? That way I can watch him and learn.

Stan

FWIW, this is a brand new problem. I have never had this issue before, so I doubt it is anything the PO did.

[Edward Buker]

Stan,

There are a lot of things on these RVs that I do not know how to do so no need to worry about that. The good thing is to know what you can and can't do and get some help when you need it...

If your electrician is familiar with generator set ups and transfer switches (which he may deal with on homes) he should be able to take some measurements at the transfer switch and see if anything in that area is not right. If he confirms that the generator is the problem and not connections or the transfer switch then you may be best served by a generator shop.

Later Ed

[Steve Huber Co-Admin]

Ed,
I'm assuming that the unit has functioned normally for Stan in the past. The problem is located somewhere from the transfer switch generator contacts back to the generator itself. The only way (I think) the Aladdin would show the amperage from both ACs on a single leg would be loss of a ground or neutral, resulting in the current for the faulty leg being reflected on the common line.  If the problem is with AC leg 1, will Stan have problems charging batteries, etc, with the geni as I think leg 2 is only used for the 2nd AC unit???

Stan,
Be sure to let us know what your electrical guy finds.  
Thx, Steve

[Edward Buker]

Steve.

The pickups for current and voltage on my coach are in a box in series with the transfer switch. I'm guessing that it is the same here. There is a small signal step down transformer for voltage on each leg that by ratio sends a voltage to the panel electronics for interpretation. It is a 10:1 step down running at 12v for a 120V input. The current sensing is by toroidal  transformer pick up off of each hot line as seen in this box. Because there is no sensing on the common or neutral line that would have to mean that one of the legs is truly carrying that amount of current. It would seem that the current sensing is working properly given the shore power monitor results. What is baffling is that with the shore power on, it would clearly show that the air conditioners are not wired to one leg and there is no automated load switching. I was wondering if there is some wacky thing going on with the surge protection monitoring that may be invoking some issue here based on its sensing circuit. One other possibility is that leg one and two hot legs are shorted together from the generator side but they are typically out of phase which would never work.... it will be good to get the final answer on this one when it is all sorted out.

Later Ed

[Steve Huber Co-Admin]

Ed,
Understand, but I think the problem is in the ground connections to the torriods, not the hot lines. We'll have to wait and see what the electrical tech finds.
Steve

[Edward Buker]

Steve,

The torroids are just inductive pick ups using the field from hot lines passing through the center. The ground and neutral just pass by the torroids through the box without any connections. We will wait and see what the electrician finds and probably all be surprised :-)

[Stan Simpson]

We got home yesterday. I called my electrician today, and he is coming over Thursday morning. I will report his findings.

Stan

[Stan Simpson]

The electrician came this morning. Checked everything. Had 120 on each leg with the generator running. First I turned on the front a/c and the amps showed 24 on Leg 2. Zero on Leg 1.  Turned on the bedroom a/c and the load on Leg 2 went to 18 and Leg 1 showed 7 and then dropped to 6. With both a/c running, turned on the microwave. Leg 2 went up to 24 and Leg 1 stayed at 6.

Electrician said system was working perfectly. Nothing burnt or corroded in the transfer switch/surge protector. All grounds and neutrals as they should be. Numbers are from the Aladdin, but the electrician's meter showed basically the same.

Scratched our heads and had a beer (well, he did..I had an O'Doul's)

Gremlins!

[Edward Buker]

Stan,

There are two things that you know from this. First is that your coach is wired properly and that all the current loads and readings are as they should be, the second thing you have learned is that beer fixes everything, even O'Doul's :-)  The air units and the charging system all start out drawing higher current and taper down. So to see some higher current when things are first turned on is normal and the gen set may grunt a little bit more until loads taper off. You can record all the normal readings now and feel comfortable that things are in good shape. Hopefully these issues are gone for good...

Later Ed