Inverter settings

[bwalz]

What do I set my inverters to when I plug into 30 amp? Should it be 15 for each or 30 for each? They are Trace inverters.

[Kevin Erion]

I would set them at 14 per side just for a little safety.

[Jon Wehrenberg]

Here is a loaded question.

Some conversions or inverters have provisions to either sense the available shore power amperage, or to have that value inputted on a control panel. Then the inverters are self limiting so they do not draw more power for battery charging than is available.

Other conversions of inverters are not as capable or as sophisticated and the amount of load they will draw has to be set manually. I have mine set for 5 amps based on how we use our coach. Since we rarely dry camp or rely on auto-start our batteries are usually topped off, or if we sit overnight and do deplete the batteries we typically will be driving the following morning and the alternator will recharge the batteries.

But our inverter settings are not easily done because we have to remove the remote panel and change dip switch settings.

I think the answer to the question is based not as much on how much shore power is available, but how does the inverter and the converter's electrical system work, does it shed load, does it sense other loads or does power management have to be done manually.

30 amps is not much and if our coach is typical we use about 10 amps just because of key off loads ranging from clocks to alarm systems to all other power drains plus the refrigerator. Plus anything else we may want on such as TVs, or an AC or the hot water heater are added on top of that before we even consider the inverter current draw.

[phorner]

Just had an "interesting" experience. While using the microwave this evening, we popped what I believed to be the pedestal circuit breaker, as we had a lot of current draw on one circuit.

I reset the pedestal 50 amp breaker and returned to the bus to find that only "Line 1" was powered up. This did not have a good feeling....

So, I went out and shut off the "bus" main breaker in the first, driver side bay; cycled the pedestal breaker back off and on; turned the "bus" main breaker back on and still no power to "Line 2"..... only "Line 1".

Back outside to go through the same routine again and this time, all is well inside. Power to both "Line 1" and "Line 2".

Could the Line 2 inverter be going bad or is it possible that some sort of thermal protection kicked in for a short time? The inverters were getting a direct shot of hot afternoon sun.

And, just because it seemed like the right thing to do, I adjusted the dip switches on both inverters to allow 5 amp charging instead of 20 amp. Probably better for power management in any event.

Any comments or suggestions? Should I be figuring on trading some diesel fuel for new inverters?

[Jon Wehrenberg]

Paul,

I don't think you have an inverter problem. What may have happened is the combination of an overloaded shore power breaker combined with an overloaded inverter.

As our coaches are set up each inverter has 50 amps of input power going to two separate circuits on the inverter itself. One circuit is the power to the charging circuit and one is the power that is a pass through. In other words when shore power is available to the inverter the inverter uses that power to charge the batteries plus supply the 120V AC output to the circuits set up in your AC panel.

When shore power is not available your batteries via the inverter supply those circuits. Your microwave is one of those circuits. I don't know what other circuits are powered along with the microwave, but they are possibly front or rear outlets, the refrigerator or the TVs. Regardless of what they are it is possible whatever circuits had loads they exceeded the 2500 watt output of the inverter so when the shore power tripped, it was followed by the inverter which likely took a bit to reset itself.

I think. Try to remember what loads were on the inverter circuits and if they exceeded 2500 watts.

The sequence may be reversed, but regardless it sounds like you exceeded the limit and the built in circuit protection worked as intended.

[phorner]

Thanks, Jon. I appreciate the comments.

The inverter "loads" don't appear to be evenly split, according to the labeling on the main breaker panel. So, it would appear that I need to keep a better eye on this.

When the missus is without both her cup of tea as well as the air conditioning, well, things can get ugly.....

[Joe Cannarozzi]

Paul

I had a failure once where I initially noticed I lost power out of a kitchen circuit. I was plugged in on 50amp shore power and the inverter was on but a/c current was just going through the inverter, it was in battery charge mode.

First instinct was to check the breakers none were tripped. Upon further investigation I began to realize I had no power to quite a few other things and eventually came to the conclusion that everything that was wired through the inverters fuse panel was dead. Another check there found no breakers tripped:confused:

What I eventually found was even though I was on shore power and A/C current is going through the inverter to its fuse panel we still had to exercise conservation and keep the total combined amps below 25 (we have 1 2500 inverter) whenever using multiple appliances and or outlets that come out of the inverters fuse panel or we would trip a breaker that is on THE INVERTER ITSELF.

To avoid this problem I needed to shut off the inverter while on shore power when I needed power simultaneously that combined added up to more than 25amp, even though coming from multiple circuits coming out of that fuse box.

For example like the toaster and microwave and the outlet in the bathroom with Deb running the curling iron, all simultaneously (all of which are wired out of that inverter fuse box), if shore powered is coming in and we simply shut off that inverter beforehand, no problems.

If that were tried on shore power with the inverter switch on, again I'd be down in the belly pulling panels to acess that breaker on the inverter itself.

I incorrectly assumed that because we were on shore power that each circuit coming out of that inverter fuse panel was capable of the rated amp per circuit simultaneous. We still could only pull 25amp max. COMBINED (2500 watt inverter) while on shore or gen. but with that inverter switch on. Otherwise I was down in the belly of the beast accessing the inverter to reset the breaker that resided there.

Is there any one else with a breaker located directly on the inverter like ours or that has experienced this?

[phorner]

Thanks for the comments, Joe. We used to have the same problem that you described in a Safari coach several years ago.

For some reason known only to the manufacturer, they had all the "heavy" loads on one side of the inverter circuit, and we were constantly having to go outside to reset the breaker on the inverter. This included all the kitchen outlets, the refrigerator and microwave oven plus the TV. I think that there were 2 breakers, a 15 amp and a 35 amp. Thanksgiving dinner was always a particular challenge....

We have succeeded in tripping the 50 amp pedestal breaker a couple of times with the Liberty, but usually I've been able to identify an obvious mistake on our part.

[Jon Wehrenberg]

Paul, I do not know why our pair of inverters does not alternate which one is charging the batteries, or why they do not equalize the battery charging duties, but they do not. I figured this out when I did the inverter by-pass.

But i can tell you that if you shut one off, the other picks up the charging load and will retain it even if you turn the other back on. On my coach it is a toss up which one is the battery charger. But....we have two separate pairs of #10 three wire cables going from the inverter circuit breakers to the inverters. One is connected to the wires that will by pass the inverter back to the CB panel, and the other is dedicated to the charger circuit. The only time that becomes an issue is if you have one leg of the 50 amp circuit heavily loaded and that also becomes the leg powering the inverter charger. That is something we do not have control over.

[0533]

Paul, I do not know why our pair of inverters does not alternate which one is charging the batteries, or why they do not equalize the battery charging duties, but they do not. I figured this out when I did the inverter by-pass.

But i can tell you that if you shut one off, the other picks up the charging load and will retain it even if you turn the other back on. On my coach it is a toss up which one is the battery charger. But....we have two separate pairs of #10 three wire cables going from the inverter circuit breakers to the inverters. One is connected to the wires that will by pass the inverter back to the CB panel, and the other is dedicated to the charger circuit. The only time that becomes an issue is if you have one leg of the 50 amp circuit heavily loaded and that also becomes the leg powering the inverter charger. That is something we do not have control over.
I'm not at all certain about the Liberty, but I believe The Marathon's Inverters are setup to operate in following way. Inverter 1 goes along with the main breaker, and inverter 2 with the Aux breaker. The Aux system runs the galley stuff, micro etc and if the system gets overloaded the Aux will shut down first as the Main has the refrigerator on it. Does this notion square with other Marathon owners?

Marathon gave me this rule of thumb when setting the inverters for power less than 50 Amps. 30 Amps set the inverters at 14/14, 15 amps 7/7, giving a small window for overloads I guess.

[Jon Wehrenberg]

Just so everyone is aware when trying to do some power management the breakers in shore power boxes are designed to handle 80% of their rated load on a continuous basis.

For example on a 30 am circuit is you exceed 24 amps continuous duty it is probable you could trip the breaker.

If you exceed 40 amps on any leg, continuous duty you could trip the double pole 50 amp breaker. Use those numbers when you are trying to determine how you want to set your inverters and what loads you can have on.

[0533]

Just so everyone is aware when trying to do some power management the breakers in shore power boxes are designed to handle 80% of their rated load on a continuous basis.

For example on a 30 am circuit is you exceed 24 amps continuous duty it is probable you could trip the breaker.

If you exceed 40 amps on any leg, continuous duty you could trip the double pole 50 amp breaker. Use those numbers when you are trying to determine how you want to set your inverters and what loads you can have on.
Thanks Jon for the good info as always.

Jon do you have a source for those so called cheater power cords, ones that can both handle 30 amps along with 20 and or 15 amps as well??? They seem to have some type of equalizer in the middle, a step up transformer?? I cannot remember the thread it was on.

[JIM CHALOUPKA]

Bruce, here's a good 20, and 30Amp, cheated. I don't know of one that includes 15A.

http://www.rvexit.com/details.asp?Product=431&SubCategory=99

[Jon Wehrenberg]

We went through this previously.

Before anybody spends the money on a cheater be aware that the current National Electric Code requires the 20 amp circuit on a temporary power outlet (the shore power boxes) to be GFCI protected. I have not seen a campground that does not have a GFCI protected 20 amp circuit in years. The protection can be in either the receptacle or the breaker.

The short version of this is that the GFCI will trip when you connect the coach. Unless you are in an ancient campground, and they do not have GFCI protected circuits, and they used #6 wire to feed the 30 and 20 amp circuits the cheater box is not going to work.

[0533]

We went through this previously.

Before anybody spends the money on a cheater be aware that the current National Electric Code requires the 20 amp circuit on a temporary power outlet (the shore power boxes) to be GFCI protected. I have not seen a campground that does not have a GFCI protected 20 amp circuit in years. The protection can be in either the receptacle or the breaker.

The short version of this is that the GFCI will trip when you connect the coach. Unless you are in an ancient campground, and they do not have GFCI protected circuits, and they used #6 wire to feed the 30 and 20 amp circuits the cheater box is not going to work.
Thats not good news Jon. I guess that is why its called cheating, as cheating never pays.

But one question. If I am in a campground with both a 30 and a 20 amp receptacle and I hook up to the 30 amp, but decide to use the 20 amp for something else, like my 20 amp whatever, are you saying that there is only 30 amps total available at the box between both the 30 and the 20 amp receptacles ? What am I missing here, as I just about flunked out of my electrical engineering class, Lightbulb 101..

[Jon Wehrenberg]

The problem we encounter is that the transfer switches in a coach do not extablish a ground instantly upon sensing shore power or switching to shore power so the GFCI trips.

To the best of my knowledge only Thompson coaches that establish a ground before connecting the hot and neutral legs will not trip the GFCI.

However, as you suggest you can plug the coach into 30 amp shore power, and then use the 20 amp circuit as an auxiliary circuit to plug in any device or appliance such as a leaf blower, boom box for nude dancing, or outside chinese lanterns on your awning.

[phorner]

Bruce, if I understand it correctly, you can't simply add the 30 amp and 20 amp services together in order to get a 50 amp service.

One issue is that a 50 amp service connection is, in reality, 2 separate circuits, as there are 2 "hot" wires, giving you a theoretical 50 amp connection on each "side". So, when you observe the gauges in the bus when connected to a 50 amp service, you can note that the total of the 2 readings inside the coach may exceed 50 amps total.

When you look at the end of a 30 amp connector, there's only 3 prongs which = single circuit. Looking at a 50 amp connector you will see 4 prongs which = 2 circuits. That's why the typical 50 amp pedestal (campground) breaker uses 2 slots in the breaker box and the 30 amp only uses 1.

My personal experience has been that when only 30 amps are available, to just deal with it. Although, sometimes it seems like it would have been easier to just dry camp for the night!

At least that's my take on it.....

[phorner]

Hey, LED lanterns use much less power....

[Joe Cannarozzi]

Just a side note about Jons comments about the cheater.

The one I had was really 2-30's with a 30 to 20amp adapter on one of them.

So if I knew I would be needing it I would try to get a spot with a vacancy next to me.

I'd remove the 30 to 20 adapter and I would take a 25ft. 30 amp extension cord into one and hook into the next campsite and the other 30 into our site.

That always got me around that GFI problem and I was able to do that more than a few times, worked great.

[0533]

After I plug into shore power and before I switch my main breaker on, I inspect the main breaker (On my Coach) to see that both green lights are on to make sure I can switch on the power to the two inverters and before the interior breakers inside the coach, Main/Aux. Doesn't this insure that I have proper polarity and grounding to my main breaker box (on the coach)?? If so, as long as I have the green lights, then I should be ok using any combination including two 30 amp cheaters with a 20 amp adapter using both a 30 amp side with the 20 amp side inline.

If I am wrong here, then why not some type of setup/Load balancing transformer in the middle of all of this.

My interest is born out of the fact that when we end up in really nice state park on the beach we mostly are confronted with a max of 30 amps, but often there is a 20 amp breaker and receptacle in the box, and I would really like to harness all of the available power.

[Jon Wehrenberg]

Bruce....go for it. Buy the cheater. Let us know how you make out.

[0533]

Bruce....go for it. Buy the cheater. Let us know how you make out.
I'm suspicious Jon when you say, "Go For IT". That is what my parents would say after they were tired of trying to convince me to follow direction.

[Jon Wehrenberg]

Sometimes a person has to see for themselves. Your converter may have set up the transfer switch so you always have an uninterrupted ground. I could use a 20 amp GFCI on my old coach, but cannot on my current one.

However, I could not use a "cheater" on my old coach even though it would work with the 20 amp adapter plug individually.

YMMV

[0533]

Sometimes a person has to see for themselves. Your converter may have set up the transfer switch so you always have an uninterrupted ground. I could use a 20 amp GFCI on my old coach, but cannot on my current one.

However, I could not use a "cheater" on my old coach even though it would work with the 20 amp adapter plug individually.

YMMV
I'll report back when I find a good source for a split 30 amp adapter. I may just run over to West marine and purchase one of theirs.

Thanks Jon for the good advice. If my Coach goes up in smoke, I may not share that info with you.