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FIRE UP · 02-09-2025, 04:40 PM

Hey gang,
We've had a couple of issues the last couple of times camping. First, some history. Our coach is an '04 Itasca Horizon 36GD with the CAT C-7 330HP. We've now owned this coach for 13+ years, and we've got right at 118,500 miles on her. It's been a great coach for the most part. Of course, it has its hiccups every now and then and I typically stumble through them in a repair or replacement of something or other.

But here's the latest deal that deals in a department that I'm just not all that schooled about. ELECTRICITY!!!!!!!! The coach came with a *Dimensions* 2000-watt Inverter/Charger when it was new. That inverter/charger lasted about 11 or 12 years or so before the charging side of it gave up the ghost. I replaced it with a 6-month-old Magnum 2012ME MSW unit that for the most part, is almost an exact replacement in all parameters. The only thing I had to do when changing that inverter/charger was I had to purchase and install a new remote for it. It's an ME-RC remote.

Sooo, here's the deal. Obviously it's been a bit cool lately in most of the country as far as camping is concerned so, we carry a small, about 12" high, little portable electric heater that will augment whichever main heating system we have going at the time. It's one of those little guys that you can push a button and it will oscillate back and forth and put out some decent heat, for its size anyway. For those who have similar coaches/styles, we have the basement heat pump (and it's also the basement A/C) and we also have your basic 12V furnace. Both of which work great. According to the basement heat gurus, you're supposed to stop using the basement heat pump when the outside temp reaches around maybe 42 degrees or below. That's when we kick in the 12V furnace.

But, to conserve propane, we set the temp in the coach to around 65 or so and let that little portable heater just keep the main furnace from cycling so much in the night. Well, that works, sort-a. By that I mean, and this is where the problem or problems come in. If we plug that little heater in in the kitchen , in an outlet that's upside down on the bottom of the upper cabinets above the sink, that heater will run and oscillate all night without issues.

But, if we plug it in the outlet that's on the bottom side of the upper cabinets
above the driver/passenger (adjacent to the front TV) that heater will run for and uncertain amount of time and the POP! It knocks out several other outlets and blows one of the receptacle breakers in the Inverter/charger sub panel. This has happened more than a time or two. Again, plugging it in the kitchen outlet, it appears to have no issues or causes no issues.

Now, each time it blows that one particular breaker in that inverter/charger sub panel, (which is at the foot of the bed in case anyone's wondering) I just reach down and flip that breaker completely off then back on, all is well.

Now, here's problem TWO. This problem may or may not be related to the above problem. On occasion, we'd be either cooking, using the microwave and having the front TV on which, also entails having a receiver on that amplifies the basic sound in all the speakers AND, we'd also have a small separate amp that runs the base speakers for the coach's sound system.

The 120VAC demand at that time is the TV which, is a smart 32" Samsung which is probably around a couple of amps to run, the receiver, which is a Marantz 200-watt unit and the base amp which is also I think around 100 amp or less, maybe 50A. Then there's the microwave. It's the basic Sharps unit that came in the coach so, I don't have a clue as to how much it draws. That little portable heater is not on at this time.

Here's the issue. On occasion, when conditions are just right, it will POP that small, white, 30A resettable circuit breaker that's on the side of the Magnum 2012ME Inverter/Charger. When that happens, all he...ll breaks loose in the coach. NOTHING of AC works! My remote panel shows nothing but a whole line of black squares on the screen. I have to at that time, put on my slippers, parka, and maybe a couple of jackets and venture outside to the shore power compartment where that Magnum lives. I then have to bend down, feel by brail, and find that popped 30A circuit breaker and push it back in. When I do that, it's all better now inside the coach, all with the exception of the remote panel screen.

In order for that screen to be back to normal, I have to remove that remote from the wall, unplug the telephone jack/cord from it, and re-insert it. Then, that remote does a self-test and diagnosis and then returns to its normal display whatever the present battery charging output it which, typically is in the "float" mode and there's maybe 3 amps or so.

Soooooooooo, I don't like long posts like this but, it was the only way to paint a good, at least somewhat clear picture of my (our) electrical issues.

Sooo, just wondering, on the first problem, with the 20A breaker in the inverter/sub panel popping on a somewhat repetitive series, is it possible that, that particular breaker is WEAK? Do they go weak sometimes? The reason I ask is because, we just don't seem to have any issues when plugging that little 1500 watt portable heater in any other outlet.

Second, is it possible that that little white pop-out 30A resettable circuit breaker that's mounted on the side of that Magnum, to ALSO be weak?

And that's another thing. And this is also about me not knowing almost ANYTHING about electricity, why, WHY do they put a 30A circuit breaker on the pass-through circuit of a shore power supply of 50A???? I just don't understand that. I think I understand that there's TWO legs of maybe 25A each in that 50A supply, correct? If so, and that 30A resettable circuit breaker is for protection of that incoming supply, then why not TWO of them, one for each of those legs?

Anyway, I'm incredibly sorry for the long post but, it's the only way I know how to bring in all the details that sooner or later, someone who's trying to help would then ask. For about 99.9999% of the time, the electrical system in our coach operates problem free. It's just these rare circumstances that stumps me. Feel free to read some of it, then take a break and go out and rebuild an engine or something, then come back and read some more. I definitely appreciate any help here.
Scott

d23haynes57 · 02-09-2025, 05:45 PM

Yes, breakers can go bad. But the other reality here is that may be overloading it. However, it is a bad practice to use heaters on inverter circuits, even on shore power with the inverter being in bypass. The transfer relay and other parts of that circuit really are not designed for that. Bad enough that it may be expected to handle a convection oven. If you must use a space heater, find a receptacle that is not on an inverter fed circuit.

SafariBen · 02-09-2025, 06:30 PM

Quote:

Originally Posted by FIRE UP

WHY do they put a 30A circuit breaker on the pass-through circuit of a shore power supply of 50A???? I just don't understand that. I think I understand that there's TWO legs of maybe 25A each in that 50A supply, correct? If so, and that 30A resettable circuit breaker is for protection of that incoming supply, then why not TWO of them, one for each of those legs?

50A is at 240V, or two legs of 50A each at 120V, or 100A at 120V total. The inverter is only capable of 30A, so that's all the wiring to feed it shore power is sized for. You can test this, or the other breaker that trips with enough electric heaters. If they have low, medium and high, then that is typically 600, 900, and 1,500W, so you can add enough to reach 25 or 35A and it should trip a 20 or 30A breaker shortly, but not trip at 18 or 28A.

Ray,IN · 02-10-2025, 03:52 AM

Yes they fail. I think, breakers are rated at 80% continous-duty cycle, 100% intermittent-duty cycle. What else is on that circuit?

Chap1021 · 02-10-2025, 04:24 AM

I understand you are plugged in when this happens. The AC electrical supply in most coaches is divided up into a shore power only side and an inverter side. If you unplug from shore power and the inverter supplies the AC, some of your appliances and outlets go dead because they are supplied before the inverter. If you plug your heater into an outlet that goes through the inverter you are subject to the limitations on the inverter. My first RV I would plug in electrical heaters and I found one outlet in the front that not supplied by the inverter. Then I used the dryer outlet in the rear since I did not have a dryer. I came off the dryer outlet, installed an accessible outlet and used it for a heater in the rear.
Using all that power through the inverter will trip the breaker. Most coaches have one line of 30 amp through the inverter. When plugged into 50 amp there is 220 supplying 2 lines of 50 amp. There should be a breaker box for the two lines of shore power with a 30 amp breaker supplying the inverter. One leg of the 50 amp supplies the inverter through a 30 amp breaker and that is the breaker you are probably tripping.

What you are describing is moving the plug from inverted power to shore power in the power system in your coach. The heater draws about 15 amps. The microwave, refrigerator, TV and rear of the coach are generally on the inverter. So if the heater is pumping out heat and you start the microwave that can be close to 30 amps on the inverter and you will trip.

My advice is find the shore power outlets and use those. Also if you get a heater with the electronic controls and the park cycles the power or shuts it off for a short time the heater will not come back on. That has happened to me, so I purchased heaters with manual controls.
To find the outlets, you can find an electrical drawing for your coach or get an outlet tester. Shut off shore power and see which outlets are dead and which have power. The ones with power are supplied by the inverter. The ones that are dead are supplied by shore power only. Using the shore power only outlets will prevent the inverter from tripping. You can dive into it deeper and figure out which leg of the shore power your loads are using to balance the amps.

l1v3fr33ord1 · 02-10-2025, 06:14 AM

Pertinent diagrams are these:

Body, 110 Volt Wiring Diagram
110 Volt Load Center/Auto Transfer Switch

These are included in the complete diagram set for the 2004 Itasca Horizon 36GD, at this link.

At first glance, the two diagrams listed above have at least one difference in the listed breaker ratings (the gold = "GLD" breaker on one is 50A and the other is 20A. I suspect 20A is correct.).

There are only four loads shown that are not on the inverter: the washer/dryer, water heater, vacuum and refrigerator. The last three run through the Powerline EMS load-shedding system.

I could err in my reading and interpretation, so other eyes and brains should review the info.

As always, the diagrams are supposed to match what shipped from the factory. "Your mileage may vary."

Dutch Star Don · 02-10-2025, 12:01 PM

For the heater, check the outlet that you use under the kitchen cabinet, I think you'll find that's not on the inverter and is why it doesn't blow.

In simple terms, even if you're plugged into 50-amp shore power (100 total amps) the Magnum inverter still only has a 30-amp breaker.

Get a Sharpie and disconnect from shore power. Go around to all of your outlets and see if they're hot. If they're hot, put a dot on them with the Sharpie. This will indicate which ones are on the inverter and help you manage your power better. I had this same issue in my 2005 Monaco Diplomat with the same Magnum Inverter.

FIRE UP · 02-10-2025, 11:25 PM

Quote:

Originally Posted by Dutch Star Don

For the heater, check the outlet that you use under the kitchen cabinet, I think you'll find that's not on the inverter and is why it doesn't blow.

In simple terms, even if you're plugged into 50-amp shore power (100 total amps) the Magnum inverter still only has a 30-amp breaker.

Get a Sharpie and disconnect from shore power. Go around to all of your outlets and see if they're hot. If they're hot, put a dot on them with the Sharpie. This will indicate which ones are on the inverter and help you manage your power better. I had this same issue in my 2005 Monaco Diplomat with the same Magnum Inverter.

Hey Don,
I surely thank you and all the others who've taken the time to respond. I'm ok with 12VDC stuff for the most part but when it comes to 120VAC stuff, well, I lack some decent know-how.

"In simple terms, even if you're plugged into 50-amp shore power (100 total amps) the Magnum inverter still only has a 30-amp breaker."

This is when things bug me. What I mean by that is, why supply a full 50A or even 100A if you're regulated to a measly 30A by a single pop-out resettable circuit breaker on the inverter???????

As for the marking of the outlets. Well, I'm one (or many) step ahead of you Partner. Today, me and the CEO did just that but, in a different manor. We have two 120VAC breaker panels at the foot of our bed. One is your basic horizontal 120VAC residential looking breaker panel. The other is a brown breaker panel that is the Inverter/Charger breaker panel.

There are (5) breakers on that Inverter/charger breaker panel. Rather than list them, here's some pics of what we're (you too!) are looking at and, there's also a list of what each "receptacles" breaker actually controls. Even though there's a "Refridge/Vacuum" on the inverter/breaker panel, there's actually NO BREAKER for those two items on the inverter/charger breaker panel.

The refridgerator and vacuum DO have a breaker on the main panel. Now, while I have many more questions, WHY do I have a 30A Inverter/charger breaker on the main panel when there's also a 30A "main/buss" on the inverter/breaker panel??? I know that behind that main panel, there's a "load shedder" system that decides what needs to be dropped if there's too much load on the electrical system. I know what it's supposed to do but, so far, I'm not sure I've ever seen any "load" actually "shed" if and or when, I'm overloading any particular circuits on either shore power or inverter power.

This is our coach, we've had it for over 13 years and I ought to know more, if not ALL about it by now but, again, I'm just not that savvy about 120VAC and we've just not had any issues with the 120VAC system 'till recently and, at this time, I'm not sure we've not caused those "temp" issues ourselves.
Scott*

l1v3fr33ord1 · 02-11-2025, 02:13 AM

Hey Scott-

I had 30A coaches, and had to be careful about activating too many 120V loads at one time, lest the 30A breaker open. One of the rules was to have only one heating/cooling load on at a time. Your coach's inverter is like my entire coach.

So, a question: Do you have the engine heater plugged in and turned on (via the switch) on those cold nights? The receptacle that feeds it is on the "RECPS 3" circuit, same as the TV receptacles with which you have problems when you plug in that stand-alone heater.

Also, a test: You seem to have no problem running the stand-alone heater on "RECPS 1," and problems running it on "RECPS 3." Plug the stand-alone heater into a "RECPS 2" receptacle. Does it behave like "RECPS 1" or "RECPS 3?"

A second question: The far-right 15A breaker in the main box has no label, and is not on the factory diagrams. Any idea what load is attached to it?

Quote:

WHY do I have a 30A Inverter/charger breaker on the main panel when there's also a 30A "main/buss" on the inverter/breaker panel?

The "INVERTER/CHARGER" breaker on the main panel feeds shore power 120V to the inverter. The "BUS/MAIN" breaker on the inverter panel is for the inverter 120V output.

PushedAround · 02-11-2025, 07:15 AM

Get one of these from HD (only $49). It is the only way to determine the current draw of a circuit to see if it is overloaded or the breaker is weak.

https://www.homedepot.com/p/Commerci...388219#overlay

SafariBen · 02-11-2025, 07:27 AM

Quote:

Originally Posted by FIRE UP

This is when things bug me. What I mean by that is, why supply a full 50A or even 100A if you're regulated to a measly 30A by a single pop-out resettable circuit breaker on the inverter???????

If things like this bug you, I'm not sure how you lasted so long in that RV?
These things evolved from when Fred rode dinosaurs around, they simply didn't have large inverters or batteries even as recently as the teens. If you put a large inverter in, the battery bank would not last, and if you put a large inverter AND battery bank, then there would be no profit left. Inverter and battery sizing were done to a minimum level determined by the marketing dept to match competitors in that price class. These days you can get a 6000w 240V inverter for under $1,500, and a ratty school bus conversion can carry more battery, inverter and solar power than a 2010 Prevost ever had.

Limiting the feed through and sub panel to 30 amps reduces the cost of the inverter, and hopefully limits overloading the inverter, just makes sense with the limitations of the time.

jl.kauai · 02-11-2025, 07:36 AM

Hey. Scott. So much great info I didn’t know. Once I worked on a fifth wheel with similar issues and after an hour we started checking battery connections. Sure enough it was corrosion on the positive cable in a four battery system in parallel. Just for grins take a good look at your cables. Maybe shut electrical down and clean them all. Just a thought. Travato John.

Dutch Star Don · 02-11-2025, 05:08 PM

The 30 amp breaker on the inverter is just what they came with when your coach was built. My Diplomat had that, and I thought it was pretty sophisticated at that time.

Now, the new coaches come with two 3000- or 4000-watt inverters and big batteries. Since everything is now all electric, the systems have been stepped up since the early 2000's.

Alpine36 · 02-11-2025, 06:31 PM

For the very reason you are encountering I re-configured most of our inverter sub panel breakers to shore/generator power fed only.
The inverter only feeds two breakers on the sub panel now. One kitchen outlet, one bedroom outlet and one TV outlet on one breaker, and one breaker dedicated to the refrigerator for a future residential fridge upgrade. We only use portable space heaters on the non inverter fed outlets, but still exercise caution using these by not exceeding 1500w (one heater) on any one circuit. Our rig left the factory with the inverter sub panel able to overload the 30a bypass circuitry of the inverter, and it did eventually damage the original inverter bypass circuit after continually resetting the inverter bypass breaker. No, doubtful it’s a faulty breaker situation you have, it’s an overloaded inverter bypass.
Who uses their microwave/convection oven using the inverter anyway?
For me it was a relatively simple wiring work around to eliminate this issue and has remained trouble free for years. We rarely use the inverter for any heavy loads anyhow, so something to consider.