Inverter By-Pass

I am in the process of adding a simple means of by-passing my inverter(s) in the event one of them should fail.

As my coach is now wired, if an inverter should fail I will not be able to get 120 volt AC current to the circuits served by that inverter. Is that a big deal? In my mind I see that as a problem because those are important circuits. One handles my refrigerator. others handle such things as the microwave, forward outlets, rear outlets, TV, auxiliary compressor, etc.

I am able to get power to the outlets in question, but to do so I have to join the wires supplying power to the inverter, to the wires supplying power from the inverter to the CB panel in my coach. If I could easily access the inverters and those wires that would not be a big deal, but I cannot. They are difficult to access and would involve quite a bit of work.

So I am going to go to the trouble of preparing for an inverter failure by installing by-pass switches. I may never need them, but if an inverter should ever fail all I will have to do is flick the switches and start the generator or be connected to shore power.

I will document what I am doing, take photos, and if there is sufficient need I will have an article posted on this site.

My question is this....how many of you have coaches that do not provide an automatic inverter by-pass in the event of an inverter failure? If you have any doubt turn off power to your inverter while the generator is running or you are connected to shore power to see if power does get to all circuits.

This issue is no big deal if you can easily access the wires into and out of the inverter. All you need to do is connect the two sets of wires until you can restore the inverter to working condition. But for those of us whose inverters and their wires are difficult to access (or who do not feel like doing electrical work while on the road) by-pass switches will make an on-road failure a less difficult situation.

Those responding to my question please list the year of your coach and the converter so we all can get a sense of the scope of the situation.

On my 93 Country Coach there was an automatic transfer switch. Whenever I plugged in, or turned on the generator, it would kick in and I could turn the inverters off.

I routinely turned off the inverters when plugged in, in fact this was my normal operation when parking the coach for long periods of time. My batteries were charged not off the inverters, but separate converters.

On my 02 Marathon I don't know yet. The battery charging comes from the inverters, but that's probably independent of having a transfer switch in there. I'll have to check this next time I get out to the hangar.

Ray

jw-

my (albeit vintage) coach had two automatic transfer switches - one took either shore or generator, and the output of that went to another transfer switch that chose between the output of the first switch and the inverter. in april of this year, i removed the 2nd of those (and the old inverter) and replaced with a shiny new inverter with more oomph (magnum magnasine). this allowed me to also remove the two old todd converters (house battery chargers) and about 3 pounds of copper.

if you put a transfer switch downstream of the inverter which would choose between shore/gen and inverter, seems all the bypassing would happen automatically. the transfer switch is nothing more than two honkin' relays and some arc suppressors.

i suspect you can find a used transfer switch somewhere to experiment with before buying a new one (if that was a requirement).

wmm

Good post Jon,

My coach's appliances will all work on gen power or shore power if the inverter fails. I had an inverter fail in my '93 and we just ran the generator to keep the refrigerator going until the inverter was replaced. Thank God for small favors;)

This could really be important if you have a freezer full of food:eek:

1999 Newell

Why would they have that design?

We too have all circuits if inverter is off. Automatic transfer switch is built in and it is as Bill described a big relay.

Additionally the power receptacles in and out of the inverter are flip-flopped so if the inverter is out for repair we can simply plug the receptacles from and to the bus directly to each other, instead of the inverter, to complete the circuits.

Jon I have a few extra new transfer switch relays if you would like one. We have a Heart.

Jon you might get some help from that fellow in Santa-Fe, Dave at Gusdorf Electronics, very friendly, knowledgeable and been around almost as long as you. His # is in a old thread Heart Inverters or I can dig it out for you if you like.

Jon,

Don't know yet about the CC, although the roof A/C's are not tied to the inverters, but my 97 Marathon was dead in the water if the inverters went south. You have to rig up a bypass such as your discussing to get power. I experimented prior to shutting everything down when replacing the house batteries, and the Coach was a dead duck without the inverters.

This is really a good point Jon is bringing up, shut off the inverters while plugged in and see what you get. In my vintage Marathon, there was no power. I mean no plugs, no A/C, no fridge, nothing. While everything was off for my battery work, I ran and extension cord to the refrigerator plug to keep that going.

Nick was going to help me with the bypass switch when he got close to Atlanta, but I sold Big Red before we could pull it off.

For those questioning the "why" of this, it is possible (unless the coach has a bypass built in) for a failure of the relay which passes shore or generator power through the inverter to fail. When that occurs no power will pass through the inverter even though it is available.

Don't assume yours will automatically transfer power or by-pass until you have tested to confirm your suspicions. The time to know is before you have a problem, and the solution is less than $100 in parts. Why some coaches were or are built without a by-pass is a question for the converters, but I do know for sure that my coach is not alone with this design.

time to drag out all those schematics, jon.

Quote:

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Originally Posted by bill&jody

time to drag out all those schematics, jon.

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That would be nice, but I seem to recall. that Liberty does not furnish electrical schematics. What do you say Jon, is that so?

The schematics are provided by Liberty, and I assume others, but not at the level relevant to this issue. My Liberty owner's manual is very detailed as to the wiring.

This is not a Liberty issue. This is strictly related to how your particular coach was set up when it was built or modified. Shore or Generator power will either by-pass a failed inverter, or it will not. If it does not I will write an article that shows how to by-pass one in the event of a failure for a few hours of work and less than $100.

In the event I am not understood, this is not related to the automatic switching that occurs when you go from inverter power to shore power to generator power. This relates solely to having power available to the coach in the form of shore or generator power, but not being able to get it to circuits normally fed through the inverter because of an inverter malfunction. Some coaches are equipped to by-pass the inverter so it doesn't matter if the inverter works or not. Others however will not.

Jon IMO this thread is a perfect example of the beauty of POG.

Let me rephrase my question from my previous post.

Why would they design that system so all circuits that are powered by the inverters could not be powered by gen. or shore when available, without needing the inverters?

If our switch fails in a manner that takes those circuits offline I simply remove the inverter from the loop. Its behind the wall behind the freezer, 10 min. max.

If you remember ours was not working when we bought the bus. All circuits continued to function and we left it in cause the battery charger end of it was still good.

Once I did remove it for repair I could plug the recepticals leading to and from it into each other to complete those circuits. On a side note that switch was one of the things that failed. A contact was burnt keeping the inverter function down but could have just as easily burnt the other side restricting shore/gen.

Seems like what your trying to achieve is exactly the set up we have and it was designed 10 years prior to yours.

Unnecessarily overcomplicated, a relatively common occurrence on many features on these campers:confused:

Jon If I were in the market for another bus and it's style was EXACTLY what we wanted but had inverters set up like yours, I'd pass, I would not be willing to risk that inconvenience unnecessarily.

It will be reassuring and informative to hear from new coach owners, and who their converters are, who do not have to deal with this.

Jon here is Daves# at Gusdorf electronics 505-983-4095. He knows inverters as well as you know norgrin valves. I'm sure he is aware of your set-up and can be of some assistance.

Joe,

I cannot defend the design except to say that was the way things were done, and yours and mine being at least 10 years apart show that the way they were installed was not a one time thing, but was common practice. I know for certain that several converters built a lot of coaches that way, and I also know of at least one Prevost owner that lost the contents of his refrigerator because he could not get power to it after his inverter failed. I also know of a coach built in 1995 for a former PP president that was specifically equipped with an outlet for the refrigerator powered by shore or generator power to be used as a backup in the event of an inverter failure. This problem is not new or unheard of.

In our coaches we have many failure modes that are capable of messing up a trip. The fact that with 10 minutes worth of rewiring gets you going says more about how your inverters are placed than the whole concept of being able to by-pass a failed device with a simple switch.

I am addressing potential failure modes in my coach one at a time. I dealt with a plumbing issue previously. I have made access to engine fuel priming much easier. I am going to deal with an inverter failure via a by-pass switch, and I am adding a second water pump solely to be used as a standby. Each time I find something whose failure will force me to repair it immediately, or which will disable us making life less than pleasant I am going to incorporate some means of dealing with it.

In the end I will still have some items whose failure will require a repair, but I am adding parts to my inventory of spares to minimize the grief. I already have a replacement control for the Webasto, a backup Watchdog generator control, miscellaneous circuit breakers, relays, air hoses, lights, etc. And those things that are not practical to replace, or to have back-up, or to repair I am going to replace based on time in service or miles such as I am contemplating for my engine air compressor or my big alternator.

If we never left the immediate area we live in I would never consider doing what I am doing. But that is not the case, so I will do the next best thing and that is try to never have a failure while on the road that will curtail a trip. At least that is the plan.

How does Thompson do it?

I cannot specifically describe how he does it, nor how the current versions of CC do it.

There may be others out there that also by-pass. My guess is that a system of relays or switches open the circuits to and from the inverters when there is shore or generator power automatically doing what I am going to do manually.

A by-pass is not anything sophisticated or expensive relative to the cost of a coach. I just think that the designers did not necessarily think about failure modes when the coaches were designed. As people became aware of the issue some converters responded by creating systems to accomplish a by-pass.

My coach is not here for a look see.
However, I will certainly be in the running to put an inverter by-pass in mine.

In the event of a failure of the inverter that powers the refrigerator my interim plan would be join the wires as mentioned by another or to switch positions of the inverters in order to restore refrigerator power. Or, depending how easy, or not, if I can get to the back of the refrigerator by removing a panel, I would run an extension cord.

So, an inverter/charger thinky: The combination inverter chargers just aggravate me a lot more than they should. In an 86 bird I lost (it failed) a Heart inverter charger and it's replacement, a Trace. In the case of this older bird there was only one. Hence, for repairs (yes, I really believed one could get them fixed) one was without the inverter, in the event of a charger failure or vice versa. Inverter failure was not a big deal as it had a propane refrigerator.

Anyway, I thought I could do better. I wanted redundancy, and easy componet, replaceability. I bought two True Charge 40s (40 amps each) and an 80 amp PDI and wired them up together. One of the True Charge 40s acted as the brains of the outfit and would bring everything, or portions thereof, on line when needed.

I then bought an inexpensive 1000W inverter and installed it separately. Granted, 1000W isn't much but it would run, individually, the curtains, TV, ice maker, refrigerator, coffee maker, or the crock pot. Obviously, in our current coaches a larger inverter would be necessary.

Wouldn't you know it. After I set it up like that, I never had another failure but I did have a system with easily replaceable componets while on the road.

Accordingly, while I will pursue Jon's fix with a by pass switch, I will also start researching building up a system with an independent 24 volt charger and independent inverter.

Also, I think if there is an inverter failure, the charger portion will be OK. Accordingly, a simple inverter of approx 1500W should keep the refrigerator going till permanent repairs can be made.

There is no doubt that Liberty and whoever else does this is aware of the compromise for doing it this way but has good reason why and I would love to find out.

jon-
i still think the right way to do this is to put a transfer sw after the inverter, with the two inputs to the switch being the output of the inverter and the output of your shore/gen power, with the switch having a preference for the inverter. the xfer sw can't be expensive (its just two relays in a metal box) and it would be completely automatic. and very easy to install.

thoughts?

wmm

WM, I agree with your solution, however while your solution on the surface seems simple, it involves running wires to my inverter location that are not already there. Additionally this is only a switch to be used in the event of a failure. My coach like yours will often have shore power or generator power on one of the lines you mention so the relay will be working each time it sees those sources of power, and as an electro-mechanical device it is something else besides the inverter that can fail. I want my fix for my coach to be cheap and simple and not prone to fail.

Jon: You don't have to debate what your doing with any of us. Please continue with your project so those of us needing it can copy it for our buses.
Thanks for another heads up change for the better.

Jon,

Unlike my Marathon, I had to check this out and I gotta give an atta boy to CC, nothing runs through the inverters as long as shore/gen power is available.

Not exactly, but I think you are close. I'm still trying to understand more than just Liberty, but right now my best guess is the CC has you set up it that when shore power or generator power is available to your coach, it goes to the battery charger portion of the inverter, but by-passes the inverter to feed power directly to the circuits powered by the inverter when not connected to shore power and the generator is not running.

Right now I have no clue how many coaches already by-pass the inverter and how many do not. I do know this however. If you have a coach set up so that you can easily access the wires into and out of the inverters, and can join the two sets together easily if necessary, don't waste any more time on this issue. You do not need to waste time or money installing a bypass. But if your inverters are not easily accessed and you do not have a by-pass, stay tuned.

Jon what you just described is exactly how our bus and Heart work. When the inverter is on w/o shore power and you introduce it the thing automatically stops inverting and starts charging, and visa-versa.

The switch happens so quickly that none of the a/c stuff that is running is even interrupted when it happens.

It sounds like you have a simpler solution to that switch but here is some pictures of the relay that Heart used for an automatic switch in ours.

Attachment 1793

Attachment 1794

Attachment 1795

I have a few so your welcome to one if you like.

jon-
i'll start off with, "i'm not positive about how this works, but..."
i think if you install this bypass switch, you need to ensure that it disconnects the a/c output of the inverter when bypassing.
if you tie the 120vac (shore) to the output of the inverter (its obviously already tied to the input), and the inverter is only intermittent, when it "comes back on", it will be feeding itself. most if not all inverters really don't like to do this.

furthermore, if you disconnect the input to the inverter (and the output of the inverter is still tied to the shore power via your bypass sw), and the inverting function still works, the inverter will try to drive the appliances as well, almost surely at a frequency slightly unequal to the shore power, and the two phases will periodically be adding then differencing. tho you prob'ly won't add up to 220, you'll surely damage something. seems that way, anyway.


just a thought.

wmm

Bill,

Once my by-pass switch is switched from the normal inverter position to the "failed inverter" by-pass position the inverter input power is disconnected from the inverter, and the inverter output circuit is disconnected from the inverter (back feeds will ruin the inverter) and connected directly to the inverter input, this going straight through from the source to the electric panel.

On inverters with separate battery charger inputs I am going to suggest leaving them connected so if that section of the inverter is still functioning I will not lose battery charging capability.

The switches should arrive this week and as I go through the process of installing the switches I will document it all and then rather than discussing theoretical solutions we can discuss specific matters.

Joe,

The issue I have with relays is if they fail, especially the relay that disconnects inverter output so there is no danger of back feeding, the "automatic" system has just ruined a perfectly good inverter all because a $15 relay failed. As I mentioned previously making a by-pass automatic is easy, but with that automation comes a degree of risk that comes with the failure of that by-pass. Joe, check your current requirements on those relays. I need to handle 30 amps and your relays will not handle that. Maybe you have lower current requirements.

My set up is strictly meant to be used as a temporary fool proof means of dealing with an on-road failure of an important component. Besides, if I wanted to go to automation I would have to run wires back to my inverters, and if I am going to that trouble I might just as well go to the trouble of relocating them so I can access their input and output wires and then I don't need the by-pass switches.

Jon,

This is how Newell handles the inverter by-pass situation. If the inverter fails you unplug the cord from the inverter outlet and plug it into the power outlet. Hope this helps.

Good idea Tuga.

They recognize the need and have taken a different approach. I'm almost done with installing the first by-pass and I am documenting it along the way.

Jon,

The only down side to Newell's approach is that if the inverter fails I would have to use a separate battery charger (which I carry onboard) to charge the house batteries. I guess that is because there is a converter in the inverter????:eek:

Yes, that is correct. Do you have one or two inverters?

I have the same type inverter as you, 24V, and it is wired so the battery charger (converter) has a separate input set of wires. I am going to leave them connected in my by-pass with the theory being that the relay that closes to automatically power the inverter circuits may fail, thus requiring me to by-pass the inverter section, but the charging circuits (converter) may still function.

With my second inverter I can still afford to lose the entire inverter including the charging section because the remaining inverter will still function as a charger.

I only have 1 inverter; it's a Freedom 2500. I can not run the basement AC units without running the generator. The dash AC is my only source of AC when the generator is not running. I wish that I had an auxillary generator that runs off of the series 60 like Bob/03's Millenium; that is one neat setup!:D

My inverter runs the refrigerator, TV, microwave, and a few electric outlets.

That's a heavy demand for a single 2500 watt inverter. Worse, but recognized by Newell, when that inverter quits you lose your most important circuits. I am surprised they did not provide a back up battery charger. That is a serious failure mode you should address before it happens. Your alternative if the inverter fails, as you are set up now is to run the engine to keep the batteries charged.

Quote:

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Originally Posted by truk4u

Jon,

Unlike my Marathon, I had to check this out and I gotta give an atta boy to CC, nothing runs through the inverters as long as shore/gen power is available.

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Tom, I think our refrigerators run only through the Inverters.

In the past there have been posts regarding inverters and how they are installed on various coaches, and what happens when an inverter is shut off, or if the charging circuit is shut off. I'm not sure what is correct for one coach, is correct for the next coach.

I have two Freedom 2500 inverters, and in the installation guide there are NINE (9) options for installation. That alone should suggest that before a problem occurs it might be best if each of us attempts to find out exactly what will happen if an inverter fails.

The project to install a by-pass switch is moving at glacial speed because I am digging far deeper into this than just installing a switch to join the input and output circuits on my coach. I will have a very clear picture of how my particular coach is set up, and what I will have when I am done with the by-pass project. It is not as clear cut and simple as originally thought, but now that I am in the middle of it I can see the logic of the system.

Every converter probably had their way of doing things and with so many choices available for how the inverters are installed it will be worthwhile for everybody to turn some switches on and off until you know what you have and how it works. You do not want to find yourself trying to deal with a failure of the refrigerator circuit at the beginning of a long day of driving through the southwest in August.

Jon,

Just thinking out loud here: if the inverter fails when I am in a CG I would connect my spare battery charger to the batteries. If I were out on the road the engine alternator would charge them and the generator would provide electricity to the accessories. I fail to see the problem here.
Under these circumstances I would start the generator to use the microwave.
I can run the refrigerator, TV, & lights for about 24 hours before starting the generator to re-charge the batteries.


Refrigerator: 110V X 6.5A = 715 watts
TV & SurSound: 110V X 4.0A = 440 watts
Total: 1155 watts
Inverter output: 2500 watts

Am I calculating correctly or am I missing something?

Tuga,

You are correct, but a hair dryer and a coffee maker added to that are too much. You just have to be careful like we all do.

Just slightly off the subject here-but in the same family: I have two Heart Inverters and one "converter charger". What does this unit do??

As I understand it, a converter charger charges your batteries.:D

Thanks for the info. BTW, would you mind me contacting you regarding your Newell??

Not at all, my email address is tugagaidry@bellsouth.net or call me at 985 381 6613.

Quote:

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As I understand it, a converter charger charges your batteries

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To expand upon this.

Inverters take a DC voltage (batteries), and turn it into an AC voltage for things like appliances etc.

Converters do the opposite, take an AC voltage and turn it into DC. The converter charger runs on 110 AC, and then charges your batteries from that. Why they call it a converter/charger rather than just a battery charger is unknown to me. Maybe for clarity.

Ray

Hmm, wikipedia disagrees with me. They call the process of DC to DC == conversion. AC to DC they call rectification. But regardless, the RV industry calls devices that take AC and turn it into DC for charging batteries, a "converter/charger".

Ray