Inverter By-Pass

[Jon Wehrenberg]

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.

[Ray Davis]

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

[bill&jody]

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

[merle&louise]

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

1999 Newell

[Joe Cannarozzi]

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.

[truk4u]

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.

[Jon Wehrenberg]

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.

[bill&jody]

time to drag out all those schematics, jon.

[JIM CHALOUPKA]

time to drag out all those schematics, jon.

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

[Jon Wehrenberg]

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.