Dual Voltage Power System?

luthj

Engineer In Residence
Inductive motors designed for 60hz running on straight AC voltage will spin slower on 50hz 20% slower approximately. The V/hz ratio will change, so magnetic flux at certain parts of the cycle will be higher than the initial design. Normally its not a bit deal, but something to be aware of regardless.
 

Neil

Observer
Which will offer crap little for electrical protection.
Further if a guy is unlucky enough their car is shocking them, They will be unlucky enough to stab that groundrod thru an underground utility.

This interesting, advice sought . I am reasonably confident that the internal wiring in the truck is sound. As said earlier I very rarely use shore electrics so it's not a great problem.

Occasionally if I am in bare feet and I ground the truck I get a tingle.

If I power my sockets from the inverter this does not happen

If I am plugged into a power source with earth this does not happen

It only happens when plugged into a power source without earth.

I am not alone with this phenomena . It has been the subject of many a fireside conversation with lots of Overlanders who have the same experiences with the same same circumstances.

I have met several who apply a wire from the chassis to a large peg in the ground so assumed this was a solution

Having an earth in a power source in South America is very rare. Nearly everything is wired with twin wire only.

Any thoughts would be useful

Neil
 

grizzlyj

Tea pot tester
Hiya

I was wondering if you had meant a wire from the chassis and copper earth pin when not hooked up, in which case does a relatively rubbish earth make any difference in any way? Like the access ladder in many cases for instance?

Our last camper hooked up gave me tingles a couple of times when the ground was really wet, me outside touching the wall.

But if a camper is earthed throughout its electrical system to the chassis and you hook up to a mains supply with no earth (or no indicated earth on a little test plug at least) what are the possible risks and consequences? I used to use both a new LED test plug and an old one with what looked like bulbs in it, and they wouldn't always agree on an earth being there?!?!

And regardless of voltage, UK plugs are the best :)
 

Neil

Observer
Earthing to the chassis isn't sufficient when it sits on rubber tyres.

I only get this tingle if I am in bare feet and maybe slightly damp.

And never get it when I am providing power from my inverter which is strange.

Earth in supplies are non existent in many countries. You have to work on the principle that you won't have an earth.

Haven't done it myself but loads of overlanders use a large steel tent peg and a wire to a big welding style earth clamp to the chassis. They claim it stops the possibility of a tingle.

This is a very common phenomena

Interesting to hear ideas and solutions.

Luckily my metal step has no contact to the chassis otherwise that last step out the door on a wet day in bare feet could have lots of comedy value

Neil
 

Grenadiers

Adventurer
Our Swiss-made Saurer 6dm is a 24v truck of course. The Swiss owners/builders built the cabin utilizing 24/230v. When we bought it, it had a 1600w Vitron Phoenix 24/230v converter. A separate 230/24v battery charger, with a plug on the outside for 230v shore power, along with the appropriate 100’ extension cord. Since the Waeco fridge and the LED lights, Truma Combi E furnace/water heater all run off that, I decided to add an additional system for US travel.

I doubled the battery bank to four AGM 4d batteries (24v), doubled the solar to 640 watts. I added a 2000w converter, 24/110v and use an Iota 24v charger when needed. Plus, for fun, I installed a 4000w loud generator we’ve never used.

To run the new setup, went to Home Depot and bought two 70amp breaker boxes. One to run the current from the battery through the 2000w unit, to several receptacles. The other for either shore power or the generator. I installed inline with that, an Isola Basics voltage regulator we picked up in Mexico.

The last four months we’ve been in the SE, lots of rain and clouds. When in state parks, I just leave the Iota plugged in and attached to the batteries. The electric system is varied for most situations and a tad complicated! But works for us. Long story short, two systems like this might work for you.
 

Alloy

Well-known member
Take a look at Victron Energy they have several inverter - inverter/chargers that will supply 110V or 220V if 2 units are linked together.

We are using a single Multiplus for 110V and didn't add a 2nd because we use propane for heat, fridge and cooking. The multi is wired in series with the shore power. We use Blue 9077 Rotary Transfer Switch to select between the front / back / generator shore power plugs. Each shore power line is proteted with a GFI breaker.


Our solar is:
4 x 330W (1320W) portable though a Victron 150/100
4 x 330W (1320W) on the roof through a 250/100. The 250/100 will allow future upgrades.

The battery bank is 940Ah@12V

We would have gone with 48VDC and a 48V-12V converter but there was 4x70amp 12V motors already installed.
 

Joe917

Explorer
Our Truck is a 230 volt truck that we imported to a 115 volt country so added a 115v inverter for small appliances.
If you are designing from scratch I would advise:
Build in your native countries voltage.
Select a charger that will take universal voltages.
Build sufficient solar and back up charge sources(battery to battery or generator) to never need to plug into shore power.
Air conditioning will be the biggest challenge, there is a huge thread devoted to it here.
I would avoid propane in the build, it can be a PITA to acquire in South America.
Being completely independent of shore power is the best solution and not that hard to achieve. If you are independent then voltage is no longer an issue.
 

dwh

Tail-End Charlie
This is a very common phenomena

Interesting to hear ideas and solutions.

First, there are what are called, "current carrying conductors". These are the actual "power wires" that do the work. In North America we use what is called "split-phase", which is a reference to how the transformer on the pole taps into the higher voltage supply wires that feed a neighborhood.

A split-phase transformer in NA supplies 3 current carrying conductors - two 'hots" and a neutral. Bridge across from either hot to the neutral and you get 120v, bridge across from one hot to the other and you get 240v.

Two wires are all that you need to have power.

Then, for safety, just purely as a redundant backup, we add an extra wire - the "equipment grounding conductor", which is properly called "EGC", but commonly referred to as "ground" or earth", since there is usually some place where the EGC is connected to the planet (but there doesn't actually have to be a connection to the planet for the "power wires" to work).

The EGC ties the metal parts (breaker box housing, metal conduit, microwave chassis, etc.) of the equipment together, and when done properly, is connected to the neutral of the transformer. In this way, if either of the current carrying conductors should come into contact with the metal parts, it provides a nice low resistance path to the transformer's neutral.

If a hot wire should come into contact with some metal connected to the EGC, it creates a dead short that should (hopefully) trip a breaker.

If a neutral wire should come into contact with some metal connected to the EGC, then it won't necessarily trip a breaker, but still provides a low resistance path back to the transformer's neutral.

Either way, the EGC helps to protect people from ending up as a current carrying conductor.


Now, since the firemen who are the "keepers of the lore" (they write the electrical codes) in the U.S. are true "belt and suspenders" kinda guys, they require multiple redundant paths for this redundant backup. So we connect the EGC to neutral in the main breaker box, and also connect it to the incoming cold water pipe, and just for icing on the cake, we also connect to rods driven into the ground OR connect to the rebar of a concrete foundation.

Sweet, sweet redundant safety.


But for the EGC to ever actually carry any current, there has to be a screwup somewhere. If the power wires are done right, they never touch anything connected to the EGC.

Again, a hot touching anything connected by EGC will normally trip a breaker, but a neutral touching often won't.

And there's the rub...

So assume some dodgy setup somewhere. May be a campground, may be some outbuilding in the South American outback. They've probably got some connection to the planet somewhere, maybe at the main building, or at the transformer. Something. But no EGC, or maybe a half-assed kinda/sorta might or might not work so-called "ground'.

And somewhere in all this hokey wiring, a neutral is making contact with some metal somewhere.

Along comes Mr. Happy Camper and plugs in. He thinks he's done everthing right when he wired his camper, because he connected his on-board EGC to his truck's chassis.

But unfortunately, there is that dodgy neutral somewhere upstream. Then he hops out in the middle of the night to take a leak, barefoot. When he touches both the planet and the truck, some electrons that have been fighting their way past a dodgy neutral connection somewhere on the property, suddenly discover that it's easier to get back to the transformer by going through the truck chassis, then through a human body, then through the planet. So they do, and Mr. Happy Camper gets a cheap thrill.

But! If Mr. Happy Camper had NOT tied his on-board EGC to the truck's chassis...he never would have become a conductor.


By "grounding" the on-board high-voltage AC electrical system (connecting on-board EGC) to the chassis of the truck, this potential is created.

By then hard wiring the truck chassis to the planet by connecting to a driven rod, or a metal plate under a tire or whatever, you do create a bypass so that your own personal body doesn't become a conductor, BUT you also make it possible for your truck's wiring to potentially end up having to carry more load than it was designed for.

So grounding the truck to the planet is not the proper solution to the problem and should never be done.

IF the shore power has a proper EGC then your truck's high-voltage AC system will be connected to it when you plug in a 3-wire extension cord. If the shore power doesn't have an EGC, or only a 2-wire receptacle to plug in to, then your truck's high-voltage AC system should remain a "seperately derived system" and not connect to anything except the the two "power wires" of the shore power.


Q. But what about the current leakage? How do you prevent Mr. Happy Camper, or his dog, from a latenight cheap thrill?

A. Ground Fault Circuit Interrupter. Plug that into the shore power 2-wire and plug the truck into that. The way this doohickey works that they run the two current carrying wires through two ceramic inductive coils, and compare the two. Under normal circumstances, the two power wires will carry the exact same current. It's balanced. But if there's a leak, say neutral to ground, then one wire carries more current. There's an imbalance, which is rightfully assumed to be a fault to ground, and the device trips.

(The name of this doohickey is deceptive, because it implies that it does something related to "ground". It doesn't. The name should probably have a colon in it to eliminate confusion. I.e., "Ground Fault: Circuit Interrupter".)
 
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dwh

Tail-End Charlie
Yea. Maybe I wasn't clear on one important point. Do not "ground" or "earth" your on-board high-voltage AC electrical system to the truck chassis. It should be a self-contained standalone system.

Then the on-board EGC works only to deal with any shorts within that standalone system. If you then plug into shore power, there is no path for the shore power to leak to the truck's chassis, and no shock potential between the truck and the planet.
 
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dwh

Tail-End Charlie
Btw, surge suppressors are known to leak voltage from their current carrying conductors to their earthing conductor. And lots of guys use them, especially in areas perceived having dodgy electric utility...

Oh yes, that...

Well in that case, plug the surge suppressor into shore power first, then the GFCI into the surge supressor. Put the leak upstream of the GFCI.
 

burleyman

Active member
I'm old enough to remember knob and tube wiring.

On two-wire 120vac outlets, I've often seen the hot (line) and neutrals reversed, which can cause metal surfaces to become energized. Tickles to hardcore jolts.

I keep a non-contact voltage detector to determine if the source is wired correctly for my rig. If a 120vac source, hopefully with a narrow and wide slots, narrow should light it up. Wide should not. It can give false positives which require further tests. Errs on the safe side.

At no time should the voltage detector, touched to vehicle/camper metal, illuminate. Drag the tester down your clothes to test. It should light up from static. If it illuminates/chirps on camper metal, it could be a false reading. Then go to the voltmeter tests below.


Another test. Use a digital voltmeter on the lowest AC scale if not autoranging, jam one lead into dirt, the other on camper bare metal. Should read no AC volts. If the dirt is dry, drive a metal tent stake and measure.

It's the potential difference (voltage) between two points that matters, especially for safety.
 

luthj

Engineer In Residence
As a note many mobile/RV inverters have an integral transfer switch. Some trasnfer switches will switch the neutral ground bond. When on shore power the chassis/safety ground is not bonded to neutral. When inverting (isolated from shore power) the chassis/safety ground is bonded to neutral at the inverter.

Most inverters give you some option to disable this switching. Some inverters have no transfer switch, and there are external transfer switch options with any combination of ground/neutral bonding, safety ground etc.
 

luthj

Engineer In Residence
My preference is to leave my shore power breaker off. Then have a reverse polarity LED by the breaker. That allows me to check before manually switching shore power. Some inverters are smart enough to refuse connection to a reversed neutral/hot connection. Depends on the model, and some require manually enabling the function.


Also, some folks I have worked with prefer to use a dumb inverter with no transfer switch etc. They run these units completely floating, with no ground bond in either shore or isolated mode. Some very cheap inverters have no safety ground at all, but these generally are not suitable for hard wired use in a vehicle. Many portable inverters are like this.
 

Neil

Observer
Can it tell if the polarity is reversed bearing in mind the current changes direction between 50 to 60 times a second depending where you are

Neil
 

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