leaking current, short, faulty fridge?

not sure if on the right place here if not topic can be closed. Not that much arduino relayed other than that the fridge is controlled by any arduino.
I have a chest freezer in my campervan. Converted it to a fridge by bypassing the internal thermostat. A thermistor inside the fridge and at specified temperatures a relay will switch the fridge on and off.

Today sitting on my couch I felt a tingle in my arm. I was touching one of the bolts I used to fasten the couch to the chassis. The fridge is also bolted to the floor. So when I touch the bare metal of the fridge hinge and anything bare metal that is connected to the chacsis I feel the tingle. Measuring this with a volt meter I get around 50v as flowing. Continuity test won't sound the beep.

The fridge is powered by an 500 watt inverter, inverter is powered from a 12volt semi traction battery.
Maybe this might be of any help, the link to the specific inverter:

e-ast CL-500 500-W 12Vdc-230 VAC

So questions are:
1 bad fridge?
2 dangerous?

  1. Maybe .
  2. Yes.

Get it sorted !

Make sure the neutral (and ground) on the inverter are connected to the vehicle's chassis.

The refrigerator's enclosure should also be connected to the chassis. (The power-plug should be wired that way.... Normally, you wouldn't need a separate ground connection.)

With everything grounded it should be "safe". If there's a short or something's miswired the frig or inverter might burn-up or blow a fuse but nobody will be electrocuted.

Today sitting on my couch I felt a tingle in my arm

:smiley: :smiley: When I was in high school, I knew a little about electricity... My mother said she was feeling a tingle from the waffle iron. I touched it and I didn't feel anything. But I was wearing sneakers so I reached-over and touched the water faucet with my other hand..... BLAM! Big jolt through my chest! I think I said, "That was stupid!"

Haha nice story DVDdoug, epic response "that was stupid"

I had a look at the inverter. The socket has a connection with the plug for ground. (It's not a hole but a sorting past of metal in Europe) the plug has the ground metal part. However not sure if that ground is actually grounded. Only way it could be grounded was inside the inverter via the negative cable to the battery. (If that makes any sense?) My battery is grounded to the chassis.

Unless something in the fridge or inverter has broken I can think of another possibility.

My guess is the inverter output is not grounded and the voltage you see is from the EMI filters.

I would first test the power available at the offending bolt. I would do this by connecting a 115V incandescent bulb from the bolt to ground. My guess is that is will not have enough power to light the bulb even slightly. If this is not the case then there is something seriously wrong and needs to be fixed.

In either case the inverter instructions and recommended connection should be sought out. Even thought the input battery negative is grounded the output may not be (and must be).

John

John I'll need some more help with your answer. English is not my first language and electronics has been a shallow hobby that is gaining more depth now so not everything is clear yet.

First part:

I would first test the power available at the offending bolt. I would do this by connecting a 115V incandescent bulb from the bolt to ground.

Offending silt is the bolt that produced the "tickle" te mean? If i just touch the built while on the couch not much of a greening but when roofing the bolt and the fridge I get a tingle. Basically touching anything bare metal that is somehow connected to the car chassis (in this case bolts to keep fridge, bed, couch in place but also screws into the metal to keep walls in place and parts where the paint is chipped away) AND the fridge bare metal lid hinge will produce the tingle. Between those I measure Between 30 end 50v dc.

So for your test I connect a bulb between the fridge and a bolt right?
Problem is I'm info Europe, not easy to get hold of a 110v bulb. Besides my French is 0 and I'm in France at the moment... any other way to test this out?

In either case the inverter instructions and recommended connection should be sought out.

Instructions tells me plus cable of battery to red connector of inverter, negative cable to black connector of inverter. Nothing more.

I appreciate you all taking your time :slight_smile:

Bringamosa:
Problem is I'm info Europe, not easy to get hold of a 110v bulb.

Yes, he was forgetting that. He means a 220 V bulb for you. A LED bulb would be fine (more sensitive to low current).

Bringamosa:
Instructions tells me plus cable of battery to red connector of inverter, negative cable to black connector of inverter.

Actually, the connections at the inverter are not so important. What is more important is that the metal fridge body is connected by a ground (green/ yellow) wire to the vehicle chassis and that the inverter chassis itself is also connected to the vehicle chassis. If there is any doubt at all that such a connection path is not provided by the relevant power cords and wiring, you need to provide a separate ground wire in each case, and so for any other appliance.

Sorry about the language.

As Paul said. Connect a bulb (any bulb) between the fridge to chassis.

The reason for the bulb is, it will limit any current if there is a strong current created by making this connection.

I would expect the bulb to NOT light up. If it does NOT light up, I would connect a wire from the fridge to chassis. This wire will solve the problem.

HOWEVER if the bulb lights up, or if you use an automotive bulb and it blows out (fails) then you have a more serious problem that needs to be discovered.

John

Bringamosa:
Continuity test won't sound the beep.

Then that suggests that the chassis of the fridge (assuming metal or electrically conductive) isn't grounded to the same spot where the bolt is on the couch. Maybe it's necessary for you to look into this. So basically..... do something to get both sides connected together to start with.

So, the 12v automotive bulb did not light up when connected to the bolt.
I did some more reading on the topic. It is a very controversial topic. Some say you should never ground the earth of the 220v appliances with the ground the battery is connected with. It is designed to go that way. Unless the inverter has a specified grounding attachment to it. Others that you'll heave to do it no matter what.
Thing is something is "wrong" info this situation we have here? To be honest it does not really bother me, but if it might get dangerous it's a different story.

Maybe this might be of any help, the link to the specific inverter:

e-ast CL-500 500-W 12Vdc-230 VAC

Your link encourages you to call their customer service people if you have questions. They even give the telephone number. Surely this problem could be resolved with a simple phone call.

Paul

Paul I would not lean to much on customer service. I had enough experience with them telling me to do things I KNOW would not solve the problem or even make it worse. Or they just tell you something to get rid of you. Ask them why they tell you because that's wat written down here. I would like to have some input from people with experience in the field too.

For example, customer service of my fridge: sir I would like to know what the peak usage of the fridge is when powering up since I want to run it from an inverter.

Answers, 120 watts.

No sir, I need to know what the peak would be when booting up, i know it's rated 120 watts I saw it on the back of the fridge but that is not what I am looking for.

Answer, this is the download link to the spec of the fridge sir, it says 120watts. I hope I have helped you enough have a nice day.

Anyways, that was my little part off-topic story time. I might shoot them an email anyways :slight_smile: thanks for your input

Always go to the technical personnel directly if at all possible, but only with an intelligent question like this.
Just ring head office and ask to speak to the technical manager for XYZ product, sounding authoratative!
(these days there may well be a technical forum, but not necessarily public)

The alternative for this kind of problem is to go and measure a few units' leakage current to see if yours
is faulty - however that requires access to several devices.

Isolated SMPS's/inverters always leak some switching frequency current, its inevitable due to the frequencies
involved, for instance my laptop metal parts feel like they have a rough texture only when on charge, due
to the slight tingling confusing the tactile sense in the back of my hand.

In general I'd also say just ground the thing, its always going to be safer than not. If there's a drastic fault
this will blow the fuse, not you...