Inverter turns on, Stove goes 12v live

[winbasic]

Hi,

I've recently had some electrical work done on the boat which included adding new house batteries, Voltage Sensitive Relay and installing a DC meter. After numerous problems with the DC meter which were finally rectified, I'm loathe to go back to the shop who did the work for fear something else will get knocked out - fix on system, stuff another seems to be the service on offer unfortunately.

So the setup I have is 3 x 105ah deep cycle batteries joined together for my 12v house supply and a separate AGM starting battery. I have a 1500watt inverter connected to the house batteries. The DC meter is connected via a shunt to the house batteries and the VSR was installed so that when the Starter battery is fully charged it automatically diverts alternator charge to my house batteries.

Everything appears ok now except when I use the inverter. If I turn it on, when I touch my stove, it is 'live' - 12v live I'm assuming as if it was 240v I don't image I'd be typing this post!!

If I plug my generator into the shorepower plug, nothing is live. If I just use the 12v supply, nothing is live - its only when the inverter is turned on and it only appears to have happened since the work was done on the electrical system. I'm assuming that its something to do with where the earth cable is located (or perhaps not located) but have no idea where to start in tracking this down.

Hope someone understands my rambles and can point me in the right direction - I'd be most appreciative!!

 

[Dunaruna]

Re: Inverter turns on, Stove goes 12v live

Yeah, I understand your ramblings

I can help you but I need more information first -

I assume it's an LPG stove, does it have spark ignition? Does it have built in lights?

What brand of inverter, is it pure sinewave or modified?

What (exactly) is plugged into the inverter?

The shore power 240 and the inverter 240 should be two completely separate circuits. The shore power circuit should have an RCD fitted (legal requirement).

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

Thanks for your help. The stove is an alcohol/electric model - not sure of the brand but I've never used the electric side of it. I've only ever poured metho in the centre of it and used it briefly.

The inverter brand is a Sinergex Purewatts 1500 (thats according to a PDF manual I have - I always thought it was a puresine but as the boat is stored 60miles away, I can't immediately confirm).

The only things plugged into it are the Microwave (not always plugged in - only when needed, same said for kettle) Television and DVD player.

As for separate circuits - I think you're correct as I have a switch with 3 settings on it - Inverter, Off, ShorePower.

 

[Dunaruna]

Re: Inverter turns on, Stove goes 12v live

Your inverter is not a pure sinewave but it is a reasonably good quality inverter.

The stove is a 240v model, are you sure that the microwave and the stove power leads are not crossed over, is it possible that the stove is plugged into the inverter?

Being a fibreglass boat, there is no other way for 12v to get to the stove, something is faulty or wired incorrectly.

Next time you are at the marina, take a look at the back of the inverter, you will see three connections. The big red one is battery positive, the big black one is battery negative, the small wingnut is common ground (earth) - this is the one that is critical on a non conductive boat. Is there a wire connected to the wingnut?

One last question - was this boat originally wired for AC110v? If the answer is yes, there may be a converter somewhere in the boat that is faulty.

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

I've posted a picture below which hopefully shows the sort of stove it is (realise it would be a better picture if the glass top was up but its the only one on file)

I didn't realise it was 240v which probably explains why I've never had any luck working it on the electronic mode. However, the 'live' has only just happened since the work was done. I think the note you made about the wing nut earth could be worth a look as I'm wondering if that has been disconnected.

However the 'live' feeling I'm sure is 12volt which is why I thought it might be a 12volt 'leak' rather than 240.

I don't believe the boat was wired for 110 originally as its an Australian boat and I'm pretty sure it would have been wired for 240 from factory.

I'll get down to the boat in the next week and take a few more photos as well as check the wing nut connection. Thanks again for your assistance with this.

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

Being a fibreglass boat, there is no other way for 12v to get to the stove, something is faulty or wired incorrectly.

One other thought on that point - when they installed my GPS, they knocked out the VHF radio and anchor light. Apparently the young fellow drilled through a wire. Now radio and anchor light are upstairs but I'm wondering if something similar could have happened when they've installed the DC AMP meter which is next to the stove. Could a compromised earth wire cause this?

 

[Dunaruna]

Re: Inverter turns on, Stove goes 12v live

Could a compromised earth wire cause this?

Yes, I see this in caravans all the time, the point of a screw through a wire but caravans have aluminum cladding - highly conductive.

In your case, the screw would need to be through something conductive that is in contact with the stove OR the tip of the screw has punctured the earth and another wire but this should trip the RCD.

The bottom line is, unless you have a 12v light on that stove, there is no 12v wiring there and being a glass boat, there is no way for juice to get there. With that in mind, the inverter is the likely culprit.

If it were me, I would isolate the inverter and test it, if that checks out o/k, I would remove the stove and and start probing for a bad connection.

It is easy for me to sit here and suggest what/where to probe and test but it is probably prudent to get a certified sparky (house sparky, not auto) to take a look and make sure the 240ac system is up to code and safe. The marina manager should be able to give you a contact.

Where are you and where is the marina? I'm up in Brisvegas mid August.

 

[Dunaruna]

Re: Inverter turns on, Stove goes 12v live

As far as I'm aware, there is no such thing as a 12v element stove, the amp requirements would be enormous. 240v/ethanol stoves are quite common in boats.

I should also add - the wingnut connection on the back of the inverter is there to safely ground out the unit if it should become faulty. While the unit is working o/k, the wingnut is inactive. Most highend (usually expensive pure sinewave) inverters do not have this feature as they are double insulated and do not ground to chassis.

 

[tommays]

Re: Inverter turns on, Stove goes 12v live

12 VDC is tough to get any kind of shock from

A meter would measure the voltage getting to the stove and most have and AC and DC setting that should be able to tell you which your getting

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

Where are you and where is the marina? I'm up in Brisvegas mid August.

I'm in the north side of Brisbane (about 30 minutes north of CBD) and the boat is at Jacobs Well which is about 30 minutes south of the CBD).

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

12 VDC is tough to get any kind of shock from

A meter would measure the voltage getting to the stove and most have and AC and DC setting that should be able to tell you which your getting

I just assumed that it must be 12 VDC as if it was 240 VAC then I'd be dead! As you suggest though, I'll take a meter with me and see if I can measure it.

 

[winbasic]

Re: Inverter turns on, Stove goes 12v live

Just a follow up to this little saga ....

I had the local sparky take a look at it and it appears that there was a failure in the grounding on the main switch which allows me to switch between shore power, inverter and off.

After resolving this issue, and replacing the batteries (yet again!) the problem has gone away and when the batteries are fully charged, I'm able to use the inverter with the Microwave or Kettle without it going into overload. Sparky says its a factory fault but at least its fixed now!

Thanks to everyone for their assistance with this.

 

[waterone1@aol.com]

Re: Inverter turns on, Stove goes 12v live

Ok, this problem is solved. I want to point out something. I doubt he was getting a 12V "shock". More likely it was many times that, however, (lucky for him) he was never in the "right situation" to realize just how high this voltage actually was. Bottom line....if you ever "feel voltage" from any appliance ( ship or shore) assume that it could kill you !!! Have a qualified electrician check it out right away. What may feel like 12v, while you are standing in dry jim shoes touching fiberglass.....could really be 220 volts. All that may be missing could be a good ground for you to touch!!!