2 electrical surprises

[gasgas]

Yesterday I added another 13A outlet socket to my Pollensa. I have a Renogy 2000W inverter which has two 13A outlet sockets. One of them ran to a couple of outlets but I need another 13A socket at the other end of the habitation area so first I went to my man shed to dig out some cable, a 13A outlet socket and a 13A plug. Or preferably I might have a pre-wired plug with cable attached. If I scrap a broken 230v appliance which has an attached mains cable and plug, I cut off the cable and keep it because for certain 'it will come in useful sometime'.

I found such a cable. I was proved right, it did indeed come in useful sometime. Isn't it a wonderful feeling when you re-use something you kept because it might come in useful? I can't remember what appliance it came from but the conductors were 0.75mm csa. So it must have been a low wattage one.

Surprise number one:
The surprise was that the moulded-on 13A plug had a label saying "Fitted 13A fuse". I pinged it open and sure enough there was a 13A fuse. If you tried to put 13A through it, the wire would at the very least get hot, and possibly melt. Anyway because the cable had 0.75mm conductors I changed the fuse for a 5A one and proceded to fit a new mains outlet to the camper.

Surprise number two:
I cut the square hole in the panel for the new socket and fitted the back box and made sure the inverter was switched off and the hab batteries disconnected and the solar panel disconnected. Not sure if the plug and cable were long enough to reach the new outlet I first plugged the 13A plug into the inverter. I fed the cable through some trunking towards the socket position and suddenly got a 230v shock. I must have touched the live conductor at the cut end of the cable. Or at least, of course I didn't measure the voltage exactly but you know the sort of shock I am referring to.
I can only think of two possible reasons. One is that there might be a charged capacitor in the inverter - but then suely it would have discharged into the last appliance that was connected. The other must be that somehow the 12v input to the inverter was still present. But the engine was switched off. I do have an 'intelligent' charging relay from ebay:
SPLIT CHARGE RELAY VSR 12V 140A 140 AMP VOLTAGE SENSITIVE CAMPERS CAMPERVAN
What this does is to sense the engine battery and if that is over 13.2v it closes the contacts and connects the hab battery to the engine battery so the hab battery gets charged. It doesn't need the purple D+ wire from the alternator. However that doesn't explain why I got a shock. Even if the engine battery had been over 13.2v and the relay closed, the inverter was switched off so it shouldn't have put 230v on the output sockets.

Answers on a postcard . . . . .

I reckon there is a charged capacitor in the inverter, but why was it charged?​

 

[Scotia]

I was proved right, it did indeed come in useful sometime. Isn't it a wonderful feeling when you re-use something you kept because it might come in useful?

I have 3000 sq foot of that may come in useful some day items.

 

[gasgas]

What you should do is to move to the Isle of Man. Before you go you have to book 6 consecuitve plots at the car boot sale

 

[trevskoda]

He has not seen my junk yard yet, i require another lifetime to clear it all out.

 

[Okta]

Always worth remembering that many inverters are not single polarity i.e. both wires are live so single pole switches do not make them safe. The plug needs to be pulled out for safe working.

 

[gasgas]

I've no idea what the remote on / off switch disconnects, but it does stop the 230v output.