Questions about fuses for inverter and converter

[John Frum]

I opened a metal electrical box in my battery compartment, which is adjacent to the currently-vacant on-board generator compartment.

Somebody pulled some wire and then didn't use it.
The other end probably goes back to the ac distribution panel.
That needs to be confirmed though.

 

[Oranjoose]

Somebody pulled some wire and then didn't use it.
The other end probably goes back to the ac distribution panel.
That needs to be confirmed though.

@Whinny @smoothJoey

I uncapped the wires in the electrical box and took my voltmeter to them.

The white and black measured 500mV when the shore was connected, with or without Main breaker on, and measured near 0 when shore was unplugged.

White to ground and black to ground measured near 0 volts no matter what.

I opened the power center panel, and found this:



It appears that the cable coming from the electrical box matches the cable with the orange jacket out of the gray conduit on the left (I don't see an orange jacket anywhere else behind the power center panel).

Ground is attached to the ground busbar on the left. White is attached to the busbar on the top. And black is attached to the Main breaker 30 amps.

But wouldn't that be shore? Now I'm confused.

 

[John Frum]

@Whinny @smoothJoey

I uncapped the wires in the electrical box and took my voltmeter to them.

The white and black measured 500mV when the shore was connected, with or without Main breaker on, and measured near 0 when shore was unplugged.

White to ground and black to ground measured near 0 volts no matter what.

I opened the power center panel, and found this:

View attachment 145607

It appears that the cable coming from the electrical box matches the cable with the orange jacket out of the gray conduit on the left (I don't see an orange jacket anywhere else behind the power center panel).

Ground is attached to the ground busbar on the left. White is attached to the busbar on the top. And black is attached to the Main breaker 30 amps.

But wouldn't that be shore? Now I'm confused.

You attachement can not be found.
Please take 2 pictures of the front of your panel with the door open.
Large enough and clear enough so that we can see the values on the breakers and fuse and see the maps.

 

[Oranjoose]

You attachement can not be found.
Please take 2 pictures of the front of your panel with the door open.
Large enough and clear enough so that we can see the values on the breakers and fuse and see the maps.

@Whinny Can you see them now?

 

[John Frum]

Ok still need your original attachment

I make the ac map to be...
Please fill in the gaps

main                30
air conditioner        20
refridgerator        15
?                    15
gfi_outlet            15
converter            15
microwave            15

 

[Whinny]

The orange #10 is probably going directly to your shore connection you might have to get around back of the panel to see if it is there...there may be a electrical box with 3 orange #10's in it in prep for the genset, might even have a transfer switch there. Disconnect the power again and check the resistance black to white at the mystery box.

 

[John Frum]

I looked into installation for inverter/chargers and it definitely looks a bit more involved, and certainly more expensive.

An inverter/charger is way simpler to install.
Sigh.

 

[Oranjoose]

The orange #10 is probably going directly to your shore connection you might have to get around back of the panel to see if it is there...there may be a electrical box with 3 orange #10's in it in prep for the genset, might even have a transfer switch there. Disconnect the power again and check the resistance black to white at the mystery box.

I tried to check resistance black to white in the muster box with shore unplugged, plugged, Main breaker on and off, and it wouldn't read any resistance in any of those scenarios. 0 ohms.

 

[Whinny]

So it's just sitting open somewhere.....or capped off in a box. If it had resistance or tested as a short it may have been a transfer switch coil resistance.

 

[Oranjoose]

So it's just sitting open somewhere.....or capped off in a box. If it had resistance or tested as a short it may have been a transfer switch coil resistance.

Before trying to tear anything out, I ran a snake camera behind the walls in an attempt to figure out where that mystery box's cable goes.

I took some photos. Pardon the really bad angles and quality. It's really tricky to get good shots back there.

The shore cable (black) and mystery box cable (orange) both enter a compartment behind the wall.



Then in the compartment, they both enter a metal box, and one orange cable emerges. Here's a close-up:



Here's a wider shot of the metal box, showing one orange cable going in, and another coming out.



The single orange cable then goes behind another wall along with another bundle of other cables. Judging from the location, I think that they are all entering behind the power center.



That orange cable I'm pretty sure is what is then connected to the Main 30 amp breaker.

I'm not sure if explained it very well. Basically, I'm not sure what's going on in that metal box where the shore cable and mystery box cable enter, and only one orange cable comes out.

Even if I tore out a wall to access that area, I'm not sure I'd know how to confirm anything.

Is there anything else I can do before I try something more drastic like wiring an outlet and plugging in a generator to see what happens? Sounds like a bad idea.

 

[John Frum]

@Oranjoose did you buy someone else's modified/messed up RV?

 

[Whinny]

That doesn't look like a regular electrical box to me. Turn off the main breaker and check resistance hot to neutral on the shore plug.
Why do they hide things like that behind walls?.....drives me nuts....
Actually against code up here.

 

[deeuubee]

@Oranjoose - " I'm not sure I'd know how to confirm anything."

You start by opening up the metal box and confirm if it's a transfer switch or not.
Then, put those loose wires in a junction box and tell the plumber to stop doing electrical work

 

[Oranjoose]

That doesn't look like a regular electrical box to me. Turn off the main breaker and check resistance hot to neutral on the shore plug.

I measured no resistance between hot and neutral on the shore cable. 0 ohms, just like the mystery box cable's hot and neutral.

I attached a probe to the ground wire in the mystery box and it did measure 0.1 ohms resistance against the ground wire in the power center breaker panel. So I guess that means that at least the ground wire is attached to ground on the other end. The shore cable's ground also measured resistance against ground in the breaker panel.

The shore cable's neutral measured resistance against the neutral in the breaker panel, but I wasn't able to measure any resistance from the neutral in the mystery box to the neutral in the breaker panel. I had to push pretty hard to measure resistance on neutral for the shore cable so I suppose it's possible my probe in the mystery box wasn't tight enough against the wire.

@Oranjoose did you buy someone else's modified/messed up RV?

Yes, I bought the RV pre-owned. However, I'm pretty confident that the RV is stock from the factory without any meaningful modifications.

 

[John Frum]

Yes, I bought the RV pre-owned. However, I'm pretty confident that the RV is stock from the factory without any meaningful modifications.

While disconnected from shore power and with inverter off.
Go to the box that you showed us where hot and neutral are wire nutted.
Check for continuity between neutral and ground.
Then assuming you don't get continuity.
Connect a jumper between the neutral and ground bars and then go back to the battery compartment and check for continuity again.
If you get continuity in the second test it means those wires are landed at the panel.
Remember to remove the jumper cable as that is a dangerous thing if you ever connect to shore power.

As someone mentioned above it looks like a plummer was fiddling with electrical.

 

[Oranjoose]

While disconnected from shore power and with inverter off.
Go to the box that you showed us where hot and neutral are wire nutted.
Check for continuity between neutral and ground.
Then assuming you don't get continuity.
Connect a jumper between the neutral and ground bars and then go back to the battery compartment and check for continuity again.
If you get continuity in the second test it means those wires are landed at the panel.
Remember to remove the jumper cable as that is a dangerous thing if you ever connect to shore power.

As someone mentioned above it looks like a plummer was fiddling with electrical.

I put a jumper between the neutral and ground terminal bars in the power center breaker panel, and was not able to measure any resistance between neutral and ground in the mystery box of the battery compartment. I was able to measure resistance between ground and neutral on the shore cable, confirming that the bars were indeed jumped.

However, interestingly I did notice that after peeling off more of the insulation and pressing harder, I was able to measure around a consistent 3.1 Megaohms resistance between hot and neutral in the mystery box.

@Whinny didn't you say that if there was resistance between hot and neutral in the mystery box, it could be an indication of some kind of switch?

 

[John Frum]

@Whinny didn't you say that if there was resistance between hot and neutral in the mystery box, it could be an indication of some kind of switch?

Open the box already.
It might be a transfer switch.
A transfer switch will have a double relay inside.
One for hot and one for neutral.
If you have one then it would stop me talking about an inverter/charger.
Oh and don't forget to remove the neutral/ground jumper.

 

[Oranjoose]

Open the box already.
It might be a transfer switch.

Sigh. I was hoping I could get away with not pulling out a wall of the RV to confirm this. I suppose that might be safer than connecting a generator to the mystery box and seeing what happens...

 

[John Frum]

Sigh. I was hoping I could get away with not pulling out a wall of the RV to confirm this. I suppose that might be safer than connecting a generator to the mystery box and seeing what happens...

Since you don't know where those wires are terminated its kind of necessary.
I'm not an electrician but it seem like a real bad ideaTM to have a box like that inaccessible.
I would a drink if the rv manufacture did that.
Although I've other horrors from the manufacturers.

 

[John Frum]

BTW you never answered my question about the bits of the map that I could not read.