Shunt location on travel trailer with batteries in front

[chrisski]

could the chassis be what is connecting the circuit for the negative wire? The neg from one battery goes to the inverter without passing through anything else. The negative from the other battery screws to the trailer frame. Would the trailer frame electrocute you if this were the case?

I don't know if it would electrocute you through the frame, but from other posters on here, an inverter really ought to be direct wired to the battery. In my case, there's a 2000 watt 12 volt inverter that could run a microwave at 130 amps while its powered up, and probably surge to 200 amps. I really don't want that going through the frame.

The more you look at the RV, the more you realize how quickly they kick the things out of the factory by cutting corners. I picked mine up and there were several little things the factory had not fixed that the dealer fixed before I picked it up, and that is almost always the case. I'm reluctant to dig too deep and "look behind the curtain," because I'm afraid of what I'll find. Right now I go with, "Heavy loads are direct wired, and light loads are frame wired." "I peeled back the curtain" and found the ground to my DC fuse box is six gauge wire straight to the frame, and then another piece of six gauge wire straight to the frame for the battery. The biggest loads on those circuits will be the slide outs. I don't like that, but have no idea if its right. There's probably millions of RVs kicked out the door just like that.

I'm the type of person that likes to read in an official source how many amps you can send through a ground frame versus thick wires, but I don't know what that source is. I thought it would be the NEC which I thought would be available for free download, but the NEC code seems to be available for hundreds of dollars, the same for finding out what a particular UL standard is. Without access to those, I'm just doing what I think is safest based off the electronics technician job I was in 26 years ago and what is said in this forums and others. At times I feel like my source is the infamous, "A friend of a friend of a friend."

 

[HRTKD]

Chris, I think the closest "code" for an RV would come from ABYC. Just think of your RV as a "Land Yacht".

 

[chrisski]

The ABYC code lead me to a course I could enroll in , but not a manual for me to look up online for free.

 

[John Frum]

The ABYC code lead me to a course I could enroll in , but not a manual for me to look up online for free.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[John Frum]

NEC tables here https://www.usawire-cable.com/pdf/nec-ampacities.pdf

 

[HRTKD]

Look for a document titled, "AC AND DC ELECTRICAL SYSTEMS ON BOATS." I have the 2008 version, which is older. I think I got it free because it's older. Or, maybe that's the latest version. Beats me.

Send me a PM with your email address and I'll pass on the PDF to you.

 

[John Frum]

I don't want mg wires getting to 105 celcius even though they are rated for it, so I use the nec tables and shoot for 75 celcius even for single wires in open air.
Bundles or inside a wall I would go with 60 celcius.
Just my opinion.

 

[HRTKD]

The ABYC PDF that I use came from the resources section of our forum. Here's a link to the subsection:

Code Compliancy Articles: NEC/ABYC/UL

diysolarforum.com

It's the last item in the list for me.

 

[HRTKD]

I don't want mg wires getting to 105 celcius even though they are rated for it, so I use the nec tables and shoot for 75 celcius even for single wires in open air.
Bundles or inside a wall I would go with 60 celcius.
Just my opinion.

The only wires going through an interior wall in my trailer are the 10 gauge PV wire, coming in from the rooftop panels. The panels themselves have 12 gauge wire, about 3' long at most. I figured that using 10 gauge would keep me safe, but I don't know how to do the calculations to confirm that. The two panels (2s) are pumping out ~80 v / ~9.3 amps. I didn't measure the cable used between the panel's MC4 connectors and the circuit breaker located inside the trailer. My guess is 25'. The TEMCo PV wire is rated for 90° C wet and 150° C dry. The link provided has an interesting comparison between real PV wire and THHN building wire.

 

[John Frum]

The only wires going through an interior wall in my trailer are the 10 gauge PV wire, coming in from the rooftop panels. The panels themselves have 12 gauge wire, about 3' long at most. I figured that using 10 gauge would keep me safe, but I don't know how to do the calculations to confirm that. The two panels (2s) are pumping out ~80 v / ~9.3 amps. I didn't measure the cable used between the panel's MC4 connectors and the circuit breaker located inside the trailer. My guess is 25'. The TEMCo PV wire is rated for 90° C wet and 150° C dry. The link provided has an interesting comparison between real PV wire and THHN building wire.

50 feet round trip 9.3 amps@80 volts.
Voltage drop for 12 guage is under 1%.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

Heat/ampacity is no problem either.

https://www.usawire-cable.com/pdf/nec-ampacities.pdf

 

[HRTKD]

50 feet round trip 9.3 amps@80 volts.
Voltage drop for 12 guage is under 1%.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

Heat/ampacity is no problem either.

https://www.usawire-cable.com/pdf/nec-ampacities.pdf

That version of the ampacity doc doesn't reference the PV wire, which is covered under UL 4703. I tried to find a similar chart, but came up empty.

 

[John Frum]

That version of the ampacity doc doesn't reference the PV wire, which is covered under UL 4703. I tried to find a similar chart, but came up empty.

Copper is copper and insulation has a temperature rating.
I don't see why those tables would not apply to pv wire.
Why do you think pv wire would not apply?

 

[HRTKD]

Copper is copper and insulation has a temperature rating.
I don't see why those tables would not apply to pv wire.
Why do you think pv wire would not apply?

Because the columns in that chart are specific to certain ratings.

 

[John Frum]

Because the columns in that chart are specific to certain ratings.

Sorry not following, what ratings?
If the wire is pure copper and the insulation is rated for 90 celcius, what do think could be the issue?

 

[HRTKD]

At the top of each column are the conductor types. PV wire is type UL 4703, which isn't shown.

 

[John Frum]

At the top of each column are the conductor types. PV wire is type UL 4703, which isn't shown.

View attachment 24623

Those are just some examples of wire types commonly used by electricians grouped by the temperature rating of their insulation.
Its not an exclusive list.

 

[HRTKD]

Those are just some examples of wire types commonly used by electricians grouped by the temperature rating of their insulation.
Its not an exclusive list.

Or, it's not there because that chart is old. The UL 4073 standard came out in 2014 according to this article: https://incompliancemag.com/ul-publishes-ul-4703-standard/

 

[John Frum]

Or, it's not there because that chart is old. The UL 4073 standard came out in 2014 according to this article: https://incompliancemag.com/ul-publishes-ul-4703-standard/

Suit yourself.
I tried.

 

[chrisski]

Look for a document titled, "AC AND DC ELECTRICAL SYSTEMS ON BOATS." I have the 2008 version, which is older. I think I got it free because it's older. Or, maybe that's the latest version. Beats me.

Thanks. I was able to download a 76 page document. I think that's the entire thing.

Heat/ampacity is no problem either.
https://www.usawire-cable.com/pdf/nec-ampacities.pdf

You've probably put this out before, but I saved it now. Thanks. I used it to make sure the wires I have don't exceed 60°C.

 

[Leo3]

Sounds like a crappie post install modification.

It’s actually a brand new trailer all this was done at the factory! They are factory add ons.