grounding 12v to trailer frame?

[len19070]

no, No, NO.

You want to keep the camper's 12V system totally isolated from your tow vehicle's 12V system.

What about when you wire to charge your Battery while towing?

Happy Trails

Len

[BC Dave]

no, No, NO.

You want to keep the camper's 12V system totally isolated from your tow vehicle's 12V system.

What about when you wire to charge your Battery while towing?

Happy Trails

Len

heres 1/2 the answer... on a 7 pin connector there's a hot from the battery (or is that the alternator); with a 4 pin I doubt it ... but you could easily run a direct hot as in the 7 pin to charge while towing ...then use one of those heavy gauge 2 pin connectors.

Cheers Dave

[BC Dave]

...!..no issue here (but why does this seem so confusing)... ok so I understand the NEC; incoming 120VAC is "green" bare copper grounded to the frame. And there should be a 12V DC negative (ground) to frame form the house battery. So why not use the 12V neg ground for power; because the to frame connection might get corroded? Right? and always be careful to insulate and fuse the 12V DC positive so no hot framing happens ... this is simple

You got it.

Bruce

I appreciate your thumbs up; thanks .

... now what's the best way to set up my 45 amp charger / converter (120ac to 12V dc) ... thinking big 10 ga ground and wire 10 ga into the fuse panel for the hot main and direct connectors to the house battery.

Cheers BC Dave

[MtnDon]

For 45 amps #8 wire would be called for, both positive and negative from charger to the battery; #10 is only good to 30 amps.

[Dale M.]

no, No, NO.

You want to keep the camper's 12V system totally isolated from your tow vehicle's 12V system.

What about when you wire to charge your Battery while towing?

Happy Trails

Len

heres 1/2 the answer... on a 7 pin connector there's a hot from the battery (or is that the alternator); with a 4 pin I doubt it ... but you could easily run a direct hot as in the 7 pin to charge while towing ...

Cheers Dave

Almost all new pickups have 7 pin connector and are used for charging brake away battery on trailer (in Calif any trailer over 1500 lbs requires brake away) and its also used on utility (enclosed) trailers for lighting when trailer is connected to vehicle and has no independent battery supply, and its a well know fact batteries in parallel is a common and very applied science in the modern world.... On my Chevy PU the 12 volt positive to 7 pin connector is protected by a 40 amp fuse...

Some new PU's have a 7 pin socket and a 4 pin socket side by side and they sell adapters adapters that plug in to a 7 pin to convert it to 4 pin... When I wired my Jeep for tow I wired it as a 7 pin and made a 4 pin adapter for trailers with 4 pin connectors only...

You can do almost anything as long as a proper "load" is in circuit and you are not actually wiring a direct short into any of the attached circuits or through any of the co-joined (common ground) circuits...

Dale

[len19070]

no, No, NO.

You want to keep the camper's 12V system totally isolated from your tow vehicle's 12V system.

What about when you wire to charge your Battery while towing?

Happy Trails

Len

heres 1/2 the answer... on a 7 pin connector there's a hot from the battery (or is that the alternator); with a 4 pin I doubt it ... but you could easily run a direct hot as in the 7 pin to charge while towing ...

Cheers Dave

[/quote]

So keeping both the TV and the Trailers 12V systems Totally isolated is not a correct statement?


Happy Trails

Len

[GuitarPhotog]

So keeping both the TV and the Trailers 12V systems Totally isolated is not a correct statement?

Yes, it is not correct, nor is it really possible if you want reliable operation of your trailers highway lights (stop/turn/clearance).

<Chas>

[BC Dave]

For 45 amps #8 wire would be called for, both positive and negative from charger to the battery; #10 is only good to 30 amps.

...yeah ...I agree .... but on the install sheet included with the Powermax specifies a minimum 10 ga up to 45 Amps (or was it 55) then go the next size bigger 8ga for 55 and up.

[MtnDon]

You can check any number of wire gauge / capacity charts and find that according to those the suggestion to use #10 for anything over 30 amps is not correct. It's also not NEC. But I suppose you can also figure that the charger is not likely to be putting out 45 amps for any length of time; the charge current will taper off as the battery charge builds up. So in that respect #10 is probably going to cause no harm. I tend to go with generally recognized good practice (and code) over what manufacturers / sellers of goods say about their particular product.

We can also look at what wire sizes manufacturers / sellers of inverters recommend and find fault with them. The recommended wire sizes there often fall short of actual rated ampacities. Why? It's just a personal guess, but I believe they don't like to mention big (expensive) wire sizes are best for fear of scaring off the potential customer.

[bdosborn]

The recommended wire sizes there often fall short of actual rated ampacities. Why?

Because they base their wire selection on automotive type wire (like GXL), which typically has a much higher insulation temperature rating than the wire you find at the home center (THHN/THWN type). Good luck finding an ampacity table for auto wire; I looked around quite a bit and never found one. Besides, most trailer builders are going straight to Home Depot for their wire, which as you pointed out, the NEC ampacity tables should be used to determine wire sizes. Or better yet, use the manufacturers ratings (as opposed to the generic internet ampacity table that people keep posting which has nothing to do with thermoplastic insulated wires )

Southwire THHN/THWN Wire

Bruce

[BC Dave]

....!....

Never stop listening; and learning; never assume; you never know it all.

... ...

[Dale M.]

Some information on wire....

http://www.usawire-cable.com/pdfs/wire%20knowledge.pdf

Something one may want to peruse when contemplating wire purchase....

http://www.delcity.net/store/Wire-&-Cable/
http://www.waytekwire.com/products/1453/Wire-Cable/

Dale