RVing out of the box

[infinitefoamies]

If someone could help me out, I am trying to figure how to wire the AC grounding in my truck, I can't simply attach to the frame because in the event that current goes through those grounds, my Negative-earth DC system would be FUBAR (correct me if I'm wrong). If I wire all the AC grounds together, when I am on shore power I would have no issue. But what I am not sure of, is how inverters handle ground. Will it be sufficient to have the grounds wired together and the inverter can handle it?

I will more than likely be towing my box trailer when I am camping, which has solar panels on the roof to keep the trailers house battery charger. I intend to wire in some single pole connectors to attach my trailers DC system to my trucks so the trailers battery will charge when the trucks alternator is giving out juice, and the trucks batteries will be charged from the solar panels are giving out juice. I am pretty sure this won't be an issue but I just want to get a second opinion, when the truck is not running, will the solar panels back feed into the alternator and damage it? and vise versa?

I am also installing an old power converter that came out of my dads old camper. It's a power dynamics pd-710(off the top of my head), When on shore power, Would this back feed into the solar panels and damage them? don't have to worry about vise versa hear because I will have the input side controlled with a breaker.

I have three 1000 cranking amp truck batteries, how can I determine an amp/hr rating? it is not marked on the batteries.

Can you link multiple non-GFI outlets to a GFI outlet? or only one non-GFI?

I am putting this part on hold for now because of funds and the monumental list of projects I have, but because I can't figure out how to do this: I want to have a 30a and a 20a shore power service(use one at a time). I have one single pole breaker for each. How do I control the common? Can I use a switching relay? that would be activated when power is hooked up.



Thanks for the help.

 

[Gary RV_Wizard]

The ground and neutral for your 120vac power always goes to the external power cord, which should always be a 3 (or 4) wire hook-up (hot, neutral and ground). Do not bond neutral and ground in the camper either - the bonding takes place in the external source.

 

[Jammer]

If someone could help me out, I am trying to figure how to wire the AC grounding in my truck, I can't simply attach to the frame because in the event that current goes through those grounds, my Negative-earth DC system would be FUBAR (correct me if I'm wrong).

The green or bare grounding conductors should be connected to the frame.  The white (neutral) conductors should not.

If I wire all the AC grounds together, when I am on shore power I would have no issue. But what I am not sure of, is how inverters handle ground. Will it be sufficient to have the grounds wired together and the inverter can handle it?

It varies.  Most inverters allow neutral to float.  A few that incorporate transfer switches bond neutral to ground when the inverter is the power source.

I will more than likely be towing my box trailer when I am camping, which has solar panels on the roof to keep the trailers house battery charger. I intend to wire in some single pole connectors to attach my trailers DC system to my trucks so the trailers battery will charge when the trucks alternator is giving out juice, and the trucks batteries will be charged from the solar panels are giving out juice. I am pretty sure this won't be an issue but I just want to get a second opinion, when the truck is not running, will the solar panels back feed into the alternator and damage it? and vise versa?

Be sure to bring out two wires of equal size -- one positive, one negative -- rather than relying on the frame ground for negative.  The ground connection across the hitch, and at various other points, is unreliable and you won't get the charging performance you want.

You won't damage the truck alternator with the solar panels as long as you have some sort of charge controller that limits the voltage to something reasonable, which you need anyway or you'll damage the batteries.

I am also installing an old power converter that came out of my dads old camper. It's a power dynamics pd-710(off the top of my head), When on shore power, Would this back feed into the solar panels and damage them? don't have to worry about vise versa hear because I will have the input side controlled with a breaker.

No, it won't damage them.

I have three 1000 cranking amp truck batteries, how can I determine an amp/hr rating? it is not marked on the batteries.

They aren't intended for deep cycling which is why they don't have an amp-hour rating.  Deep cycling will shorten their useful life.  Typical truck batteries with a 1000 amp CA or MCA rating have a 700 amp CCA rating and will hold roughly 75 amp-hours, when new.

Can you link multiple non-GFI outlets to a GFI outlet? or only one non-GFI?

There's no absolute upper limit.  Some building codes specify a max of three, because more than that makes nuisance trips more of a nuisance and harder to find.

I am putting this part on hold for now because of funds and the monumental list of projects I have, but because I can't figure out how to do this: I want to have a 30a and a 20a shore power service(use one at a time). I have one single pole breaker for each. How do I control the common? Can I use a switching relay? that would be activated when power is hooked up.

Most people do this by wiring for 30a service (only) and using a 30a-to-20a adapter, which you can get for less than $10 anywhere.  If you wire for both you need a transfer switch.  Standard practice is to leave neutral connected to both sources all the time rather than switching it, and most codes specify that, though there are reasons to switch the neutral as well.

 

[infinitefoamies]

"The green or bare grounding conductors should be connected to the frame.  The white (neutral) conductors should not."

In this case, couldnt any voltage traveling over the ground to my frame, then travel into the negative side of all the dc power devices and fry them? (and the batteries)

"It varies.  Most inverters allow neutral to float.  A few that incorporate transfer switches bond neutral to ground when the inverter is the power source."

so what does this mean for me if the ground is needed by a device?

  "Standard practice is to leave neutral connected to both sources all the time rather than switching it"

then someone could get zapped from the plug that is not in use?

 

[Ned]

The AC ground should not carry any current in a properly wired installation.  It also should not be grounded to the frame of the RV or tied to the neutral line but is carried through the power cord to the load center that sources the shore power.  It's at that point that the neutral and ground are bonded and tied to an earth ground.

 

[infinitefoamies]

The green or bare grounding conductors should be connected to the frame.  The white (neutral) conductors should not.

The AC ground should not carry any current in a properly wired installation.  It also should not be grounded to the frame of the RV or tied to the neutral line but is carried through the power cord to the load center that sources the shore power.  It's at that point that the neutral and ground are bonded and tied to an earth ground.

so then your original statement is incorrect for this particular situation? also isnt the ground incase there is a wiring issue?

 

[Ned]

What original statement?  I've only posted the one message and that reiterates what Gary said about the neutral and ground.

 

[infinitefoamies]

oops, didnt notice the poster name, sorry. ok so, do i attatch the ac ground to the frame or not? I am worried that if something is not wired properlly it could destroy my dc system. if ground will never see current then why have it?

 

[infinitefoamies]

Can someone reccomend a battery isolator or combiner? or should i not bother? I will often have the trailer attached with solar panels but there are some times when i may not...

 

[Ned]

The AC ground has nothing to do with your DC system and should be wired as Gary and I have described.

 

[infinitefoamies]

because it is a truck not designed to have an ac system, the negative of the battery is connected to the frame.

 

[Gary RV_Wizard]

I'll amend my original statement to note that it is perfectly ok to connect the RV/truck chassis to the 120vac ground (green or bare wire). This provides additional safety in case the 120v hot ever accidentally touches the vehicle frame. Most all household appliances and portable tools that have metal casings also do this. There is no voltage in the ground except when some other wiring fault occurs and it will not harm your DC system if it does as long as the ground is connected to the external power ground wire.

 

[Jammer]

I'll amend my original statement to note that it is perfectly ok to connect the RV/truck chassis to the 120vac ground (green or bare wire). This provides additional safety in case the 120v hot ever accidentally touches the vehicle frame. Most all household appliances and portable tools that have metal casings also do this. There is no voltage in the ground except when some other wiring fault occurs and it will not harm your DC system if it does as long as the ground is connected to the external power ground wire.

Gary is correct.  Even if the grounding conductor for the 120vac distribution system isn't connected to the RV frame deliberately, chances are that it will be connected most of the time through some indirect route.  Having a solid connection reduces the potential for electric shocks and RF noise from capacitive coupling across weak or corroded points of contact.

 

[Jammer]

In this case, couldnt any voltage traveling over the ground to my frame, then travel into the negative side of all the dc power devices and fry them? (and the batteries)so what does this mean for me if the ground is needed by a device?

Your question doesn't make any sense to me.  What do you mean by "voltage traveling over the ground to my frame?"  Voltage between what two things? 

then someone could get zapped from the plug that is not in use?

It's a sticky wicket because with RVs the bonding point is physically disconnected.  Some transfer switches bond neutral to ground when on generator/inverter but not when on shore power, which is one way to solve it, although if you have a generator plug that's accessible but not in use I suppose someone could "get zapped" from whatever voltage drop there is in the neutral between the bonding point and the transfer switch, no more than a few volts if the campground pedestal is wired properly.  Where this becomes a problem is if the polarity on the campground pedestal's 30a outlet is backwards.

 

[Jammer]

The AC ground should not carry any current in a properly wired installation.

Well, not much, anyway.  There's always some leakage current, and you can measure it.  Most electronics and appliances are certified to UL 1278 which allows up to 5 mA per device.  Surge protection devices are particularly prone to producing leakage current, whether stand-alone "surge strips" or the devices built into electronics. 

It also should not be grounded to the frame of the RV

Not with you there.  Ground is ground and the safest installation connects all accessible conductive objects together to preclude the possibility of unsafe voltage between them.  The aluminum frame of my Airstream is deliberately connected to the 120v/240v ground.

... or tied to the neutral line but is carried through the power cord to the load center that sources the shore power.  It's at that point that the neutral and ground are bonded and tied to an earth ground.

I think we can agree on that part.

 

[Jammer]

if ground will never see current then why have it?

It will see some routinely.  Draining that away to reduce the shock hazard is part of its purpose.

And it will see a good deal of current when someone, say, drops the electric beater, while it's still running, into the sink full of sudsy water, as the the crowning failure of an earnest but misguided attempt at mashed potatoes.

 

[infinitefoamies]

just bought the inverter from harbor freight. 2000/4000 watt cen-tech. retail for $199, had a 20% off coupon, payed $138 including tax. Don't know how that math worked out but im not complaining.

Debating mounting in the center console, or under the rear seat(remove carpet and make sure its well ventilated obviously). It has a ground on the input side, I've never seen a dc device with a ground, would this also attach to the frame with the ac ground and the dc negative?

 

[Gary RV_Wizard]

An Inverter is both an ac and a dc device and it does require a chassis ground in addition to the battery positive and negative terminals (input power to the inverter).

Be aware that you can't use anywhere near that much inverter power (wattage) unless you add lots of batteries. Even 1000 watts of power draw requires a steady 90+ amps from the batteries.

 

[Jammer]

I don't think I'd put a 4000 watt, $138 inverter anywhere near anything I care about. 

 

[infinitefoamies]

Be aware that you can't use anywhere near that much inverter power (wattage) unless you add lots of batteries. Even 1000 watts of power draw requires a steady 90+ amps from the batteries.

The truck currently has two 1000CCA batteries, I will be adding a third and when towing the trailer i will have a deep cycle marine + solar panels. as for the three 1000CCA batteries, would that handle the inverter for a bit while the truck is not running or for the length of the trip with the engine running? If i am using a device that uises says 400w, would the inverter consume less power?

I don't think I'd put a 4000 watt, $138 inverter anywhere near anything I care about.

its a 2000w and retailed for $200