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Old 12-25-2014, 09:30 PM   #61
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Floating ground is when your ground does not have a physical connection to the earth. As in an RV, its grounded to the chassis. Still plenty of steel to dissipate whatever current you'd be running without worry about you being the ground instead... unless we're talking about some serious voltage, lightning for instance.

You run into safety issues when you have a poor ground and you are the path of least resistance instead of the bus.
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Old 12-26-2014, 05:06 AM   #62
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thanks. so a floating ground system is same as typical 12v automotive? the generator i bought has a tt-30 plug that states floating ground, and the breaker panel i got from a rv is wired where the grounds and neutrals are kept separate, but everyone has been telling me that my 110 side of my bus must be grounded.............im confused!
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Old 12-26-2014, 01:35 PM   #63
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Yes automobiles use floating grounds. You get into issues when you have multiple grounds and multiple sources of power. Basically you just want to make sure your ground is coming from the same place as your power feed. You can test resistance of your ground to make sure its adequate (lower is better), but not having much experience with rv's and DC systems I can't confidently suggest what is an acceptable threshold.
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Old 01-24-2015, 09:45 PM   #64
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Setting up Bus A/C

Ok I have these components 50 Amp power panel, 30Amp power panel Automatic transfer switch 50 Amp, 10K diesel generator presently set up
as 120 volt only plus a 4k inverter charger with auto transfer relay built in as well as auto generator start switch. I would like to use the power panel 50 amp for shore power input running thru the transfer switch 50 amp to the power panel then have the other side of the transfer connect both buses of
the panel together to run off of 120 volt from the generator. Question is
should I have a manual switch or something fail proof to prevent shorting the two buses together when plugged into shore power? The Inverter charger will be mounted further down the line coming out of the main panel and feed into the 30 amp sub panel for protection. Having hard time figuring out a proper diagram for my setup so here I am approaching the Guru for
greater knowledge and enlightenment.
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Old 03-09-2015, 04:25 AM   #65
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Hello all. I have been lurking on this site since last year and this is my first post. I Purchased a 1981 crown 855 turbo cummins, in september of last year and have been converting it since. I have now come to the time where I will be running my electrical.

I will be purchasing solar panels and will have a battery bank and an inverter. I am running 10gauge direct bury wire for my 120 volt appliances as I had some left over from a previous project. I ran this above my insulation on the floor and below my hardwood floor I just installed unfortunately I was unable to put it through conduit but it being direct burial I think it should be ok ( though i know more prone to vibrational wear). This one 10 gauge wire will operate a 6amp freezer and a 5amp freezer converted to a kegerator

I have some basic knowledge of electricity about breakers and wire gauge and such wiht AC but not any with DC or with an RV. I purchased a cummins marquis gold 5500 and will have solar panels installed as well with a battery bank

I have done a lot of reading but want to get some direct input.

#1 Will grounding the AC and DC to the chasis interfere with each other?(Can I ground my inverter and DC circuit and generator to the chasis?)

#2 the generator came with a transfer box for shore power. I was reading previously in this thread about being able to bond and unbond your neutral and your ground. What exactly does that mean and how does one do that? What exactly does this transfer box do ?

#3 In terms of circuit breaker box I will want a 30 amp breakers since I am running 10 gauge wire. Do those wires all connect in breaker box and then a larger gauge wire that can hand all of my loads at once comes out of the breaker box and to the inverter. Where does a GFCI get installed?

#4 Can I run DC power cables alongside AC power cables?


Thanks

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Old 03-09-2015, 07:43 AM   #66
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So you have a Crown? We will need pics!
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Old 03-09-2015, 09:19 AM   #67
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Quote:
Originally Posted by HunteR0se View Post
#1 Will grounding the AC and DC to the chasis interfere with each other?(Can I ground my inverter and DC circuit and generator to the chasis?)
You don't have a choice. For safety reasons you really need the biggest, most available chunk of ground material (the chassis) to be the "ground" in your AC system. It is possible to pick up some noise this way, but in practice this is less of a big deal than a lot of people think. A bus is a HUGE ground path.

Quote:
Originally Posted by HunteR0se View Post
#2 the generator came with a transfer box for shore power. I was reading previously in this thread about being able to bond and unbond your neutral and your ground. What exactly does that mean and how does one do that? What exactly does this transfer box do ?
Electrical boxes (usually) have two bus bars, bars with lots of holes and screws to attach neutrals and grounds to (the hots go to the breakers, of course). "Bonding" means the neutral and ground are tied together. This is the default in a lot of cases. However, NEC calls for some circuit configurations to be "unbonded", which means the connection between the two needs to be separated.

The circumstances in which this is required aren't 1-sentence-summary material. The ultimate goal is to make sure the ground wire is always "available" for its safety purpose and not actually carrying current at any one time. You should be able to grab ahold of it and not get electrocuted, even sitting in a bathtub full of water. That's why it's usually bare, not insulated - it's supposed to be a safety wire, not a current-carrying wire.

Neutral IS a current-carrying wire. They're tied together at the main panel in a house, for example, because that's the final exit point of electricity. There's a ground rod tied in there, too. Few houses actually have a true "neutral" out to the pole, especially in the US. If you look at the wire into your house you'll see it's actually just two conductors, one for each side of 240V. Your ground rod creates a "center tap" between the two that lets you get 120V out of each. Those wires to the pole aren't hot and neutral - they're both hot. And the steel carrier cable isn't hooked up to anything.

Anyway, that means neutral and ground are the SAME THING in the main panel in your house - and probably should be in your RV, too. But only at that one location. In almost all configurations, everything downstream (sub-panels, other boxes, etc.) should be "unbonded". Current should never be allowed to jump from neutral to ground anywhere other than at that panel. The reason is that if your neutral breaks (and wire breakage is one of the main failure modes these things are designed to deal with), you do NOT want current jumping over onto the ground wire and making that, essentially, a "hot" wire on the way back to the panel. Fires, electrocution, and other unreasonably nasty things await.

I haven't even begun to get into how this is all supposed to work - I'm paraphrasing, and I'm not even an electrician myself. If you're at ALL less than 100% certain how this should all be wired, consult one! Most charge < $100/hr, and since you aren't going to be getting a CO for this stuff, an hour or two of consultation is probably all you need - they're not going to sign off on anything. It's totally worth it.

Quote:
Originally Posted by HunteR0se View Post
#3 In terms of circuit breaker box I will want a 30 amp breakers since I am running 10 gauge wire. Do those wires all connect in breaker box and then a larger gauge wire that can hand all of my loads at once comes out of the breaker box and to the inverter. Where does a GFCI get installed?
A GFCI can be installed anywhere - it's usually point-of-use (in the bathroom, kitchen, etc.) There are GFCI devices that can "chain" or be installed "upstream" - examine your device for installation instructions.

Yes, your upstream wire needs to be able to handle the total capacity of what's in the panel.

Quote:
Originally Posted by HunteR0se View Post
#4 Can I run DC power cables alongside AC power cables?
Yes, but the further apart, the better. Actually, it turns out to be more important to consider where they CROSS than where they run PARALLEL for very long-winded explanations I won't get into here (but a CAT5 cable installer knows all about). A few inches apart is actually remarkably good at isolating noise. If you're really concerned, throw in a few lengths of EMT conduit. It's cheap, easy to cut, and if you ground one end (JUST ONE END) is a very effective noise isolator.

Grounding both ends can make ground loops - do not do this thinking it will be better.
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Old 03-09-2015, 07:47 PM   #68
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... and if you ground one end (JUST ONE END) is a very effective noise isolator.

Grounding both ends can make ground loops - do not do this thinking it will be better.
In my system, I attached the green ground wire to the ground bar inside the circuit breaker box and the other end to each metal outlet box and the ground connection on the outlet itself. The breaker box is grounded only to the inverter, which picks up the ground from the shore feed when I'm plugged in.

At least three of my outlet boxes are also attached to the metal skin of the bus. I have used tools and lights plugged into these outlets, but so far have not had any problems.

Should I go back and somehow isolate those boxes from the outer skin to prevent a ground loop? Or am I misunderstanding this whole concept?
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Old 03-09-2015, 09:05 PM   #69
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No, not unless you have a lot of system "noise" on your radio. Ground loops are the things that give you "alternator whine" when you're driving. No problem => no change.

My point was more about how electrical systems are full of misunderstandings. You figure, hey, it's a shield. I should ground it everywhere, right? But what happens is some ground current ends up flowing through the shield itself, and then it's not a shield any more - or worse, it's an antenna. Counter-intuitive, but...

Technically, if you have metal electrical boxes attached to the metal of the bus with a good connection, and so is your breaker panel, you don't need a separate ground wire - and the NEC would say you're not supposed to install it (you use a ground in the wire bundle, OR ground the conduit at the upstream end - but not both). But all of this is for houses, and your setup isn't going to hurt anything. Just make sure you do provide a neutral. If your bus is a safety ground, don't use it as a return path, too.
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Old 03-10-2015, 02:24 AM   #70
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Task

Thanks for the lengthy response. I have another question that sort of related to PD's question. I was wondering if I could just ground he outlets to the bus skin right by the outlets since the whole bus skin is aluminum. Or even better there is a I want to say 12 or 14 gauge steel upside down L that the bus coving was attached to that runs down both sides of the bus and is wrapped by the aluminum inner skin of the bus. I was thinking this would be enough metal to dissipate the charge. I could then ground my battery bank to the chasis and there would be less interference....I think. What would be the advantages/disadvantages to doing this. What would happen if I did this for neutral instead of the ground and grounded the battery ground and the inverter ground to the Chasis instead? This would be bad right?

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We have been documenting the conversion and will post it up on here in the next month or so. It is in amazing condition and we have painted it green and kept the black stripes
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