| Author | Message | ||
| Buddy Tennison (Buddyten)
Rating: N/A |
We have an '80 Eagle. In it we have installed an Onan 7000 Marquis Genset, which has seperate 30A and 20A legs. We use the vehicle as a tour bus, and not for camping, so we originally thought that we would not be using any power source other than the genset. However, we are finding more and more that we need to start using campgrounds facilites, hence the need to start using "shore power". When we wired the bus for 110V, for ease, we simply installed two separate 60A breaker boxes. We ran 8GA wires down into the generator bay from each breaker box, installed a male plug on each. Then we installed a female plug onto each of the 30A and 20A legs of the genset. Our question is this: We want to install a 50A shore power cord. Rather than having to re-do all our current wiring, can we take a 50A shore power cord, install a "pigtail" type connection with female plugs to simply plug in where the genset plugs. Essentially, we would have to unplug the genset, and plug in the shore power. According to what I have found, the 50A shore power has two "hot" legs, one neutral, and one ground. Could we hook one hot to a plug, another hot to another plug, splice the common white or neutral, and splice the ground to formulate this arrangement. If I understand correctly, this would give us 50A going to each plug, and supply 50A to each of our breaker boxes. If there is a better way to do this than haveing to rewire the bus using transfer swithches, etc, could you please share it with us. Thanks. | ||
| DebDav (Debdav)
Rating: N/A |
Yes | ||
| Jerry Liebler (Jerry_liebler)
Rating: N/A |
Buddy, If the main breakers in your present boxes are 60 amps the wires between the plugs and the boxes should be 6 guage, solve this by changing the main breakers to 30 amp or rewiring. The best way to add a 50 amp shore cord is to also add a breaker box, with only a single two pole breaker, near where the shore cord enters the bus, usually the left rear bay. This breaker serves as the, possibly, required disconnect and in your case the two pole breaker could be a 30 amp unit to avoid needing to rewire your plugs. From the added breaker box you could use 6 guage wire (4 conductors, in conduit) to a box near your generator and in this box put two outlets just like you have for the generator. Regards Jerry 4107 1120 | ||
| John MC9 Rating: N/A |
Buddy - See if this web site is of help. Things are explained in a nice, common sense manner: RV Wiring There are commercial devices that do exactly what you want to do. I.E.: Use multiple plug/socket configuration to provide 50 amp service at a 30 amp power pole. And RVrs have been rewiring their 30 amp service to be able to make use 50 amp service, for quite awhile. Making up your own 50 amp plug and socket conversion is totally possible and usable. Since you already have "two separate 60A breaker boxes...... ..... a male plug on each" for the power from your genset to plug into.... using a commercially made 50 amp cord, and fitting it with two receptacles for those plugs, is the easiest way to solve the problem. You can buy 50 to 30amp plug adapters, at any RV shop or Walmart, by the way.... Take great care to note the comments about the ground lead, and the use of a GFI. | ||
| herman Rating: N/A |
Does your genset have breakers at it for the two legs? If not, everything upstream of your 2 boxes is unprotected. What exactly do you mean by "60A breaker boxes"? My interpretation is that this is the ampacity of the bus bars therewithin; it says nothing about the complement of breakers that they contain. I'm not going to comment on wire sizing, as I'm ATM too lazy to dig up the tables. Using separate main panels for the separate genset legs does not strike me as a good idea. If they are out of phase with each other, i.e. this is a 120/240 genset vs. a pure 120 unit, then it's likely a code violation. Now, if the actual genset has breakers then it could be construed as a main panel in and of itself, and thus the downstream panels are merely branch panels. But, when you add shore power, then that whole scheme goes south. I can't say that I particularly like Jerry's scheme, either. If you're going for 50A 120/240V shore service, then, if you want to go with the plugs and sockets route, use the 4 wire 50A connectors. If you don't want to pull new wires, then you need a panel upstream of them that properly protects them. Also, you want a service entrance breaker panel for the shore power, so that you don't have to trust Campground X's shore breakers to protect you. Ideally, that'd be at the shore end of the cord, so that it would protect the cord as well, but, code may require one at the actual point of service entrance to the vehicle, regardless. And, as I said before, your other source, i.e. the genset, should have its own breakers, to protect its windings. So, 3 sets of breakers: 1 for each source, 1 for the loads. It should be readily apparent that they comprise a "Y" topology. Whether the body of the Y, i.e. that which connects them together, is 1 plug and 2 sockets, or a transfer switch is a separate issue; I'm not fond of the plug scheme, and wonder if it's code compliant. Whatever you do, make damn sure you're doing it right, as this stuff can kill you, yours, and/or innocent bystanders who merely touch your bus, (e.g. a campground employee maintaining the landscaping) and do so in a heartbeat, quite literally. | ||
| Jerry Liebler (Jerry_liebler)
Rating: N/A |
Herman, I may not have been clear that what I meant was a standard 4 wire 50 amp shore cord from the added breaker box with a dual 30 amp breaker in it. The 30 amp breaker allows the 30 amp wiring now in place and limits what can actually be 'pulled' from the shore line. This added breaker box serves as a disconnect, a junction box between the shore cord and bus wiring and limits the curent to the 30 amps per leg. I too am not a fan of the plug and socket type of transfer switch but it can be done completely within the NEC. Regards Jerry 4107 1120 Regards Jerry 4107 1120 | ||
| Jerry Liebler (Jerry_liebler)
Rating: N/A |
Buddy, When you connect to shore power it becomes very important that your ground and neutral wiring is not tied together. You need to make sure your existing panels do not bond ground to neutral and also make sure that the neutral and ground are connected together at your generator. Regards Jerry 4107 1120 | ||
| bobm Rating: N/A |
the guy who designed my 4104 electical system gave me a box that he made. it has two 110 female plugs and one male 220 plug for my bus input it also has a small light in it. if the light goes on i have 220 from two 110 campground plugs if no light i only have 110 ( i have an electric stove and need 220 for the oven and burners) don't know how it works but it does | ||
| herman Rating: N/A |
Jerry, no prob with the clarity thing. Also, thanks for giving the requisite Bonding Screed; I'm only good for maybe one of those a month these days... | ||
| Brent Coursey (Busboy)
Rating: N/A |
John, You need to be careful if you use one of those "50 amp from a 30 amp pole" boxes. I know in our park you won't get 50 amps if you plug one side into the 30 amp plug and the other into the 20 amp...because both are on the same leg coming from the panel. I'm not sure what would happen but something might get melted... -Brent | ||
| John MC9 Rating: N/A |
Brent - Re: "you won't get 50 amps if you plug one side into the 30 amp plug and the other into the 20 amp...because both are on the same leg coming from the panel. " Are you saying both the 30 and 20 amp outlets are held to the same fuse/breaker? Good grief? That offers absolutely no protection to anyone using a common 15amp 110v extension cord. With all sincere respect.... This is a topic this forum has argued about for a couple years (at least).. I suppose it's worth repeating... No matter if it's a fancy $$$ KOA, or a backwoods, downtrodden four pad campground, you can not depend on the wiring to be up to standards. If they say "50 amp", you may be getting a 20 and a 30 combined, or two 15 amp legs... or the correct 100 amp 220 service... or any combination between. I have been to more campgrounds that do not meet the standards, than do. Every camper should carry a voltage presence tester (probe), a voltmeter, and a simple outlet tester. You can buy 'em at Home Depot, Harbor Freight, Sears, Walmart.... Each of us are responsible for our own safety; don't leave it to someone else. | ||
| Brent Coursey (Busboy)
Rating: N/A |
John, We have 50 amp pods that have both legs running into them and they are safe and up to standards as are our 30 amp pods. On our 30 amp pods, only one leg is running in and there is a 30 amp plug hooked to a 30 amp breaker and a 20 amp plug hooked to a 20 amp breaker. Both breakers are on the same bus bar being fed by the same 1 leg of the power. If you put your magic 50 amp device in the 30 amp plug and the 20 amp plug your not going to get what you expect...but I'm not the electrician, so I can't explain what would happen. I agree with you that you should check the plugs before plugging in. You should also check what condition the blades are on your plug and the receptacle your plugging into. If they are burnt, you set up resistance which will start the meltdown process...I've seen this happen. As you've stated, lot more than just pluggin in. -Brent | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
I believe you can only get a total of 40 amps. This is assuming there is an equal load on both the 30 amp and the 20 amp circuit. Any total load above 40 amps will start overloading the 20 amp breaker since the current is shared equally. Richard | ||
| John Jewett (Jayjay)
Rating: N/A |
Buddy, what you suggest is highly illegal, and so is the current hookup you are using. Find a competent electrician that is familiar with the National Electrical Code, and especially Articles 551, 404, 250 and the tables at 310 and 312. Get him to advise you on remodeling your coach safely. Cheer...JJ | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
JJ, instead of just telling Buddy that his system and scheme is highly illegal and leaving him to find a "competent electrician" (If there really is such a thing when it comes to bus systems, which as time goes on I tend to wonder) ...perhaps you could explain to him (and the rest of us) why it is so illegal, and what he could do on his own to correct it. Half the reason we're all here is to learn.. being told that you're wrong without lending at least a few correct suggestions and alternatives, never teaches anyone anything. And this goes for all of us, not just JJ... Personally, unless I'm missing something big, I don't see what is so horrible about his current system. Given the comments that have been generated, apparently nor do many others here or we'd have heard about it by now... ???? It certainly sounds safer than many a hairbrained scheme I've seen describd on this board...Just curious. | ||
| JW Smythe (Jwsmythe)
Rating: N/A |
I'm not an electrician, but I think I can already smell an electrical fire.  I'd have to see a diagram to figure out exactly what he's suggesting. I agree with what a few others have said. Don't trust anyone elses power. Just because you can splice something up to work with one system, don't mean the next place will be the same way. For my own wiring, I'm going to have a friend who does kick ass high voltage work, plus runs a huge DC plant, to look over my final sketches, and tell me how much I screwed up. | ||
| herman Rating: N/A |
Brent, what in creation, exactly, is a "pod"? | ||
| John Jewett (Jayjay)
Rating: N/A |
Well Gary-and Buddy, for starters: 1) You can't have two breaker boxes from one power source. 2)You must have fused main disconnect., not two plugs in a foreward bay. 3)Electrical service shall be within 15 feet of the rear bumper. 4) It is impossible to properly bond the grounding system at present. 5)Wire size (#8AWG) is wrong 6)Using SO or SJO cord for a feeder is wrong. 7) Hand wired plugs for a service entrance are wrong-they must be molded heads. 8) Service entrance wiring has to be in conduit. These are just off the top my head. I'm a licensed Master Electrician and Electrical Inspector with almost 40 years of experience or I would not speak up about his problems. Without being there to see/show him, I would not attempt to provide advise on a physical layout for his service. There is far too much involved for inclusion on this 'Board. Types/local availability of switches, styles of breakers etc. are too numerous to contemplate. Currently I don't see how he hasn't smoked the bus or somebody, and I wish him the best of luck and implore him to seek competent (local) help soon. It's not rocket science, and it is clearly spelled out in the National Electrical Code on how to make a safe system. He desperately needs help-soon. ...JJ | ||
| John MC9 Rating: N/A |
Buddy - I do not have the credentials of Mr. Jewett. I am not an electrician (I'm a retired Telco guy, but I have a very varied vocational history). I've learned a lot about RVs through the years... And I've also taken note, that many very qualified home and industry electricians knew little of the standard practices of the motorhome industry. Most referred RVrs to the RV shop, when something electrical went south... That said: Most all older commercially made motorhomes using 30 amp service, and using a genset, were wired as you have yours wired. The service was split with one air conditioner on one leg, and the other, on the other leg (feed). Some other outlets usually complimented each circuit as well... For simplicity, let's just say the "two legs of 120 power" power from the genset were split between the front and rear halves of the motorhome. The genset supplied two legs of 120, providing each 1/2 of the RV with power separately. When you unplugged the power cord from the genset receptacle on all those models, 1/2 the RV remained connected to the genset. Plugging the power cord into the power pole, provided power to the 1/2 not connected to the genset A simple transfer switch inside the RV allowed one to choose which 1/2 to supply power to. To modify the older motorhomes, and adapt them to be able to use the full motorhome at 50 amp (two legs of 120) power poles, the genset outlet and transfer switch were rewired to allow the user to plug into the 50 amp outlet, thus supplying all of the motorhome, and safely using both air conditioners at the same time. There was nothing "unsafe" or "illegal" about this practice, but there should be great concern regarding the grounding and bonding of the neutral and grounds, and the ability to shift that bond from the genset/interior panel, to the power pole box, as the use directs. The neutral and ground bond, should always be at the source of the power. Using a 50 amp cord and two outlets to plug your present cords into, likely meets standards. But do check the bond. (someone else can explain it better than I) If doubt has been raised and you're concerned, bring it to an RV shop for a looksee.. They should have a qualified RV oriented electrician working there. | ||
| John MC9 Rating: N/A |
John - Not to do battle with you, but only to clarify: Replacement shore cord plugs and receptacles are plentiful, and used not only for repair, but to make up shoreline power cords as needed. Perfectly legal. A plug and receptacle can be considered a main disconnect in the RV industry (and usually is) (this was covered fully in an archived thread). There were no "main disconnect" boxes in any RV I've owned. Do the brand new RVs have these? The entrance panels were fused (of course) but not used as a "main disconnect". The power system is usually neutral/ground bonded at either the genset power feed, or at the power pole, from what my weak memory serves. I have never owned an RV, nor have I -ever- seen an RV, that had it's service entrance wire in a conduit. I will include the top-of-the-line motorhomes in that statement. Since the RV manufacturers are quite liability conscious, I sincerely doubt they would allow such an indiscretions to take place. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
John, thanks for your response to JJ. I started to respond but I had so many questions that I decided not to since I did not want to get into a pi$$ing contest with a Master Electrician and an Electrical Inspector. In general I suspect he is confused between residential wiring and RV wiring, but what do I know! LOL Richard (Message edited by drivingmisslazy on April 27, 2006) | ||
| T. (Bluegrass)
Rating: N/A |
A-men Richard I am like you I believe that he Is confused between house between residential wiring and RV wiring. Tony | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Interesting. JJ, do you have some specific references to some of your ideas such as: "7) Hand wired plugs for a service entrance are wrong-they must be molded heads." as applies to RV's? I have a hard time believing that one, and if it's not correct, I would wonder the validity of the rest of it all. In truth, a moulded connection is reliant on an unseen spotweld between the spade of the plug and the wire. Compared to a properly done "hand wired" connector, it's hands down not as reliable, especially the most common of moulded plugs that come from offshore. Crap, a lot of it, and no way to tell. So Code or not, I'll take the hand wired plug thank you... And I've never heard of conduit being required for an RV service entrance. Heh heh "Honey, we are about to leave... could you please coil up the conduit for me"... ??? If you have actual RV code references I'd love to learn. If you are truly correct in all your points, my bus according to you is a disaster waiting to happen. ...Ah... although one thing for sure is that bottom line, the electrons don't care one way or the other. As long as the wiring is well done and thought out with true knowledge behind it, it will outlast both of us and safely, code notwithstanding. And I will absolutely argue with you that what is "code" is not necessarily safe. For example NEC states that bare ground wires in residential outlets be joined with crimps. Soldering is illegal. Anyone who has been in the electronics business knows that crimps are one of the most unreliable methods of joining wiring that exist. They are cheap and reliable enough for most things thus commonly used in many industries, but as compared to soldered joints, they are not even close in reliability. But since average Joe doesn't know how to solder, crimps became code and solder is not. Thus a situation came up in my life where an inspector condemned a job that had soldered ground connections, and made the installer change them to crimps.. He then passed the inspection. I came later and took a look at the crimp job, and I wouldn't have let that pass as safe for any amount of money or coercing. Loose crimps, lightly twisted ground wires, absolutely horrible. But that was satisfactory to the inspector because it followed "Code". It happens all the time this way. CODE is not the be-all end-all solution to good design. It's just one way of many to help make things work safely. Bottom line is keeping the smoke inside the wiring. It boils down to this: All the code in the world given to a stupid electrician is going to make for an unsafe wiring job, even if it's inspected and passed (because you know well that inspectors don't look at every little thing...) On the contrary, Zero code given to someone with decent knowledge of what he's doing will result in a safe system. Somewhere inbetween is what we all live with every day. So as far as your comments above, as seen from a building inspector's point of view, perhaps. But as Richard said, there is a difference between what the NEC spells out for buildings and what is "code" for RV's. A big difference.... And I'm going to take the side of Buddy here, and propose that while his system may not pass a building inspector's set of standards, it's likely not going to let the smoke out either. Yes he needs to get with someone who UNDERSTANDS grounding and make sure he's ok. But as far as his system as he's described it, he's probably very close to being safe. And I say "Very close" simply because I'm not there to look at it in person. I'll agree with you that he needs to have someone knowledgable take a look at it. And I'll also recommend that person NOT be an electrician who does houses and buildings, because those guys don't usually have a clue about how RV's are supposed to be wired. | ||
| niles steckbauer (Niles500)
Rating: N/A |
Please - no matter what you take from these posts - understand the consequences of improperly creating (or not) a ground/bond for each and every power source with which you intend to use - the whole idea of this board is to provide a safe and secure place for you to find the SAFE AND CORRECT way for you to convert your coach - do not take the info provided (which in itself is not incorrect) in its own connotation without correctly acertaining its applicability to your applicaion - I can not find any fault with JJ's admonition to consult your local licensed electrician if you feel questionable about the above mentioned opinions rendered - the code has an absolute basis in history and you may not understand its relevance to your application or you may not have considered it to is final end result - that does not make the CODE invalid, only misunderstood - FWIW | ||
| JW Smythe (Jwsmythe)
Rating: N/A |
Niles, Just adding to what you said.. I believe (and there may be corrections by others) you cannot combine your 110V ground with your 12V or 24V ground. So, don't try to ground your appliances to the bus chassis. Definitely do provide yourself with a good ground path, through nice heavy gauge wires. With that said, one of the houses I lived in a couple years ago was wired with almost exclusively 2 prong outlets, no ground wire provided. I felt like I was living in a fire hazard. It made me less comfortable when I crawled through the excuse for a basement, and saw all the ancient wiring. The house was built in 1924, so this was the style for the time. I was content fixing the telco wires, which were a rats nest of connections until I cleaned them up and labled everything. I'm not an "electrician", but I've done a good bit of electrical work, and a LOT of telco and network wiring. I'll still have an electrician babysitting me when I do my wiring. I'm sure it'll be fine, but I want to make very sure I don't let the magic smoke out. I've felt the effects of bad wiring more than once. Yes, even a ringing phone line can make you tingle in the wrong ways. The last wiring job I fixed was a "professionally" installed clothes dryer. It mysteriously stopped working, and when I pulled it forward an inch, a live wire that wasn't properly secured hit the metal of the dryer. One loud "POP", and I went looking for the breaker box. I wrongly assumed that I could just pull it forward and unplug it. It left a nasty burn on the back of the dryer. I prefer that to a nasty shock to me. With all the crap behind your typical home washer/dryer, it was a beautiful formula for a house fire. | ||
| John MC9 Rating: N/A |
Niles - ".....the code ............. .................you may not understand its relevance....... " I wish JJ, et al would understand the point I try to make to them... Rather than simply quote "codes", explain the reason behind the code; explain in detail, the code's intention. It's through education, that we become knowledgeable, not through fear... (I left out that "absolute basis" in your comment; the NEC has become more ego driven, than practical. Need I mention (again) the NEC's approval of Aluminum wire for homes, some years back....? And how it had to be totally replaced, years later?) | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Thank you John. Well put. We're here to learn, not get spanked and sent home without explanation... And JW, 12 volt grounds and 110 volt grounds are all the same. There is only one "ground" and if your bus frame is 12 volt ground, there's no alternative but to make that your 110 ground too, or you'll really be in hot water! I believe what you may be trying to get across is that it would be a better system to use green wires from every outlet to carry ground back to a central point, like your breaker box tie-point, yes that is good. But that tie point MUST be strapped to chassis ground somewhere, or a major hazard will exist. | ||
| herman Rating: N/A |
Gary, are you actually asserting that it would be acceptible to use the vehicle metal as a ground for the AC outlets? I would hope not! And, the problem with explaining in lieu of spanking is that the questions get asked, over and over, and over again. And often enough by folks who, judging from their posts, may need a whole lot more than what can be done via a forum in order to achieve safety. Of course, if folks actually used the archives, that would help. Oh, wait! I know of a really good archive, distilled down to a set of best practices - it's called the NEC! | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
herman, AC ground MUST be connected (bonded)to the chassis of the coach! Where else would you connect it? Where are you getting your electrical information from? And Gary is talking about single point grounding to prevent ground loops. This is very common in, at least, the large computer industry where all grounds are returned via an insulated conductor to a common ground point. Richard | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
...and you know what? I'm going to stick it right out there and tell you that yes, on my bus, I use the frame as ground. For the 120 volts, for the 12 volts, and that's that. It's a solid ground, it works quite well and is quite safe. AND I fully know what I am doing. So have at my throat guys, and enjoy it. | ||
| herman Rating: N/A |
I was referring specifically to: " I believe what you may be trying to get across is that it would be a better system to use green wires from every outlet to carry ground back to a central point, like your breaker box tie-point, yes that is good. " It's not better or good, it's the only way to go, vs. e.g. grounding outlets directly and individually to the frame... Grounds and neutrals should have the exact same topology as the hot(s), i.e. where a hot goes, so goes a neutral and a ground. | ||
| freddd Rating: N/A |
Herman, You have absolutely no idea what you are talking about, and are in fact promoting information which can get people critically killed!! The safety ground (green or bare wire) in the AC electrial system MUST be bonded to the chassis AT ALL TIMES! In certain cases, the neutral (white wire) MUST be bonded to the safety ground (green wire)(e.g. inverter, generator). In certain other cases, the neutral (white wire) MUST NOT be bonded to the safety ground (green wire)(e.g. shore power). At no time can the hot wires (black or red wires) be bonded to the chassis, neutral (white wire), or safety ground (green wire). | ||
| John MC9 Rating: N/A |
Hot and neutral are independent from the "ground", the ground is common. All Telco and cable TV service grounds get bonded to the same ground as the electric in your home. The home's plumbing is grounded to that same ground. The frame of a mobile home is bonded to that same electrical ground as the power, TV, phone, and plumbing. An RV is no different. This thread's gone insane. Get a grip, guys.. (Jeesh, and me without a duhplumoana) | ||
| John MC9 Rating: N/A |
(I think we're all answering Herman, fredd!) | ||
| herman Rating: N/A |
Ok, I'm feeling a wee bit misunderstood.... The post of Gary's that I was responding to was construable as asserting that it was acceptable to attach the ground wire of an outlet directly to the frame/chassis, but better to run it back, along with the hot(s) and neutral (if any) all the way to the main panel (via whatever intermediate panels may exist), which I assert is the _only_ correct method. >>> I said nothing whatsoever about bonding, guys! <<< Get a grip, indeed..... | ||
| Stan Rating: N/A |
Since I am somewhat under educated compared to some of the posters, I keep a dictionary handy. Since I never heard of the use of the word topology as it related to wiring, I looked for it in the dictionary. No luck there, so I went to Google and this is what Wikipedia has to say and I still don't know how it affects wiring a bus. Topology From Wikipedia, the free encyclopedia For other senses of this word, see topology (disambiguation). Topology (Greek topos, place and logos, study) is a branch of mathematics concerned with spatial properties preserved under bicontinuous deformation (stretching without tearing or gluing); these are the topological invariants. When the discipline was first properly founded, in the early years of the 20th century, it was still called geometria situs (Latin geometry of place) and analysis situs (Latin analysis of place). From around 1925 to 1975 it was the most important growth area within mathematics. | ||
| John MC9 Rating: N/A |
Aww, come'on now Herman, no insult to you was intended. (besides, I lost my grip long ago.) I really respect your knowledge, and usually either agree, or learn from your posts, but this one is, well.... If you're going to quote Gary and argue with his thoughts, quote his whole statement: "And JW, 12 volt grounds and 110 volt grounds are all the same. There is only one "ground" and if your bus frame is 12 volt ground, there's no alternative but to make that your 110 ground too, or you'll really be in hot water! I believe what you may be trying to get across is that it would be a better system to use green wires from every outlet to carry ground back to a central point, like your breaker box tie-point, yes that is good. But that tie point MUST be strapped to chassis ground somewhere, or a major hazard will exist." Essentially, each AC outlet and switch will also be grounded to the chassis, if not at the outlet, at the panel, or "tie point". Apples and Avocados, Herman... Ain't it? The comments referring to the use of the same common ground for both AC and DC....? I don't know of any commercially built Motorhomes that are not wired in that manner. DC ground leads are connected to the chassis ground. The AC ground is also bonded to the same chassis ground. What are we arguing about? | ||
| herman Rating: N/A |
Stan, I understand it as 'study of shape', with a very liberal interpetation of shape, depending on what properties one is focusing on. E.g., an apple skin (still on the apple) and a tin can are topologically identical, in that they can both be viewed as continuous, enclosing surfaces without any edges / boundaries. If you punch a couple of holes in the tin can, or core the apple, they become identical to a donut. As I used it, I was referring to a perspective where line segments, or arcs, can be substituted for wires, and dots, or nodes, can be substituted for connections; the length of a line segment does not need to correspond to that of the wire it represents. From this, one can draw a graph on paper of a circuit, i.e. a schematic. Here the topology is the way that the nodes are interconnected by the arcs. Consider 3 identical nodes; there are 4 possible ways to interconnect them all: 3 "V" shapes, and 1 triangle shape. All the V shapes are topologically identical, though, so actually there are only 2 topologies. However, in electrical wiring, a pair of nodes (a node can itself be composite object such as an entire outlet or an atomic object such as a single blade on that outlet) are differentiated as sources/lines, and sinks/loads; further, a node that is source to another node may itself be a sink to a third node. With dissimilar nodes, topologies get more interesting. Setting aside the concept of multiple sources, e.g. as discussed in the "paralleling inverters" thread, there is only one topology that is considered to be correct. This is the tree topology, which has a single node, the source, as its root; all other nodes connect to the root, either directly via an arc, or indirectly via multiple arcs and 1 or more intermediate nodes. Further, for a topology to be a tree topology there must be, for any 2 nodes in the system, exactly 1 path that interconnects them. So, the arc / wire essentially establishes a source/sink relationship between two nodes; the basic rule is that you can't run a wire from one load directly to another. If you individually connected the ground terminals your outlets (as well as the shore cable) directly to the frame, it would be a tree topology, but it would not be identical to the topology of the hot and neutral wires. | ||
| John MC9 Rating: N/A |
Stan - Re: "I am somewhat under educated compared to some of the posters" Do not -ever- assume that. Talk and screen pixels are cheap.  | ||
| John MC9 Rating: N/A |
Ok Herm... NOW, I have a headache. (HAR) | ||
| herman Rating: N/A |
John, Gary described a topology that he asserted was better than an implied other topology; I assert that that is untrue, that rather there is only 1 correct topology (which he seemed to be describing as the better one), which is one that is identical to the topology of the current carrying conductors, i.e. the hots and neutrals. Actually, yes, there are differentiations, e.g. the chassis/frame ensemble, viewed as a single node, joins to the intra-vehiclular root ground node, and there is the arc/wire/bond that joins the neutral and ground networks, either intra- or extra- vehicularly, depending on what source the vehicle is using. So, yes, in these respects the ground network is a superset of the current carrying network. However, when considering only the subset of nodes that are subordinate to the intra-vehicular root node, they are identical. | ||
| John MC9 Rating: N/A |
Yessir. I totally agree. It's as clear as the nodes on my face. (wtfhta?) | ||
| John MC9 Rating: N/A |
All in good fun, of cuz.. What was this topic about, anyway? It's been a long time... | ||
| John Jewett (Jayjay)
Rating: N/A |
I cannot begin to cover all of the aspects of the NEC on this Board, and as I keep saying- find a competent electrician to assist you in your conversion. House VS RV wiring systems? there is no difference under the law (NEC), with the exception that Article 551 is an additional, specialized addendum, that covers the peculiar aspects of RV's. Gary S. you are absolutely correct. A ground is a ground is a ground-no matter where you do it. AC/DC-doesn't matter. Just remember that an AC circuit will bond at multiple points. I won't go into capacitive loops and other esoteric electronics...we're building custom motorhomes. My only justification ever for posting, is to assist unknowledgeable people to produce a safe place for the kids to sleep. I'm appalled at the dearth of poor/dangerous advise in the posts above. NO, I will not enter into the fray. Remember that if you hook up the plumbing wrong, you'll ruin the carpet. but if you screw up the wiring you may kill/cripple someone, and get to donate half of your income for the rest of your life due to losing a wrongful death suit. Good Luck ...JJ | ||
| John Jewett (Jayjay)
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As an addendum to my above post. I cannot see why factory built motorhomes/bus-conversion systems creep into these discussions. They have a different play book than we do, and have resident NEC inspectors that regularly grant exclusions/exceptions to the NEC, as a one time type certificate. The exclusion is for that make. model,and style of coach, and the exclusion is not valid for any other application. ...JJ | ||
| John MC9 Rating: N/A |
John, John, John..... Re: "I cannot see why factory built motorhomes/bus-conversion systems creep into these discussions. They have a different play book than we do, and have resident NEC inspectors that regularly grant exclusions/exceptions to the NEC......." With that, you have very successfully and delightfully undid, all that you have tried so vainly to do. To sum up neatly: The NEC is controlled by politics and big business. "Do as we say, not as we do", comes immediately to mind. As stated earlier, please explain the intent of the "code", instead of simply citing them. Provide an education, so individuals can make proper and good decisions for themselves. Do you really think the "NEC inspectors" are more intelligent than any reader here? They have some sort of "higher intellect"? You do no give the average individual enough credit for their intelligence and good common sense, John. All they need, is good information and decent answers to their questions. Logic and common sense. Please. (whew) | ||
| Stan Rating: N/A |
JJ: When I was manufacturing in Canada I could get a specific approval under CSA for something that was not covered in the book (usually high volgage electronics) but I could not violate the CSA rule books Are you saying that a US manufacturer can get a specific approval for something that is in violation of the NEC? eg: Most high line bus conversions have a service cable made up with plug and connector hand wired. You say this is a NEC violation but the bus is sold with a RVIA label which means it is supposed to meet all applicable rules. | ||
| Richard Bowyer (Drivingmisslazy)
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I manufactured a lot of electrical devices for many years to meet UL. To my knowledge there was no such thing as a NEC inspector. The UL inspector never would deviate from the interpretation of the NEC. Richard |