| Author | Message | ||
| Brian Brown (Blue_velvet)
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 As I was pulling all the wires out of this goofed-up main disconnect to wire it properly, it occurred to me… why do I need a main breaker??? I have a breaker on my genset that protects it from overload. There’s obviously a breaker on any receptacle I plug the shore cord into. Isn’t a “main disconnect” in my case redundant? If I need to cut all the “juice” in the bus, I can always just unplug the shore line or turn off the breaker at the genny when on genny power. Any other good reason(s) to keep it? Thanks, Brian Brown PD4106-1175 | ||
| Jim (Jim_in_california)
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Huh. Come to think, we're wiring my rig like so (all 30amp): Genset (or shore cord) to surge suppressor to inverter in; inverter out to 8-way GE-style breaker box with a variety of 15a and 20a breakers for each chunk of the 110. The genset plugs into the surge suppressor via 30amp round connection; if I want shore I just unplug gennie and plug shore to the same point. Which is also where I can unplug all external 110v. If I need to cut the line between inverter and house 110 wiring, I open the panel and flip all eight breakers. Works for me...and the guy doing it all seems to know code. I strongly suspect that's what you need - individual breakers. As it was explained to me, once we sort out which breaker each section represents, we'll label it - and if an appliance on that line pukes and dies it will trip the breaker and not barf all over everything else. You have no such protection with that thing you've got! If a rooftop aircon decides today is "entropy day" and it goes blewie, everything from your microwave to computer are liable to all go commit hari-kiri in sympathy. (The inverter 12v input has a 300a fuse.) | ||
| Brian Brown (Blue_velvet)
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Jim, I should have mentioned that I do have branch circuit breakers downstream of this disconnect. They're housed in two panels, I guess for ease of installation for the guy that converted it. I'll also rearrange my breakers to try to balance the loads between L1 and L2, mostly between the two roof-top airs. So, the circuits are indeed protected. I just don't know why I need the main??? bb | ||
| Brian Brown (Blue_velvet)
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pic to follow | ||
| Brian Brown (Blue_velvet)
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| Jim (Jim_in_california)
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Ah. Right. Yeah, mine had four factory, the box could only do six, so we scored another box that can do eight. <scratcheshead> The single main input breaker might have some advantage if the power pole input goes completely wonky (lightning strike or similar) but if that's your main protection in such event, your inverter isn't protected. Not cool. Was it this forum or another where somebody opened up the park power pole breaker box and found an absolute mess from hell - and posted pictures? In any case, I've seen too many horror stories on park wiring (esp. 30a) that not running a main input surge protect rated 30a or 50a is just crazy. | ||
| David (Davidinwilmnc)
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I've always had a main breaker on our campers. I've also always been told, when connecting to the power pole, to turn off the main breaker (in the camper), plug in the cable, then turn it back on. Of course, you can do this at the breaker on the pole. I've known of about five breakers in the past that wouldn't trip. Those five could have caused a major problem. I've had two that would not disconnect when the handle was put in the off postion. Why wouldn't you want a main breaker? $9 for a 220V/50A breaker and $13 for a small breaker panel seems awfully cheap to me for the knowledge that my system is protected by a funtioning breaker. | ||
| Jim Ashworth (Jimnh)
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From the picture in the initial post, the whole bus may need to be rewired. Black and white to the hots and red to neutral?? and it continues to the downstream breaker boxes!! AND the bare grounds are connected to the neutral bus bar. Before you go too much further a thorough inspection of the entire electrical system is in order. Jim | ||
| ChuckMC9 (Chucks)
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1.) DooD! What's going on with that wiring? I'm with Jimnh. Looks scary. 2.) "Over-current protection should be provided within 18 inches of where the shore line enters the coach. This is needed to avoid having unprotected wires in the walls. The primary circuit breaker for the shore line should be in the post with the campground's outlet, but one still is needed on the coach's end." "Designing Electrical Layouts for Coach Conversions" by George D. Myers © 1998, Chapter Two > 120/240-VAC > p. 97. I have a seperate main disconnect, and I'm much more comfortable with it than if I hadn't had it. We went thru this before on the bbs, but that thread was so obfuscated that I won't even point you to it. 3.) Some units have two panels - one for inverter only, switched thru a transfer switch so both panels become live when shore is attached. I'm in a rush now to go get the coach lubed, so HTH. | ||
| ChuckMC9 (Chucks)
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Can't even walk out the door without saying that even if the colors were ignored, that still doesn't make it ok. You *don't* want neutral and ground to be bonded anywhere in the coach except at the inverter or generator. Just a few months ago a kid was killed in an RV when this occurred. | ||
| Dale L. Waller (Happycampersrus)
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Brian, that box is all wrong. I would pull the covers off your "small" breaker boxes. I would suspect that they are not right either judging from the way the red is joined with the grounds. Or did they just use the heavy RED for the ground feed?? If not what you have there will cause feedback and probably will give you a buzz and I don't mean the good kind. When I redo my transfer I am going to leave a main disconnect, even with the plug method. It wouldn't hurt, plus you already have it in place. I looked at some larger coaches while camping and I believe you are right on about the 6/4 cord. Dale | ||
| Dale Hendricks Rating: N/A |
Brian, Don't let everyone scare you about your wiring. It looks like they are using the white for the neutral,black for the hot and red for the ground (some green tape around the red wire would help oliviate some of the confussion). The grounds appear to be seperate from the neutral. They have it set up to disconnect the neutral and the hot when the breaker is shut off. It is not proper however ,to have more than one set of wires under each lug. Also if there are more than six handles in a breaker box , it is supposed to have a main disconnect either in the panel box or seperate like you have. But that code is for houses and may not necessarily apply to motorhomes. Make sure there is a ground wire that bonds to the frame of the bus from the disconnect and that all neutrals do not and you should be ok. Are both panels 120 volt? If so, run your wires from the load side of the disconnect to the main lugs of the first panel using wires large enough to carry the full load of both panels,and sub feed the second panel off of a breaker from the first panel. 12 120 volt circuits in one 35 foot bus... My 2000 sq.ft. house only had eight when it was built. Good luck. | ||
| James Maxwell (Jmaxwell)
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Brian, as I recall, you featured this main once before and we hashed it all out as to what color of wire went where. Hope I'm not confusing yours with someone elses. Based on my sometimes faulty memory you had all the mixed up colors sorted out and were aware of the neutral/ground bond pictured. To the redundant breaker: You don't need it. Your thinking is straight, your already protected at each source, the park pole and the genset. I tend to do redundant things (like 3 or 4 meters telling me the same thing) but in this case I would eliminate the incoming main as just something else to fail and cause problems. | ||
| David (Davidinwilmnc)
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James M, isn't there a requirement for a main disconnect within a certain distance of where the cord enters the RV? I've read that many times, but haven't verified it. Without the main, what protects the wiring leading to the main panels in the event that the park power pole's breaker malfunctions? It's there; leave it, but wire it correctly. I guess my question would be why should you NOT have the main disconnect? I can't think of any good reasons not to. | ||
| Brian Brown (Blue_velvet)
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Yeah, Dale's got it right... red is ground, and he's switching the neutral at the breaker also. It's a 60A breaker, so it's undersized. Neutral and ground are not bonded anywhere, though. The wires to the sub-panels are #10 and will have to be upgraded to #6. My reasons for not wanting this disconnect is because I believe it's redundant. I'm protected at the pole, and at the genny. Correct me if I'm wrong, but it's not unlike a house that has a main disconnect out at the service entrance and a panel inside the house some distance away. There's never a second main disconnect at the interior panel, nor have I seen a sub-panel (out to a garage/shop,e tc.) with a disconnect. My bus' system seems the same to me. Heck, my 50's-era rental property across town has no main disconnect and no overcurrent protection on the wires that feed the panel from the elec. co. wires. Just a sign at the meter that reads "100A max." For 50 years and counting. My inspector told me that this was "code for it's day"... but I digress. On my bus, if a shore breaker fails for some reason, it's only an overcurrent protection I'm losing anyway (unless I find a park that actually has 50A GFCI). And I physically can't overload a 6/4 shore cable with the loads I have in the bus presently. If it's just the "it can't hurt" philosophy, that's great, but I'm looking for some substantial reason/ concern, NEC violation, etc. Thanks, BB | ||
| Chris Rating: N/A |
I personally followed the quote by Chuck above. I placed a primary disconnect, under the bus, with 18 inches of where the shore cord enters the bus, then ran wires inside to the breaker box, which is really a subpanel as it does not have a main breaker itself. Grounds are connected to chassis at several points, neutral is isolated. | ||
| CRANE Rating: N/A |
I do not feel the disconnect at the bus is redundant. It is an important link that allows you to plug in at the box with no load, or to pull the plug no load, then you test your power to be sure it is connected the way it is supposed to be, hot to hot, neutral to neutral, ground to ground. Then you can close the mains in. If you were to pull the plug under loading, you can get a flash, same with plugging in under load. With some equipment, if you are only partially connected, or plugged in, you can burn the equipment up. The disconnect assures you that all contacts make up at the same time. This "redundant" switch is a safety item that really should be kept in place. It is the fastest, safest way to disconnect/connect from/to power in an emergency. CRANE | ||
| Brian Brown (Blue_velvet)
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Well stated, Crane. Sounds reasonable to me. I'll wire up the disconnect correctly and put it back online. Thanks for posting! bb | ||
| James Maxwell (Jmaxwell)
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There is no requirement for the redundant disconnect that I am aware of. If u want to get into what ifs, what happens when yours fails also? He has individual circuit breakers. If u want to plug into the pole under no load, disconnect the breaker at the pole power (you should anyway) and turn it on after u have plugged in. The only wiring necessary to check (if u did yours correctly to start with) is the power pole, and u do that before u plug into it. | ||
| CRANE Rating: N/A |
No requirement at all, just convenience. THe house breakers are probably in the coach, if you don't have mains, are you going to open each one? With a disconnect in the storage compartment, at the end of the cable that plugs into the land source, open/close is right handy and if you connect an outlet and plug in one of those continuity tester, the test is already done by the time you walk over to close the disconnect. The concern about wiring is not the coach wiring, it is the wiring at the pole, as had been stated in the past, can be a problem. Obviously, this is the only recourse, it is one way of many that can be used. Use whatever way you feel safer with, or more at ease. I only posted one way of thinking about this type of equipment. I did not intend to stoke up anyones fire. Have a nice day Crane | ||
| Brian Brown (Blue_velvet)
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Got her done.  Thanks all, bb | ||
| Jim Ashworth (Jimnh)
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Nice to see the separate ground bus. And the colors correct. Now I can sleep without fear that you will not be around tomorrow. Thanks for the update. Jim | ||
| ChuckMC9 (Chucks)
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What a pleasant sight after a long day of discovery of more big $$$ expenditures on my immediate bus horizon. Isn't it delightful to have the satisfaction of knowing you built it in the best possible way? You rock, BB. | ||
| Rob King Rating: N/A |
Hi Guys I am no electrical expert but I have read George Myers book cover to cover several times. He states on page 97 as Chuck said above in the 0920 posting plus "This protection is required by NEC Article 551-31(e). To me, if you don't have the main disconnect and all wiring per the NEC and then have a problem; I would guess you would be wide open liabilitywise and maybe no insurance coverage.I agree it is redundant but maybe for good reason. But hey, do it your way! Rob | ||
| Dale Hendricks Rating: N/A |
Hi all, One other thing to consider about a main disconnect being required or even necessary. Did everyone find a disconnect for your batteries on you coach even though you have fuses or breakers for each circuit? Makes you say uummmm????? Nice job Brian. That pesky red ground wire was sure creating a stir for everyone. Now they can sleep peacefully at night. Ha Ha. Also there have been a few advancements and changes to building codes over the last 50 years. Plus the demand from all of the electrical gadgets that we have now will overload most systems designed in the 50's | ||
| CoryDane Rating: N/A |
I like the redundancy, period! How versitle this allows your bus to become now! I know that some of the cheaper Rec Vehicles dont have this switch, but the manuals want you to go inside and open the breakers before plugg-in or unplugging. The other side of the view is this gives your coach an additional safety incase of trouble. The breakers at the pole, if available, some are not convenient, being located centrally at a distant pole, have the effects of weather and may not open right away if needed. I have always said that you must be careful when deciding to do things "Your Way". This is because YOUR WAY may not be the safest way and may be chosen for the wrong reasons, such as COST. I don't really promote the YOUR WAY mentality for that exact reason. I do agree that every one has their own way of design, build and taste but there are some areas where the YOUR WAY method does not belong because SAFETY becomes an important factor. And this will come up many times in the threads during discussions, WIRING always comes to mind first. The "do it your way" line comes up a bit too often I think. I know some think I may be posting just to hear myself think but I do post with safety and knowledge of systems behind me having been involved in rving for near 20 years now. This particular thread could have gone either way but Brian seems to have gone the extra distance for his project and this should reap a lot of convenience in the future. Hopefully it will not be needed for a safety issue but now he is covered for this as well. I like that test connection idea at the disconnect also. Sounds like a neat package. Good Job CD | ||
| Chuck Newman (Chuck_newman)
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Chuck MC9, I agree with you and George M. totally. The entrance breaker not only is a cheap convenience, but redundant safety from a possible weatherized, non-maintained power pole breaker. I have George's book and Article 551-31(e) he refers to does not exit in NEC 2005. May be a typo in the book. Not going to take the time to search all of Article 551. But I do agree with the intent. As does all commercial RV manufacturers. Brian, how do post pictures to a thread? Is the size limited to 20KB as in the profile photo? Thanks, Chuck Newman Oroville, CA | ||
| Brian Brown (Blue_velvet)
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Thanks for the kudos, guys. And the advice, as always. Chuck N., you just add a tag to your posts (I can't type it here, but I'll make a graphic of it)...  All other inline goodies (italics, colors, etc.) are here on the BBS: http://www.busnut.com/cgi-bin/bbs/discus.cgi?pg=formatting BTW, image sizes are now <30k. With moderate compression, you can get some fairly detailed images on here. Regards, bb | ||
| John Jewett (Jayjay)
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Code: you may not use green tape to designate a ground wire if the wire is less than 2/0 AWG. (that's BIG wire for you non-electrical types) Article 551.31.e says: POWER SUPPLY NOT LESS THAN 30 AMPERES The external power-supply assembly shall be permitted to be less than the calculated load but not less than 30 amperes and shall have overcurrent protection not greater than the capacity of the external power-supply assembly. The above reference to 30 amps should be transposed to 50 amps if you have that size service. This is one of those confusing sounding statements in the NEC that we run into from time to time, but read it about a hundred times and it will suddenly become clear as to the intent. Also you should NEVER switch a neutral, since this is a sure way to kill someone-or your puppy, as they are really sensitive to being the ground path for your total connected amperage load. Nice to see an emphasis on safety with wiring systems. Should you hook up the plumbing wrong you ruin the carpet, but do the same with your electric and you may get to buy a casket! Do it your way? Yes, just use the NEC. ...JJ | ||
| Jim Ashworth (Jimnh)
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JJ- Don't you mean never switch a GROUND? Neutrals are always switched when changing sources, but the green/bare ground should always be connected. Just a clarification. Jim | ||
| Jack Conrad (Jackconrad)
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I think JJ meant "do not switch ONLY the neutral". Such as on a typical wall switch that switches only one wire (leg). This would leave power flowing to the the appliance and if touched would complete the path through you. When switching sources such as generator to shoreline both hot and neutral should be switched. At least that is how I interpeted his post. Jack | ||
| Chuck Newman (Chuck_newman)
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Jim/Jack, You're both right, for the right reasons. Just for information, my NEC 2005 book published by NFPA shows the section to be 551.31(D). It is unusual for them to change a section number. Typically they will delete a section or add exceptions to it. Just another obsticle to deal with. If it's a typo in the 2005 code, I expect better from NFPA considering the price they charge for their material. Chuck Newman Oroville, CA | ||
| Chuck Newman (Chuck_newman)
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Forgot to mention, Brian your panel board installations really look nice. Chuck |