| Author | Message | ||
| Bill Kennedy (Staugbill) (206.30.205.106)
Rating: |
Converting an MCI. Should the body of the bus be grounded to the AC house system or not? Have used "burial ready" wire and protection at bulkheads, etc., to help avoid chafe problems but, I don't want to complete the circuit when boarding if a wire does chafe. Will an AC grounded frame interfere with DC system? | ||
| Molsdorf (208.18.102.77)
Rating: N/A |
Yes it should be grounded, if not it will light YOUR lights. The grounds from shore-gen are all common, never switch the grounds. You can switch ground, or I should say neg since I'm talking about low voltage unit DC here. I assume you have a circuit breaker panel you are feeding from the shore-gen switch (and as I said don't switch these grounds), that way you will not mix to different sources. As far as the DC you will not have a problem, they are isolated (here I speaking of the 110V). | ||
| Steven Gibbs (12.148.43.7)
Rating: N/A |
Bill, Neutral/Safety Ground bonding is a very important and complicated subject. It is really impossible to explain and cover properly on bbs posts. George Meyers explains it very well in his book "Designing Electrical Systems for Converted Coaches" To start to answer your direct question... yes, the safety ground from the shore power, genset, and/or inverter must be grounded to the coach body, HOWEVER, the neutral and safety ground MUST not be bonded (shared) when you are on shore power. Please purchase and read and understand George's book before you proceed with wiring. Steve Gibbs MC-9 Pontiac, MI | ||
| DaveD (216.18.113.69)
Rating: N/A |
Neutral and phase connections must both be isolated from the bus chassis and ground must be connected. This is a code requirement and is essential for proper protection. DaveD | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
Gee, I hope we do not get started on another long series of posts on this subject, like what has happened in the past, but I have to respectfully disagree with you, Dave. The neutral of the source must be connected to ground when that source is supplying power to the bus. When shore power is being utilized, the ground/ neutral connection is supplied by the utility company. When genset power is being utilized, the ground/ neutral connection must be made at the genset. It is mandatory that these connections be broken when that particular source is not the active source of power for the bus. In other words, the utility neutral and the genset neutral must never be connected together. Richard | ||
| DaveD (216.18.113.69)
Rating: N/A |
Richard, I'd agree, but that connection should be be at the genset ahead of the output connector or transfer switch. For connection to shore power, neutral must be isolated. Applicable ANSI or CSA standards for RVs are probably a better reference. We could probably go on for days on this subject. DaveD DaveD | ||
| Tom Connolly (148.78.247.10)
Rating: N/A |
Sorry I have to say Dave looks to be correct! The shore power Ground, Neutral, and line/s are all isolated. The Ground is bonded to the chassis and other conductive surfaces, like copper plumbing & LP lines. The Ground and Neutral are NOT bonded. Yes they (neutral & ground) are/may bonded in the campgrounds panel but not in your coach. The usual issue is keeping Ground and Neutral isolated on the generator side of the Gen/Shore switch so you do not trip the Ground Fault Interrupters (the coach's & campgrounds) when you plug in to shore power. | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
Dave D, I agree that the bonding between neutral and ground for the genset must be before any output connector or transfer switch. Per the code, it should be bonded at the source. This was the point I was trying to make in the original post. Many people have made the mistake of bonding the two genset conductors after the transfer switch and end up with the neutral of the genset connected to the neutral/ground conductors of the utility power. Tom, your statement “The Ground and Neutral are NOT bonded” is not correct. The code very specifically states that neutral must be bonded to ground at the source. It really does not matter what that source is. It could be the genset, the inverter or the shore power supply. The utility power company or the campground bonds neutral to ground at the source. They are not (or should not) be bonded at the outlet where you connect your shore cord. It is the converters responsibility to properly bond the neutral/ground conductors of the genset and the inverter which means that neutrals from different sources are never connected together. Richard | ||
| Tom Connolly (148.78.247.10)
Rating: N/A |
Richard, Our understandings of the national electrical code differ. The code as I remember reading it is clear that shore power connections are isolated neutral / ground, the coach panel is considered a sub-panel and not the source, the source is the panel connected to the power company and it would be neutral/ground bonded. in single phase, the power co would provide service by 3 wires, 2 feed lines and a neutral through a meter, the meter and service entrance panel would have a common ground connection to a driven ground rod, the service panel would have a neutral/ground bond, after that the subs would be 4 wire with neutral & ground isolated. All though I would consider a re-established bond completely safe and I am not arguing a safety issue. Bonding at the coach panel would trip any ground fault that the shore line was plugged in to, hence the dilemma, how to isolate the genset / inverter power so that those "sources" with a neutral/ground bond don't trip the shore service when it is also connected. Starting the genset to charge your batteries, While plugged in to the shore "Source". When the transfer switch kicks in and the bond circuit is complete out goes the shore power. Some have solved this by using the inexpensive manual transfer plug method, I personally chose a 3 pole contactor and on a time delayed transfer open the shore power, 2 feed lines and neutral. Leaving the ground intact, this way the coach body and shore utilities are at the same potential should your body come in contact with both. Tom C | ||
| Donald Ames (Donames) (67.242.33.161)
Rating: N/A |
As an electrician for over 27 years I agree with Tom and Dave. The ground and Neutral are to be bonded in the “Main Panel” only and isolated in all Sub-panels and devices. This means that the first panel at the RV Park after the meter is bonded but the sub-panels, receptacles, power cords, and coach panels need to be isolated. I agree with Tom that the two ways to keep it isolated when on shore power but bonded the rest of the time is either through a set of receptacles for each source that you would plug the coach panel into, or the three pole transfer relay that would also switch the neutral. You would therefore bond the neutral to the ground at the generator. I had figured all of this out when I converted my 4903 but did not give enough thought to the inverter. I use a Trace 3624 inverter that has its own transfer relay built in. I just ran one leg of the main feed through the inverter so that even if I am on shore power and there is a power outage my selected circuits will function without interruption. I just assumed that Trace engineered the bonding and switched neutral into the inverter since I spent the extra money for a UL approved model. I did not check it however. Don Ames PD4903-394 | ||
| Jayjay (65.142.15.96) Rating: N/A |
FWIW, read (and understand) Articles 250, and 571 of The National Electric Code. Buy a copy to keep with you when you travel, so you can refer to it when some ignorant individual (or inspector) gives you some lip about your coach. New trick on the block is: RV Park proprietor waits until you are hooked up (got your money) then the local elect. inspect. shows up for an inspection. You fail. Pay fine. Loose park fee. etc. etc. Portsmouth,OH Riverfront Park is one, another is Snowy River Campground in Bend,OR also the home of tainted water. Cheers...JJ | ||
| Quest (198.29.191.147) Rating: N/A |
Hi guys, so am I to understand, that the shore power ground AND the genset ground AND the bus ground are all tied to the chasis of the bus and the neutrals are bonded by the source only?? IE shore power, genset or Inverter. (that is, only the source supplying power is bonded, all others are isloated.) this makes a lot of sense. So have I followed the thread correctly? q | ||
| Tom Connolly (148.78.247.10)
Rating: N/A |
Quest, Correct, That is the way I did mine, based both on my understanding of the code and my working knowledge of electrical. Tom C | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
Yep, I agree also that that is the correct way to do it. Richard | ||
| Tom Caffrey (Pvcces) (64.114.233.190)
Rating: N/A |
Mine's not that way now, and it blows GFIs. I will be changing it to bond only at the source. By the way, I don't remember much comment about the need to install only an RV inverter for this reason. I understand that RV inverters stay unbonded unless the inverter is on. Tom Caffrey PD4106-2576 |
