Posted: 12/13/2007 4:51:30 PM EDT
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I was a little confused about what I needed to do using a transfer switch with a portable generator that has the netural bonded at the generator. According to what I've read I need a transfer switch that switches neutral also. I plan to hire someone for insurance reasons, but I want to be informed about what they will be doing. Here's the info I found. Bonding Info Generator neutral and ground rewiring Standby Generator Installations General Generator Info Generator FAQ members.rennlist.org/warren/generator.html |
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I went through this recently. As a rule most, if not all, portable generators are neutral bonded. Even the 12KW that I purchased last year, which is definitely not portable, had a bonded neutral. When using these with a transfer switch problems can appear. The big thing to look for is whether or not the transfer switch switches all poles or just hot is the main consideration, if it does not you have a situation that you can energize the neutral and possibly cause a back feed if the ground / neutral point at the distribution transformer is better than at your breaker panel, electricity seeks the path of least resistance. From what I have learned operating a gen set that is neutrally bonded with an additional ground rod for the gen set is a big no-no, better to let any spurious current dissipate at the panel. Needless to say that I have pulled the ground rod, and will be converting to a floating neutral next time that I have the panel for the generator open. My neighbor is an electrician and he tried to explain this all to me at length, and some of it still makes no sense to me  Bottom line is that electricity can behave in some interesting ways, not all of them being productive. Be safe out there.. YMMV on this one, better to seek a professional. |
| There was a real good thread not to long ago that went into this. The one thing I got from it was that most gen sets do have a bonded and grounded neutral and will need to be modified to run on a transfer switch that is installed after the main pannel. It is my understanding the if you have a service rated transfer switch installed between the meter and main pannel and you are powering the whole pannel, the bonded and grounded neutral is not a problem. If you are using one of the popular transfer switches that allow you to run a pre-determined amount of breakers and wire in on the load side of the pannel you will need to free-float the neutral on the gen set. There are some instruction floating around on how to make a new switch on the gen set to do this. I am no expert here, so if someone could weight in with a little better wordered explanation. |
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Is this the one you're referring to? www.ar15.com/forums/topic.html?b=10&f=17&t=607662 |
Yes that is the one. I do not want to leave anyone out but dac46 and Blackhawkhunter are right on the points and advice. I have also had some conversations with dac46 and he helped me understand much better what some of the issues with emergency power which is helping me speak the language while I try to find someone to do the work. I plan on doing a service entry rated transfer switch between the meter and main pannel and powering the whole pannel. Yes I will be turning off a lot of the breakers untill I can up the size of the gen set. Right now I will be using an 8000kw with a 13,500 surge. Right now there is a 75kw Onan gen set, 100 gal tank, tool box, all mounted on a new trailer for sale on craigs list for 7,500. The seller has a video link of it running. http://stlouis.craigslist.org/tls/519896554.html My neighbors would just have a cow if I parked that behind the house. There has been a lot of threads started on this topic. I am sure the bad weather in the midwest has a lot to do with it, but It would be nice to see a dedicated thread to this topic. |
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Isn't 75KW a little overkill? A 200A household line is only 48KW if you were able to pull full capacity from it. The fuel bill would also probably be prohibitive at best for that turbocharged beast. Nice gennie though if you're also going to power the rest of the block 
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You can buy a transfer switch that will handle a bonded neutral. I emailed reliancecontrols.com they sell these at northern tool. This what the rep sent back. "Great, just about all of our transfer switches will work with floating neutral generators. The only product we have that switches the neutral is the XRC-series Transfer Panel. I would suggest one of our Pro/Tran models - we have 6, 8 or 10 circuit models for 20, 30 or 50 amp generator outputs. You will want to know what sizes of household branch circuits you want to run (ie. 15 and 20 amp circuits only, or maybe 30amp water heater circuit). You can find a list of our Pro/Tran switches on our website by selecting “Pro/Tran” or “Q-Series” from the “Products” drop down menu. If you need any additional assistance or have any questions, feel free to contact me. " |
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I don't understand fully, please explain Based on the rule below, is it allowed to field modify the genny wiring to 'UNbond' the neutral from the bonding conductors [earth ground] inside the genny? "The grounding of the standby generator neutral is accomplished by one of two possible methods. The method to be used will depend on whether or not the generator neutral is connected to the generator frame or case by the manufacturer. The status of this connection should be provided by the manufacturer, as required by CSA Standard 22.2 No 100-95, and should be indicated on the generator itself or in its documentation." Generator Joe's has the XRC sws. |
I wouldn't change the generator if you are going to use a transfer switch, just get the correct switch, but if you plan to back feed you would probably need to unbond the neutral at the generator otherwise neutral will be bonded to ground in two locations. |
So, it's OK under the code to modify the genny to either bond or unbond the neutral inside of it? Ignoring the original state it was hooked up as by the manufacturer. |
I'm not sure about the code. |