MEP-003A hook up question

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bsorcs

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another pilgrim seeking counsel

I had an electrician out to discuss how to wire the 003 to the house. Based on the extensive threads here and elsewhere, and exploration of numerous manufacturer and supplier sites, the simplest, and least expensive, solution for me seems to be an interlock [~$75], as that would enable me to select the circuits [in the 200a main and 100a sub] that I'd want to power from the genset, even though it likely would mean going out in a bleeding storm with a flashlight and ginning up a circuit checklist beforehand. It also would entail 'sacrificing' some circuits for a ?60a? breaker. I assume that, as part of installing an interlock, the electrician would install some sort of outlet that would in turn be wired to the main. So he shows up, greatly admires the genset, then shows me a pic of a Lowe's outlet box [w/30a breaker appropriate to the genset he was working with] he just installed for someone. He wired the box into the main somehow and said essentially that use entailed opening the main breaker, plugging into the box, and firing up the generator. A promise to open the main breaker each time, plus $15, will get you a Cuban cigar in any airport duty free shop outside of the US! From an operational standpoint, his suggestion sounds to me to be the equivalent of using an interlock, but w/o the security. Think I'll go with the interlock. Install would be quick; I'd need an outlet box [do not want permanent connection], breaker, plug, wire, and interlock. I don't see separation of the neutral and ground, so to use the genset for the house, using either his idea or an interlock, I'd have to break and isolate the neutral at the genset frame and not have a 2nd ground rod connected. To infrequently power a future woodshop I have only to attach the neutral to the frame and connect the 2nd ground rod, as the house cable will be deployed only during or in anticipation of an outage. I'd just have to remember to break the neutral bond and disconnect the 2nd ground rod after any shop use [I know, I know, another promise]. Question: am I correct in my read of this? I gave the electrician printouts of some of the thread discussion and Speddmon's figures...many resources out there; none as good this forum!
 
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Munchies

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Bsorcs
I will tell you what I do at my rental home. (military move alot)
Main disconnect into fuse panel ( I recommend an interlock)
70 Amp breaker. Breaker goes out via conduit into attic and over to the other side of the house. Drops down on the wall and comes to this. http://www.homedepot.com/p/Eaton-50-Amp-1-Space-1-Circuit-Temporary-RV-Power-Outlet-Box-CHU1S/100565603#.Uh4ixBush8E

I replaced the plug with a Nema 14-60 60 amp plug, (biggest they go before pin and sleeve) .
Generator plugs into the RV power box, via a 14-60P plug on the end of a 35' 6/4 SO cable. Long cord lets you move it away from the house a bit.
Multiple Checks of breakers being in correct positions is required to avoid an accident, or a live dead man plug in your hand. I make sure the genset breaker is the very last thing closed, right before double checking the main disconnect. An interlock would be nice, but it is not my equipment.

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storeman

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Went to a close friend's house to help with a MEP-003a starting problem today and, after fixing, noticed that his electrician had sunk and connected to a ground rod, maintained neutral connection at the frame of both units and ran 3 wires to his panel at the house using an interlock kit on each 200 amp panel. Friend has a trailer-mounted power system of two 10 kw units. Just sent him links to Speddmon's post 25 and 32 and suggested he read and print, especially the diagrams, and get his electrician back to review installation. Work done a year or so ago. Any documented safety incidents associated with the grounding/neutral bonding issues?

Jerry
 

Isaac-1

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Such stories on generator installations are all too common, it seems more Electricians get it wrong than get it right. The worse part is they get very offended if you tell them they have been doing things wrong
 

Munchies

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The fact is most home backup sets at least in my experience are already set up with a separate neutral and ground, and an electrician who doesn't care to investigate things, and just wants to hook up wires and leave (continuity between L0 and ground. takes 2 seconds!!!!!!!) is just lazy.
 

johnray13

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I don't think I would use the word lazy. The code is confusing when discussing this. The confusion all comes down to 'separately derived source'. Intuitivly, a generator is a separate source. But what actually defines that phrase is how the neutral is treated at the transfer switch.

Interestingly, most RV transfer switches switch the neutral. And who is gonna drive a ground rod anytime they fire up the generator? I haven't looked but I suspect the code treats RV grounding differently and allows the neutral to be switched and bonded without a separate ground.
 

screejunk

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This blog post at GMG can help: http://greenmountaingenerators.com/how-to-wire-a-mep002a-or-mep003a-diesel-generator/

The knob that selects what the meters should behave must be matched to the phase selector on the distribution box...The meters can work multiple ways (i.e. single and three phase)...So they need to be 'talking to each other.' You can't have the phase selector set to three phase and the meters monitoring single phase...e.g. I would also consult a licensed electrician as this is extremely basic for them and you don't want to get zapped or do something that will negatively affect the unit.
 

m16ty

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I'm getting ready to hook my 003 up to the house and have read this whole thread several times. I do better with pics than I do text though.

I've made some crude drawings on what I take is the two different ways to tie the 003 into the house wiring. Comments or suggestions are welcome.Gen neutral bond.jpggen unbonded neutral.jpg
 

Munchies

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No. In the first picture the neutral and ground are bonded INSIDE the panel and no ground rod is needed.
This is often overthought. If you have utility power you are going to have a neutral bonded to ground already. Bring 4 wires from the genset. Remove the neutral bond at the genset and use the one in the panel. NO ground rod, your bringing ground out to the generator.
Gen neutral bond.jpg
 

m16ty

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Andy and the rest of you guys. I would have jumped into this discussion earlier, but I have been out of town.

GROUNDING!!!!!!!!! You DO NOT NEED to disconnect the neutral ground of the generator. You also DO NOT NEED to drive a ground rod at the generator! As a matter of fact, you should not drive a ground rod at the generator. The NEC states that only one earth ground shall be installed. This was done at your main service panel when your house was wired and built. You do not drive a second ground rod at the generator, the military does this because these sets are the main power source out in the field. They are not the main power source in your home.

To install them properly, you should be running 4 wires from the generator to the transfer switch/hook-up spot in your house. Two of those wires should be the two "hot" legs of the generator, one wire should be the "neutral" from the generator, and the last wire should be a continuous unbroken ground going back to the grounding bus in the main panel. You could also do as Ike suggested and isolate the neutral bond at the frame of the generator and then drive a second ground rod. This is safe to do, but depending on your electrical inspector you still may have a tough time getting it to pass muster, because as I've stated the NEC specifies only one (1) ground rod shall be driven!

The reason for only having one ground rod is this. If you look at your main electrical panel you will notice that the neutral buss and the ground buss are bonded together, they are essentially (electrically) the same buss. If you drive a ground rod at the generator and do not remove the neutral bond, you now have two (2) pathways for the neutral current to get back to the generator, the neutral wire and the earth ground because of the second ground rod you drove....this is a big NO NO!!!! The current will parallel the two pathways and now the earth ground becomes a current carrying conductor, and as per the NEC this as a violation. The ground shall NEVER be a current carrying conductor. If you feel better doing as Ike sugested, you can go to the trouble of disconnecting the neutral bond on the generator and driving a ground rod, but if you want to go according to the NEC, that is still not a proper installation, is it safe? Yes!

If you have not hooked up the generator yet, save yourself the trouble and hassels, and just run the 4th wire (the ground) back to your panel and do it the easy way. If you have 4 wires going from the generator to your house already, leave the ground wire hooked to the generator frame and remove the one going to the second ground rod (just be sure the neutral bond is connected to the frame).
Munchies, I see what you're saying but it kind of contradicts the above post.

I'm mainly interested in the second drawing. I already have some 6/3 SO cord (that I got free) that I'd like to use so I'd like to use a 3-wire setup if I could.
 

Munchies

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It does not really contradict. The main thing is grounding. You need to stick with one ground . You will need to pull it from the house to the set or from the set to the house. The dual neutral bond is kind of wishy washy, and I along with many others choose to only have one in the panel. This was clarified a bunch in this thread.
 

Isaac-1

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The problem is you can't be code legal with 6/3 SO cord, you could run a separate ground wire, but I think that this is an NEC violation since it is not in the same multi conductor bundle. I am not a professional though, so hopefully someone else can confirm. Regardless of the issue of neutral bonded to frame ground at the generator or at the service entrance you need 4 conductors between them if running 120/240 split single phase (household current), 2 hots, a neutral and a ground. The frame bonding jumper should only be left connected if you are using a transfer switch that switches neutrals, most residential transfer switches have solid neutrals and only switch the hot lines. There is a good reason for this, as you never want to have a floating neutral and building a transfer switch that reliably simultaneously switches both is more difficult as you have to account for things like flexure in the mechanism, etc.

Ike
 

m16ty

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Thanks for the responses. It seems to me it would be safe to run 3 wires, remove the neutral bond, and ground the generator to earth (ground rod). It seems to me that if the generator is grounded to earth and the panel is grounded to earth, it's the same as running a wire. I'm not really worried about passing code but I do want to be safe.
 

Isaac-1

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Better yet get a lightly used or never used 50 ft 50 amp rv cord off ebay which will likely be 6/4 or 3 #6 conductors and 1 #8 ground, these often much less expensive than you can otherwise buy SO cord. I picked up 2 35ft lengths with damaged plugs that way a couple of months ago for $60 delivered.

Ike
 
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