wiring up to a generator from a cabin

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  #1  
Old 08-28-01, 04:43 PM
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Unhappy

i am preping wiring for a cabin
my power source will be a generator (5500)
do i need to install a breaker box for this?
in the cabin i have 5 lights,6 plugins and 4 switches
should one breaker be for lights and switches
the other breaker for plugins?
how big should the breakers be (15 amp)?
i know nothing about wiring..been reading lots...hmmmmm!
 
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  #2  
Old 08-28-01, 08:46 PM
Wgoodrich
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I am on the understanding that you have no Utility Company providing power connected to this cabin. This generator is also a 240 volt generator. If this is true, try the following as a start, then maybe others will pop in to help with their thoughts and suggestions.

I would buy a 6 circuit main lug only panel for inside use. Install this panel in the cabin. You have a good idea separating your lights from your panel in case you overload the generator then you can shut all breakers down to the lights and phase on the rest of the breakers one at a time. Keep in mind that if this generator is a 240 volt generator then you should install two hots and a neutral and an equipment grounding conductor from that inside panel to a weatherproof receptacle 240 volts and 30 amp rated. Install a weathershield so that this receptacle can accept a plug left unattended. Now make a cord made of heavy usage rubber cord and with two male plugs one on each end. You should have a 220 volt receptacle on that generator. Match one male plug to the generator receptacle and the other male plug to the house recepacle. Plug the generator in to the cord then the cord into the building receptacle. This allows you a removable connection between your generator and you cabin.

You will need a grounding electrode installed in that cabin if you have no metal plumbing in direct contact with the earth for 10' minimum. Install an 8 awg copper conductor from that ground rod to the neutral bar of the panel joining both the neutral bar and the grounding bar together inside that panel.

Run your branch circuits as you suggested connecting to 15 amp breakers if with 14 awg branch circuit conductors or 20 amp breakers if with 12 awg branch circuit counductors.

Once you have all ready to try to energize and test remember that you are dealing with a generator. This means that you need to turn each breaker on one at a time allowing the genrator to catch the increased load and come back to speed before you add an other breaker to the load of that generator. If you see the generator slowing down in RPMs then back off adding any more loads until things catch up.

Hope this helps

Wg
 
  #3  
Old 08-29-01, 10:39 AM
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No, no, no, Wg! It is illegal to install two male plugs on a cord! Think of the consequences when the generator is running and someone trips on that cord pulling it out!!!

There is a special plug & receptacle combo designed exclusively for use with generators. The receptacle is recessed with a diameter to match the plug, but here's the difference: inside the recess the receptacle, which is connected to your panel, actually has male prongs. The plug, which is connected to the cord coming from the generator is actually all female, with only slots. Can you guess why that is? It's because if you had a male plug connected to a running generator you'd easily be able to fry yourself! And we're all quite comfortable around male plugs because all our lives every one we've ever touched was dead - because if we're touching the metal prongs it was obviously UN-PLUGGED. An unwary person who found your male plug laying around wouldn't hesitate to pick it up by the end and POW!

This type of receptacle is available for exterior use, and is angled downward as it is installed in a box to keep rain out.

If you have no utility connection, wire from the main lugs, neutral and ground buses to the special receptacle. Get the matching plug and wire it to the cord going to the generator. Plug the two together to power the house panel.

Wg indicated rubber cord, this should be "SJ" or "SO" cord, available at most home centers. #10-3/with ground should be adequate, since at 240 volts 5.5 KW is just under 23 amps, and #10 is rated for 30.

If you do have a utility connection you would be required to install a transfer switch, but it doesn't sound like that's the case here.

Wg mentioned adding your loads incrementally, this is called load-stepping. Dumping all your load on the generator will choke it and it'll stall. If you ever drove a stick shift and popped the clutch all at once you'd know what I mean. The alternator on the generator, which produces your AC power, resists the turning of the engine with electro-magnetic force during the initial inrush of current to the starting load. This is particularly true with motor loads. Once the RPMs get back up to normal the generator is ready for another increment of load.

Good luck and be safe!

Juice
 
  #4  
Old 08-29-01, 10:58 AM
Wgoodrich
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Juice is right, I must have had a brain lapse. The two male plugs on a cord would be a hazard. Where was I thinking? The specialty plug he is talking of is the correct way to install the connection on the home.

Wg
 
  #5  
Old 08-29-01, 12:05 PM
resqcapt19
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WG,
Most if not all portable generators are supplied with a connection between the neutral and the frame of the generator. This is because 250-34 permits the frame of the portable generator to serve as the grounding electrode. If this is the case, then the conenction of the grounding electrode conductor and the equipment grounding conductor to the neutral at the panel is a code violation. If you just connect the grounding electrode conductor to the equipment grounding conductors at the panel the installation will be code compliant.
Don(resqcapt19)
 
  #6  
Old 08-29-01, 12:38 PM
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Don, 250-34(a) permits the frame to serve as a grounding electrode under two specific conditions, not in general terms. This is permitted only if generator-mounted equipment and plug-connected equipment plugged into generator-mounted receptacles are used. My take on this is that if connecting a house panel via a cord from the generator-mounted receptacle you are not utilizing plug-connected equipment.

The other condition is if the noncurrent-carrying pmetal parts of the generator and the equipment grounding conductor of the receptacle are bonded to the generator frame. To me that almost goes without saying.

Also, this article says the frame "shall not be required to be grounded" and "shall be permitted to serve as the grounding electrode". There's no requirement here. Just that IF you choose to use it as the ground rod it has to be under the conditions above.

250-34(c) goes on to describe what Don informed us is the practice of bonding the grounded conductor to the frame. Don says "most if not all", and I would tend to think they all do because of this article. It does not say the following, but the NEC handbook does: "Portable and vehicle-mounted generators ...are required to have the neutral conductor bonded to the generator frame.". The middle part, which I skipped through, just lists different systems which have neutrals, and 120/240v single-phase was one of them.

This leads me to wonder why Don cautions against bonding the grounded conductor at the house panel. Does the generator's panel become the "service equipment", being the only place where ground and neutral can be bonded? Does the house panel become a sub-panel, which most of us recognize is a place where you never bond G&N?

Juice
 
  #7  
Old 08-29-01, 06:43 PM
resqcapt19
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The neutral is only permitted to be bonded once. This is a separately derived system and not a service. The rules in 250-30 only permit one point of bonding. If it is bonded at the generator it shall not be bonded at the house. If you want to bond it at the panel, then you must first remove the bond in the generator. If it was my installation, I would install it like Warren said except that I would leave out the bonding jumper between the grounding electrode conductor and the neutral at the panel. The grounding electrode conductor would be connected to the EGC from the generator and the EGCs in the cabin.
Don(resqcapt19)
 
  #8  
Old 08-29-01, 09:50 PM
Wgoodrich
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Juice, in my opinion Don has some accurate points. However I disagree with his wiring style if you leave the bonding jumper to frame on the generator and install the grounding electrode at the structure.

In my original reply, I failed to mention that the bonding jumper must be removed from the frame of the generator to the neutral bar.

This generator is a seperately derived service. There is no Utility company or transfer box. The generator is the replacement for the transformer of the utility company. The Utility company grounds their structure holding the transformer because this pole is a permenant structure.

If this generator was a seperately derived system and the generator was a permenant mount then the same wiring method should prevail as if it was the Utility company's transformer having a grounding electrode at both the generator and at the cabin structure with the neutrals and grounding married together at both locations and with a three wire system. This wiring style should look familiar to you.

This generator is a portable unit, yet a separately derived system too. It was my intentions to marry the neutrals and grounds in the cabin panel then run an equipment grounding conductor with the feeder from the portable generator and remove the bonding jumper causing the marriage between the metal frame and the neutral at the generator. This would allow two hots connected to the windings and the neutral connected to the windings. Then the equipment grounding conductor would ground that generator from the dwelling as allowed with portable generators because of the portablility. A grounding electrode can not be trusted to be connected to that generator on location every time they carry the generator to be hooked up. Therefore I was leading for the grounding electrode being permenent at the cabin structure and the equipment grounding conductor ran with the feeder to the generator making the separation at the generator.

If it is wired as Don suggests I have no problem with his wiring design but feel the grounding electrode would have to be located at the generator instead of the cabin making the cabin a sub from the generator. If we installed the grounding electrode in don's wiring design, we would then have to carry the grounding electrode sized as a grounding electrode through the panel in the cabin through the SO cord and to the generator, then back through an equipment grounding conductor to the sub panel in the cabin.

I believe my wiring design placing the grounding electrode at the permenent structure, then using the equipment grounding conductor to bond the metal frame of the generator from the cabin and locating the joining of neutral and grounding in the cabin as allowed for portable generators. I just did not tell him to remove the bonding jumper in the generator.

Don what do you think? Am I right about your wiring style dictating the location of the grounding electrode to be at the generator if you separate the neutrals and grounding conductors at the panel in the cabin?

I even have second thoughts as small as this job is being only two 20 amp 120 volt circuits whether you would even need the panel in the cabin. Just plug one 220 volt branch circuit from the generator into the cabin wiring and use a common neutral. Using the plug as a form of emergency disconnect and the breaker in the generator as the main overcurrent device. What do you guys think about this wild idea?

Curious

Wg
 
  #9  
Old 08-30-01, 09:09 AM
resqcapt19
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WG,
I think you have a good point that the grounding electrode should be at the generator. The smallest grounding electrode conductor permitted by Table 250-66 is a #8 and that would be a problem for the cord connection. I don't think there is any code compliant way to connect the neutral and grounding conductors in the cabin panel unless the internal generator bond is removed. I don't really see any safety problem in putting the bond and grounding electrode at the panel. I just see it as a "technical" code violation.
Don(resqcapt19)
 
  #10  
Old 08-30-01, 09:22 AM
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I also have a preference for an electrode being at the house, however, being a portable generator the NEC does not permit you to remove the bond between the neutral and the generator frame. The Code obviously deems it to be a safe installation bonding at the generator and using its frame as your grounding electrode so long as it is a portable unit. The only variation on this theme would be if Canim were to permanantly install the generator as a pad-mounted unit.

Speaking of Canim, where did you go, buddy? Haven't heard from you in a while.

Juice
 
  #11  
Old 08-30-01, 10:29 AM
resqcapt19
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Juice,
In my opinion the only time that you can use the generator frame as the grounding electrode is when the generator is serving cord and plug connected loads. I don't think that a panel in a building, even if it is connected to the generator by a cord, is a cord a plug connected load. We therefore must provide a grounding electrode for this proposed installation. If the internal bond at the generator can't be removed, then the grounding electrode will have to be installed at the generator location. A supplementary grounding electrode could be installed at the panel and connected only to the EGCs.
don(resqcapt19)
 
  #12  
Old 08-30-01, 10:37 AM
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Don, I spaced! I said it myself just yesterday, that I didn't think connecting the generator cord to a house panel would be considered plug-connected equipment. I must have CRS!

Juice
 
  #13  
Old 08-30-01, 04:57 PM
Wgoodrich
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I have read and reread and an positively without a question unsure of what I am about to say but think I am right. The bonding jumper can be either installed in the main service rated panel in the cabin, or may be installed in the generator. But it can not be both. If a bonding jumper is installed in both then you have created a paralleling between the neutral and the equipment grounding conductor. All the rules applying to this circumstance is not rather confusing it is really very confusing. This is the best I can come up with. Read the following and forget any exception concerning cord and plug connected equipment with generators. I agree with Don that this cabin can not be considered as cord and plug connected eqiupment. It is a structure. I believe you could install a ground rod either at the generator or at the main service rated panel but definitly not both with a bonding jumper installed in both the generator and the main service rated panel in the structure. I would lean to use the equipment grounding conductor to bond the frame of the generator to the grounding system without installing a ground rod at that generator. This is real confusing to me and probably to most everyone else. Check out the NEC copy below.

(1) Bonding Jumper. A bonding jumper in compliance with Sections 250-28(a) through (d), that is sized for the derived phase conductors, shall be used to connect the equipment grounding conductors of the separately derived system to the grounded conductor. Except as permitted by Section 250-24(a)(4), this connection shall be made at any point on the separately derived system from the source to the first system disconnecting means or overcurrent device, or it shall be made at the source of a separately derived system that has no disconnecting means or overcurrent devices. The point of connection shall be the same as the grounding electrode conductor as required in Section 250-30(a)(2).
Exception No. 1: A bonding jumper at both the source and the first disconnecting means shall be permitted where doing so does not establish a parallel path for the grounded circuit conductor. Where a grounded conductor is used in this manner, it shall not be smaller than the size specified for the bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth is not considered as providing a parallel path.

Best I can come up with but still unsure, the more we talk the more I am not sure.

Wg
 
  #14  
Old 08-30-01, 05:43 PM
resqcapt19
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WG,
The problem with removing the bonding jumper at the generator and installing one at the cabin is that if the generator is used as a portable generator at another location there would be no fault clearing path because the jumper is missing. I wouldn't recommend the removal of this jumper unless the generator is permanently fastened in place.
Don(resqcapt19)
 
  #15  
Old 08-30-01, 06:29 PM
Wgoodrich
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Don I agree with what you are saying about not removing the bonding jumper in the generator. However I believe you have the bonding jumper on a portable generator between the receptacle equipment grounding connection to the frame of the generator and not between the equipment grounding conductor in that receptacle and the neutral of the generator. I may be wrong, been a while. What I was saying was to install the ground rod at the structure as required for seperately derived systems, then use the equipment grounding conductor ran with the feeder from the generator receptacle leaving the bonding jumper from the equipment grounding connection in the recepatcle but seperate from the neutral to bond the frame of the generator making it an equipment grounding jumper. Then making the main bonding jumper in the cabin main service rated panel. I also was trying to say that a ground rod should not be installed at the portable generator. I believe this to be compatible with the NEC but am not sure. Boy am I not sure!

Best scenerio I can come up with for all options involved.

Wg
 
  #16  
Old 08-30-01, 07:20 PM
Guy
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What if you put all the rules and regulations aside for a minute and consider what the rules and regulations are trying to accomplish instead? Look at this in electrical terms, risks and all. What electrical mishap could happen if the panel in the cabin is treated like a regular service entrance, with ground and neutral bonded and connected to a grounding rod (and supposing that the ground wire and the neutral between the cabin and the generator are of the same guage)? I would like the experienced people here to examine it fom this standpoint and explain their reasoning for doing it this way or not. On the surface, it looks OK to me to do it that way, but I might be missing something (shock or fire hazard) that you guys know...thanks.
 
  #17  
Old 08-31-01, 06:27 AM
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Many or the things said here, particularly by Wg, pertaining to separately derived systems, generally speaking, are true. However, the NEC has seen fit to pidgeon-hole "Portable Generators" into a separate category. And I feel that is deliberate and not arbitrary, due to the portable nature and the resulting fact that being used in different locations and possibly by different personnel. A modification to the safest practicable system prescribed by 250-34 (which may indeed be a compromise) may not be evident to another user. And a permanent grounding electrode at a portable generator in lieu of the accepted grounding electode means prescribed in 250-34 of using the generator frame as the electrode, is therefore the safest means of system grounding (when using plug-connected equipment) regardless of where it is located, used, how often it is moved and who may be using it. I would guess that perhaps 75% of portable generator users are not sufficiently trained or familiar with the Code to know what lattitude they may have for safe use if the basic factory-installed grounding/grounded conductor arrangement were altered for one specific use or location.

This is why I offeed that if Canim were to permanently install the generator as a pad-mounted unit, the choices of where to install grounding electrode and where to bond open wide up within the normal restrictions and requirements of Article 250. However, if Canim desires to continue to have this generator be portable he will be as safe as possible and legal if he does not alter the factory-installed grounding/bonding.

I agree with those who suggested that a permanent grounding electrode be installed given that this application is not plug-connected equipment as it will be connected to a house panel. I would choose a location where I would always want to set the generator. I would install a ground rod adjacent to where the generator would always sit. I would dig a small pit around the top of the rod, (the top of the rod would be approximately 6" below grade). I would get a 12" to 18" piece of 4" schedule 80 PVC conduit and drive it into the ground around the rod so that it protrudes maybe 2" to 4" above grade and install a cap when no generator is connected. This is for protection of the rod and so it would not become buried and thus un-findable iover time. I suggest 4" so you can get a wrench on the grounding clamp. I would buy two listed grounding clamps, one for the rod, one for the generator frame. Diameter of each to match diameter of rod and tubular generator frame. I would sand or file all the paint off the area of the tubular frame where I would place the grounding clamp. I would buy a couple feet of #6 copper grounding electrode conductor. When using the generator I would clamp this conductor to the rod and generator frame. I would do all of this because I am not using plug-connected equipment when patched into my cabin panel.

What do you think, guys?

Juice
 
  #18  
Old 08-31-01, 09:19 AM
resqcapt19
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WG,
I believe that the "neutral" is connected to the generator frame in a portable generator. The EGCs are also conencted to the frame.

Juice,
Your plan looks fine to me.

Don(resqcapt19)
 
  #19  
Old 09-02-01, 06:20 AM
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Thanks, Don. I agree with you about the grounded and equipment grounding conductor being bonded to the generator frame. That's the way it reads to me in 250-34. Hope you're having a great holiday weekend.

Juice
 
  #20  
Old 09-05-01, 12:44 PM
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just my 2 cents here...
a Grounding Electrodes existence is for lightning protection and voltage gradient, so there would be little protection in that respect if the genny were 300' away.

As long as there is no parralleled noodle, i don't see why you could not have G-rods at the genny, as well as the cabin...

p.s---you are ALL good reading here.
 
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