200 amp upgrade and generator install

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  #1  
Old 06-09-13, 09:54 PM
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200 amp upgrade and generator install

I am currently upgrading my 100 amp service to 200 amp and adding a 60kw genset we have everything put on the house and ready to go with a 400 amp throw switch for the generator between the new meter and 200 amp breaker box with 2/0 copper wire running through everything. I was wanting to know if I would be defeating the purpose of going to a 200 amp service if I use the old large 100 amp breaker panel already installed in the house as an extension panel for the new outdoor 200 amp breaker box with main breaker. "the 100 amp panel doesn't have a main breaker and I will be using 2/0 wire to connect the panels"
 
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  #2  
Old 06-10-13, 05:38 AM
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No, you are not defeating the purpose.

It is perfectly okay to keep the old 100 amp panel in place and feed it from side breakers in the new 200 amp panel. An additional subpanel can be run directly from the new panel to take advantage of the added ampacity.

(The old panel, if it originally contained the first main disconnect, will need to be modified so that neutrals need to be segregated and not bonded to the ground wires and the panel frame.)

It is quite common to keep the old panel, even an old fuse box or fuse block, in service by feeding it from a new panel and new upgraded service drop.
 
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Old 06-10-13, 07:00 AM
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I think someone should look at whether you actually need a 60 kW genset. Why do you think you need one so large?
 
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Old 06-10-13, 09:56 AM
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The reason for the having the 60kw genet is it will be running a couple of other things and not just this one panel. In total it will be running the new panel which is for a 3000 sq ft home, a 100 amp service in a 1600 sq ft home and a welding shop which has two welders in it and and a air compressor that has a 9 horse motor on it
 
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Old 06-10-13, 05:17 PM
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The reason for the having the 60kw genet is it will be running a couple of other things and not just this one panel. In total it will be running the new panel which is for a 3000 sq ft home, a 100 amp service in a 1600 sq ft home and a welding shop which has two welders in it and and a air compressor that has a 9 horse motor on it
And how are you proposing to feed these other loads from this generator. From your first post I was assuming you were installing a 400 amp manual transfer switch between the 200 amp meter and the 200 amp service panel. Is it manual or is it automatic? Regardless of your answer, I don't like the way you are setting it up.

Is this a diesel generator?
 
  #6  
Old 06-10-13, 07:38 PM
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With the transfer switch just after the meter, all circuits in the house will be eligible for generator power (altough not all loads going at the same time).

Only a 200 amp transfer switch is needed here but you probably have some reason to install a 400 amp switch, perhaps the store was running a closeout on the 400 amp switches at a nice price.

My uncle had a setup like this although I forget the exact amperages. I think the service was 200 amps and the (diesel) generator was 70 amps. The house was all electric with heat pump and central air.
 
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Old 06-11-13, 10:49 AM
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Im sorry CasualJoe I realized I worded that weird the way it is setup is after the manual transfer switch the wiring enters a small outdoor 200 amp panel were I have two 100 amp breakers that are for a 100 amp subpanel in the large home and a 100 amp subpanel in the smaller home which also feeds the shop. For your question AllenJ the 400 amp transfer switch came off our chicken farm when we put automatic switches in. The generator is a DMT 60-JD, it is diesel and at 240 volts it puts out 250 amps. I hope this answers your questions and clears everything up.
 
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Old 06-11-13, 08:05 PM
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I have also heard of dirty power that generators produce can someone please explain this to me
 
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Old 06-11-13, 08:24 PM
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You are going to need to use either 250 kcm copper conductors or paralleled 1/0 conductors to connect that generator to the switch. If you use parallel conductors then the switch and generator lugs must allow for multiple conductors and the individual conductors MUST be exactly the same length.

As for the issue of "dirty power" it is probably not an issue with a generator of that size.
 
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Old 06-11-13, 08:46 PM
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I have wired the generator already with 2/0 stranded copper THHN for the two hots and 1/0 stranded copper THHN wire for the ground/neutral. I drove two 8ft ground rods to ground the generator and a 8ft ground rod at the new 200 amp panel.
One thing I know for sure after this install is you do not want to buy any copper wire right now because the price is through the roof!
 
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Old 06-11-13, 09:02 PM
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I'll bet you haven't had this installation inspected, have you? 2/0 copper is only good for a maximum of 175 amperes. 1/0 is only good for 150 amperes. Your generator puts out 250 amperes. Assuming the generator has a circuit breaker it will be rated at least 250 amperes and possibly as high as 300 amperes. Your wiring from the generator to the load transfer switch is woefully inadequate. What size wire did you use for your grounding electrode (ground rod) conductors? With the proper size conductors on the generator they should be no less than #2 copper. Did you tie all the grounding electrodes together?

You ONLY undersize the neutral conductor when the majority of your loads are at the line-to-line voltage. Even then you MUST take into consideration the maximum unbalanced current that could (not what would be normal) exist. Depending on how your loads are connected and further how they are used it is possible you could severely overload that 1/0 neutral conductor.
 
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Old 06-11-13, 10:02 PM
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I had an electrician hook the generator up the generator does not have a breaker and does not put out 250 amps constantly this is just the maximum draw that can be put on the generator at once the electrician said that the 2/0 cable was sufficient for what we would be running and it meets the Rural Electric Associations standards for 200 amp service
 
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Old 06-12-13, 05:33 AM
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that the 2/0 cable was sufficient for what we would be running and it meets the Rural Electric Associations standards for 200 amp service
Wire must be sufficient for output of generator not anticipated load. Power companies do not follow NEC . Your generator must follow NEC or local code. not power company code.
 
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Old 06-12-13, 05:48 PM
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the electrician said that the 2/0 cable was sufficient for what we would be running and it meets the Rural Electric Associations standards for 200 amp service
The electrician is correct that the NEC allows 2/0 copper for residential 200 amp service entrance, but this is not a service entrance installation.
 
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Old 06-12-13, 07:59 PM
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Guys, I think that Watson has made up his mind that the generator installation is just peachy keen and A-okay. Of course it is not, but I think we are wasting our time in trying to explain.
 
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Old 06-12-13, 11:07 PM
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I am listening to your suggestions! I am just trying to figure out how to go about this because the way it is installed. The current wire is in conduit that comes up through the slab of the generator house so it is not coming out without breaking the slab apart. So would I be able to run a 1/0 wire parallel for each of my 2/0 hot wires and then a 2/0 parallel to the 1/0 ground. I would have to come through the wall with conduit for this wire but there shouldn't be more than a foot of difference in length or do the wires have to be pretty much the exact same length and size.
 
  #17  
Old 06-13-13, 12:52 AM
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Your first mistake was hiring an electrician that knew nothing about how to design such an installation. That is totally understandable when a person does not understand the requirements of the job. The electrician gives a big story of how qualified he/she is and the poor lay person hasn't a clue as to whether or not he/she is being bamboozled. The person that you hired MAY be an excellent electrician in other matters, maybe even in installing smaller standby generators but in your particular case he/she was in way over his/her head.

I can't really blame you for doing anything wrong, with the possible exception of not asking for references to other similar jobs this electrician had done. Most of us have at one time or another been completely snowed by a contractor that simply couldn't deliver. Getting permits and inspections for the job can often help but is no guarantee, especially where permits are mostly a means of revenue and the inspections are lax.

Now my personal feelings are that any large generator installation, say any over 10 kw, should be required to have stamped drawings from a registered electrical engineer and these plans should be reviewed by an independent electrical engineer as part of the permitting process. That sounds expensive and it is expensive however electricity is an equal opportunity killer and care needs to be taken to make every installation as safe as possible.


I'm sorry that your conduit may need to be dug up and replaced, that is just the way it is now. You cannot simply add additional conductors to the existing ones. Paralleled conductors MUST be of the same size AND the exact same length to within an inch or so. Yes, deviation of even an inch will cause the conductors to not equally share the load and could cause the failure of first one conductor and that failure will immediately be followed by the failure of the second conductor. There are also rules about how many conductors of a certain size may be placed in a single conduit and various other "conditions" that need to be taken into consideration.

You absolutely DO need a circuit breaker at the generator for short circuit protection of the conductors and also for overload protection of the generator and the conductors. With the manner that your generator's load is spread out among several panels after the transfer switch there is a very real potential for overloading the generator-to-transfer switch conductors without ever tripping one of the downstream circuit breakers.

Then there are the rules for "grounding" and "bonding" of the generator, the transfer switch and the utility service that needs to be addressed. These rules are among the hardest for even electrical professionals to understand yet they are vital for a safe installation.
 
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Old 06-13-13, 06:18 PM
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I said earlier that I wouldn't have set it up the way you described. That being said, I have never seen a standby generator that didn't have an output circuit breaker, even the little 60 KW ones always have an output breaker, but it may have been removed.

Assuming you cannot replace the missing breaker with a 200 amp breaker, what I think I would do is this. Hang a 400 amp fusible switch on the generator and feed it with the generator output with 3 - 250 MCM copper conductors and a #2 copper ground. I'd fuse the switch down to 200 amps. I would install a 200 amp service entrance rated NEMA 3R automatic transfer switch between the meter and new 200 amp service panel. The automatic transfer switch would contain a 200 amp main breaker fed by the utility power from the meter with the 2/0 copper conductors. I'd feed the emergency circuit to the transfer switch with 3 - 3/0 conductors and a #6 ground from the 400 amp switch on the generator. I would use 2 1/2" conduit for this circuit. You do not need a ground rod at the generator unless it is a separately derived system, but most inspectors want to see one so I would install one 8 foot ground rod at the generator and connect it to a ground lug on the generator frame with #6 bare copper. The load side of the transfer switch is part of the service entrance so I would connect the load side to the 200 amp service panel with 2/0 copper conductors. The service panel and all subsequent panels fed from the service panel are now all subpanels and will require both a 4-wire feed and also require the neutral and ground conductors be separated.

You'll also need at least two additional conduits to the generator pad. One will be for two 20 amp 120 volt circuits for the battery charger and the block heater (assuming a diesel generator). The second conduit is for two (usually two is all that are necessary) start wires from the transfer switch. If you have a remote annunciator, you'll probably need one more conduit. The newer annunciators use a computer type cable, but if this is an older used generator, you could need up to 14 conductors for a remote annunciator.

If you can determine where the output breaker should be and can replace it, replace it with a 200 amp breaker and you can eliminate the 400 amp fusible switch.

Who is the manufacturer of the generator, do you have a model number?
 
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