Portable generator and grounding

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  #1  
Old 09-04-14, 11:55 AM
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Portable generator and grounding

I have purchased a 6500 watt portable generator and the electrician is going to be wiring a 200 amp manual transfer switch to allow me to cut off from the utility and use the generator to run whichever breakers I select in my main panel. The transfer switch he is installing is the following. GE 200 Amp 240-Volt Non-Fused Emergency Power Transfer Switch-TC10324R at The Home Depot

Will use a 10 foot 30 amp generator cord to connect generator to a inlet box connected to the switch.

with this set up does the generator need to be grounded? If so do I connect it to the homes existing ground rod or run a new ground rod? Obviously I would prefer that it not need to be grounded. Kind of a pain to have to connect it each time we want to use it.

Thoughts?
 
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Old 09-04-14, 12:05 PM
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Why are you installing a 200 amp transfer switch for a generator with 30 amp output? The transfer switch needs overcurrent protection since it is now part of the service.

You electrician should know the rules and any local requirements for connecting a standby power source.
 
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Old 09-04-14, 12:24 PM
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My main electric panel is 200 amp. This is a whole house transfer switch versus one that only connects 6-10 circuits. While I will only be able to run a certain number of circuits at a time, I still have the option of choosing between all of my circuits and not just 6-10 of them.

So what about grounding from a safety standpoint? Since it's connected into the homes wiring does that provide the ground or does the generator needs it's own ground?
 
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Old 09-04-14, 01:30 PM
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Grounding and bonding depend on too many factors to answer your question based on the information provided. Are you switching the neutral and creating a separately derived system? Are the neutral and ground bonded in your generator? Are you installing the switch between the meter and your panel? In that case you need a 200amp service disconnect between the meter and the switch. Your electrician should be able to answer your grounding question and confirm that your installation meets code. You are getting a permit - right?

An interlock setup would make more sense, economically, to meet your objective, IF one can be found listed for your panel and your local jurisdiction permits its use.
 
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Old 09-04-14, 01:50 PM
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In addition the NEC requires a load calculation to properly size the genset along with load shedding when the genset is not large enought.
 
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Old 09-04-14, 02:05 PM
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Yes it is between meter and panel and there is already a 200 amp disconnect installed. The local government does not require a permit for this type of work. I do not know if the generator ground and neutral are bonded.
 
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Old 09-04-14, 02:07 PM
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Load calculation for a manual switch?

I'm not supporting the OP's scheme. I think it's actually more of a trap to have the manual switch separated from the panel as proposed. At least, with an interlock the circuit breakers that need to be disabled BEFORE transfer are right there with the interlock breakers.
 
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Old 09-04-14, 03:36 PM
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Here are part of the requirements.

702.4 Capacity and Rating.
(A) Available Short-Circuit Current. Optional standby
system equipment shall be suitable for the maximum available
short-circuit current at its terminals.
(B) System Capacity. The calculations of load on the
standby source shall be made in accordance with Article
220 or by another approved method.
(1) Manual Transfer Equipment. Where manual transfer
equipment is used, an optional standby system shall have
adequate capacity and rating for the supply of all equipment
intended to be operated at one time. The user of the
optional standby system shall be permitted to select the
load connected to the system.

(2) Automatic Transfer Equipment. Where automatic
transfer equipment is used, an optional standby system
shall comply with (2)(a) or (2)(b).
(a) Full Load. The standby source shall be capable of
supplying the full load that is transferred by the automatic
transfer equipment.
(b) Load Management. Where a system is employed that
will automatically manage the connected load, the standby
source shall have a capacity sufficient to supply the maximum
load that will be connected by the load management system.
 
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Old 09-04-14, 06:27 PM
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Generator ground and neutral are not bonded
 
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Old 09-05-14, 08:59 AM
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Grounding and bonding are based on whether or not you are switching the neutral. Your electrician is the one qualified to make that determination. For example, I have a standby generator that does not switch the neutral in a whole house service entrance automatic switch. The neutral is bonded in the switch and not my panel, nor my generator, and no ground is required at the generator. You have not provided a complete description of your planned setup. An electrician on site is a better source to answer your question than a DIY forum where not every detail is provided.
 
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Old 09-05-14, 06:52 PM
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Yes it is between meter and panel and there is already a 200 amp disconnect installed.
I would suggest replacing the existing disconnect with a 200 amp service entrance rated transfer switch.
 
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Old 09-05-14, 08:06 PM
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While a backfed side breaker pair in the panel with mechanical interlock (slider, cam, etc.) is workable in most instances, a whole house transfer switch upstream of the panel is preferred if you want to be able to use any combination of circuits with your generator.

Since your service is 200 amps the whole house transfer switch has to be 200 amps.

You can connect the generator side of the transfer switch to a generator of any lesser size provide that the generator has its own breaker or other overcurrent protection.

The generator may not be started automatically in the event of utility power failure unless it is large enough to handle whatever load is given to it which could be the entire household load at the moment.
 

Last edited by AllanJ; 09-05-14 at 08:23 PM.
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Old 09-06-14, 09:04 AM
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There is nothing wrong with a non service rated transfer switch as long as there is a service rated disconnect prior to it. The OP's question is about separate grounding for the generator which cannot be completely answered without more information. If, as he says, an electrician is going to be involved in the installation, his question should be answered by his electrician who would be onsite and know the relevant rules.

Nominally, a generator ground should not be required IF the neutral is not switched, the generator ground is not bonded to the neutral, and the neutral is bonded to ground at the switch and not in his panel. Without posters here knowing his exact setup, it should be left to his electrician.
 
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