Whole House Generators

[Radioman91]

It has been stated by local inspectors that when you install a whole house generator with a main breaker transfer switch. If the house was wired with a 6/2 romex range connection, you now have to replace the wire, receptacle and cord with a 6/3 romex, so that the neutral and the ground are fully separate since you had changed the main panel into a sub panel and have separated the neutrals and grounds. Is this correct?

YES. When you install a "Whole House: SE rated transfer switch for a standby generator the following MUST be done:

A) The new SE rated transfer switch is now your "Service Equipment". Since the SE transfer switch contains NO branch circuit devices ALL downstream panels now become by definition "Sub-Panels". Your system bonding jumper is located in the new SE transfer switch. You MUST also move your GEC, water pipe bond, and gas pipe bond (if required) to the new SE transfer switch (your service equipment).

B) All existing panels now become by definition "Sub-Panels". This requires that they be fed by a four wire connection including an insulated neutral conductor and a separate EGC sized per NEC 250.122 table. You MUST remove the existing system bonding jumper in what is now a sub-panel and install a ground bar kit. The neutrals and the EGC's MUST now be separated and relocated to their own respective buss bars.

C) For range and dryer circuits to use the grounded circuit conductor (neutral) as their EGC, ALL (4) conditions noted under NEC 250.140 Exception MUST be met.

Ex (3) -- and the branch circuits originates at the service equipment.

Since this is no longer possible you MUST upgrade ALL stove, range, counter mounted cooking unit, and dryer circuits to the four wire type with a separate equipment grounding conductor.

D) For all standby generator installations the conditions in NEC 702.4 MUST be met. This REQUIRES that you meet the conditions noted below:

NEC 702.4(B) System Capacity - The calculations of load on the standby source SHALL be made in accordance with NEC Article 220 or by another approved method.

NEC 702.4(B)(2)(a) Full Load - The standby source SHALL be capable of supplying the full load that is transferred by the automatic transfer equipment.

OR

NEC 702.4(B)(2)(b) Load Management - Where a system is employed that will automatically manage the connected load, the standby source SHALL have the capacity to supply the maximum load that will be connected by the load management system.


It has been my experience that very few of the installations that we are called to service meet the conditions and requirements as set forth in the NEC for standby generators. Most generator manufacturers' require that installing contractors in addition to the NEC also meet ALL of the installation requirements contained in the owners and install manuals supplied with their units.

Most manufacturers' warranty programs DO NOT COVER errors, omissions, mistakes, and NEC violations by the installing contractor.

THIS IS THE INSTALLING CONTRACTORS RESPONSIBILITY!

 

[Little Bill]

C) For range and dryer circuits to use the grounded circuit conductor (neutral) as their EGC, ALL (4) conditions noted under NEC 250.140 Exception MUST be met.

Ex (3) -- and the branch circuits originates at the service equipment.

Since this is no longer possible you MUST upgrade ALL stove, range, counter mounted cooking unit, and dryer circuits to the four wire type with a separate equipment grounding conductor.

Excep. 3 doesn't say all branch circuits must originate at the service equipment in order to qualify to remain a 3-wire/use the neutral as an EGC. It says that IF the neutral is bare and part of a SE cable, then that circuit has to originate from the service equipment.

3) The grounded conductor is insulated, or the grounded
conductor is uninsulated and part of a Type SE service entrance
cable and the branch circuit originates at the
service equipment.

Notice the comma (in red above) after "is insulated". That is the first part of the sentence. Everything after that is the second part. The "and the branch circuit originates at the service equipment" belongs to the second part of the sentence.
If the writers had meant all circuits had to originate at service equipment they would have put a comma after "...service entrance cable".

ETA: Actually if they meant all circuits had to originate from the service equipment, there would be no need in mentioning both insulated and uninsulated conductors. So only the latter needs to originate from service equipment.