Portable Generator Connected To Service Via 'Interlock Kit' Neutral

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Ravenvalor

Ravenvalor

Senior Member
Location
Triad region of NC
Occupation
Electrician
Hello,

Does the 2014 code require the utility neutral conductor to be opened when using a portable generator and a manual transfer 'Interlock Kit'?

Thank you,
 
I don't know of any instance where the grounded service conductor is required to be opened by the transfer switch, in itself. It is usually bonding and/or ground detection conditions which impose a necessity to open the grounded conductor.
 
PS: There are some issues with not more than 15kW portables (GFCI and frame bonding) but IMO, as long as the generator is connected with insulated 4-wire cord, I don't see any major safety issues.
 
Good to hear. I have never run into that situation with an inspector in the past but wanted to be certain before calling him on Monday.

Thank you Smart$
 
Ravenvalor said:
Good to hear. I have never run into that situation with an inspector in the past but wanted to be certain before calling him on Monday.

Thank you Smart$
Click to expand...

Depends on how tough the inspector is.
From UL

ENGINE GENERATORS FOR PORTABLE
USE (FTCN)
GENERAL
 This category covers internal-combustion-engine-driven generators rated
15 kW or less, 250 V or less, which are provided only with receptacle outlets
for the ac output circuits. The generators may incorporate alternating or
direct-current generator sections for supplying energy to battery charging
circuits.
When a portable generator is used to supply a building wiring system:
1. The generator is considered a separately derived system in accordance
with ANSI/NFPA 70, ??National Electrical Code?? (NEC).
2. The generator is intended to be connected through permanently
installed Listed transfer equipment that switches all conductors other
than the equipment grounding conductor.
3. The frame of a Listed generator is connected to the equipment grounding
conductor and the grounded (neutral) conductor of the
generator. When properly connected to a premises or structure, the
portable generator will be connected to the premises or structure
grounding electrode for its ground reference.
4. Portable generators used other than to power building structures are
intended to be connected to ground in accordance with the NEC
Click to expand...
 
ceb58 said:
Depends on how tough the inspector is.
From UL
Click to expand...
Just a couple comments on that...

First, best to not have such a generator on-site during inspection.

Second, 2014 added a requirement for just such a situation in 702.7 (should have mentioned this earlier)...

(C) Power Inlet. Where a power inlet is used for a temporary
connection to a portable generator, a warning sign
shall be placed near the inlet to indicate the type of derived
system that the system is capable of based on the wiring of
the transfer equipment. The sign shall display one of the
following warnings:


WARNING:
FOR CONNECTION OF A SEPARATELY DERIVED
(BONDED NEUTRAL) SYSTEM ONLY

or

WARNING:
FOR CONNECTION OF A NONSEPARATELY
DERIVED (FLOATING NEUTRAL) SYSTEM ONLY
Click to expand...

Additionally, AFAIK, nothing prohibits defeating a portable generator grounded-grounding bond to make it a non-separately derived source. Depending on generator, it may void listing and/or warranty... but Code does not require portable generators to be listed.
 
Powerful Stuff !!! I've been using Interlock Kits for years and have never been turned down. I will definitely get the new inspector's approval before proceeding.

Thanks
 
Smart $ said:
Just a couple comments on that...

First, best to not have such a generator on-site during inspection.

Second, 2014 added a requirement for just such a situation in 702.7 (should have mentioned this earlier)...



Additionally, AFAIK, nothing prohibits defeating a portable generator grounded-grounding bond to make it a non-separately derived source. Depending on generator, it may void listing and/or warranty... but Code does not require portable generators to be listed.
Click to expand...

Unless you live where Ravenvalor and I do. The inspectors can require that the equipment be listed by a NRTL.

Ravenvalor said:
Powerful Stuff !!! I've been using Interlock Kits for years and have never been turned down. I will definitely get the new inspector's approval before proceeding.

Thanks
Click to expand...

Have we even gone under the 2014 yet? Last I heard we were staying under the 2011 for 6 years. All thanks to the NC Home Builders Association.
 
ceb58 said:
Unless you live where Ravenvalor and I do. The inspectors can require that the equipment be listed by a NRTL. ...
Click to expand...
Lifting the bond shouldn't be a problem, even if it voids listing... falls under 250.6(B). Inspector should be aware of this if he is the least bit Code savvy.
 
Last edited:
Smart $ said:
Lifting the bond shouldn't be a problem, even if it voids listing... falls under 250.6(B). Inspector should be aware of this if he is the least bit Code savvy.
Click to expand...

I don't think an inspector will allow this but
I will use this a a litmus test for the inspector's Code savvyness level.
 
Smart $ said:
I don't know of any instance where the grounded service conductor is required to be opened by the transfer switch, in itself. It is usually bonding and/or ground detection conditions which impose a necessity to open the grounded conductor.
Click to expand...

The inspector said the 'Interlock Kit' that I use will be accepted. No need to worry about breaking the neutral also.

Thanks.
 
Ravenvalor said:
I don't think an inspector will allow this but
I will use this a a litmus test for the inspector's Code savvyness level.
Click to expand...
Unless you have a local amendment, the inspector cannot require you (actually, the owner) to use a listed portable generator when Code does not require one.

That said, if lifting the bond is in the instructions, he cannot flag it.

I understand the AHJ approval process varies, so let's not get into that aspect. But for your "litmus test", ask him what he proposes one do for a Code-compliant implementation of [2014] 702.7(C) "floating" signage and using a listed generator with OEM bond.
 
Ravenvalor said:
The inspector said the 'Interlock Kit' that I use will be accepted. No need to worry about breaking the neutral also.

Thanks.
Click to expand...

Spoke with the vice chief inspector for NCDOA today. He said that even if UL had that requirement it could not be enforced because the wiring is done in the field and UL has no jurisdiction on that.
On a side note he said he did not know when or if, we NC, would go under the 2014.
 
If you break the bond on a portable gen to supply a premise wiring system through an interlock kit, is there anything to be aware of as far as using the receptacles that are mounted on the gen housing.

In other words do you compromise the equipment grounding system for the portable recs. that come with the generator.

Should instructions be given not to use the rec. at the generator location?
 
david said:
If you break the bond on a portable gen to supply a premise wiring system through an interlock kit, is there anything to be aware of as far as using the receptacles that are mounted on the gen housing.

In other words do you compromise the equipment grounding system for the portable recs. that come with the generator.

Should instructions be given not to use the rec. at the generator location?
Click to expand...
If you break the bond but wire the generator output through a transfer switch that does not interrupt the neutral then the receptacles at the generator are properly, although circuitously, bonded.
But if you disconnect the line from the generator to the house, the receptacles become a source of an ungrounded SDS.
Not good, and at least worthy of a placard about the bond being removed.
This is a serious concern, since the setup will often use a plug and receptacle to connect the generator. And it might also be moved for use elsewhere.
 
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