Break neutral...yes or no?

Texpower

Member
Location
Houston
Occupation
Voltage management
Hello gents! I’m installing a generator inlet and transfer switch for a client and have a question about wether or not to break the neutral.
The clients existing home setup includes a exterior utility disconnect panel and two sub panels (branch panels) located in his garage. The neutral & ground for the utility is bonded inside the exterior disconnect panel (first point of disconnect). The neutral then feeds to the neutral buss on the sub panels (inside garage) and ground is sent to earth (via rod) and to sub panels ground buss.

I will be installing a manual transfer switch (with inlet box) between his utility disconnect and branch/sub panels. His generator is bonded and will be installing ground rod (for earth ground). Here’s my question: With the generator being bonded, should I break the neutral (3 pole) at the transfer switch or not (2 pole)? I’ve heard arguments for both and just want to do what’s best. Thanks!
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
It is a design choice: you may have a bonded generator and a transfer switch with a switched neutral _or_ you may have a non-bonded generator with a shared neutral.

I believe switching only the hots is most common for residential applications

Jon
 

Texpower

Member
Location
Houston
Occupation
Voltage management
It is a design choice: you may have a bonded generator and a transfer switch with a switched neutral _or_ you may have a non-bonded generator with a shared neutral.

I believe switching only the hots is most common for residential applications

Jon
The client wants to leave the generator bonded. So with that being the case, am I required to switch the neutral...or is it really up to me?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Either both sources are bonded and you switch the neutral, or neither source is, you don't switch it, and it's bonded.
 

tom baker

First Chief Moderator
Staff member
It is a design choice: you may have a bonded generator and a transfer switch with a switched neutral _or_ you may have a non-bonded generator with a shared neutral.

I believe switching only the hots is most common for residential applications

Jon
Yes. The issue can be with a generator with GFCI protection on the outlets. The GFCI will trip when it sees the main bonding jumper at the service.
If you use a bonded neutral generator there will be some objectionable current. If you unbond the neutral then the generator is not safe to use, no fault current return path.
What you need to do is to match the correct generator to the type of transfer switch, and install the correct signage on the inlets 702.7
I did a generator inlet last fall, and the floating neutral generators were not available. The most common generator at Harbor Freight etc is the bonded neutral type.

And you don't have any control over what type generator the home owner will have. If the homeowner gets a generator with GFCI protection (as required 445.20 the GFCI can trip. I have not seen a generator per 445.20 A,

You could try explaining this to the homeowner. Most electricians and myself have a hard time explaining it.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The client wants to leave the generator bonded. So with that being the case, am I required to switch the neutral...or is it really up to me?
If the client wants the generator bonded then you must switch the neutral.

For a small residential manual transfer generator my guess is this will be much more expensive.

Jon
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The GE generator I purchased for myself last winter was bonded, the instructions include having your electrician determine if the bond should be removed along with how to remove the bond.

Jon
 

Texpower

Member
Location
Houston
Occupation
Voltage management
Yes. The issue can be with a generator with GFCI protection on the outlets. The GFCI will trip when it sees the main bonding jumper at the service.
If you use a bonded neutral generator there will be some objectionable current. If you unbond the neutral then the generator is not safe to use, no fault current return path.
What you need to do is to match the correct generator to the type of transfer switch, and install the correct signage on the inlets 702.7
I did a generator inlet last fall, and the floating neutral generators were not available. The most common generator at Harbor Freight etc is the bonded neutral type.

And you don't have any control over what type generator the home owner will have. If the homeowner gets a generator with GFCI protection (as required 445.20 the GFCI can trip. I have not seen a generator per 445.20 A,

You could try explaining this to the homeowner. Most electricians and myself have a hard time explaining it.
Tom, the generator is over 15kw...no gfci. It’s a Generac GP17500E. The receptacle I will use is a 50A (14-50R) non-gfci. Is tripping the GFCI from objectionable current the only concern? In other words, if there’s no gfci, and both the service and generator are bonded and grounded (via rods)...do I still need to switch the neutral? Thanks!
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
It is a design choice: you may have a bonded generator and a transfer switch with a switched neutral _or_ you may have a non-bonded generator with a shared neutral.

I believe switching only the hots is most common for residential applications

Jon
I agree. There's also a further choice that's not only costly but it's heavy. Probably not the way to go.
...
 
Top