Portable Generators for Residenal stand-by systems

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augie47

augie47

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State Electrical Inspector (Retired)
The more I am reading the more I am confusing myself.
We have a residence with a "generator" panel fed thru a 2PDT manual transfer switch.
250.24 requires there be no grounded-grounding connection on the load side of my service
disconnect so the T/S has an isolated neutral and in this case, unswitched.
The customer is going to rely on a portable generator which is not on site.
Connection will be made thru a permanently installed "inlet" via a cord & plug to the generator.
All of the 50 amp generator inlets I have found are 240/120 3 wire which would not allow for an equipment grounding conductor to the generator.
On a permanent generator install, if we the T/S switch did not switch the neutral, we would need the equipment grounding conductor to the generator. Are portable generators handled differently ?
 
Reliance makes a 50amp 4-wire inlet part #PB50

Neutral and ground should not bond at transfer-switch or generator with what you have described. The neutral to ground bond is at the Main Service Switch...which connects to the GES.

Generator must Float the Neutral...
 
On closer look I see the equipment ground on the PB-50 Thanks.
 
shortcircuit2 said:
Reliance makes a 50amp 4-wire inlet part #PB50

Neutral and ground should not bond at transfer-switch or generator with what you have described. The neutral to ground bond is at the Main Service Switch...which connects to the GES.

Generator must Float the Neutral...
Click to expand...

I agree, the manual transfer equipment does not switch the neutral so this in not an SDS and uses the existing structure GES.

Also has anyone noticed a change by portable generator manufacturers to not require a ground rod at the unit? I was watching a Mike Holt video where he stated that he was a consultant to Generac and was trying to get the industry to change this as part of the generator instructions.
 
The Generac instructions used to say...

?Connect an approved ground strap to the grounding lug on base frame and to an approved earth ground or grounding as required by local regulations.?

This was interpreted by many AHJ's and installer's that a ground rod was required.

The part "as required by local regulations" meant to me that if the Code (Here in Massachusetts) required it...install an electrode. This would only be "required" if the gen-set were connected as a SDS.
 
shortcircuit2 said:
The Generac instructions used to say...

?Connect an approved ground strap to the grounding lug on base frame and to an approved earth ground or grounding as required by local regulations.?

This was interpreted by many AHJ's and installer's that a ground rod was required.

The part "as required by local regulations" meant to me that if the Code (Here in Massachusetts) required it...install an electrode. This would only be "required" if the gen-set were connected as a SDS.
Click to expand...
Do you call an inspector out everytime you plug into a portable generator? Who makes sure these ground rods are being used? If all you are installing is a power inlet, no ground rod is needed for the power inlet. Instructions typically say to connect the rod to the lug on the generator frame, generator often is not there until the time comes it needs to be used.
 
kwired said:
Do you call an inspector out everytime you plug into a portable generator? Who makes sure these ground rods are being used? If all you are installing is a power inlet, no ground rod is needed for the power inlet. Instructions typically say to connect the rod to the lug on the generator frame, generator often is not there until the time comes it needs to be used.
Click to expand...

No, not always for a portable generator setup. I have had to verify that the portable floated the neutral. 2014 requires a warning sign at the power inlet regarding bonded or floating neutral.

I have never had an AHJ ask for a ground rod for a portable...just for a permanent automatic install.
 
shortcircuit2 said:
No, not always for a portable generator setup. I have had to verify that the portable floated the neutral. 2014 requires a warning sign at the power inlet regarding bonded or floating neutral.

I have never had an AHJ ask for a ground rod for a portable...just for a permanent automatic install.
Click to expand...
What if you are installing an inlet for a generator that has not yet been purchased or maybe not even selected yet? Or what if owner gets rid of one generator but replaces with another that may or may not have floating neutral?

My point here is an inlet is an inlet and there are thousands of generators that could supply it.
 
kwired said:
What if you are installing an inlet for a generator that has not yet been purchased or maybe not even selected yet? Or what if owner gets rid of one generator but replaces with another that may or may not have floating neutral?

My point here is an inlet is an inlet and there are thousands of generators that could supply it.
Click to expand...

Agreed. True we can't prevent the end user from installing the wrong generator with how we connect now.

But the industry and the Code are taking some steps to address this.
 
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