Properly installed portable generator inlet?

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ritelec

ritelec

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Hi, trying to figure out what would be needed to properly install a portable generator with a manual transfer switch/panel.
This transfer switch from Generac seems to be the only one that disconnects the neutral.


However I have some questions about them.

Specs for the 6852 say 30 amp max @ 240V yet it is to be supplied by a 50 amp breaker from the main panel.(?)


For the 50 amp version it's calling for a CS6377 inlet. From what I see that inlet is rated for "125V". Why would they specify that connection and not a 14-50P ?

Why the differences between pc5019-14, cs6364 which look similar to the CS6377 but are rated at 250V?

Also, I know all loads won't be on at the same time, but for the 6852 model 30 amp version, it seems like alot of circuits to be fed off the main power of the panel. Maybe the max amp line is for generator power side of transfer switch rating, and main breaker in load center line is rating of house panel power side of transfer switch?

transfer specs.pngcs6377.png14-50.pngpc5019-14.pngcs6364.png
 
I don't see anything in 702 of the 2020 NEC that requires portable generators to be listed. I do see that if you use a power inlet then you need to put warning sign up describing the whether or not the neutral is a SDS or non SDS meaning a floating neutral generator is acceptable.
 
I'm guessing maybe it's how a generator is listed when it's constructed and removing the bond at the generator voids it's listing?

???
 
SO, question is, how to legally install a portable generator ?

I much prefer the interlock installed to the cover and backfeed the whole panel, but it has to be listed for the panel it's installed on and there's the bonded neutral issue.

There are manual transfer switches that don't switch the neutral and the Generac listed above which does?

Looks like if a permit are being pulled, the Generac is the way to go.
 
The transfer switch needs to match the generator, SDS or non SDS, or neutral bonding.
A solidly bonded generator would use a transfer sw that transfers the neutral. A unbonded, or floating neutral generator uses a trans switch that does not transfer the neutral. The reason is to avoid objectionable current. More practically, if the generator has GFCI on the outlets, as required, the gfci will trip when it sees the MBJ at the service panel.
Also the inlet has to be labeled according to the type of bonding for the generator, see reqirement in Art 702.
Most portable generators are solidly bonded.
Most homeowners wont know what the label on the inlet means.
A unbonded generator does not have a fault current return path and OSHA won't allow on a job site.
 
ActionDave said:
I don't see anything in 702 of the 2020 NEC that requires portable generators to be listed. I do see that if you use a power inlet then you need to put warning sign up describing the whether or not the neutral is a SDS or non SDS meaning a floating neutral generator is acceptable.
Click to expand...
Only language I can find for portable generator listing is in 445.20 for the integral 125-volt 15&20amp receptacles. UL does have a standard for listing portable generator, UL 2201

I'm trying to understand how a GFCI will work on a fault to ground on a unbonded generator... 445.20(A)? I guess it will only work if the fault involves the neutral also. A fault to ground has no path like Tom stated.
 
ritelec said:
I'm guessing maybe it's how a generator is listed when it's constructed and removing the bond at the generator voids it's listing?

???
Click to expand...
Some of the generators have instructions on removing the bond in the alternator. This would render the generator to be only safe to use for the dwelling backfeed where there is a bond at the service equipment. Your supposed to label/mark a generator that is converted... 445.11 last paragraph
 
Installing a generator inlet, wiring and mechanical transfer setup is common and a practical way to provide temporary power to a dwelling during an outage. The inlet, wiring and transfer equipment is covered by the Code. There is no control on the type of portable generator provided for the setup and the only guide to the correct generator is the label on the inlet per 702.7(C)...and like Tom said, the homeowner won't understand what a floating neutral is (as well as many electricians).

An easy test to see if a portable generator is bonded...do a continuity test between the ground and neutral on the 125-volt receptacle on the generator. (While the generator is OFF)

Using a bonded portable generator to backfeed a dwelling that has a bond at the service is a violation of 250.24(A)(5) and creates a hazard in that all electrically grounded metal is part of the return path of unbalanced current. Given this hazard it is important that you educate your customer/homeowner of the correct generator for the application.

Of course the the most important guidance for the user of a portable generator setup...make sure it is a safe distance away from the dwelling when in use.
 
I just purchased a Westinghouse portable generator for my own home.

Right in the manual are instructions for removing the bond and an instruction to have your electrician determine if the bond should be removed.

For residential use switching the neutral is really overkill, IMHO.

Jon
 
tom baker said:
A unbonded generator does not have a fault current return path and OSHA won't allow on a job site.
Click to expand...
just a question out of curiosity....is there any risk, or possibly to receive a shock from a ground fault from a floating neutral genset since there’s no path back to the source?

example... metal power tool with phase conductor broke loose touching exposed frame. Since there’s not EGC and neutral bond and it’s not physically grounded.Any possibly way to still shock?
 
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Dsg319 said:
example... metal power tool with phase conductor broke loose touching exposed frame. Since there’s not EGC and neutral bond and it’s not physically grounded.Any possibly way to still shock?
Click to expand...

For a small system such as a home, with an 'ungrounded' supply, a single fault has very little chance of causing a shock. Basically if you have an ungrounded system, the shock path must be from the fault, through the person, and then via _capacitive coupling_ back to the source. For a small system the capacitance is small, so this shock path is not very large. This is exactly the reasoning for operating room isolated power systems.

The big problem is the risk of undetected faults, because the second fault is what will get someone or cause problems. In a grounded system the first fault would trip a breaker.

-Jon
 
winnie said:
For a small system such as a home, with an 'ungrounded' supply, a single fault has very little chance of causing a shock. Basically if you have an ungrounded system, the shock path must be from the fault, through the person, and then via _capacitive coupling_ back to the source. For a small system the capacitance is small, so this shock path is not very large. This is exactly the reasoning for operating room isolated power systems.

The big problem is the risk of undetected faults, because the second fault is what will get someone or cause problems. In a grounded system the first fault would trip a breaker.

-Jon
Click to expand...
Thanks, I didn’t believe it could from my point of view. But I do need to study up on capacitive coupling to have a better understanding of it.
 
tom baker said:
A unbonded, or floating neutral generator uses a trans switch that does not transfer the neutral. The reason is to avoid objectionable current. More practically, if the generator has GFCI on the outlets, as required, the gfci will trip when it sees the MBJ at the service panel.
Click to expand...

? I had hooked up a bonded generator, it did not trip gfci. Unbonded the generator, it did not trip gfci. ??

shortcircuit2 said:
I'm trying to understand how a GFCI will work on a fault to ground on a unbonded generator... 445.20(A)? I guess it will only work if the fault involves the neutral also. A fault to ground has no path like Tom stated.
Click to expand...

Don't we install gfci's when there is no egc at outlet location? I mean Gfci's measure load out of device and returning back through device. ???
Am I missing something?
 
I don't condone creating objectionable current by hooking up a bonded generator to a bonded service. BUT MAYBE... just in this case it would be acceptable and exemptions for use, insulated ground conductor, warning labels. It's not that way but Just a thought..
 
I think ActionDave has a good point.

If the generator neutral is bonded and not switched, then there will be a parallel neutral bonding path. Neutral current from the generator will find a parallel path on the generator EGC.

But for small residential generators the EGC is quite similar in size to the neutral. For 30A circuits the neutral and EGC are probably both #10, and for 50A probably #8 and #10.

This is a violation but probably only a small hazard.

If the generator output has a GFCI then this parallel path on the EGC will trip it.

Jon
 
ActionDave said:
I think there is tons of misplaced worry and hand wringing about this. There is more objectionable current flowing on metal parts of a properly wired, code approved service when the house is using utility power than there is on the rubber cord feeding the power inlet when using a temp generator.
Click to expand...
Understood. But what gets a green sticker? Thank you all.
 
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