Automatic Transfer Unit (ATU) w Portable Generator

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W4MSL

Member
Location
Georgia
Occupation
Retired
Generac SALES advised me that, though not specifically INTENDED for this purpose, that a whole-house capable ATU could be configured to accept input power from a PORTABLE generator (which obviously could NOT power an entire house). This would require that the ATU be placed in MANUAL mode, as a portable generator will not respond to a signal as would a standby unit. The unneeded house circuits would also have to be manually disengaged at the breaker box to prevent potential overload of a lower capacity generator.

Why would I want to do this? Because I want to be able, if and when needed, to use the same ATU if I decide to purchase a whole-house stby generator. I'd prefer to avoid having to purchase and then replace a manual transfer unit in that case.

Is there any reason to think that this can be done within code (Georgia) and in a manner which is reversible (if/when I need a stby generator)? And would not compromise warranty coverage for either the ATU or the stby generator?
 

PhenixFord

Member
Location
Cabot, AR.
Occupation
Industrial Systems and Controls
Right or wrong, here are my thoughts.

I don't think that there would be a problem installing the ATU without a back-up power supply (with plans for future completion of the project)? As long as the ATU is installed correctly, this would not be any different than what you already have? Even if the ATU actuated with "loss of power", you would still be dead. However, once you get past that point in the discussion, the possibility of problems could be endless. I haven't really studied the reg's associated with this area. The only thing that comes to mind are the reg's on the service matching the distribution. Also, I'm sure that your homeowners insurance would have a thing or two to say about this installation too? So I would go ahead with the plans for the ATU. But after that - your on your own.
 

W4MSL

Member
Location
Georgia
Occupation
Retired
Agreed. I suspected it was a cockamamie idea, but it was worth asking to have my suspicion onfirmed. Sounds as if I'm well-advised to put in the appropriate TU for the portable generator, and expect to upgrade everything if necessary to go w a stby unit. Thanks.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I don't see an issue with this install. It is alot easy to upgrade later so why not do it if you have the money for it
 

W4MSL

Member
Location
Georgia
Occupation
Retired
Thanks. Nice to get different opinions. Sounds as if you would be willing to pull permits for such a job and get it through an inspection. Maybe there are contractors in GA with the same confidence and expertise. If you can get that approved in CH, it should be possible here. Would placing the ATU into manual mode absolutely guarantee that output from the portable generator could not feed back into the power co grid? And, are you aware of any actual situations where this has been done, meeting code and inspection requirements? I'm NOT making this a DIY project, btw.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
There's no issue with an idle ATS, except for expense. If the question involves a new service, it's better to do it now.

An Interlockkit is more economical for an existing installation, especially if the ATS is an unsure thing.
 
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