single phase Generator hook up to a 3 phase panel

[Shine Your Light]

Would any inspector pass a 7 kw 120 /240 portable generator with a 10 circuit transfer switch into a 3 phase panel. There would not be any 3 phase branch circuits hooked up inside the main panel through the transfer switch. Just curious ..

 

[Bigrig]

From a designer

From a designer

I know that the engineering firm I work for recently designed a building at 208Y/120V-3ph with a single 120/240V-1ph (technically 120/208V-1ph) panel served from a single phase transfer switch and 120/240V generator. This was due to the client wanting to utilize a generator to provide power for several small medical refrigerators. We did not have any AHJ issues, just issues regarding the ATS. There was concern that the ATS originally submitted for review would never switch back from generator to normal power. This was due to the 240V ATS not sensing a sufficiently high voltage on the normal utility. The supplier went to a slightly more expensive but infinitely more adjustable ATS to allow the setpoints to be set for the 208V normal service.

 

[texie]

I know that the engineering firm I work for recently designed a building at 208Y/120V-3ph with a single 120/240V-1ph (technically 120/208V-1ph) panel served from a single phase transfer switch and 120/240V generator. This was due to the client wanting to utilize a generator to provide power for several small medical refrigerators. We did not have any AHJ issues, just issues regarding the ATS. There was concern that the ATS originally submitted for review would never switch back from generator to normal power. This was due to the 240V ATS not sensing a sufficiently high voltage on the normal utility. The supplier went to a slightly more expensive but infinitely more adjustable ATS to allow the setpoints to be set for the 208V normal service.

You make valid comments. In the OP case, I think if it is an existing installation and he is adding an optional standby system there may be issues with the original wiring haveing MWBC's based on the original 3 phase system. If he can work around that, I don't think there is anything wrong with the proposed system.

 

[hillbilly1]

I know that the engineering firm I work for recently designed a building at 208Y/120V-3ph with a single 120/240V-1ph (technically 120/208V-1ph) panel served from a single phase transfer switch and 120/240V generator. This was due to the client wanting to utilize a generator to provide power for several small medical refrigerators. We did not have any AHJ issues, just issues regarding the ATS. There was concern that the ATS originally submitted for review would never switch back from generator to normal power. This was due to the 240V ATS not sensing a sufficiently high voltage on the normal utility. The supplier went to a slightly more expensive but infinitely more adjustable ATS to allow the setpoints to be set for the 208V normal service.

I've done a couple that way using a Generac generator and automatic t-switch and had that same concern, but Generac apparently has a wide threshold on the incoming voltage that I did not have any issues with their standard transferswitch. I think the OP is using a manual switch, so there shouldn't be any issues.

 

[raludovico]

So do we say it is possible for a single phase generator to supply power to a 120 208 3 phase system through a 3-phase transfer switch ( of course not expecting 3 phase power in emergency mode).

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[Bigrig]

So do we say it is possible for a single phase generator to supply power to a 120 208 3 phase system through a 3-phase transfer switch ( of course not expecting 3 phase power in emergency mode).

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I would recommend using a dedicated single-phase sub-panel served by a single-phase transfer switch. You do NOT want someone a few years down the road putting 3-phase loads into a panel that will go single-phase when on emergency power. No matter how well it may be labeled accidents happen.