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Yes, I didn't even think about that. :sad:
I personally am not that concerned about the what-if. But it would be a relatively easy thing to check now that we know about it. With the mains off, check for continuity between the panels at the load side of each main. Well, that might still ring due to the neutrals being tied. So continuity isn't the right check. Resistance. There should a high resistance. If it is close to zero, then there is a direct tie.
 

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Can't Remember
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If you had two interlocks, one interlock and one panel not backed up, or a selected circuit panel, my guess would be if you see voltage at the main when the generator is running, then you have what Hack describes.
 

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Yeah, you're right. Even a typical 6 circuit transfer switch has the ability to do what I said.

Forget I said anything, I am so stupid :sad:
 

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Can't Remember
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No, I've never given that much thought so it may be something worth checking next time I install one.
 

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Hackenschmidt
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@HackWork, those Reliance PowerBack! alerts you install would help with this... did you ever have one go off on a backfeed?
 

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Super Moderator Beam Me Up Scotty
Elechicken
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Yeah, you're right. Even a typical 6 circuit transfer switch has the ability to do what I said.



Forget I said anything, I am so stupid :sad:
You could get an ATS and feed a small sub panel. You'd have to hack some of the wiring on it so that it'll shut off the generator power if it sees any power on the utility side (as opposed to if it sees one leg it'll transfer to generator power.)...

I guess you could use 2 contactors with 120 volt coils with double pose double throw. Wire one phase to one contact and the other phase to the other contactor. Wire the generator into one contactor, then the next (contactor in series). Then if there's a hot connected to a non-generator circuit the contactor will open the generator power cutting the power... except it would cycle continuously... but you'd know it's backfeeding and you'd have to identify the wrong joint and fix it. Then it should work fine.

This is a lot of work, just sell a 400 amp transfer switch

Sent from my SM-G920W8 using Tapatalk
 

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I have a customer that wants to do the same thing, run a 320A/dual 200 service with a portable generator. Instead, I gave him a price on a standby 25KW natural gas generator with dual 200A, service entrance rated transfer switch. He hasn't decided yet.
The problem with a portable generator is, most are not rated for computer, electronics and circuit board use, and they're loud. The potable Honda EU7000iS is a good choice but costs almost $5,000. Another problem is gasoline storage.
For a $5,600, I can purchase both the 25KW and transfer switch.
I know this is an ancient topic but I have a similar situation. 320a, 1ph 240v service and a 16.5kw propane Generac. I’m Set up with 1 ea 200amp panel and 2 ea 150amp panels. Want to split out to all 3 loads.
can you tell me what equipment you used for switching and a simple diagram if exists.
thanks in advance for any help.
 

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Either a small 6 place outdoor breaker box, or inlet -> splice box -> 3x interlocks.

If you're worried about the back feed issue above, turn off panel b and c, with A still on, check for power at each breaker. Turn off A, on B, check again. Off with b, on with C final check.
 

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Super Moderator Beam Me Up Scotty
Elechicken
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I know this is an ancient topic but I have a similar situation. 320a, 1ph 240v service and a 16.5kw propane Generac. I’m Set up with 1 ea 200amp panel and 2 ea 150amp panels. Want to split out to all 3 loads.
can you tell me what equipment you used for switching and a simple diagram if exists.
thanks in advance for any help.
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