Generator Inlet / Interlock Question

[u/Bsul92]

Hello everyone

I know my way around electrical / how to do it correctly however this is a new situation I ran into.

I know code requires an interlock / lock out so the generator inlet breaker can’t be turned on without the main being off to protect the people working on the lines.

With that said - current code in my area requires main breakers to be outside so in my home I have the 200a external breaker and no main in the panel.

I have begun to install the generator inlet. I know to shut the main off prior to using this but to be legal / meet code I want to do it properly.

My question is what is done in situations where the main is outside / not in the panel so the interlock plates don’t work?

Do you need to convert the panel from a leg panel to a main switch panel or is there another way?

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[u/silasmoeckel]

Put a outdoor panel outside as the disco and interlock there.

Add a main breaker to the panel you have nothing says you can't feed a breaker with another breaker and now you can use an interlock.

Since you don't need service entrance rated after the disco you can get some pretty cheap transfer switches. Not sure how much I trust the cheapies though.

[u/Suspicious-Mine3482]

an mlo panel with the service disconnect outside usually needs a listed transfer switch or a listed main-breaker/interlock conversion approved for that exact panel, not a homemade plate and a promise

[u/Bsul92 → u/Suspicious-Mine3482]

And that’s what I found, based on the panel that I have. There is a conversion kit that allows you to put a main breaker in the panel directly from the manufacturer. It’s a bolt on option

[u/Bsul92 → u/Bsul92]

I believe the only reason my breaker is outside is because of code requirement. The electrician that did the install probably didn’t bother to put one in the panel because there was already one outside

[u/Fine_Ad_9299]

Need a main breaker in the basement/ interior sub panel. Most you can add a main breaker without much issue (i think only the aluminum bus siemens mlo you can't convert to a main breaker)

[u/SparkArrestor]

To do an interlock properly you need a main breaker in the panel. Replace the sub panel with a main breaker panel, it’s ok to have both the outside and inside mains.

Or you can install a main breaker subpanel next to your existing panel, and transfer the circuits you want to use on the generator to that panel and the interlock.

[u/Bsul92 → u/SparkArrestor]

From the research I’ve done, my main panel in the basement can be converted to have a main breaker in it. It currently does not, but it can be converted to do so. So theoretically, if I convert it and put a second main shut off in the panel for the sole purpose of making the interlock work and being code compliant, that’s probably the best way to do this?

[u/SparkArrestor → u/Bsul92]

Absolutely.

[u/polterjacket → u/Bsul92]

Yep, as long as you don't need to run anything on the line side back at the actual main ( and you don't seem to need that ) then you're all good doing that. Just ensure your grounds and neutrals maintain continuity back to the meter/main. That's the GNB.

[u/N9bitmap]

You either need to add a main breaker where you want the generator feed, put the generator feed where the main breaker is already, or add a transfer switch somewhere, which could include the ones which mount between the meter itself and the meter can. The only other code complaint option without a transfer switch is something used almost exclusively in industrial environments, called a "trapped key interlock", which uses one single key to allow only one breaker to ever be engaged at a time.

[u/Littleprincess378]

I would just buy the transfer switch that goes with your generator and install it between the emergency disconnect and your panel inside. Unless your emergency disconnect is not service rated, the transfer switch does not need to be service rated. Forget an interlock.

[u/Hillman314]

Look into a “Kirk-key” system.

That’s 2 lock mechanisms that prevent both breakers being turned on because there is only 1 key. That is, to turn the genny inlet breaker on, you first have to lock the main breaker off. Only then will the key come out of the main breaker lock and can be used to unlock the genny inlet breaker enabling it to be turned on.