Sizing Meter Socket for Grid Tie PV System

[ACDCBag420]

Im installing a couple of schneider multi mode inverters that are going to have an inverter output circuit connected to a 125 amp breaker in the main distribution panel. This circuit is going to be run outside and will include two enclosures one for the ac system disconnect and the the other for the gross production meters. The inverters inputs are both 60 amps so the circuit will have a full load current of 120 amps. Would I be able to use a 125 amp meter socket for this instalation or would I need to apply the 125 percent rule and use a 150 amp socket? sizing the disconnect was much easier, manufacturers seem to only make 100 amp or 200 amp rated disconects.

 

[jaggedben]

You need to multiply the inverter continuous output current by 125A. So if the output spec is 60A each, you need a 150A or greater meter bank. If the inverter outputs are actually 48A each, requiring a 60A circuit each (48A×1.25), then 125A is fine.

 

[ACDCBag420]

so the inverters can only backfeed or sell 25 amps a piece. So if these were grid tie inverters the inverter output circuit would be (25 x 1.25) x 2 = 62.5 amps. Thats all fine and that is actually the amount of selling amps these multi mode inverters will produce but the 60 amp breakers that accommodate the inverters ac connection also supply the battery charger and provide power the the critical loads sub panel. So without over thinking it the 125 percent rule for the inverter output circuits applies to the full load of the circuit regardless of what percentage of the power in that circuit are for selling. I guess while I have some feedback, these inveters are a bit confusing. they have a 12000 watt surge. on the spec sheet they give you a 6000 watt continuous output, but then also included is a 52 amp max output and thats sustained for one minute. I am getting a main lug only sub panel. Would I want to size this for 125 amps, that would more than cover the continuouse output rating and also is off by the max output 1 minute surge by 5 amps. I guess my guestion is why do they give the continuous rating in watts and the max output in amps and should I use the continuous output or max output for my panel sizing. Of course for sizing conductors i am using the max output rating.

 

[wwhitney]

705.60(A) clarifies that what matters is the maximum current the inverters can output. If that is 25A per inverter, with 2 inverters, then the relevant computations involve 125% * 2 * 25A.

Also, I think the 125A rating of the meter base is a continuous rating? Not sure on that.

Cheers, Wayne

 

[ACDCBag420]

yes that would make sense, thanks for the insight.

 

[ggunn]

One AHJ we deal with requires the capacity of the PV meter to be equal to or greater than the rating of the PV AC disconnect, not the rating of the installed fuses.