Multiple inline fuses on 1 Disconnect

[solartrenches]

Is it permissible to have 3 string inverters with integrated AC disconnects located on a roof, and parallel those 3 circuits using inline fusing at a tap point in a separate enclosure off the roof with the main feeder connecting to a singe fused service disconnect at the point of interconnection?

The idea is that since the inverters already have integrated AC disconnects, can the secondary fused disconnects at the tap point be removed and just install inline fuses in their place?

Does 240.40 permit this or are their exceptions that do?

Has anyone seen this done before?

Thanks,
ST

 

[jaggedben]

I've never seen it done.

I don't see a problem with 240.

I'm not quite sure if I think that each inverter has a dedicated disconnect and overcurrent device per 705.12 (D)(1). But I'm also not sure if I think it's required or if they are all one 'source.'

Finally, it's been a few years since most inverter manufacturers actually included an AC integrated disconnect; most are just DC now. So I'd want to double check that if I were signing off on this.

 

[ggunn]

I've never seen it done.

I don't see a problem with 240.

I'm not quite sure if I think that each inverter has a dedicated disconnect and overcurrent device per 705.12 (D)(1). But I'm also not sure if I think it's required or if they are all one 'source.'

Finally, it's been a few years since most inverter manufacturers actually included an AC integrated disconnect; most are just DC now. So I'd want to double check that if I were signing off on this.

For one thing, an OCPD at the inverter would be useless; inverter AC output conductors need to be protected at the service end. Fault current comes from the service.

As to the OP's question, whether or not it would be a violation, I have never seen it done and would never do it myself.

 

[Carultch]

Is it permissible to have 3 string inverters with integrated AC disconnects located on a roof, and parallel those 3 circuits using inline fusing at a tap point in a separate enclosure off the roof with the main feeder connecting to a singe fused service disconnect at the point of interconnection?

The idea is that since the inverters already have integrated AC disconnects, can the secondary fused disconnects at the tap point be removed and just install inline fuses in their place?

Does 240.40 permit this or are their exceptions that do?

Has anyone seen this done before?

Thanks,
ST

Are your inverters connected phase-to-phase, or phase-to-neutral?
Are your inverters single phase or three phase?

I've seen three single phase inverters "parallelled" in a fusible disconnect, when the inverters were connected phase-to-neutral.

Any other configuration, and I'd strongly recommend using a panelboard for combining.


In 240.21, if you are using the outside unlimited tap rule, the overcurrent device needs to be an integral part of the disconnect, or immediately adjacent thereto. The other tap rules have length limitations.