Neal30
Member
- Location
- Gainesville, ga, USA
We are going through some design scenarios. One of our electricians has brought up the method of interconnecting multiple 28KW string inverters on one circuit, utilizing taps and no individual OCPD's for inverters. The basic design that I feel more comfortable with, involves landing each inverter on a 3 pole breaker inside a 200A panel, then running back to a 200 A fused disconnect. There are costs associated with the panelboard and breakers, but I am just not 100% that they are interpreting this tap rule correctly.
A basic design layout below:
Option #1
28 KW String inverter Max AC Current 39 Amps, 480V wye output. We are installing about 24 of these inverters, my thought is to put 4 inverters, each on a 3 pole 50A breaker, into a 200 A panel board, and then to a 200 A fused disconnect, then connecting to the transformer.
(6 times)
Option #2
28 KW String inverter Max AC Current 39 Amps, 480V wye output. Proposed connecting 4 inverters via a tap connection using a polaris lug in a tap box, or some type of direct burial rated tap underground. They are thinking that we would not need any OCPD on each inverter, due to the tap rule. The entire circuit of 4 inverters would be protected by a 3 pole 200 A fused disconnect, then connected to the transformer.
I would like to get some insight from an industrial or commercial standpoint, my gut feeling says that if there was a short in the inverter, then the full load up to 200 A from the utility and up to 117 Amps from the other three inverters (39x3) would be available on those tap wires.
These inverters have integrated AC and DC disconnects, the DC strings are fused internally in the inverter. There is no internal AC OCPD in the inverters.
Thanks for your time, any insight is appreciated.
A basic design layout below:
Option #1
28 KW String inverter Max AC Current 39 Amps, 480V wye output. We are installing about 24 of these inverters, my thought is to put 4 inverters, each on a 3 pole 50A breaker, into a 200 A panel board, and then to a 200 A fused disconnect, then connecting to the transformer.
(6 times)
Option #2
28 KW String inverter Max AC Current 39 Amps, 480V wye output. Proposed connecting 4 inverters via a tap connection using a polaris lug in a tap box, or some type of direct burial rated tap underground. They are thinking that we would not need any OCPD on each inverter, due to the tap rule. The entire circuit of 4 inverters would be protected by a 3 pole 200 A fused disconnect, then connected to the transformer.
I would like to get some insight from an industrial or commercial standpoint, my gut feeling says that if there was a short in the inverter, then the full load up to 200 A from the utility and up to 117 Amps from the other three inverters (39x3) would be available on those tap wires.
These inverters have integrated AC and DC disconnects, the DC strings are fused internally in the inverter. There is no internal AC OCPD in the inverters.
Thanks for your time, any insight is appreciated.