TKing92
Licensed Master Electrician
- Location
- Southeast Iowa
- Occupation
- Electrician, Solar Focused
(Apologies ahead of time. I already posted this in "Electrical Calculations / Engineering" and was recommended to post here for more insight.)
I'll try to keep this short. I've been installing solar for 8 years and have always followed a specific rule that has always been hearsay without representation in all my training. Apologies if this seems obvious.
For this example, I'm installing a 200A Fusible disconnect which will be fused to 150A, and is being fed directly from a 400A CT cabinet. When running conductors to the line side of this equipment, is it mandatory that the wire be sized to the equipment potential of 200A, or is it possible to size just to the 150A potential given that the fusing will prevent more than 150A on these conductors? I've always installed with the idea that too much isn't too much, but I've also never found this in the code book. For more insight, the inverters installed are rated for a total of 104.2A before calculating for the 125% rule.
[LC]---[200A Disco (150A)]*---*[400A CT]
Given that these are service entrance conductors, I've tried referring to 230.42, and (A) states: "Service-entrance conductors shall have an ampacity of not less than the maximum load to be served." then (1) states: "...the minimum service-entrance conductor size shall have an ampacity not less than the sum of the noncontinuous loads plus 125 percent of continuous loads." This speaks 150A to me, but I figured asking for insight can't hurt when the risk is reinstallation or damage. Always something to learn, it seems.
Thanks!
I'll try to keep this short. I've been installing solar for 8 years and have always followed a specific rule that has always been hearsay without representation in all my training. Apologies if this seems obvious.
For this example, I'm installing a 200A Fusible disconnect which will be fused to 150A, and is being fed directly from a 400A CT cabinet. When running conductors to the line side of this equipment, is it mandatory that the wire be sized to the equipment potential of 200A, or is it possible to size just to the 150A potential given that the fusing will prevent more than 150A on these conductors? I've always installed with the idea that too much isn't too much, but I've also never found this in the code book. For more insight, the inverters installed are rated for a total of 104.2A before calculating for the 125% rule.
[LC]---[200A Disco (150A)]*---*[400A CT]
Given that these are service entrance conductors, I've tried referring to 230.42, and (A) states: "Service-entrance conductors shall have an ampacity of not less than the maximum load to be served." then (1) states: "...the minimum service-entrance conductor size shall have an ampacity not less than the sum of the noncontinuous loads plus 125 percent of continuous loads." This speaks 150A to me, but I figured asking for insight can't hurt when the risk is reinstallation or damage. Always something to learn, it seems.
Thanks!