We have (14) sunny boy tl us single phase inverters,the original plans called for 3 phase inverters long story, but they got changed to single phase (note) this is a 208 3 phase grid.the original plans called for a 10amp 3 phase breaker for each of the 14 inverter never seen a 10 amp CKT breaker we just put 15 amp with 10 AWG wire , we jumped the gun and did not wait for the changed plans. new plans are calling for 40 amp 8 AWG wire for each inverter. Inverters will be drawing 28.8 amps X1.25 = 36. We already passed inspection with the single phase inverters with the original approved set of plans containing the 3 phase inverters, I'm thinking the inverters will never draw the max amps and if it did it would not be for very long, would it be a safety issue if I just put 30 amp ocpd for each inverter and not multiply by 1.25 thank you
1.25 percent
- Thread starter SAP
- Start date
- Status
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
What inverters only deliver 8A of current? Assuming such a thing exists, why would anyone design a system with 14 1.7kW inverters? This all looks too weird.
But no, the minimum OCPD you can put on an inverter output is 1.25X (not 1.25 percent) the nameplate maximum inverter current no matter what you anticipate its situational maximum output will be.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
:thumbsup:
You have to divorce that factor of 1.25 from the 1.25 multiplier for continuous loads. For one thing you have sources, not loads and the inverters supply current not draw it.
If the inverter is not overpaneled, it is not likely to deliver full nameplate current for three hours or more, but that is totally irrelevant to the code discussion.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Well, a microinverter circuit could. But the OP said they are SMA TL's, so yeah, the 'engineer' made a mistake. Then again, he said 28.8A which doesn't match any TL on the datasheet. My educated guess is that they are 6000W inverters and that the 'engineer' is incorrectly dividing 6000W by 208V (28.84amps) instead of using the datasheet output, which is 25A. Hence my putting 'engineer' in scare quotes.
I feel for the OP, it seems he's working for someone whose managing the project badly and he's asking if he can 'get by' with something that's really probably going to be safe and functional. I'll be honest, depending on how long the wire runs are I'd probably do what he's suggesting if it's not going to be inspected. Actually, 35A breakers would be a good compromise. The real current rating requirement is 31.25A (probably, if my assumptions are correct). It's almost code legit if you ignore the asterisks in table 310.15(B)(16).
Continuous load is 1.25 percent of the load, by multiplying the the loads rated amperage by 1.25
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
I would never do such a thing, and if I did I would never admit it in writing on an internet forum.
So we shall surmise you have done such a thing and are now openly denying it. :lol:I would never do such a thing, and if I did I would never admit it in writing on an internet forum.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
You may surmise anything you like and I have nothing to deny.
JK... so lighten up.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Oh, sorry, forgot the smiley. Here it is:JK... so lighten up.
- Status