mnlara
Member
- Location
- Oakland,California
Can any one provide me with the exact formula to calculate what breaker size to use for any inverter of a PV System. Was it ((inverter size x efficiency rating) / operating voltage x 1.73) x 1.25)
PV Inverter Breaker size Calculation to be used at service panel
- Thread starter mnlara
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Typically it is: OCP-rating ≥ inverter continuous output current rating ? 125% (excluding stand-alone systems), contingent on conductor ampacity
SIRSPARKSALOT
Member
- Location
- Northern NJ
[kw/(V*1.732)]*1.25
I don't think efficiency comes into play.
The breaker and feeder must be sized for the full rating of the inverter. Even if you have a 500kW inverter with 250kWDC feeding it, you must wire at the full rating.
You can double check yourself by referring to the inverter cut sheet. It will tell you the output ampacity.
I don't think efficiency comes into play.
The breaker and feeder must be sized for the full rating of the inverter. Even if you have a 500kW inverter with 250kWDC feeding it, you must wire at the full rating.
You can double check yourself by referring to the inverter cut sheet. It will tell you the output ampacity.
Yes. All of the above.
1.
Eff. does not matter.
That is because the inverter size (wattage) is rated at the AC output power the inv. can deliver, not input DC watts.
2.
Fine point:
Use max cont. amps of inv. if provided by mfctr.
If not, then: Inv. W / 240 VAC (or relevant AC V) gives you the above.
In either case, always multiply by 125%.
using the cont amp rating can save you from needing larger breakers than otherwise necessary in some cases. It is also the right way to do it.
1.
Eff. does not matter.
That is because the inverter size (wattage) is rated at the AC output power the inv. can deliver, not input DC watts.
2.
Fine point:
Use max cont. amps of inv. if provided by mfctr.
If not, then: Inv. W / 240 VAC (or relevant AC V) gives you the above.
In either case, always multiply by 125%.
using the cont amp rating can save you from needing larger breakers than otherwise necessary in some cases. It is also the right way to do it.
mnlara
Member
- Location
- Oakland,California
sample SMA SB3000-US (240V) inverter
[(3000 * 96%)/(240V * 1.73)] * 1.25 = 8.67 A approx.
thus use 15A or 20A breakers?
[(3000 * 96%)/(240V * 1.73)] * 1.25 = 8.67 A approx.
thus use 15A or 20A breakers?
Spec's say 13A maximum AC output current operating at 240V.
13A ? 125% = 16.25A
Minimum standard breaker rating 20A. Minimum 12AWG conductor required.
Last edited:
mnlara
Member
- Location
- Oakland,California
Thank you.
WizBandit
Member
Breaker size requirement
Breaker size requirement
Check the installation instructions first. A lot of the time for Grid-Tied Inverters less than 10Kw the manufacturer will dictate the breaker size which shall be used. Then the only thing you need to calculate is wire size and voltage drop.
Breaker size requirement
Check the installation instructions first. A lot of the time for Grid-Tied Inverters less than 10Kw the manufacturer will dictate the breaker size which shall be used. Then the only thing you need to calculate is wire size and voltage drop.
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