svetz
Works in theory! Practice? That's something else
Have the same microinverters randomly turning off for 5 minutes every so often? It so, it might be a Voltage Rise design issue in your setup. This thread explains the problem and some quick fixes.
Symptoms
The same microinverters turn off randomly multiple times per day.
General Causes
Microinverters are set to anti-islanding, so if the voltage/phase detection goes outside of some fairly tight bounds they shut down for 5 minutes. The usual causes are:
From the table, the maximum current for 11 IQ7+s in a branch circuit is 13.3 amps. From that a voltage drop calculator shows that .26% is the voltage drop from 20' or 6 AWG (~40 amps), .22% is the voltage drop from the longest run of 20' of 10 AWG, and .86 is from the Enphase table for 11 microinverters. The total of 1.34% is less than 2%, so it's a good design.
Quick Fixes
Increasing the gauge of the homerun wiring reduces the voltage drop, another solution is to use a center-fed configuration:
Here, the maximum resistance from the Q-Cables is .12% from the table and the design works. Note that without the center-fed design 1.25% + .26% + .86% exceeds a 2% voltage rise.
Symptoms
The same microinverters turn off randomly multiple times per day.
General Causes
Microinverters are set to anti-islanding, so if the voltage/phase detection goes outside of some fairly tight bounds they shut down for 5 minutes. The usual causes are:
- Grid issues - when this occurs it's usually more than one, and typically not the same ones
- A bad microinverter - As a microinverter starts to fail it might not fail all at once, it may start producing harmonics or be slightly out phase that can negatively impact other microinverters.
- Voltage Rise - Typically occurs with the same inverters at the end of a cable run and is caused by resistance greater than 2% voltage drop.
It's not clear to me, but if your grid voltage is normally high, it might need to be even less than 2%. The table to the right is Enphase's 240V quide for IQ7+s. For other Enphase microinverters or more details, this link might help. For non-Enphase microinverters, I'm not sure how you'd measure the voltage rise. Here's an example of 3 runs of eleven IQ7+ microinverters: |
From the table, the maximum current for 11 IQ7+s in a branch circuit is 13.3 amps. From that a voltage drop calculator shows that .26% is the voltage drop from 20' or 6 AWG (~40 amps), .22% is the voltage drop from the longest run of 20' of 10 AWG, and .86 is from the Enphase table for 11 microinverters. The total of 1.34% is less than 2%, so it's a good design.
Quick Fixes
Increasing the gauge of the homerun wiring reduces the voltage drop, another solution is to use a center-fed configuration:
Here, the maximum resistance from the Q-Cables is .12% from the table and the design works. Note that without the center-fed design 1.25% + .26% + .86% exceeds a 2% voltage rise.
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