diy solar

diy solar

Am I required to use a fused/breaker combiner box and where can I put it?

Since we are cutting it close, what is the lowest temp you want your SCC to handle? (As in survive)
Honestly, I don't think we got into single digits once this year. Would it be better to keep the inverter inside the house? The range inside the house is always 60-77 degrees F.
 
10F = -12.2C so 37.2C drop

46.81V x 37.2 deg drop x .0035= 6.1V increase
Temp compensated Voc 52.9V

550/52.9=10.4 panels
600/52.9=11.34 panels (the hard limit is 11)

11 x 37.2Vmp = 409V
At 77F a string of 11 in series will run at 409V

Is your panel Vmp really 37.2V?
that seems odd (low compared to Voc).
 
10F = -12.2C so 37.2C drop

46.81V x 37.2 deg drop x .0035= 6.1V increase
Temp compensated Voc 52.9V

550/52.9=10.4 panels
600/52.9=11.34 panels (the hard limit is 11)

11 x 37.2Vmp = 409V
At 77F a string of 11 in series will run at 409V

Is your panel Vmp really 37.2V?
that seems odd (low compared to Voc).
37.33 volts max power

1647906822274.png
 
So, if the outside temperature ever drops below 10F.
You'll need to keep the panels disconnected, until the sun warms them up. Or, risk ruining the charge controller.
 
If you connect a meter to the panel side of the disconnect, you'll know when it's safe to connect.
 
You would think the inverter would be designed to shut off when Volts peak to high.

The inverter doesn't see PV volts. The solar charge controller does.

The rule to never, ever violate is: PV output voltage must never exceed the Max PV Input Voltage of the solar charge controller.
 
The inverter doesn't see PV volts. The solar charge controller does.

The rule to never, ever violate is: PV output voltage must never exceed the Max PV Input Voltage of the solar charge controller.
It sounds like the ONLY real way to know, would be to wait for a really cold, full sun clear day and test the output with a voltage meter with the strings disconnected from the inverter. I honestly think that the online calculators are designed to play it too safe by suggesting far less panels than systems can handle. I've tried four different calculators, putting the same numbers in them, and I get 4 different results.
 
It sounds like the ONLY real way to know, would be to wait for a really cold, full sun clear day and test the output with a voltage meter with the strings disconnected from the inverter. I honestly think that the online calculators are designed to play it too safe by suggesting far less panels than systems can handle. I've tried four different calculators, putting the same numbers in them, and I get 4 different results.

The only calculator that mattered to me was the Victron one since I was buying a Victron solar charge controller. I camp at below 0° F temperatures, so I was very careful about ensuring my panels wouldn't fry my solar charge controllers.
 
In Raleigh, N.C., the lowest low in the last 3 years was:
Oct. 2021 +42F
Nov. 2021 +25F
Dec. 2021 +28F
Jan. 2022 +17F
Feb. 2022 +27F
Mar. 2022 +27

Oct. 2020 +48F
Nov. 2020 +29F
Dec. 2020 +24F
Jan. 2021 +25F
Feb. 2021 +23F
Mar. 2021 +25

Oct. 2019 +40F
Nov. 2019 +24F
Dec. 2019 +27F
Jan. 2020 +27F
Feb. 2020 +23F
Mar. 2020 +25F

Yeah, it could hit -5 degrees once every 36 years (that was the all-time low), but how rare is that? Honestly, I'd be comfortable planning for +15F and putting some kind of thermostat to shut down the DC current coming from the panels when it hits 20F, if there is such a thing. It makes zero sense to me to skimp on the number of solar panels to plan on a 36-year event to occur every year or very low lows that only occur every dozen years for one or two days a winter. Why not add the additional panels and put some kind of safety thermostat switch on the PV strings?
 
In Raleigh, N.C., the lowest low in the last 3 years was:
Oct. 2021 +42F
Nov. 2021 +25F
Dec. 2021 +28F
Jan. 2022 +17F
Feb. 2022 +27F
Mar. 2022 +27

Oct. 2020 +48F
Nov. 2020 +29F
Dec. 2020 +24F
Jan. 2021 +25F
Feb. 2021 +23F
Mar. 2021 +25

Oct. 2019 +40F
Nov. 2019 +24F
Dec. 2019 +27F
Jan. 2020 +27F
Feb. 2020 +23F
Mar. 2020 +25F

Yeah, it could hit -5 degrees once every 36 years (that was the all-time low), but how rare is that? Honestly, I'd be comfortable planning for +15F and putting some kind of thermostat to shut down the DC current coming from the panels when it hits 20F, if there is such a thing. It makes zero sense to me to skimp on the number of solar panels to plan on a 36-year event to occur every year or very low lows that only occur every dozen years for one or two days a winter. Why not add the additional panels and put some kind of safety thermostat switch on the PV strings?
I wouldn't worry about a 36 year low.
Just yearly, or biannual.
 
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