Why do east facing panels really outperform west facing?

softdown · October 14

Panels follow roof contours. House is not exactly south facing. Pretty close.

Southern array performs great except for summer months. Panels at 42 degrees to maximize winter production.

East and west panels at 10 degrees. Racks were included with main south facing racks. Free.

The west panels are simply 180 degrees from east panels.

I never get more than 8.5 amps from three 5.2 amp panels at high, sunny location. West Side disappointment.

37 degrees latitude.

JRHill · October 14

Temperature. Unless they are covered with ice or snow. Then they are about the same.

Miller_Ranch · October 14

Looks like you have plenty of room for a ground mount that faces south.

softdown · October 14

For several days I had not production from the westerly panels at all. Bad MC4 connection going to the wires going to the CC. Messed around with it and got power. But unsatisfactory power.

Could a poor hand made MC4 connection be lowering production by about 50% or so?

BB. · October 15

If 3x parallel wiring, then one bad connection will kill output by 50%.

In general, a bad connection will overheat, burn the connector, and or melt the contact housing.

Connectors don't have the ability to dissipate waste heat without damage (unless current flow is very low).

-Bill

softdown · October 16

BB. said:

If 3x parallel wiring, then one bad connection will kill output by 50%.
In general, a bad connection will overheat, burn the connector, and or melt the contact housing.
Connectors don't have the ability to dissipate waste heat without damage (unless current flow is very low).
-Bill

3X serial wiring. It does seem like production is at ~50%.

~126 volts.

I could point a remote thermometer gun at the connections I would think.

JRHill · October 16

This is frustrating. Are you too old to keep doing this stuff?

A thermo gun on a hot roof during production?

BB. · October 16

I do have a typo there... Intended to type 2x for 1 open connection giving you 50% harvest...

Since you have parallel connections... Open a breaker per string or cover a couple panels, etc.. and see how much the output drops per string.... They should all drop equally, if connections (and panels) are OK.

You could also get an AC+DC Current Clamp meter and measure the current of each string -- Again looking for equal current flow if all OK.

Lastly, how do you "know" that your output is down by 50%... From what I have seen over the years (with my Grid Tied System), the "nominal" current flow is proportional to amount of light hitting panels (pretty close to actual sun--i.e., if sun is down by 50% do to clouds, shading, etc., then current is down by equal amount).

Also, need to be more specific if your are 50% of Power (Watts=V*I), voltage, or current... Seeing 50% to 70% of Watts is pretty much standard derating from "Standard" to "real life" solar performance.

Parallel strings--Then variation in voltage can change current flow dramatically (I.e., 2x strings at "normal voltage" and one string with a bad panel/shading at less than normal, and current fall dramatically).

You have a battery based system... Also array harvest is based on on both available sun, and controller "needs" (battery state of charge, loading, etc.)... Obviously, this is not a "single variable" equation.

Which is why I suggest the per string measurements of current first (by shading or current clamp meter). If all are equal current (parallel strings to a single controller), then more than likely "all is normal".

If you have one poor performing string, then you need to do things like disconnect/shad the 2x good strings, and measure voltage/current of the poor performing string. Likely lower voltage is possibly a bad panel. Near zero voltage would be a bad connection, etc. Then per panel tests (voltage/current shorted/into test load, etc.). Again looking for comparison with "known good performing panel vs questionable panel").

-Bill

cleancurrent002 · October 17

That’s a pretty detailed setup! Sounds like you’ve optimized for winter performance nicely. Any plans to tweak the west array to boost output, or are you keeping it as-is for balance?

Why do east facing panels really outperform west facing?

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