Did I get the panels I paid for?

solarnewbie440

Hi: My first post!!! New install: I am supposed to have 435 watt panels, but the data logger shows as the total as tho they were each 425 watts. Could this be that because the house faces SSE, so that the panels face the sun at SSW, accounting for the slight loss? Or did I not get the 435 watt panels? Looked for a sticker on the backside with a mirror but did not see any, tho I do not want to lift one up to give a thorough look for obvious reasons.
I don't want to hassle the installer unless the answer is obvious. Reading was 1 PM full sun: 0.367kw average per panel.
Thanks for your help and excuse my ignorance.

Photowhit

solarnewbie440 said:

Hi: My first post!!! New install: I am supposed to have 435 watt panels, but the data logger shows as the total as tho they were each 425 watts. 

I don't know what the 'data logger' is, but would think the info would have to be manually entered.

solarnewbie440 said:

I don't want to hassle the installer unless the answer is obvious. Reading was 1 PM full sun: 0.367kw average per panel.

This is fine. Panels are rated in a 'flash' test (Standard Test Conditions, STC) and not allowed to warm up. There is also a Normal Operating Cell Temperature NOCT value which is typically about 75% of the STC. So 367/435 = about 84%, Which is very good.

BB.

As Photowhit says--Those are basically "marketing" numbers. As cells get hot, their Vmp (voltage maximum power) falls. Pmp=Vmp*Imp -- Imp changes a little (actually rises a bit as panels heat up)--But the change is small enough that we normally ignore Imp-Hot/Cold changes.

Here is a thread that talks about how solar panels "work" in our systems:

https://forum.solar-electric.com/discussion/5458/two-strings-in-parallel-with-unequal-string-voltages

-Bill

solarnewbie440

Hello: The data logger (PSV6) is an interface that connects to the L1 and L2 cables in main breaker box & elsewhere to provide info on the voltages being used, how much is being generated by the solar system, and how much comes/goes from or to the utility that you read out on their app. I did notice on the contract specs that the system is rated 3.92KWp (DC), while the output is shown as peak AC output of 3.34KWp, so maybe it's just semantics. Panels are Maxeon gen 6, hopefully M435's, and not M425's.
Thanks, I appreciate your input.

petertearai

The ability to detect real world differences between 435 and 425 panels will be difficult .