Reddit reviews Camco 02363, Silver/Pewter
We found 1 Reddit comments about Camco 02363, Silver/Pewter. Here are the top ones, ranked by their Reddit score.
High Watt Density heating element240V/5500WUL ListedEasy to InstallMinimum tank diameter 11"
Going that route you always have the option of easily adding an MPPT controller if you find you need more heat.
Just eyeballing an IV curve for a similar panel and applying 3 series 2 parallel, you probably want a heating element resistance of 8-15 ohms to maximize power, depending on solar irradiance. 10 seems like a decent compromise. The 120V, 1500W is close to this at 9.6 ohms. Another option is a 240V, 5500W (10.5 ohms) element which is readily available and would alleviate your concerns of burning out the element.
https://www.amazon.com/Camco-02363-Screw-Foldback-Element/dp/B0006IX8AK/ref=mp_s_a_1_5?crid=250KCI9AZDCMP&keywords=5500w+240v+water+heater+element&qid=1551025629&s=gateway&sprefix=5500w+&sr=8-5
Edit: Even though the 2x3 panel array can exceed 120Voc, it won't burn out the element because the load would drag the voltage down to the intersection of the IV curve and the straight line resistance. Solar panel voltage drops under Voc as soon as you start drawing current from it.