RIMS element for 240v controller

[WesBrew]

Aiming for a compact RIMS solution for 240v Brew Commander controller. I'll probably not go with a rims rocket (weird plug location and no thermowell). Likely to be used for big brews and10g brews where the mash tun is needed.
A 12" tube is too short, that leaves a 16 or 18 TC tube setup. Where should one be on watt density for the element? Is that simply calculated by watts/element length? It seems if I opt down on power to a 2500w, it gets shorter but with the above sketchy math, would be a little lower watt density.
I have a low watt density dernord 3500W foldback. Is this a non-issue for scorching or enzyme denaturing if I'm able to reduce power % to the element, assuming there is good flow and the temp probe located at the tube exit?

 

[Broken Crow]

You won't reach max power on a RIMS element (or at least you never should!) Opt for the one with the greatest surface area to distribute that power. Here's the best price I found on RIMS hardware; (*conditional):
https://www.aliexpress.com/item/1005006120679696.html?spm=a2g0o.store_pc_allItems_or_groupList.0.0.45a0430cllOVWw&pdp_npi=4@dis!CAD!C$ 99.33!C$ 99.33!!!70.99!70.99!@2103251f17157060156677130e9e03!12000035845553886!sh!CA!0!
..It includes a crap element (I saved mine for a heater for my keg-washer) but for the price you can easily ignore that and buy a proper element and enclosure; here's the best one you get:
https://www.brewhardware.com/product_p/element5500.htm
https://www.brewhardware.com/product_p/etc.htm
..it's a perfect fit especially if you have @Bobby_M include the offset..well worth it.
Also: It works best with and Auber DSPR320...will never scorch.

 

[Bobby_M]

The 3500 foldback is likely the lowest watt density you'll find and then you can fine tune it with the BC output power maximum setting. I'd set the max power by first selecting the desired output temperature, set your pump flow rate to 1.5 quarts per minute and then see how low of a power setting you can run while keeping the output temperature steady at the set point. Set the cycle time in the advanced menu to the lowest value possible, it's either 1 or 2 seconds but is defaulted to 6 and way too slow for RIMS.

 

[WesBrew]

Got it together last night. My Element fit perfect, no bending no touching. 50mm tw might be a bit short but works at the exit. Did a shakedown run with water, no element power. All good, no leaks.
Power test . 1sec cycle time, 30% power, 3 gallons of water. MT water temp rose from 87-97 in 14minutes, temp set to 100. Just an easy ramp for testing.
Maintained MT temp with +3.5 temp set. Theres some slight futzing with the flow to get the tube temp to hold steady but that only took a few seconds. Ive got some work to do on positioning, tube length, etc. this should be fun.

 

[WesBrew]

The flow was obviously throttled down prior to power testing