Can someone please talk me out of using convoluted copper for a HERMS build?
I am planning a E-HERMS build using an inverted keg as a bottom draining tank. I do not have 240V access, so I will be using two separate 120v, 20A lines to heat the water and a single line to regulate the temperature. I currently do not have a second pump to stir the HLT/HERMS, but I will be using an air pump to avoid stratification.
I would prefer a SS coil for ease of cleaning (and bling ), but the cost for 1/2" and difficulty in forming has me leaning towards copper. I will only have one 120V line on a pid to regulate the temperature, so the smaller I can keep the thermal mass the easier/faster it will be for me to ramp my mash temperatures. My concern is if 25 ft of copper (in an appropriate amount of water to cover the coil) heated with 2k watts is enough to ramp temperatures in my mash.
Can anyone confirm if 25ft of 1/2" copper is enough HX area for 5 gal batches with the occasional 10 gal?
Anyone with experience with the convoluted copper? Would 25ft of 5/8" give me the heat transfer equivalent of 50ft? If so, it seems using the convoluted copper would allow me to use a smaller thermal mass in the HLT which would make it easier for me to ramp. The disadvantage is that I am dropping some serious cash and still won't be able to clean like I would if I dropped that cash on SS.
If I am willing to drop 170$ (gulp) on 25ft of copper, should I just buy 50ft of SS and never have to worry about upgrading again? Would one 2k watt element have enough juice to regulate the temperature for that much mass (enough water to cover 50ft)? Otherwise I will need to buy another SSR and have both run simultaneously. This might also require another circuit as I will have a pump running for constant re-circulation of the mash.
If I do end up needing a second pump, it seems that I should just buy a convoluted counter flow chiller and do my heat transfer there. Perhaps put a heater element inline to control the temperature...
Also, while I have your attention. Where are people placing the temperature probes for PID control? Outlet of the the HERMS coil? in the body of the HLT? I will definitively have temperature reading in both places, but which one should drive the PID?