is the heatloss significant enough to warrant insulating a rims tube/system?
I don't really know at this point, but I don't think that it could hurt to insulate it. The RIMS tube should be able enough to have the exiting wort be at any temperature that you want it to be. It would seem to me that the less heat loss from the exit of the mash tun to the RIMS unit (and including the RIMS shell) would mean that the RIMS element would be on less. And that would be a good thing.
I have four temperature zones with my RIMS, and I think that this would be true with any RIMS or HERMS, but the variance between them would be defined by each set-up. The top of the MT, the mid-to-bottom of the MT, the entrance if the RIMS/Herms and the exit of the RIMS/Herms. I want to try and keep all zones as close as possible.
In my case since I use a grant I'll have more heat loss going into my heat exchanger than others who don't use one. The wort in my grant seems to be 4-6 degrees below that of the grain bed. The RIMS PID has a +4 degree bump and I might need to bump that up. BUT,my last batch (Saison)had wheat malt which slowed the sparge flow which in turn seems to had made the temperature gaps worse. That was my second run, the first was an IPA where I recirculated almost wide open. My system seemed more efficient then.
What does all of this mean towards making good beer? I don't really have a clue. I imagine as long as you don't scorch the wort and get proper conversion that is all good. I know that I have a much more stable and regulate-able (is that a word?) mash bed than when I didn't have the RIMS.
I just want to keep everything as tight as possible. If I'm worried about what I'm doing to the enzymes I could probably and very easily just throw in a handful of base malt every 15 minutes or so.
sorry for the rambling, cheers