240 V element. I recirculate at about 0.5 max while I stir in the grains with the heat off, then I throttle back to about 0.25 max and stir again gently, all of this with the heat off. Sometimes the ball valve will get blocked after stirring, but I just pulse it fully open a couple times and that clears the blockage. Once I'm happy and the returning liquor is relatively clear, maybe 5 mins, I turn the heat back on.
I've never had grain block the pump or collect in the RIMS using this technique. When I first built the system I would shut the pump off when I added the gains and stirred, then let the grains settle for a few mins before turning the pump and heat on. Sometimes it worked well, but many times I would get a huge amount of grain coming through the plumbing, and had a lot more trouble with grain blockages or stuck mashes. My working theory is that the additional flow results in better dispersion of the particles as they gelatinize, making a less viscous grain bed at the beginning of the mash. This could probably be fixed by additional or more vigorous stirring at dough-in, but my techique works well.
On a side note, I had a problem for a while with scorching in the RIMS tube when using rye and wheat in large percentages. Since adopting my new dough-in procedure I get significantly less buildup on the element and have not had a scorching event. I only use rice hulls on grain bills >30% rye or wheat, and dont' really get stuck mashes or sparges as long as the recirculation rate is kept at a reasonable level.
As to the element power, my system allows me to switch between 120 and 240 V. I have the PID tuned to the 120V setting, since most of my beers are single step and I don't generally mash out (makes no difference in my experience), so I don't need to step temps. When I am doing a step mash I click it over to 240 V and increase the flow rate a bit to avoid boiling in the RIMS hex. I experimented with decreasing the PID's max output to avoid boiling, but found this to be ineffective. The best solution for me was to orient my RIMS vertically with the temperature probe orthogonal to the fluid flow and the outlet above the inlet and well below the return port to the keg. I just make sure to keep my eye on it for the first couple minutes of the step (when the PID is still figuring out that the response is more sensitive to its output than it used to be). If there is any foam in the tubing coming out of the RIMS (think tiny amounts of hot break) I shut the element off for a few seconds, then turn it back on. I rarely have to do this, though. I have also done makeshift ramp mashes using the element on 120v and decreasing the max output to achieve the desired ramp speed. I haven't seen any boiling doing this, but I'm running a 5500 W ULD element on 120V, so I have extremely low heat flux using this techique, and with a 120V element the results may be different.
For your setup I think your element will be fine. You could step up to a 2 kW element, but I think that's your call. I went with the big element because I wanted a two vessel system and use the RIMS to heat my strike water in the mash tun and to provide on demand sparge water so I don't need an HLT. Otherwise I could get by just fine with my 5500W element putting out 1325 W, so your 1500W element would be sufficient for me. Of course your results may vary.
The power to tax, once conceded, has no limits; it contains until it destroys. I was not joking when I told them to dig into their own pouches. It may not be possible to do away with government sometimes I think that government is an inescapable disease of human beings. But it may be possible to keep it small and starved and inoffensive and can you think of a better way than by requiring the governors themselves to pay the costs of their antisocial hobby?
R. A. Heinlein