I run my own L3+ using APW3++ (1600W) on 220v supply. With these I find the best results with the following settings:
475M 100% manual fan speed - 620Mhash
462M 100% manual fan speed - 600Mhash
Some miners get higher hardware errors above an acceptable level at 475M so they are set at 462M. We are able to run all miners at these two settings and have consistently low hardware errors (max 0.2% and usually less than 0.1%). We have not had hardware failures over many months on these settings.
What temperatures do your chips have and how do you cool them? Mine are in a data center with 18°C cold air but my chips run as hot as 65-70°C with only 450M and 580MH