Concerning "A" models only. The internal circulation pump removes flow rate requirements and prevents the "cold water sandwich" effect. The factory settings are shipped incorrectly, and the circulation pump is not being used. The user manual is wrong regarding automatic and timed circulation options.
The internal bypass is set for internal circulation, but on the bank of 8 dip switches the #4 dip switch must be turned on and the #5 switch left off to enable the circulation pump. Turning #4 off and #5 on will allow for timed circulation using the controller. Automatic circulation is recommended.
Read Directors Advisory FS-187-11 - Here