Chris M came out due to previous visits and still no answers. Performed diagnostic. Found that the auto feed and back flow are not giving pressure to the vessel. Found that the side arm water tank was not wired correctly. Found expansion tank on side arm is on the hot side. This should not be on the hot side. Manufacture instructions states to place on cold side to work effectively. Got permission to replace auto feed and back flow preventer. Replaced and set pressure to 15 psi. Rewired the side arm tank for priority. The aquastat for the side arm was not faulty. Once that was all completed. Tested system. System is heating and operational at this time according to manufacture specifications. 2 years parts and labor warranty on repairs made today. Charging customer add on pricing due to failure of repairing this issue the first two visits. Customer paid in full on cc.