If you`ve a project manager on site over seeing the works, he should have the details of your heating system. This should include heat loss calculations and proposed hot water requirements for the property. The price reflects the fact that the work was subbed out to another firm. But in my view...
The primary heat exchangers have a thermal fuse in them too. If it`s tripped due to excessive heat, no resetting, full replacement! Although on the ecotec range it`s an easy job. I like them and think they`re good pieces of kit. Only time will tell. Thought the same thing about my ex wife too...
Sounds like you`ve a sludge problem, and pumping over to the f/e tank. Try turning your pump speed down and see if the noise in the loft stops. You need to flush your system out and put some inhibitor in afterwards.
Best get an engineer out, ask them if they`re familiar with this boiler, and be cheeky and ask if they do a "no fix no fee". Then you`ll probably only get one to show up who`s comfortable in the knowledge he/she (politically correct) will be able to diagnose and fix the problem.
Agile is probably correct (as usual) it being the pcb by the sounds of it. If the leads were faulty i`d doubt you`d be getting a higher reading than normal. You`re getting the same reading for the closed and open position. This should not be the case.
You should be getting a reading of 2.5Vdc checking green and black, and the same figure checking green and red when the tap is running.
Check the red and black with the tap off.
The flush sytem on these can become dodgey over time. The round rubber seal on the bottom starts passing water by. You may be lucky and have one of the servicable ones that twists 90 degrees and pulls out. Then you can replace it without stripping the toilet. Best to replace it and see if it...
Try pushing one of the buttons down, and pull the top of the other one off. Then remove 2nd button. On some models you`ll see a plastic posi-drive screw. Try that.