A corgi registered company have just installed a Vaillant ecoTEC plus 418 (via my housing association). It has not worked properly once. It will start up and shut off several within a 5 - 10 minute period. Then it will shut down with the error code F.23. I have had them back round to figure out and fix the problem, however nothing has changed - still doing exact same thing. Engineer reckoned there might be a bit of air in system and to press reset (flame) button if it happened again. Every 5 - 10 minutes I am resetting this stupid device just so i can have some heat and hot water. If i don't keep pressing the reset F.23 just displays and nothing will happen, which means NOTHING HEATS!!!!!!!!! Can anyone please, please offer suggestion???!!!???