I have a vokera linea 7 boiler and i get a 01 error code

SOURCE: my vokera linea 7 boiler

The pipe you call over flow. This would be the P/R valve and is set to relieve pressure in system. The first thing that needs to be checked - the expansion tank two types of tanks one would be what is know as a extrol tank, Most likey just hanging off pipe, it has air pressure on one side of rubber dia. and boiler water on other. The 2nd type is just a tank at ceiling height (most of the time). You would see a hose bib off the one end. Tank holds some water but must have air for boiler water to push into as it is heated. If you have the first tank it should be replaced. The 2nd type needs to be drained of all water. Shut off feed line to tank hook up short hose and drain into a bucket. if water stops you must break the vacuum raise hose above tank air should go into tank. repete draining till all water is out of tank. Some tanks have a way to open a valve to let air in as you drain if so use it. When all water is out of tank valve off everything (no air should leave tank) Open back up to system now you should have aplace for the water to expained to.

SOURCE: No heating and no hot water, my boiler won't fire up

If there is a hi-limit switch, maybe it's open, reset the switch, and monitor the temperature, if the temp. increases over the set temp. replace stat, and clean lime off from the tank, if does not have a filtering system