Pressure too high

After you bled the radiator, did you refill the system properly? You say the pressure should be 1.5 Bar, but is that when hot or cold?

The radiator could simply be turned off at one of the valves. Turn the valves fully open, the same way you turn on a normal sink tap. If you have a thermostatic valve fitted on one side, then make sure it is at its maximum heat setting of 5.

See FAQ.

There may be something wrong with your system. How did the pressure get so high?

Possible reasons I can think of:

1. You filled it up too high.
2. You left the filling loop connected and the valves are leaking/not closed
3. There is a leak in the heat exchanger that is allowing high pressure mains water into the central heating loop.
4. You have measured the pressure when the system is hot and the pressure vessel is shot/uninflated.

Unless you know (1) applies, you may have some fixing to do. To reduce the pressure, you need to get water out of the system. Find a drain point, attach a hose and let the water flow.

Also, the pressure relief should usually operate at 3 bar and dump water out of the tube, but I suppose it could be set at 3.5 bar in this case.

Christian.