No it is not safe, boiler pressure is way too high. You can remove some of the pressure by opening an air vent on a radiator and catching the water in a bag/tub. Open vent let some water out, close vent and check pressure, repeat till 1.2/1.5 bar reached. Could also let some pressure out the relief valve but sometimes valve doesn't seat properly and can pass.
You can use the radiators air bleed valves to reduce the pressure .big towel to catch the water !!!. If your boiler pressure is 3 bar when cold ,and you turn on the central heating , the pressure will rise as water heats and expands ,and your pressure relief valve will open. So you should reduce the system pressure to 1 bar before running the boiler / central heating.
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