Boiler cutting out

[DC]

My condensing boiler keeps cutting out. The boiler has been off for six months while I renovated the property. The radiators have been removed and will be replaced later this year. Currently the pipes leading to the radiator points have end stops on them. I only want to have hot water at the moment. When I started the boiler up for the first time I set the water pressure too high and it cut out. I then set it to 1 bar and everything worked for about 5 minutes until the system cut out again. I noticed the the pressure was creeping up to 2 bar again. I've turned everything off until I have more knowledge. Hoping you guys can help.

What possible causes are there? How to I test them? I could call an expert but I have that DIYers desire to save money until its the only option.

[htg engineer]

you need at least one radiator in place, so that when you turn the hot tap off the boiler has somewhere to put the excess heat. At the moment the heat will go down the flow but the water will be unable to return to the boiler.

[DC]

Thank you. Sounds like I should install the bathroom towell radiator.