I have a four story house with the hot water boiler in the basement. I figure it is about 50' from the boiler to the top radiator. It is a new boiler and I am afraid the contractor who installed it does not know too much about pressure settings.

Now, someone that knows more than me please correct my assumptions or give me advice:
Have heard I should have about 5 psig on the top radiator, so this gives me a setting of about 27 psi at the boiler. Although the boiler is rated at a higher pressure, it has a 30 psig relief valve. I am scared to set the boiler so close to the relief.

Double checking the boiler rated water pressure, should I change the relief valve and operate the boiler at the higher pressure? And then fill the diaphragm tank (empty) with air at my operating pressure?

I noticed this because the top floors are chilly!!