Depending on the boiler, 30# might be normal, but that seems high for just two stories. To keep the pressure semi-constant, the expansion tank needs to be working. This could be an older style air over water tank, or a newer bladder tank. You may need to replace the bladder tank or purge the old tank to get it to regulate properly. Also, if you have an autofill valve, it could be worn out and letting new water into the system. And, if you have a tankless coil, it could have a leak in it, raising the pressure.