Responded to a report of a leak at the boiler. Upon arrival, I found the temperature and pressure relief valve dripping steadily, and I confirmed that the expansion tank had water in the bladder. With approval, I replaced both the failed relief valve and the EX-30 expansion tank. After completing the replacements, I purged air from the system and confirmed proper circulation of hot water. Kim also brought to my attention additional concerns involving the boiler, including a loud rumbling noise during operation and a communication issue between the thermostats and the contact relays. When I first arrived, the burner was off on reset. Carl reported that he has had to press the reset button before to get the basement zone to circulate heat, although he has not needed to reset it for the first or second floor. I pressed the reset button, and the burner lit immediately and continued to run without any problems. I tested the cad cell and confirmed consistent power delivery from the hydrost