Need some help with water overheating in gas boiler

AlexZ6655

A little background....Burnham Series 2 boiler, supplies heating to two floors and basement.

So there are three zones, Zone 1: basement (rarely used), Zone 2: living room (first floor), and Zone 3: remain rooms in first floor and second floor.

When open Zone 3 (typically used), everything runs fine in the beginning, when boiler turns on for about 20-30 mins we start to hear water banging sound in the house and water will drip from the pressure release valve.

Most time when we're home, we will lower thermostat to turn off the boiler. After boiler is off, the temperature on gauge will rapidly goes pass 200°F.

So I think the boiler overheats the water to boiling which cause the banging sound, but I am not sure why the water won't "return" or the gauge won't correctly do the measurement.

Please let me know your input, and thanks in advance for answer and help.

EBEBRATT-Ed

Need pictures. I am assuming a hot water boiler and not steam?. You need to check the water pressure in the boiler and you may have a bad expansion tank.

You best bet is to check "find a contractor" on this site and have a professional go over your boiler

Big Ed_4

Seems the boiler get the signal "call for heat" constant . For what you are typing . Check the relay , And then what pulls in the relay which would be upstream in the low voltage wiring ..

hot_rod

Scaled up boilers will sometimes over shoot temperature like that from sludge build up and hard water coating on the sections.
They can also make different noises when heating, called percolation. No harm in getting a can of cleaner and squirting it in.

As mentioned, be sure the expansion tank is not waterlogged causing over pressure.