this is actually the way this situation occured.
i have a single zone hot water heating system with an
external coil. the circulator is continuously run for domestic hot
water. the problem started with gurgling sounds from the baseboard
radiators. it sounded as if air may have gotten into the system. i had
a "heating prof" in and he filled sysem and bled it from a valve
located near the boiler. i live on the first floor and the heating
pipes run from boiler, overhead, and then down to baseboard radiators.
when he first filled and bled the system i heard almost nothing from
the radiators or the boiler. the next day i heard some bubbling noise
from the radiators when the burner came on, and the noise became
progressively worse each day. i bled the system again. initially the
radiators were much quieter, but again began to gurgle louder. upon
closer inspection i determined the gurgling/bubbling sound is coming
from the expansion tank each time the burner comes on, and the noise i
hear from the radiators is actually coming from through the pipes from
the expansion tank/ boiler room. the burner comes on at 170/180 and
goes off at 200 degrees. could the expansion tank be faulty and
somehow letting air into sysem? could the system actually be running
hotter than gauge reads and aquastat is set for? or could the hot
water be surging as soon as the burner comes on? i believe the
expansion tank is one of the newer ones with a bladder. thanks for any
help.email me at email@example.com just remove the 5 for spam
purposes. or post message with any help. thanks again.