About 3 months ago, I noticed that the expansion tank was leaking at the seam...so I replaced it with new. For about 3 weeks, the system was very loud, even after purging as much air as I possibly could out of it. Eventually, all the air purged through the auto fill valve and the noise is gone.
Recently, the master bedroom zone temperature wasn't varying at all as it should with our programable thermostats. At night, the temperature is about 70 at 10pm, and rises to between 72 and 77 by 6am...then drops back to 70 during the day. We have it set to 58 during the day, 68 between 6 and 10, and 65 overnight. So I turned the thermostat off, but the same behavior exists. The baseboard is always warm to the touch.
The other zones were fine, until a few weeks ago. The dining room zone will not move off of 70, even though we have a similar heating patern programmed into the thermostat. I turned off the thermostat and the temperature dropped like you'd expect it to. Turn it back on and we're right back to 70 again.
Anyone have any ideas as to what might be happening? Our heating bills are nearly $400 a month now and I assume that the heating issue has something to do with it.