Sticky Aquastat

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djblech

Feeling the Heat
Hearth Supporter
Jul 7, 2008
310
Bruno MN
The aquastat that controls my damper seems to be sticking. A couple of times while I was firing I waited to make sure it was turning off at 190* or so. As the temp was rising past that point I tapped on the stat with a screwdriver and it kicked out. This morning I noticed the temp down to 175, I opened the door and got smoke. I shut the door hard and the stat kicked in and opened the draft. Anybody ever had this problem? I have a 2nd high limit but I should probably replace that aquastat.
 
Aquastats are snap action type switches, if it is near the point of open or close any outside force will make it respond. Is the probe in a well? If so I believe the instructions advise that it make physical contact with the bottom of the well. The cap tube should be free of any kinks or sharp bends. A strap on needs good clean tight physical connection and a little insulation wrap wouldn't hurt. Have you checked the differential setting?
 
Check the bulb fit in the well. If it has any looseness you may need to use some thermal conducting paste to speed up the response. A loose fitting bulb will cause delays in the switch action at each end.

Mike
 
thats wierd, mine did the same thing yesterday. i think? my water pressure was down to 10 lbs so i openened up the auto fill by hand and put more water in the system this brought up the lbs in the system and it seem to be working now. i did lower my cut down to 180 with the weather being warmer.if iwas low on water the flow switch would not let the damper open also. hope it was just low on water. but why didnt the auto fill work??
 
It is in a well and has been working up to about 4 wks ago. My furnace overheated in Feb and I was wondering if that could have affected the aquastat. I have a high limit that shuts the damper at 200*. I have seen that kick in once when the stat didn't. I adjusted the differential to 10*. I'll have to watch and see if it does this consistently, and replace if it does. I have been idling at about 203*- 205* with this warmer weather, is that to high?
 
djblech said:
It is in a well and has been working up to about 4 wks ago. My furnace overheated in Feb and I was wondering if that could have affected the aquastat. I have a high limit that shuts the damper at 200*. I have seen that kick in once when the stat didn't. I adjusted the differential to 10*. I'll have to watch and see if it does this consistently, and replace if it does. I have been idling at about 203*- 205* with this warmer weather, is that to high?

Whoa! It probably did get screwed up with the overheat situation. It will only handle so much. I hate to say it but it ain't gonna fix itself.............

Mike
 
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