Chronotherm III Calibration?

I believe that my Honeywell Chronotherm III thermostat (T8611G) is reading the room temperature as higher than it really is, by about 4 or 5 degrees. This opinion comes from comparing it to other freestanding thermometers that I place in the same room near the Honeywell. Right now the Chronotherm shows 71 degrees while another electronic thermometer nearby reads 67. The room seems chilly, so I am inclined to believe the lower reading is the more accurate one.
Honeywell's troubleshooting wizard on their web site covers this issue, but all their solutions point to other problems or causes, in essence saying that their thermostat CAN'T be the problem.
Does anyone know if the Chronotherm can be calibrated?
Thanks.
- Earl remove both x's from my email address to respond via email
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E Jones wrote:

There are no bias adjustments for temperature on the Chronotherm III. http://hbctechlit.honeywell.com/techlit/PDF/69-0000s/69-0348.pdf
Probably time for a new (batteryless) thermostat anyway - I'd suggest the VisionPro http://www.hotfreshcool.com/vp_demo.html
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Most thermostat theremometers can be calibrated, either in program or by a screw if it is spring type, but you need an accurate source most I see are 1-3 degrees off. A taylor probe style digital is usualy accurate. I had several older mecury bulb Chronotherms , all I could calibrate behind the thermometer. Calibrating the thermostat took a special thin wrench.
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Sometimes, if thermostat is just above furnace room and if furnace room has leaks in vents that makes furnace room much warmer, and if heat can travel where thermostat wires are, it can affect thermostat temperature readings.
Could you try to insulate hole behind the thermostat and see if this helps.
Regards,

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I appreciate your reply. Thanks! But if your theory were true, wouldn't the thermostat on the wall read HIGHER than one on a nearby shelf? The wall the thermostat is on is in the middle of the house. (The other side of the same wall is another room.) Little chance for a draft or creeping heat from within the wall being the cause of the discrepancy.
Also, the thermostat is not mounted above the furnace room, nor on the same wall with any heat vents or air return vents.
- Earl

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The Honeywell Chronotherm III electronic thermostat uses a logritmitc program [Adaptive Intelligent Recovery control brings the room temperature to temperature setpoint at the programmed time, maximizing comfort and energy savings.] "anticipate" the need for cooling or heating (as the case maybe.) Sometimes the thermostat will show a different setting & temperature because it is compensating using the programming set up by Honeywell. You can defeat the logritmitc program. Call your local HVAC technician to change the Adaptive Control Setting or turn it "off."
This feature came out around 1980 with the first T8600 series and was meant to bring the heating on earlier than the program was set for so, AT the time the thermostat was told to be a certain temperature, it would be, not that it 'came on' at that time. (Mostly an advantage for heat pump use.)
--
Zyp
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I had a similar situation though not as severe as yours. My two readings were about 2-3 degrees apart. However, it turned out the difference was attributed to the location of the other thermometer. When I place it directly on the wall next to the thermostat and let it sit there for a few hours, guess what? The two agreed on the temperature. Previously, I had them placed close near one another but apparently, "close" was not close enough.
Jay M Hillsboro, VA USA

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