we have a honeywell programmable thermostat for a water-based heating
system.
it often gets much hotter in the house than I se the thermostat to, and I
always attributed this to the fact that the baseboard heaters are located at
the extremities of the house while the htermostat is in the middle of the
house, with no heater close to it.

today, however, I woke up to a temperature of 73 fahrenheit while the
thermostat is set at 71. I just saw the thermostat turningon the heating
system, even though the temp has been a constant 73 since this morning, it's
not too cold outside and the temp is still set at 71.

what on earth could possibly make this thermostat turn the heating on when
it's set at 71 and the temp reads 73?

the anticipator is off, or the thermostat is out of calibration. or
maybe its bad. A pro will come along with the correct answer, Im
guessing. My digital I can recalibrate. How old is it.

"mark Ransley" wrote in message
...
the anticipator is off, or the thermostat is out of calibration. or
maybe its bad. A pro will come along with the correct answer, Im
guessing. My digital I can recalibrate. How old is it.

1 year

"j j" wrote in message
.. .
we have a honeywell programmable thermostat for a water-based heating
system.
it often gets much hotter in the house than I se the thermostat to, and I
always attributed this to the fact that the baseboard heaters are located
at
the extremities of the house while the htermostat is in the middle of the
house, with no heater close to it.

today, however, I woke up to a temperature of 73 fahrenheit while the
thermostat is set at 71. I just saw the thermostat turningon the heating
system, even though the temp has been a constant 73 since this morning,
it's
not too cold outside and the temp is still set at 71.

what on earth could possibly make this thermostat turn the heating on when
it's set at 71 and the temp reads 73?


Is your stat electronic or analog (mercury bulbs)? If it's analog, make
sure it's level and calibrate it with a calibration wrench and an ACCURATE
thermometer.

If it's electronic (digital), it could be a couple of things. First, make
sure that the anticipator is set for baseboard heat. You don't say whether
your baseboard is oil or gas fired. Makes a difference. Consult the owners
manual. Remove the stat from the sub-base and look on the back.. You'll see
at least one, maybe two or three set screws. These set the anticipator.
Follow the instructions molded onto the back of the stat for proper
settings. While you have the stat off the base, stuff a good-sized wad of
insulation into the hole that the wires go through. Make sure no drafts are
coming up BEHIND the stat and throwing off the reading. Also, blow any
dirt/dust off the thermistor (sensor) on the stat.

Second, check your programming. Honeywell takes the liberty of programming
adaptivity into its electronic stats. In other words, setting a 6-degree
increase in temperature at 6:00 AM might cause the stat to begin "ramping
up" as early as it needs to in order to have the temperature up BY 6:00 AM.
This could mean several hours if the system is undersized or in high-load
situations. Even though the SETPOINT might be 71, the stat is "looking
ahead" at having the temp at 75 in a couple hours. Rather than blast the
heat for a half-hour to get there, it brings it up a quarter-degree at a
time over a 2-hour period. It varies, too. The stat "learns" how long it
need to accomplish the feat, and adjusts seasonally. Nice feature, but
takes some getting used to. On the back of the stat, there should be another
screw which will turn off the adaptivity, making the stat operate like a
mechanical setback model most people are accustomed to.

I've also seen spark ignitions make digital stats go haywire. The ignitions
in some gas furnace/boilers, and all oil-fired equipment, is very high
voltage and may cause spikes to reach the stat. Although this was an issue
which was addressed long ago, some older equipment may still cause problems
for newer stats. An isolation relay in the circuit usually cures this.

Good luck and post the results.
--
C.J.

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