8870 Temperature wrong

[arctec37]

I have installed three Aprilaire 8870 Thermostats (addresses 1,2&3) using the protocol adapter and the distribution panel to my ELK M1G system. All works fine except that the room temperatures shown on the displays are about 3 degrees off! Anyone know of why this would be or how to adjust them?
Thank!

 

[sic0048]

First off, are you sure they are wrong? The best way to make sure is to have a thermometer that you can "calibrate" by placing it in a bowl of water with lots of ice in it. After letting everything sit for a while, the water temp and therefore the thermometer should be close to 32 degrees. I recently installed a new thermostat in my house and took all the thermometers I could find and tested them in the ice water. Only one out of 5 gave me accurate results. The others showed temps from 34-37 degrees while the one that was accurate showed 32.6. The most accurate thermometer was also the only digital thermometer out of the bunch. I then took that thermometer and held it up to the new thermostat. In my case, the new thermostat (an RCS TR-16) was accurate. The old thermostat was not (a 30 yr old analog thermostat).

According to the Aprilaire manual:

TEMPERATURE SET-UP – The first and second stage differentials can be changed, as can
the display temperature offset. The differentials set the tightness of the temperature control.
If the equipment is operating too often, or the
temperature swings are uncomfortably large,
the differentials can be increased or decreased
respectively. The temperature offset (calibration)
allows the user to “customize” the temperature
shown on the display. Consult a qualified service
technician before changing any of the values in
this Sub-Menu (Sub-Menu not shown).

TO ACCESS THESE FEATURES – When first powered up, the Message Display will scroll
through the current mode status, fan status, and Heating/Cooling output status. This is
referred to as Passive Display because you do not interact with it. To get into the set-up
menu, press the ENTER button and MODE button at the same time.

So if you find that the thermostat is really three degrees off, you can adjust the temp displayed up/down three degrees to match the actual temp. I hope that helps.