OmniStat2 Temperature offset adjustment

[pete_c]

My "production" in place Omnistat2 temperature is off and always has been. I can adjust it and if it loses power (on and off a few times in a matter of say 30 minutes) then my offset is lost.

I do recall with the HAI RC-80 a temperature adjustment offset would remain in place after removal of power to the thermostat.

I have tested how off the temperature is with the Omnistat2 using two different thermometers adjacent to the Omnistat2.

Today decided just to attach a remote temperature module instead to compare temps and if the remotely connected temperature sensor is more accurate then will use that one instead for the Omnistat. Long term though I would prefer to attach multiple sensors directly to the thermostat to work with the sensors attached to the OPII. I purchased a few of these a while back.

Unrelated but I also have external and multiple internal temperature / humidity sensors connected to the HAI OPII. I do not have one though installed where the thermostat is at; just a 1-wire sensor there.

Is there a way to calibrate the temperature sensor on the thermostat? Like maybe via a direct serial connection with my PC to it?

 

[pete_c]

I've been comparing the numbers for the offset. The OmniStat2 is 5 degrees off; which is a bit much to configure the offset to.

 

[lupinglade]

Check that your thermostat is not mounted over a duct space or return air space. If it is, you need to seal the hole where the wires come through so that hot/cold air does not get pushed or pulled into the thermostat.

 

[pete_c]

The newer RC-2000 replaced the older RC-80 and it is not over a return space / hole where the wires come out is sealed. Switching from the external to the internal temperature sensor back and forth now for a few days and have confirmed that the internal temperature sensor is 5 degrees off.

I like the new retro look of the RC-2000 and the added feature set but really liked that the RC-80 just worked all these past years with no or little intervention. I really never look at the thermostat except for lately and more concerned with function these days.

In contradiction to my above posting' maybe

1 - I will put multiple external temperature sensors and do an average of those and not include the one that is built in.
2 - go Zigbee in addition to using X-10, UPB and Z-Wave on my OPII.

 

[ano]

I agree that HAI needs to adjust these better.  The Omnistat2's are consistently read 3.5 to 4 degrees too low.  Mine replace the RC-80's which were pretty close.  You'd think for a thermostat that costs $350, they could do a better job at calibrating them.  I've already returned two because their case didn't mate correctly with the back. 

 

[Ernie]

Just my two cents worth, but there are two things that I have found that can have an impact on accuracy:
 
1. Look at the thermistor on the circuit board of the tstat.  For best accuracy, the thermistor should be standing up (perpendicular to the circuit board).  I have found that they are sometimes layed down where the thermistor is almost touching the circuit board - this will cause the temperature to read 2-3 degrees higher.
 
2. If the display option is set to "Always On", it can also cause the temperature to read 2-3 degrees higher.

 

[ano]

These Omnistat2's also have other "strange" behaviors that I don't fully understand at this point.  I replaced a RC-80 in the bedroom with a RC-1000.  The RC-80 has always worked great, but to match my other thermostats I needed to update.  In the bedroom I have a standing fan and a ceiling fan both controlled by UPB. (I live in Phoenix, so lots of fans.)  Anyway, these fans are controlled by the temp read on the thermostat.   I do this because the wife gets hot and cold as the AC kicks in and out. 
 
So with the new OmniStat2 I notice the fan goes on and off and on and off about ever 30 seconds.  I look at the thermostat and I notice that it keeps oscillating between two temps like it just can't make up its mind.  If this was a plain-old thermostat, nobody would probably even notice this behavior, but one that can control other things, this is a problem. I'm hoping I can find a setting that will stop this.

 

[Del91574]

Without me digging in, many other units offer hysteresis settings that help smooth out the peaks/valleys. Maybe tweak the settings slightly for a different on/off value that is separated by more than (I'm guessing) a single degree or two?

 

[ano]

Unfortunately I don't see a hysteresis setting on it. 
 
Like all thermostats, it doesn't keep the temp exact, it spans a range. If the set point is 75 lets say, it will turn on at 76 and turn off at 74.  Then with the AC off, it will slowly rise from 74 back to 76 and repeat.  My wife can go from hot to cold over the span of a degree, and it always feels colder when the AC is on then off, even if the temps are the same. 
 
So I have a fan that turns on and off based on the exact temp, and if the AC is running.  That makes the wife happy, and it worked great until I installed the new OmniStat.  I'm going to need to either add a hysteresis effect in the software programming, or use a timer to help smooth the temp changes.  I can do all that, but it bugs me that I have to do it because HAI didn't work on their design a bit more.