Omnistat 2 - heat does not turn off! Overshoots by 15+ degrees

I replaced my original omnistats with Omnistat 2 and now have a new problem that is super bad.   The Omnistat 2 continues to call for heat well beyond the set-point.    
 
One day one room got to 93 degrees!   The omnistat didn't show it was calling for heat (it was set to 68 degrees).  I used the mode button to turn the heat off and I could hear the relay click when I did that.
 
HAI tech support initially responded to my message and suggested turning off EEC, which I did.
 
However, since then this problem has continued.   HAI is no longer responding to my emails :-(
 
Here is a youtube showing the failure.  
 
http://www.youtube.com/watch?v=ShSTuB4FqdQ
 
My system is forced air
EEC is now turned off
 
Anyone else face this problem?
 

Hi,
 
What type of equipment are you controlling?
 
I have Water Furnace equipment with zone controllers.
 
The outputs of the Omnistat 2 were incompatible with the inputs of the zone controllers.
 
I had to add relays controlled by the thermostats which in turned controlled the inputs of the zone controllers.
 
I have NO idea if this could be related to you problem or not.
 
Frederick

That's not my problem. I'm using the Honeywell zone controller. It is compatible with standard tstats.

Like I said the system worked well for 10 years with the original omnistat model.

PhilG said:

That's not my problem. I'm using the Honeywell zone controller. It is compatible with standard tstats.

Like I said the system worked well for 10 years with the original omnistat model.

Click to expand...

 
Well supposedly the WaterFurnace zone controller was compatible but something about the outputs of the OmniState 2 prevented it from working. Leviton/HAI even makes a relay module for this purpose so it's been a problem in the past.
 
It may have nothing at all to do with your problem but it sure caused some head scratching here as the zone controller just wasn't responding correctly.
 
Good luck find your problem.
 
Frederick

Are you doing any automation of the thermostat via the Omni Panel / automation programming lines?

Have you made any changes to the programming lines in the OmniPro panel?

Should be a like for like swap between the old and the new OmniStat 2.

Here recently switched furnaces (HVAC), connected up the HAI relay / power supply but not yet the OmniPro2. I had an issue relating to the wiring from the thermostat to the furnace which I missed and was seen by my HVAC guy. The heat wouldn't start here.

It's been a few years ago that I installed my OmniPro - RC80 thermostat. That said I did have some issues with it and mostly a suggestion to remove the thermostat from an old friend that owned an HVAC company. He was old fashioned and didn't like that I was automating the thermostat via the OmniPro 2 panel. Testing the functionality at the time he suggested that I use a regular manual style Honeywell thermostat and going direct to the HVAC motherboard shorting wires manually which I did and it did work fine. Over time did adjust the RC-80 to work fine. I did have power issues with it such that I installed an HAI relay board and power supply (issues related to power stealing) which fixed other issues with it.

That said I was also using a Homeseer plugin that connected serially to the OmniPro2. The software would change the heat hard number settings on the thermostat randomly. This was very low on the WAF so I disconnected the thermostat piece from the software. The suggestion at the time was to just connect serially from the software to the RC-80. I never did. I updated over the years to the Omnistat2 and final release of HS2 OmniPro plugin. This last release did work fine with my thermostat.

Another issue that affected the thermostat here was a network port issue which would ding the time and all serial connections of the OmniPro 2 (thermostat and Omnitouch screens was issues that I could see right away). Testing the fix here was disconnecting the NIC / warm reboot and all would be fine. Opened a ticket with HAI and they told me it was related to a promiscuous NIC. That said here put a micro firewall between the NIC and the rest of the network and have not had issues since then (relating to time sync, serial, network).

Call HAI and let them walk you through some diagnostics with the thermostat via a voice conversation (not emails). Open a ticket. I did this originally with my new Omnistat2 serial issues.

Suggestions:

1 - disconnect the serial connection to your Omni Panel - thermostat should work fine without the connection. Then connect it back and...
2 - open a new ticket with Leviton / HAI and have service person do a diagnostics of the Omnistat 2 with you on the phone
3 - puchase a $20 cheapo thermostat, remove the Omnistat2, connect the cheapo thermostat and test it. It will probably work just fine.

Anything else happening with your OmniPro 2 panel that you consider unusual? Does the time go way off in a matter of 24 hours? Way off means maybe an hour or two?

Mine has always overshot on heat, but not that bad.  Under "setup," "installation setup," "anticipator control," you should see both a "heat anticipator" setting and a "cool anticipator."  Try raising the heat number as high as it goes. This may help.

I have discovered the hard way, that smart thermostats, and sensors, all have inherent problems with sensing. This applies exspecially to Wi-Fi thermostats and other breeds with CPUs and RF transmission electronics built in.

The problem lies with the sensor detecting the heat from the electronics.


Sure, you say, they can compensate for this by recalibrating the sensor response, subtracting a few degrees...

But... that is the problem, created.


You mount the stat on a wall with a hole into some air movement, and a protected pocket of air, that doesn't heat at the same rate as the room air, or there is a draught in the room, even caused by the thermostat itelf turning on the fan of a forced air system. It doesn't take much.

The air movement takes away the effect of the sensor compensation calibrated into the stat.


Now, while the air is moving with furnace fan draw, inside the wall cavity, or just in the room across the ceiling, the stat displays low due to the removal of the radiant, and/or conducted heat, from the electronics.

When the temperature is satisfied and the furnace fan shuts off, now the effect of the stat electronics becomes a factor again, so the stat now senses 2, 3 or even 6, 7 degrees higher then it displayed just as it shut off.


This all appears as overshoot on the stat but if an independent sensor is placed very close to the stat's sensor it can be seen that the stat did it's job perfectly and within 01-0.2 degrees.

If you think you may be a victim of wall cavity draught, take the stat off the wall and hang it off the wall a few inches by the wiring, and let it operate.

Be careful not to be fooled by the proximity of your warm body. Readings and adjustment must be made very quickly as the proximity of your body radiating heat can also affect the reading within a minute or two, even as much as a few degrees.


This is a problem for all smart thermostats now, that didn't exist with the old mechaincal stats, producing no internal heat, and could be calibrated properly to the true temperature and therefore were not affected by draughts, inside, or outside, the wall cavity.


Make sure you fully insulate and seal your wall cavity to isolate from your smart stat on the wall, if you want to have temperature stability.

Also put another sensor for a better indicator and do not rely on the reading from the front of a stat to judge it's behaviour. I use a group of CAO Tags Pro version for 0.4C accuraccy and use an average, watching for outliers.

Here my Omnistat 2 ECC is set to 5 (default) and heat anticipator is set to 5 and cool anticipator is set to 3.
 

 
Thinking that the RC-80 had the identical set up.
 
I originally purchased the Omnistat 2 when first released and never installed it until 2-3 years later.
 
The RC-80 that I had some voltage issues (power stealing) and installed the HAI relay board and Elk 24VAC additional power supply.
 
Intially tried the HAI 30A00-2 Thermostat Power Supply Module and it didn't help my issues with power stealing.
 

 
I then went to the HAI 29A00-1 Thermostat Isolation Module which solved my power stealing issues with the RC-80.
 

 
I left the Thermostat Isolation Module in place when updating to the Omnistat 2.
 
I had issues relating to temperature display and settings (while connected to the OP2 with no software connection).
 
Opened up a ticket with HAI support.  Did diagnostics and HAI did replace it twice.  It was then when I first noticed that I was having some time sync issues and network issues.  When those were corrected then my Omnistat2 worked fine.
 
When I put back in place the RC-80 to test it; it worked fine which to me was puzzling.
 
Temperature wise I did notice that the thermostat was some 1-2 degrees off and different from an HVAC testing thermometer and external Omnistat2 temperature sensor.  I adjusted the Omnistat2 to match the external sensor and sealed the small hole for the HVAC wiring.
 
Today (recently) have a different HVAC furnace and when I connected the Omnistat2 to it had same power stealing issues such that I installed the old thermostat isolation module in the furnace next to the motherboard.  I had to remove the motherboard and metal backing to drill holes for the plastic mounting spacers of the isolation module.  (a bit of a PITA).
 
I keep the old RC-80 as a hot spare, then gave it away and then purchased another one as a hot spare.  Well thinking someone gave it to me.  
 
A bit of a tangent here...
 
Currently testing the Homeseer 3 HAI plugin workings with the thermostat.  Working well here.  Next is testing it with two Omnistats.  Compared changes between the thermostat and remote consoles speed wise.
 
Put in weather data and removed a few temperature sensors on my touchscreen interface here cuz it got too busy looking (and that is low on the WAF).  Originally had outside, attic, 2nd floor, main floor and basement temps displayed.  I don't really ever touch the settings and the touchscreen display is just another remote for the Omnistat2 (also utilize Omnitouch 5.7/5.7e's for remotes).
 

The OmniStat2 actually has a wall temp sensor and an air temp sensor, so its probably more sophisticated than most smart thermostats (and more expensive) but getting it all to work requires good firmware, which was never a Leviton strong point.

Thanks for the comments and hints.
 
I'm still communicating with HAI on my problem... They asked for a bunch of data which I gave them including my pc access file, etc.
 
Consistently I only have two omnistat 2 that have this problem.   And let me be clear again... I talking about overshooting by many degrees.   All seem to overshoot by 1 degree, which I believe is to try to run the furnace less (which is fine).
 
My install is not too complicated.  I'm using the honeywell zone controllers and they had been working perfectly with omnistat 80 for years.     
I have 3 furnaces in the house with 3 zone controllers.
 
The failures are happening on two different furnaces / zone controllers.  One omnistat 2 on each furnace / zone controller goes crazy... Sometimes.
 
Out of desperation I replaced one of the omnistat 2 with a new one.   Knock on wood... It has not failed again.      The other one continues to fail sometimes.
 
--
So for the suggestions above.  
 
@pete_c Based on HAI recommendation I disabled EEC.  That didn't help.
 
@petc_c I guess I could try the Thermostat Isolation Module, but I think the zone controller is essentially doing that already.
 
@Ano I don't think it is the wall sensor / air sensor theory.  As I said it overshot one time (before I caught it by 25 degrees!)
 
@LarrylLix I'm not concerned about shooting over 1 or 2 degrees.   I talking 10+ degrees. If you look at the video you can see on the display that the omnistat 2 has stopped calling for heat (no indication), but continues to call for heat.     This makes me think it is not a component failure, but some kind of software failure.   I will take your suggestion however and ensure that the cavity is sealed. 
 
Thanks everyone.. if you have more ideas let me know.    I will certainly post when I have a solution.
 
phil

PhilG said:

Thanks for the comments and hints.
<snippage>
 
@LarrylLix I'm not concerned about shooting over 1 or 2 degrees.   I talking 10+ degrees. If you look at the video you can see on the display that the omnistat 2 has stopped calling for heat (no indication), but continues to call for heat.     This makes me think it is not a component failure, but some kind of software failure.   I will take your suggestion however and ensure that the cavity is sealed. 
 
Thanks everyone.. if you have more ideas let me know.    I will certainly post when I have a solution.
 
phil

Click to expand...

Maybe I understated the problem. If you are using ForegnHeat I have seen cases, in help forums, up to about 12 degrees F.
With Nest stats, and A/C I have seen complaints up to 15 degrees, but that was overheating the contact from a heavy contactor on A/C.

Good luck with it. Plugging the cavity hole completely will give you an indication if this is part of the problem and go further from there, if so. I ended up mounting my stat on a piece of styrofoam painted to look like the wall.

I plugged the cavity... Didn't make a difference.
 
HAI suggested I use Zone mode (although that should not be required) and since doing that my system has been working properly.   Negative side effect is that I loose the ability to engage 2nd stage heating :-(   In the bay area this is not needed that often, but I hate loosing the feature.