I have a Trane thermostat TZEMT400BB that suddenly has an inaccurate temperature reading. This is a rental house and guests were present when the issue started. I also have 2 multisensors that measure temperature and historically the thermostat has been about 2 degrees below the living room temp sensor during the day (25 ft away in the same room). Today it has been reading 3 to 4 degrees above. I noticed this when the A/C ran continuously today and when I checked in the tstat read 76 while the room temp sensor stated 73 (the other also read 73 providing consistency between the two sensors). My guess is the actual temp at the tstat was 71. A bit chilly and answers the question as to why the A/C ran so long.
I know the Trane allows the temperature to be recalibrated so one concern I have is if one of the guests played with the system and set a 4 or 5 degree calibration adjustment. Otherwise the only thing I can think of is that the tstat temp sensor has gone amok.
Question, can you reset the calibration bit via z-wave? If not does anyone have a suggestion how to remedy this?
On the [tt]Device Options[/tt] tab of the Trane, you could set up variable 143 to [tt]monitor only[/tt] and then after reload is completed and a refresh of the browser, check the current value of the offset.
As far as I can tell, it’s read-only though. But at least you’ll be able to see if the offset is still what you expect it to be.
(BTW, IIRC, the display lock you can set remotely.)
I followed what you indicated. It shows current value -1. I have not previously adjusted the calibration. Does that mean it has been adjusted locally? Does -1 mean to make the reading 1 degree higher than the actual measurement?
The last comment in parenthesis. Does that mean there is a method that can be done remotely to prevent someone on-site from manually adjusting the settings? That would be excellent. Can you share the how to?
How would you attempt to change the calibration value? In device options if I select the monitor only pull down it asks 1 byte hex, 1 byte dec etc. what is the selection and how would I place the propped value?
Sorry about all the questions but I am really not all that knowledgeable with the behind the scenes operation.
How did you know it was variable 143? Is there a more detailed manual of some sort available?
I couldn’t change the value on my Trane (FW 01.00.13; would have to look up the model number); but I suppose you could give it a shot. Given the range, a size of 1 byte seems sufficient; so try ‘1 byte dec’. If that doesn’t work, try ‘2 byte dec’. And if that doesn’t work ‘4 byte dec’.
(What happens though, on mine, is that Vera writes the config, then reads it back, sees they don’t match and declares something along the lines of ‘Failed setting user configuration’.)
(I monitored all params and looked to see which one changed.)
I tried various data size settings for variable 143 and had no luck. Though I see on your picture the value of 255 shown and wonder how that is possible if the max allowed offset is 7 degrees.
For parameter 9 my system current value is 3 in comparison to the choices of 0 or 1. Any idea as to what that means?
Thanks again for your help. I wonder if anyone has a detailed manual with all of the parameters described. I see you opened up a feature request in Nov 2011. Anything come of that?
Well this may never be solved. I called Nexia to gain help in understand what appeared to be a drifting temp sensor reading and after explaining the symptoms they offered to mail a replacement out.
Now my new dilemma: how to have the thermostat replaced while I have guests staying in the house. Major problem to be undertaken is to get a new thermostat connected to my z-wave system. Does anyone know if you can connect it using the high power setting? The tstat is about 8-10 ft from the Vera and inside a locked closet.
Update. I was wrong. Nexus sent a level for return shipment. Not a thermostat. Back to square one as being a rental I cannot have a repairman go to remove the thermostat have it returned and then sometime later have a replacement installed. Won’t work. So I have to try troubleshoot from here or buy a new tstat and have it installed. And you can bet it won’t be a Trane given the complete lack of support. The " we would trouble shoot it if you had a Nexia controller" is BS.
Do you have to fix it now ?
Do you let the guests change the Temp while they are present ?
Then they can set it to any temp that makes them happy.
As far as temperatures to set during the night and absent …
If you know you have a 3 degree shift … just change your setback settings by 3 degrees.
You really do not want to mess with this kind of stuff remotely.
If you get an HVAC specialist to install a thermostat … they will likely not be able to include it with Vera.
You are taking a chance to do this remotely if it will not include even in High Power mode.
You could use the Program Logic Event Generator plugin to turn on/off, and or set the setpoints of
your thermostat if the aux temp measurements indicate excessive settings.
Well I need to retract things about Nexia. They did indeed send a replacement and I have it in hand. I plan to set it up from here for all the setup options and then mail it to my other house. Installation should be a snap by only removing the old tstat from the faceplate and snapping in the new. As for getting it included into Vera I am hoping that I can do it using the high power setting. As I indicated it is only about 8 feet away from the Vera. Not foolproof by any means. But in case it does not work I can have them swapped right back.
As for the question about fixing it now the answer is yes. With summer approaching having a tstat that reads 3-4 degrees high and has sluggish spells (where the reading stays high even when the actual temp drops by 6-8 degrees and then slowly recovers over an hour or so period) would fail the a/c system due to continuous use.
The thermostat is in the dining room at the hallway entrance. Part of a great room. The Vera is in a closet across the hall. I have watched the temps for the past 3 years and have a good understanding of the differentials between the 2 wall mounted 3 way sensor readings (about 8 feet high at opposite ends of the house) in comparison to the tstat. Generally the 2 other sensors have been 1 to 2 degrees above the tstat. Partly due to being higher and partly due to sun loading on the walls that they are mounted (east wall and west wall). During the night they come close to the same reading, but never lower than the tstat that I can recall.
One day about 2 weeks ago suddenly the tstat was 3 degrees above the other sensors. Other than a few times it seemed to hang it has followed that way. Like a delta temp was input. However I checked the calibration setting and it shows -1. Strange as I never adjusted it, but not enough to account for the change.
I do not have an answer for the sudden change. But I seriously doubt the other two changed in synch. The other thing that caught my attention is on the day it changed the outside temp was at a high of 90 and the air conditioner ran for over 12 hours straight. Never happened before even in mid summer. And when it occurred the 2 temp sensors were down to 70/71 while the tstat was holding at 75. Strange happenings indeed.
Yes, Vera is in the closet. I may have said it in a confusing manner before. The tstat is in a pretty normal area for tstats. I wish I knew how to attach a picture as I have a layout of the house with all the z wave components identified.
Probably not the best location for Vera but it needs to be in a locked area so guests do not play with it. I plan on adding a separate antenna to help with connectivity at my next visit. Note I have 65 devices currently installed and the tstat is actually the closest one that is not in the closet itself.
