nest home thermostat not tracking state properly

Posted on
Wed Dec 06, 2017 6:23 pm
dduff617 offline
Posts: 407
Joined: Jul 05, 2006

nest home thermostat not tracking state properly

I was testing a configuration where I have Indigo controlling a radiant heater by having it turned on when Indigo senses that my Nest thermostat is calling for heat and then turning off when it is no longer calling for heat.

Recently, I noticed the radiant heat was on and it was making that part of the house uncomfortably warm. When I examined the situation, I found that Indigo was not correctly tracking the state of my Nest Thermostat -- Indigo said the thermostat was calling for heat and the temp was 67; looking at the actual Nest device on the wall said heat was off and temp was 71. I selected the Nest thermostat in Indigo and clicked the "Send status request" button and it immediately seemed to start tracking again.

I'm not sure how long the "outage" lasted, but I suspect multiple hours. Actually grep'ing indigo logs indicates there were no updates in the last two days! While poking at the logs, I noticed there is what I guess is the Nest Home-specific log "NESTHomeErrors.log", but it simply says the log was reset a few minutes ago, so if it ever had any info about the problem, it seems to be lost now.

I'm wondering if anyone else has seen this problem - specifically Indigo not updating the state of Nest Home devices (for long periods)?

I had the feeling Nest Home has been working well for me (for a few years now), but up until recently, I mostly used it for adjusting set points, ether manually or via schedules/triggers. Thus, I wasn't really paying attention to whether Indigo was tracking Nest status accurately, so perhaps I've been having this problem all along and just not really noticing it.

Anyone have experience with this? Might there be a condition I can trigger on to detect a problem (such as "last update time" is more than 5 minutes ago or something)? If so, I would try to have NestHome reconnect or resync or whatever, and if it still doesn't update, then send me an error message.

Posted on
Wed Dec 06, 2017 7:19 pm
dduff617 offline
Posts: 407
Joined: Jul 05, 2006

Re: nest home thermostat not tracking state properly

Some additional observations: I see by Nest Home thermostat objects in Indigo have some interesting custom states and I maybe some possible signs of other problems.

One custom state is "last connection" which seems to be an absolute date/time string and seems to have a value that is about 9 minutes old or so. Another custom state is "time_since_last_connected", which has a value of "-1 days 19 hours 5 minutes and 36 seconds". This makes it seem like something is out of whack.

So I was thinking of writing a trigger to check if these get out of whack, but I'm confused as to what the different states represent and what a large negative time value means. What should I check for?

Any insights appreciated.

Posted on
Fri Dec 08, 2017 9:47 am
dduff617 offline
Posts: 407
Joined: Jul 05, 2006

Re: nest home thermostat not tracking state properly

So as I reported, I was trying to use NestHome in a new way involving tracking state info and using triggers based on changes to "Is Heating?".

Here's a summary of what I'm observing:

I am finding that my NestHome thermostat objects in Indigo sometimes DO NOT TRACK the actual state of the Nest Thermostats in anything close to what could reasonably called "real time". This appears to not be an isolated event in my configuration, but rather I have observed it happening several times and lasting for periods of at least several minutes at a time and at times for multiple hours. If I click "refresh" on a thermostat in Indigo, it appears to change to the correct state at that instant.

"Active control" of Nest devices - e.g. changing set points and things like that, which are the only things I had been using NestHome plugin for until recently - seem to work and take effect within a few seconds.

My configuration:

In the NestHome plugin settings, the "time between updates (secs)" shows as 60 in my configuration - so it seems as though it should be updating regularly.

My NestHome config has 2 thermostats and 5 nest protects.

Running Nest Home v. 2.0.50
Running Indigo 7.1.1

Things I've tried:
Reloading plugin.
If I turn on debug-logging in the plugin settings, I can see that it is attempting to connect about every minute (as expected). I also see a lot of other warnings and messages, which I assume are not critical, but haven't had time to analyze in detail (also the plugin config warns that sending debug info to the logs is "not recommended", so I assume this is why.

Since it's been a while since I started using NestHome, I went back and looked at the docs which list as one of the features "Know exactly what your system is doing with real time access to System State (heating, cooling or off)", so I believe what I'm trying to do here is supposed to be within the bounds of what the plugin can provide.

Posted on
Tue Dec 26, 2017 3:45 pm
mikeL offline
Posts: 45
Joined: Apr 30, 2010
Location: Gatineau, QC

Re: nest home thermostat not tracking state properly

I have noticed a similar failure of the plugin to respond in real time to on off state changes of the heater or air conditioner controlled by my Nest thermostat. In my case, I’m computing the total HVAC running time, and by inference, the cost of power required to heat or cool my house. When the heating or cooling turns on Indigo grabs and saves the current time (turn_on_time in seconds) and when heating or cooling subsequently turns off Indigo subtracts the turn_on_time from the new current time to get the running time. The resulting value is logged, analyzed and plotted.

So, big problems in the data set occur if the plugin misses the turn_on or turn_off events from the Nest. I’ve added code to my analysis routines to ignore data sets where either a turn_on or turn_off time is missing. But, I sometimes have to go into the log files and adjust the data to fix any problems that occur when the times are present, but much longer than I think they should be. (I can only guess what the actual times are, but obviously the plugin failed to see a turn_off event in real time when my heater is apparently still running after 5-6 hours—it’s rarely that cold here!) This type of error occurs once or twice every couple of months.

I don’t know why the plugin misses these events, but this is a general problem for real time communications between asynchronous systems. There are better solutions to ensure higher reliability such as MQTT with its Quality of Service levels. Perhaps Mike’s plugin could take advantage of MQTT, but I don’t know the technical details and cannot say how much effort this would require for our benefit.

Here’s an example of how I use the data I get from the Nest plugin. I’d say something went wrong between Sun 18:00 to Mon 00:00 because the furnace is apparently on, but the Inside temperature has continued to fall. In fact, the Nest was in Away mode at that time, so the heater was most probably off—an example of a missed or delayed turn_off event.



Cheers,
MikeL
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Posted on
Wed Jan 03, 2018 11:57 am
dduff617 offline
Posts: 407
Joined: Jul 05, 2006

Re: nest home thermostat not tracking state properly

I appreciate the input, MikeL. Good to know it is apparently not something specific to my system/devices.

Also, I will take inspiration from your plot to setup my own so I can keep a closer eye on my system going forward.

Posted on
Thu Jan 04, 2018 8:23 pm
mikeL offline
Posts: 45
Joined: Apr 30, 2010
Location: Gatineau, QC

Re: nest home thermostat not tracking state properly

dduff617 wrote:
I appreciate the input, MikeL. Good to know it is apparently not something specific to my system/devices.

Also, I will take inspiration from your plot to setup my own so I can keep a closer eye on my system going forward.


Yes, having this visual record has improved my insight into how my system works. For example, I can set the temperature back enough at night to earn a Nest Leaf knowing that the house will never cool down that low.
Cheers,
Mike


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