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Nest not calling for heat

jrbloom
Community Member

I have a Nest Thermostat E wired to an electric heater in my workshop. It has been working perfectly for several years. 

This weekend i went out to a cold workshop. Initially assumed my custom control box was failing. However, going into the troubleshooter on the thermostat and forcing it to call for heat fired the heater up immediately. So looks like wiring is ok.

The temp is set well above room temp but it doesnt seem to be calling for heat.

Any ideas what might cause this?

77 REPLIES 77

jrbloom
Community Member

I feel like i am spamming with all of these replies. My appologies ...

I have reopened my ticket to explain that the downgrade fixed 'E' but not my non-E thermostats. I have spelled out that it affects more than just the Thermostat E.

I will do my best to keep nagging until i see a fw change on the house devices. It is likely easier than you guys wading through the same first level support treacle that i faced (it took several hours of stupid pointless box ticking, to get an escalation, and the detailed description was too much - these guys are just following a script of predefined issue resolvers).

Cant promise it will make any difference. But i will do my best. Additional complaints wont hurt tho if you are feeling very patient 🙂

Jon

I don't mind.  I'm just happy you found the problem!!    Note: I tried adding the tag "Nest Thermostat" to one of my replies to get the thread to appear more broadly, but it didn't seem to take.   Maybe you can edit the original post to add that broader label.

jrbloom
Community Member

I've edited the original post to fix the tag to Nest Thermostat.

freezing-in-nd
Community Member

Just wanted to +1 this exact same issue and thank you for the efforts @jrbloom.  I have radiant floor heat in my garage and a small shop that two different gen3 thermostats control.  It's not uncommon for the safety temp to get triggered if I open the garage door or shop door when it's -20F outside for pretty much any amount of time (i.e. to bring in the groceries or move something in/out of the building).  So far, I've usually had to end up manually restarting the thermostat to get it to trigger a heat call, but as others mention, it's a total pain since you have to physically be there in person.

Spoke to three different techs from nest today, spending almost 2 hours with them.  First tech said it was my HVAC setup and that I should call a nest pro installer (was very rude and didn't even relay back the question), second tech was nice but couldn't understand the issue so they supposedly escalated to a senior engineer.  Senior engineer spent less than 2 minutes with me and was unwilling to do anything without a factory reset (which I couldn't do on the call at the time).  Brutal customer experience to say the least.

Ah. Yes - the factory reset (ctrl-alt-del?) cop-out. I just said I did it already - twice. And I said others on the Forum also had the issue. The 'tech' was dismissive and said there had been no reports. Eventually I also got handed to a senior 'tech' who simply tried to take me back through all the same steps the previous assistant did. It wasn't fun.

They aren't techs though. Just low paid staff following a script. They are following orders. I THINK they really did escalate in the end since soon after my thermostat downgraded. But I'm still sceptical.

This is the worst support experience I have ever faced that's for sure.

I actually am an certified HVAC tech...  I just do that part-time, as I normally am a software dev...  So, you might say my work experience is in both of these areas.   And yes, I totally agree with the whole worst customer experience ever!!!   It all started for me with not even being able to install the stupid thing because my email is a G-suite account.  Apparently, Google Home will not work with a G-suite email address.   D'oh!!  That took me a couple of hours to figure out and then get around (and of course, all while I had already ripped out my existing thermostat and wired in the Nest while it was 5F outside).   I am really regretting not just sticking with a tried and true Honeywell thermostat, of which I know them pretty well and they work great!!   But, I figured I should get some experience with these devices, so you know, when I have to help some customer...   Well, any future customer asks me about them, my advice is definitely going to be avoid it like the plague!

jrbloom
Community Member

I'm also a sw engineer, with electronic design experience. So like you, not so easily fobbed off with pointless box ticking exercises.

I was certain this is a fw issue by the time I called support. It was so frustrating having to patiently explain over and over why it MUST be a software issue only to be asked to describe my wiring setup again. At one point, they asked me which Android device and Nest App version I was using. I lost it a bit at that point and the poor support lady had to patiently explain that it was a box she needed to fill in to raise the escalation. Like I say - not their fault Google's system is useless. They just get the flack because they're customer facing.

Elswann
Community Member

I still think 6.2-22 (or whatever) had something to do with my issues, but since cleaning my flame sensor it seems to be working better.

I watched this video and my furnace was doing this exact thing.

https://www.youtube.com/watch?v=tYwR9qL4lnk

It was a bit scary watching it, but cleaning the sensor wasn't hard. I just did what he said. 

A lot of furnaces will have a flame out indicator light (typically a series of blinks) that will indicate that was why it failed to heat.   That carrier in the youtube video definitely does, so I'm a bit surprised he didn't show it blinking out that diagnostic.   But, yeah, easy to clean (or even replace if you have to).    And yeah, pretty easy to diagnose that situation.    This particular scenario is the thermostat locking itself out of calling for heat because the indoor temp puts it in a safety operating mode.

jrbloom
Community Member

That's a different issue for sure. My workshop Nest is controlling a pair of electric wall heaters.

bill6
Community Member

I am having the same safety point problem.  thank god this thread has provided a workout that is working

dmasiero
Community Member

Same trouble. 6.2-22.

danieljin
Community Member

Same issue on 1.1-9. This is the google nest thermostat: https://store.google.com/us/product/nest_thermostat?hl=en-US

brucemarc
Community Member

I believe the following is happening...  The "Y" wire controls the AC relay.  This is located outside.  It takes more energy to power these relays when its really cold outside.  So between the energy hog called a Nest and the cold relay there is power issues.  I would not buy a nest if you live in a cold climate.  If you want to temporarily fix this, detach the Y wire in the winter and reattach it in the summer.  Bummer

I disagree; I don't have a Y wire in my setup (radiant floor heat) and am able to reproduce the issue.

This would not explain why changing the safety temperature suddenly causes the Nest to start calling for heat.   And it's clearly the Nest not calling for heat as it doesn't even indicate it is trying to heat.   There's a big difference between the Nest calling for heat and the furnace just not heating versus the Nest not even calling for heat (even though it will when the indoor temperature drops below the safety temperature).

I also do not have an A/C unit at all, nor do I have "call for cooling" (Y) connected to anything.

But, maybe in your case, this could be a problem.   Older relays can require more power to activate, though normally colder temperatures do not - most relays are merely a magnetic coil which actually operate more efficiently with cold.

I'm unsure of the technology the Nest uses internally to switch on the call for heat/cooling, but many thermostats will use an internal mechanical relay to isolate the power.   However, I'm pretty sure the Nest uses a solid state type relay.

Not having enough power to activate the relays would be a function of the transformer not being powerful enough (eg, it's VA rating).   But, you are right in that powering a Nest does take some energy and if the original transformer was barely providing enough power to activate the original relays, then adding the Nest could certainly put it near or over the power that the transformer can deliver.  And in that case, you may have intermittent activation problems - but in that case the Nest would still call for heat/cooling and the system would just not run.    The solution in that case would be to merely install a more powerful transformer.

If temperature was the issue, then how does restarting the nest thermostat or disabling and enabling safety temp, immediately make the thermostat call for heat?

I still am convinced this is software related after all the testing.

jrbloom
Community Member

Me neither. In any case we can reliably get nest to turn the heating on by manually manipulating the safe temp. So clearly there's no actual electrical issue here.

bill6
Community Member

It clearly is the safety point problem thank god we know how to work around it but Nest should be ashamed at having this diagnosed and reported problem unresolved for so long

And don't forget how they annoyingly refuse to listen to most of us about it being an actual problem... 

MarkLR
Community Member

I’m having this issue on a Google Nest Thermostat (Model: Thermostat 1.4) running software version 1.1-9, but my issue does not happen when it reaches the safety temp. It has happened 3 times since mid December when I first hooked it up. I have 2 Nests, but the issue only has happened on the one downstairs. The Nest should kick on to 68 in the morning, but I’ll go downstairs and it’s reading 59 or 60 degrees, the one upstairs is running fine when this happens. Manually changing the temp seems to do nothing and the heat won’t kick on. Only a restart of the system will get it to start calling for heat, and as stated can only de done at the unit and not through app. 

Clearly this is a different issue than the Safety temp problem.

You mention you have two Nests, but no other details.  Are these Nests controlling separate units or separate zones within the same unit?   Are they somehow wired together controlling a single furnace (that could be problematic)?  Is the Nest calling for heat, but your furnace is just not running (it will have an orangish background and orange numbers when calling for heat versus just having a black background & white temp number)?

Note: If you are trying to control a single furnace based on temperatures from multiple locations, you should be using Nest Thermostat sensors in the location.

Also, you mention "Only a restart of the system" - what exactly are you restarting?  Just the Nest?  Or the nest and the furnace?   I'm just trying to isolate whether your problem is really with the Nest or is actually with the furnace.

Anyway, some more details would be helpful for any of us to be able to give much more advice.

MarkLR
Community Member

Sorry you're right, I could see how that info could be confusing.  Here's the details, and while some of this might sound like I know what I'm talking about... I only do a little bit.

I have 2 Nests (Model: Thermostat 1.4), upstairs and downstairs, hooked up to an oil boiler with 2 Taco zone valves.  There's some other complicated stuff going on here because I'm using a FAST-STAT common maker because I only have 2 wires.  That being said, it's hooked up, displays properly, wiring looks good on the unit display and app, all seems ok there and works fine... except for when this happens.

When the downstairs unit becomes unresponsive, the upstairs unit still seems to be working fine.  The downstairs unit shows orange numbers like it's calling for heat, allows me to change the temp setting to crank it up higher, but the boiler never kicks on for that zone (again upstairs zone on that Nest is running fine during this).  

I wondered if the Taco zone valve was maybe bad the first time it happened, but when I restarted the Nest unit, it suddenly starts working and the boiler starts going for that zone.  I do not need to do anything at the boiler, although the first time I literally turned everything in the whole house on and off and jiggled every wire available, but once I found that restarting the Nest unit got it to start being responsive again, that's all I've done the last 2 times.  

Okay, that is somewhat of a complex setup.  One suspicion is that you may be having some 24vac power issues assuming that you only have one transformer that is supplying power to both zones, valves and thermostats.   It could be that the power rating of the transformer isn't enough to consistently supply power to the Nests while also switching the control valves.   If that is the case, you could install a larger transformer (higher VA rating).   However, really the only way to know whether that is the problem is to measure the amperage being pulled from the transformer while under full load.

Also, I do not have any experience with how multiple Nests might behave using a shared transformer.   It is quite possible there could be some interference going on between them when one (or both) of them is calling for heat. 

Third, with such a complex setup, there is always the potential for something to not be wired exactly right, even though the Nest is reporting that it "sees" the wiring is right.   For example, if the wire from the transformer that is being used as "common" is different between the two thermostats, then there can be scenario's (like when both units call for heat), that could cause the AC amperage to actually cancel each other out and lead to no actual voltage being present.   That could in turn be what causes one of the thermostats to get into a locked up state.  It would also cause the control valves to not actuate.

One approach to dealing with your multiple zones/multiple thermostats would be to use two separate transformers to power each zone's thermostat and control valves.   This is actually a fairly common approach to make sure this kind of cross-wiring doesn't happen.

Another approach would be to have used the more expensive Nest Learning thermostat or the Nest-E (both of which can handle multiple zone systems) and then use a remote temperature sensor in the other room and configure that remote sensor to directly control the 2nd zone.

Anyway, at this point, I would recommend that you have a on-site tech inspect your setup.  They could then confirm the wiring and perform any voltage/amperage measurements as well as doing a functional check on your control valves and such.  Probably not the answer you would want to hear.

HTH

I disagree with the advice in dhx227's post.  Easiest way to confirm the suspicion is check the "Battery status" info on both nest units meets the specs documented here: Nest thermostat's technical information - Google Nest Help.  I have a very similar setup as MarkLR and mine has worked fine for years. I confirmed mine with nest support, when I opened a case for this safety temp issue, as they pushed really hard/wanted to pin this whole problem on my physical setup as well, but given my setup aligns with every single one of their supported specs, they finally broke down and admitted it wasn't a hardware issue (rightfully so, as a reboot of the thermostat kicks in a heat call as expected, arguably reboot would pull more power than a regular heat call kicking in). 

@dhx227, it's not uncommon for the 24v to be shared between stats on the Taco boxes.  In addition, as far as I understand, you cannot wire a single nest unit to kick in the heat pump for multiple zones as well; you need a stat per zone: Zoned system compatibility with Nest thermostats - Google Nest Help

Fair point about the Nest and multiple zones.   I had thought I saw that the Nest-E and Nest Learning could control multiple zones from the single thermostat, but I must have just misinterpreted that from multi-stage support.  Thanks for the reference to the specs.   So, yep, they do suggest using multiple thermostats for each zone.

However, not having seen nor verified the wiring in this situation, I can just tell you there is lots of room for it to get miswired - even if one Nest tells you it's fine.    And yes, it is not uncommon for a single transformer to be shared in this setup.   However, depending on the control valves used, the power rating of that transformer needs to be considered.   Most 24vac transformers are 40va - that's only 1.6a.   That may not be enough to drive the two Nests and the control valves (and whatever else is drawing power).   And sure, I'm definitely not very familiar with these Nests to know how well they handle momentary low amperage.

Also, merely looking at Battery status will not tell you in any way if common's are cross-wired between the thermostats.  I've seen it done too many times to count and the results are always erratic behavior.

 

dhx227
Bronze
Bronze

BTW, I noticed this weekend that my Nest is now on version 1.1-11 which was just released on Jan 26.   I do not yet know if this version addresses this problem.

bugmills
Community Member

Thanks.  I checked this morning and 1 of my 3 has updated to 1.1-11.  The other 2 remain on 1.1-9.    Based on one test, the one that updated seems to work correctly now (no longer stuck in Satefy land).   We'll see how it goes.

I tried manually searching for update on the nest itself, but it says it's up to date on 1.1-9

danieljin
Community Member

@dhx227 any update on if the update fixed your issue?

Unfortunately I don't have any update.   For me, the situation would only present itself when my mountain home lost power for over a day.  In December and the beginning of January that was happening every week.   Things have seem to stabilized in terms of power (yay).

I think we will need to rely on the people using the Nest in their shops where they regularly get that cold.   Eg, @jrbloom or @bugmills (who already gave his update above).

On another note: I think I now have a new problem.  The Nest seems to drop connection with the server and won't reconnect.  I didn't previously have that problem.   The weird thing is once I get to my mountain home, the Wifi is fine (works for all the other devices connected to the Wifi).  The Nest also says it's connected to Wifi, but gives error code g.co/nest/m22 when you click on the check Nest Server option.   It takes a restart to get it to reconnect.  UGH!  This thing is really proving quite useless for remote control!!

Today, a second one of my three updated to 1.1-11, and now seems to be working properly.  The third one is still on 1.1-9.

CBFox
Bronze
Bronze

FYI, the original issue on this thread (Nest's brain gets fixated on Safety Temperature and can't be persuaded to obey any other commands) whacked a lot of us during the northeast blizzard last weekend.  I've been referring people to your excellent workaround and your efforts to engage Customer Service in fixing the bug.  Thanks to those of you who spent time on this!

m_courteau
Community Member

Wanted to share what worked for me. We had both of our thermostats set to Eco with the lower temp being 13 degrees BUT the heat would not turn on until it reached the safety temperature of 7. Obviously not good!

I actually didn’t notice this for a couple months because this was our cottage and we do not go there in the winter. 

To fix it, I turned off the Safety Temperature temporarily. 

Here are the steps:

1.  Turn off the Safety Temperature. 
2. Turn the thermostat to Eco and adjust the temp by a degree or two. 
3. The heat turned on. 
4. I left the Safety Temp off for a few hours and monitored the temperature remotely. 
5. The temperature was increasing, good. 
6. After it increased a few degrees, I turned the Safety Temp back on to 7 degrees. (Eco was set to 13). 
7. One thermostat did turn off when I turned on the Safety Temp, but I just turned the Safety Temp off again, adjust the Eco temp by a degree and the heat turned back on. Then I was able to turn on the Safety Temp again. 

I’ve been monitoring it remotely for the last two days and everything seems to be working. I also lowered the Eco temp to 10 degrees with no issues.

geekfarm02
Community Member

I've had this happen to both of my Nest devices.  My E device that was out in the garage was doing it about two months ago.  Now the thermostat that I have in my house is doing it.  Woke up to a house 5 degrees below the regular temp.   Bad part about that is that it is no where near the safety temp threshold to try to get it to reset itself.  Might end up going to buy a different thermostat.  I'm not going to put up with this crap.  Devices like this that control people's ability to live in places where it's below freezing should have support people who can help/monitor situations like this.  Obviously this is something that is happening more than once.

 

https://www.reddit.com/r/Nest/comments/rkqmqm/nest_wont_turn_on_heat_issue/

taarheel
Community Member

Same problem.  Same situation with a vacation home.  Fortunately my brother was going there today and did Restarts on both the thermostats, and the problem went away.  My theory is that I provoked this software bug when I was trying to remotely adjust the Eco setting.   I was having some other problem, and I turned both thermostats to Off, then back to Heat.  After that the system just behaved as if it was Off, although all the settings appeared to be as I had set them -- including the  Mode showing Heat at the the thermostat.   This is the discontinued original Nest Thermostat.  Might be a bug unique to that product, and for all I know they aren't fixing bugs on it any more.

I like Google, but they really kind of have their heads up their a**es with the inconsistencies on how they manage these thermostats.  Some things you can only do in the Next app, some things only in the Home app, some things only at thermostat.  Come on Google, get your freaking act together.  I know these products are like a flea on an elephant, but they're kind of giving you a bad rep far beyond their bottom line impact.

 

GregSo
Community Member

I want to add that I also experienced this exact issue on my Nest Learning Thermostat Gen 3 today. A reboot of the thermostat resolved the problem. 

Google, y'all need to get your heads out of your asses and fix this firmware (6.2-22). 

JaredOberhaus
Community Member

Try this:

Choose Equipment, and find Equipment Settings (navigate through some intermediate panels), then find Heat Pump. The setting "Use the heat pump auxiliary heat when the outdoor temperature is below:" might be too low. Auxiliary heat will not activate unless the outdoor temperature is below this setting. I assume that the value you choose here is dependent upon how efficient your heat pump is.

This setting is different than "Safety Temperature."