"Smart" thermostat

[Nil]

I installed a new programmable digital thermostat in my house a few days ago, a Honeywell RTH7600D. It has a feature they call "Smart Response Technology", which is supposed to "continually learn when to pre-heat and cool your home so you are comfortable at your programmed time". The feature seems to be included all but their most bare-bones products. I'm not sure it's working correctly.

I have it currently set to be 70 at 8:30 AM. The first morning after I installed it, I woke up at about 7:15 because it was so warm, and by that time it was already at 70, so it obviously had been on for a while. The next night I woke up at about 5:30 - I think I may have heard the furnace blower kick on, and sure enough, the heat was on. I managed to doze and wake enough times to guess that it reached 70 in about an hour. Since then, I know it started heating early, but haven't been able to rouse myself to know exactly when, only to know that reaches 70 well before 8:30. This seems way too early - it's costing me money to heat the house for as much as 3 hours or more when I don't need it.

I called the 800 number on the box and talked to someone who didn't really know that much about it. She was familiar with the feature and understood my complaint, but she couldn't tell me if it was coming on unusually early, or how long the thing takes to "learn" it's task.

The feature is turned on by default, but I can disable it, which I probably will anyway. However, I don't want to have spent my money on a defective machine, even if I don't use that feature. If it seems that it's not working the way it's supposed to, I'll return it.

So, for anyone who owns a Honeywell or other brand stat with this or a similar feature...

- is this normal behavior, for it to come on several hours earlier than the programmed time? That seems excessive.

- will it really, as they claim, "continually learn" to turn on at a reasonable time (for me that would be 1 hour or less), and how long should I expect that learning period to take?

[trader_4]

I have two different models of the Honeywell VisonPro series which have the same kind of adaptive response for recovery from setback.

I've never seen them come on anywhere near that early. They do err on the side of getting there a bit early, but overall, it works very well and if it's early, it's by more like by 20 mins. I really like the feature and would want it in any thermostat I buy. For example, recently it went from outside nightime temps in the 30s, to temps around 12F, resulting in the inside temp dropping more over night. The thermostat correctly started the furnace about an hour earlier and got it to the correct temp just prior to the time it was supposed to.

Mine were never anywhere near that far off, right out of the box. They do learn and adjust though based on experience. I would give it a week and see what happens. If you're worried about it getting there too early, you could temporarily set it for a later time and see how it behaves. If it starts getting closer, zeroing in on that time, then you could reset the time again. But given that it's off so much, it sounds more to me like something is wrong with it.

Are you sure it's installed correctly? IDK what has to be set on yours, but mine you had to set whether it was a heat pump system, furnace, etc. If it thought it was a heat pump for example, it might fire it up sooner, IDK. I'd review all the install settings.

[Tony Hwang]

Hi, What is the temp. you set for sleep? 'stat needs some time to learn the pattern. After a few days it'll learn how much it takes to bring up the temp. from sleep to wake and gradually adjusts it. Isn't it logical, is it? I always used Honeywell 'stats and my favorite is Pro 8000 series. I am using wireless one at home now. You are a bit impatient, aren't you?

[Tony Hwang]

Hi, Also did you have a look, extra things in the installer options to fine tune it?

[Nil]

On 15 Jan 2015, Tony Hwang wrote in alt.home.repair:

60 F.

Is it logical that it should take almost a week to adjust, is it? Is it logical that it should come on more than 3 hours early, is it?

I don't think so. You are a bit impertinent, aren't you?

[Nil]

On 15 Jan 2015, trader_4 wrote in alt.home.repair:

Then maybe you can answer another question I've been wondering about: If I reprogram the times and temps, will I also have to go through this painful training period all over again? What about if I lose power?

That's a big difference - 3+ hours vs. 20 minutes.

I installed it 10 days ago, but I only programmed it to my schedule not quite a week ago. I guess I have to get up very early to know for sure how much it's adjusted itself, if at all. Maybe it's getting better, I don't really know, I just know it's not there yet.

I did check out all the fine-tune settings a couple of days after I installed it. All the out-of-the-box settings were appropriate except that it was originally set up for a low-efficiency gas furnace. I changed it to high-efficiency. Otherwise, I think the other settings were good.

I guess I'll give it a couple more days and monitor it more closely. I just hate to think of all that expensive heat going up the proverbial chimney.

[gregz]

I can't think why any difference in furnace efficiency. It would have to know btu output also and dwelling size, and heat loss. Can you change time one day and monitor temps while your up ?

Greg

[mike]

Might be interesting to run some experiments to graph temperature decay time from 70 to 60 and back from 60 to 70. First tells you how much heat you're losing. Second tells you how much you're adding. The difference should tell you something about the thermal mass of the house.

My thermostat has the smart predictive on-time to get the house at the right temp at the right time.

I have a running graph of the on-time of the furnace. It's sensitive enough that I can see the % on-time throttle back when I get up and turn on my computer. After watching it for a while, I convinced myself that the amount I saved during the setback interval was only slightly more than the energy it took to heat all the thermal mass back up. I turned off all the automagic stuff and set the thermostat for 66F. The better your insulation, the less you save with setback. The more you're home, the less you save with setback.

[trader_4]

With regard to changing times and temps, no, it doesn't affect what it's learned regarding the adaptive recovery. It just learns how long it takes to raise the temp. It knows that it has to raise it X degrees. It also knows how fast and how far the temp dropped during the setback time, how much the furnace had to run, if at all during the setback period. From that it can calculate how long it's going to take to get the temp back up.

Losing power has no effect, it has batteries. IDT even changing batteries matters. It probably stores the learned parametet in flash memory with the settup parameters, etc.

I'd take it back. A week is more than enough for it to be close to correct. Like I've said, I've got two of them, neither did anything like what you're seeing, even first day.

I highly recommend the Honeywell VisionPro. This is similar to the one I have:

They also have a wifi model. If that was available when I bought mine, I would have gotten it. I have enough times when I don't know for sure, when I'll be back. With wifi, you can have it resume it's normal temp from your smartphone when you're on your way back from the airport, etc. They also just showed a new round, stylish thermostat that looks like the Nest at CES. IDK anything about it, just mentioning it in case you have any interest.

The only big negative about Honeywell is that with the better thermostats, eg VisionPro, if you're a consumer, they won't answer any questions about how to set it up, install it, etc. They just tell you to F off and call a contractor, even if you just want to ask how to change one of the basic settup parameters. The documentation is good, but if you have an install problem, you're on your own. You can find them on Ebay, that's where I got mine.

K

You're not really wasting much in terms of heat by it getting the temp back up to normal 2 hours early. Like someone said, during the night, when it's set back, you're slowly depleting the thermal mass of the house, all it's contents. The vast majority of the energy it's burning during recovery is to put that heat back in. It has to do that whether it starts at 5, 6, or 7. The savings come from the fact that while the house is at 65, during the night, it's losing a bit less energy per hour than if it were at 70. Let's say it was set at 70 and over 6 hours, when it's set back, the temp drops to 60. That's an average temp of about

1. So, what you're saving is about the difference between having had it set at 70 for those 6 hours versus 65. It makes a difference, but it's not even close to the hour of constant running that the furnace does in the AM to get it back up. It's just a small percentage of that.

The temp loss due to heat conduction is proportional to the temp difference. Let's say it's 20F outside, 70F inside. That's a delta of 50F. At night, if you set it back to 60F, let's assume it gets there after 6 hours, about the time it's going to go back up. That means you had an average temp of ~65 for 6 hours, that would be a 45F delta over outside. So, instead of a 50F temp delta, or driving force for heat loss, you had a

45F one. That's a 10% difference. So whatever fuel you would have used during those 6 hours, you probably saved ballpark 10%. Even if you're spending $400 a month for fuel, when you get down to it, the difference tha set back makes is definitely worth it over long periods, but the furnace starting back up 2 hours early, for a week with that thermostat is probably only a buck.

I'd just return this one now. From what I've heard, something is very wrong. Even if it started up 2 hours too soon day one, by the next day it should be down to an hour, then maybe a half hour, something like that. It doesn't take a week+ to figure out it's way off.

[Tony Hwang]

Hi, During that one week period was the outside weather steady? My house is R2000 spec.'d pretty air tight, outside weather does not impact much to maintain indoor comfort. Mine is set at 17.5 and 20.5 in Celcius I usually get up at 7 AM, furnace comes at around

6 AM every day. Give or take few minutes.

[Peter]

That's not been my experience with a Honeywell adaptive thermostat. My experience is that even temporary overrides of a learned program will require the thermostat to relearn the original program. As an example, when I want to keep it somewhat warmer than usual on a particular winter night (guests visiting) and use either the "temporary" feature or the "hold temp" feature overnight, after resuming the program with "run program", for the next 3-4 days the furnace will come on at least an hour earlier in the AM than it would prior to the temporary override, even though the outside temps are about the same.

Mine generally takes about 3-4 days to stabilize start time after changing a setting - either by override or by changing the programmed setting. However, the more modern models may learn more quickly - my Honeywell Chronotherm III is more than 10 years old.

[Tony Hwang]

Hi, It also depend on what kinda furnace. ie. single stage vs. two stage. variable speed ns. single speed blower, etc. I seldom see 2nd stage coming on. Having wireless thermostat I moved it around to find a sweet spots as well for winter or summer.

[trader_4]

Well, maybe the lower part of their product line is junk. IDK. All I know is how the VisionPro implementation of adaptive recovery works and it works very well. And if the other ones work as you say, they are indeed junk. Because changes like that should have nothing to do with the thermostat having to learn all over again. If it already knows that given the past history, it takes 1 hour to get it from 65 to 70, then it can surely predict with good accuracy about how long it's going to take to get it to 72 or 75. Changing the time by an hour or two, similarly shouldn't require learning anything all over.

No such problems here with the VisionPro. I can set it to any override temp, change the programmed times, and it takes it to that temp, at that time, etc. So, maybe that's the difference, he needs to buy the better model. But if they work anything like he says, I would think they would be returned in bucket loads.

[trader_4]

The thermostat doesn't have to know btu output, dwelling size, etc. It has all the basic info from experience. The thermostat quickly learns how long the furnace has to run to raise the temp one degree, or two or

5 degrees. That will vary somewhat based on whether it's 10F outside or 40F. If it can raise the temp 5 deg in an hour when it's 40F outside, maybe it can only raise it 4 deg/hr when it's 10F outside. But it also knows if it's closer to 10F outside or 40F. How? If it's been maintaining the temp, then it knows how many mins the furnace ran in the last hour. If it's in set back, then it knows how much the temp has dropped in the last 6 hours, the last hour, etc. That's the pertinent information.

And I don't see why any adaptive recovery program couldn't get the recovery temp and time close after just a day or two. Just the fact that it started 2 hours too early the day before, like the OP is saying happened is a huge input. It ain'r rocket science to have an algorithmn that say, OK tomorrow cut that time in half. Adaptive recovery isn't worth spit if it's that dumb.

[Nil]

On 16 Jan 2015, Peter wrote in alt.home.repair:

Well, mine is brand new, though with a 2012 copyright on the manual. But it may be acting like yours, where if I adjust the settings it has to learn all over again. That makes the feature just about useless, especially if it responds that way to touching the temporary change buttons.

In any case, I decided that mine is either defective, or of a poor design (if what you claim is true.) I'm going to return it for a new one and that should tell me if the first case is true.

[Nil]

On 16 Jan 2015, trader_4 wrote in alt.home.repair:

As you say, it shouldn't be that dumb or slow or hard to deal with. It should just work, and if temporarily changing the temperature throws its whole learning off and requires a new week of adjustment, that makes it useless.

I don't know if that's the case, but I'm pretty sure mine is defective. I got up 3 1/2 hours early this morning, and the furnace was off. Then I got up again an hour and a half after that and the furnace was on and the stat read "Recovery". That means it started up at least two hours early. If it is, indeed learning, it's learning too slowly to be useful.

I'm taking it back to Home Depot to exchange for a new one. If that doesn't fix things, I'll have to look for another brand or model.

Thanks very much for your feedback. I had nothing to compare it with, so this was valuable to me.

[Scott Lurndal]

This one should make you happier.

[thekmanrocks]

When it comes to thermostats, K.I.S.S. is the best feature! :)

[Tony Hwang]

Hi, Not interested in saving energy cost a bit and improving indoor comfort year round? If not, I am sure K.I.S.S one will do.

[Nil]

On 16 Jan 2015, [e-mail] (Scott Lurndal) wrote in alt.home.repair:

I like simple, but this one won't control my AC.