Eliminate Thermostat

[DrLumen]

I have been toying with the idea of replacing the thermostat with a rPi or even a net enabled Launchpad to sidestep all the ZWave stuff. I was going to replace the current tstat with a web enabled touchscreen - just for old time's sake.

 

Anybody do this yet and have you run across any pitfalls? Anybody know of any potential issues? Granted the programming will need to be bulletproof but it's not like they are overly complicated.

[Teken]

I have been toying with the idea of replacing the thermostat with a rPi or even a net enabled Launchpad to sidestep all the ZWave stuff. I was going to replace the current tstat with a web enabled touchscreen - just for old time's sake.

 

Anybody do this yet and have you run across any pitfalls? Anybody know of any potential issues? Granted the programming will need to be bulletproof but it's not like they are overly complicated.

 

Besides not certified, tested, proven . . .

 

The largest investment of your life which is a persons home using a DIY approach to manage the environmentals in ones home. Where the temperatures can range from +50'C to -50'C I can't see anything going wrong.

 

- Loss of human & animal life

- Property damage due to freezing, burst pipes. 

[G W]

I have been toying with the idea of replacing the thermostat with a rPi or even a net enabled Launchpad to sidestep all the ZWave stuff. I was going to replace the current tstat with a web enabled touchscreen - just for old time's sake.

 

Anybody do this yet and have you run across any pitfalls? Anybody know of any potential issues? Granted the programming will need to be bulletproof but it's not like they are overly complicated.

I'm working towards the same goal. The controller for the HVAC will actually be controlled by other devices. I'm essence there will be no thermostat on a wall but air-gapped thermo probes in every room. A central controller to monitor each probe and then send the proper instructions to the HVAC controller.

[ScottAvery]

I would interpret Teken's sarcasm as, "don't do that."

 

 

Besides the real risks of catastrophic failure, you should consider that thermostats are a billion dollar business and there is more effort invested in them than you could ever hope to equal in your home office with an RPi.

 

And you aren't really going to save money.  At a minimum you need 24v relays for the heat, cool, and fan calls, and you will need a temp sensor on top of the RPi and screen.  The Insteon thermostats go on sale from time to time for dirt cheap.  $50 I would guess after sale/discount.  You could then use your ISY to control all aspects of the Thermostat and leave it there as a dumb terminal.

[Teken]

I would interpret Teken's sarcasm as, "don't do that."

 

 

Besides the real risks of catastrophic failure, you should consider that thermostats are a billion dollar business and there is more effort invested in them than you could ever hope to equal in your home office with an RPi.

 

And you aren't really going to save money.  At a minimum you need 24v relays for the heat, cool, and fan calls, and you will need a temp sensor on top of the RPi and screen.  The Insteon thermostats go on sale from time to time for dirt cheap.  $50 I would guess after sale/discount.  You could then use your ISY to control all aspects of the Thermostat and leave it there as a dumb terminal.

 

Yes, it was my failed attempt of the lowest form of humor ~ sarcasm. 

 

Other considerations are home owners insurance which impacts the level of *Risks* to the property. Most certainly assuming they (Insurance Co) even covered a person for a home brew system that failed and killed grandpa, cat, and pigeon. That person would more than likely see insurance dropped, increased, or black listed.

 

The idea and concept of multi zone heating and cooling has been used for more than 25 years through out the world.

 

There have been countless gadgets that have come to market flaunting their benefits to the end consumer. From smart TSTAT's like NEST and similar with remote sensors etc. Then you have controllable vents and ducts which the vendor promotes X vs Y.

 

Yet what 99% of the population fail to think, consider, or even realize these are band aids to a larger HVAC issue(s). When I read someone has spent $1200.00 and upwards on a smart TSTAT, vents, ducting etc. Yet didn't have the common sense to to complete a energy audit to see how *Leaky vs Tight* the buildings envelop is via a door blower test.

 

Worst case just a $0.99 package of incense to see where the smoke was being sucked or blown away from windows, doors, outlets, etc?!?! No TSTAT, Vent, Duct, will supersede the need to identify and resolve air leakage and reduce air exchange per hour, ever. The next thing is insulation and thermal mass which none of these toys or ideas will address because you will still be cold / hot regardless of what these *Smart Solutions* offer.

 

I have more than 100 sensors deployed through out my home and its super structure . . .

 

The primary role of these sensors is to obtain hard statistics so I know where more insulation, thermal mass, to heat / cold deflection needs to be. Having the ability to know factually how warm vs cold a room, floor, zone allows me to automatically regulate the air flow in the home.

 

Air flow regulation is not to be confused with heating / cooling even though they are tightly linked to one another. Air flow helps manage and offset heating and cooling to extend the comfort level of the human.

 

Which indirectly impacts cooling / heating run time in the home.

 

People need to stick the basics of thermodynamics as its not rocket science . . . 

[larryllix]

I'm working towards the same goal. The controller for the HVAC will actually be controlled by other devices. I'm essence there will be no thermostat on a wall but air-gapped thermo probes in every room. A central controller to monitor each probe and then send the proper instructions to the HVAC controller.

Get better insulation and/or circulation. I can't detect more than a 1 degree C difference for anywhere in my house. That is more accurate than the sensors they provide you with for HVAC.  

The ecobee Follow Me sensors have become useless except for a monitoring pass-time.

 

Setback for sleeping comfirt becomes a problem though. Whens it time to cool down the house I start anywhere from 3:00 PM to 11:30 PM and on warmer days in early or late winter the house never cools down to the setpoint, dropping 2 degrees C.

 

I need to install a A/C coil under the bed and forget all that nonsense. LOL

[larryllix]

Yes, it was my failed attempt of the lowest form of humor ~ sarcasm. 

 

Other considerations are home owners insurance which impacts the level of *Risks* to the property. Most certainly assuming they (Insurance Co) even covered a person for a home brew system that failed and killed grandpa, cat, and pigeon. That person would more than likely see insurance dropped, increased, or black listed.

 

The idea and concept of multi zone heating and cooling has been used for more than 25 years through out the world.

 

There have been countless gadgets that have come to market flaunting their benefits to the end consumer. From smart TSTAT's like NEST and similar with remote sensors etc. Then you have controllable vents and ducts which the vendor promotes X vs Y.

 

Yet what 99% of the population fail to think, consider, or even realize these are band aids to a larger HVAC issue(s). When I read someone has spent $1200.00 and upwards on a smart TSTAT, vents, ducting etc. Yet didn't have the common sense to to complete a energy audit to see how *Leaky vs Tight* the buildings envelop is via a door blower test.

 

Worst case just a $0.99 package of incense to see where the smoke was being sucked or blown away from windows, doors, outlets, etc?!?! No TSTAT, Vent, Duct, will supersede the need to identify and resolve air leakage and reduce air exchange per hour, ever. The next thing is insulation and thermal mass which none of these toys or ideas will address because you will still be cold / hot regardless of what these *Smart Solutions* offer.

 

I have more than 100 sensors deployed through out my home and its super structure . . .

 

The primary role of these sensors is to obtain hard statistics so I know where more insulation, thermal mass, to heat / cold deflection needs to be. Having the ability to know factually how warm vs cold a room, floor, zone allows me to automatically regulate the air flow in the home.

 

Air flow regulation is not to be confused with heating / cooling even though they are tightly linked to one another. Air flow helps manage and offset heating and cooling to extend the comfort level of the human.

 

Which indirectly impacts cooling / heating run time in the home.

 

People need to stick the basics of thermodynamics as its not rocket science . . . 

I said it first but you type a lot faster even though you e-l-ab-o-r-a-t-e-d more!.

[Teken]

Get better insulation and/or circulation. I can't detect more than a 1 degree C difference for anywhere in my house. That is more accurate than the sensors they provide you with for HVAC.  

The ecobee Follow Me sensors have become useless except for a monitoring pass-time.

 

Setback for sleeping comfirt becomes a problem though. Whens it time to cool down the house I start anywhere from 3:00 PM to 11:30 PM and on warmer days in early or late winter the house never cools down to the setpoint, dropping 2 degrees C.

 

I need to install a A/C coil under the bed and forget all that nonsense. LOL

 

Its important to note placement of a TSTAT used to be a very basic and common sense approach. But given the millions of elements in a home a TSTAT in any location is going to be a mixed bag. Those who have a multi zone heating system with multiple TSTATS obviously have more flexibility to adjust each zone to the comfort level they require etc.

 

But this too is a band aid for a much larger issue which goes back to air exchange per hour, thermal mass, and passive heating & cooling. I encourage anyone who is remotely serious about energy savings to Google *Passive Hause* techniques. These old age and proven techniques and technology have been used all over the world and will save you where it matters in the pocket book.

 

The over all comfort to *Human* is real and the investment in such techniques add 10~35% to a new build depending upon how far you want to go. 

[larryllix]

Its important to note placement of a TSTAT used to be a very basic and common sense approach. But given the millions of elements in a home a TSTAT in any location is going to be a mixed bag. Those who have a multi zone heating system with multiple TSTATS obviously have more flexibility to adjust each zone to the comfort level they require etc.

 

But this too is a band aid for a much larger issue which goes back to air exchange per hour, thermal mass, and passive heating & cooling. I encourage anyone who is remotely serious about energy savings to Google *Passive Hause* techniques. These old age and proven techniques and technology have been used all over the world and will save you where it matters in the pocket book.

 

The over all comfort to *Human* is real and the investment in such techniques add 10~35% to a new build depending upon how far you want to go. 

"New build". If you mean the resale price is would have to disagree. Real-estate people will tell you making things fancy will only scare most buyers off. Solar panels and HA need to be removed from most homes to sell them. Homes with pools here have separate listings and many fill them in to get their prices up. HA may have changed somewhat now , depending on the area. Here, Millennials do not have any money or a job and live with their parents or off their wife, who slings food in a restaurant. Yes, a depressed state but I suspect that is common in rural communities. Older folks typically have more money but will not tough HA with a 10 foot pole. What would they do if they broke it? Who would they call if it stopped working? What if it all burst into flames and everybody died?

 

When I lived in a more crowded area they same attitude prevailed but that was 10 years ago and thing might have changed slightly.

 

OTOH: If I was selling a $2-5 Million home the HA would likely enhance the selling price. There was lots of high-tech money from RIM excecs and other upstarts.

[MWareman]

Given the junky nature of the Insteon thermostat, it’s hard to imagine that a Rpi would be worse. But. A full Linux OS has *way more* attack surface than even a zwave ‘stat.

 

I wouldn’t even consider moving away from what is a fairly bullet proof stand alone controller for such a function.

[DrLumen]

Gary, that is pretty much my thoughts except there would not be a separate HVAC controller. It would be the end point for a temp sensor or two and would serve to feed info to the ISY and take mode and setpoint commands.  Here is the relay array I am considering. $11.50 from Amazon. It would also work for an irrigation controller. I might do one of those first.

 

https://www.amazon.com/gp/product/B0057OC5WK/ref=ox_sc_act_title_8?smid=ATVPDKIKX0DER&psc=1

 

As to insulation and energy conservation, the house is fairly new, brick, insulated well, heat barrier at the roof deck, double-e glass, 16 seer Heat Pump, a 8.4kw roof mount, grid tied solar array, etc. Me wanting to change the thermostat is not really an attempt at conservation or some kind of t-stat cost saving but consolidation of control and better integration into HA. A ZWave stat would be acceptable but they are not perfect. From what I have seen, there are only 1 or 2 that ISY supports, so that is an issue. I would go completely manual before using an insteon,er, anything. Call me an old timer, geezer, whatever, but I don't trust all these nodes or cloud anything for that matter. Even if the nodes are on my LAN, that is just more to go wrong. To me the less of that shtuff the better. I could do it with a couple of fibaro controllers and the relay array controlled

 

As to the Pi, that was really a second choice and only if a must. I was looking at the Programmable Logic Controllers like the TI Launchpads. With those, you do the programming, testing, etc and then flash it into memory like firmware. As long as it has power and the program is valid, it does the rest. That should eliminate any rebooting or startup issues. It's also highly unlikely anyone would hack into it as they would need to change the firmware to infect it in any way. I think with 2 cooling and 3 heat stages, I can make it relatively bulletproof.

 

I also have to say that conventional t-stats can and have failed. I never known an insurance company to care that one of those have failed or that the air handler might have gone out 6 months ago... Also, if you look at energy management systems for large buildings, there is no central t-stat per se, just sensors and an EMS system that controls all the HVAC systems. I might add that some of those subsystems may rely on pneumatic controls - like that is bulletproof.

 

Anyway, thanks for the thoughts - not so much for the hyperbole.

[G W]

@DrLumen, the main controller is a fail-safe.

[mwester]

 

In fairness to the posters who've expressed negative thoughts about your thermostat replacement, I have to point out that they all hail from parts of the country where HVAC is not a matter of *comfort*.  And yes, that includes me -- and I've also spent lots of time in Texas in the summer.  And while it's true that lack of HVAC in Texas in the summer can make one WISH they were dead, it's actually up here where death (and major property damage) is a real possibility in the face of an HVAC failure.

 

So, I've not dispensed with my thermostat, and like some of the others on this thread I've also spent enormous effort to balance the HVAC system, to insulate, to add thermal mass, and all that.  In terms of HA, I just monitor the HVAC systems -- a primary geothermal system, and a backup propane boiler (yep, two independent heating systems, and there's also a fully-functional wood stove big enough to keep the house livable, should the worst befall us... like I said, heating is NOT optional up here!)

 

As for your idea -- go for it.  If the worst happens, you'll sweat a lot while you repair/reload your RPI or whatever   If the best happens, I bet you can do a lot better in terms of managing your energy consumption and comfort.

[kck]

Without jumping into the good or bad idea I'll just note that if you intend to do a lot of DIY control you may want to look at the Chinese sites (Banggood is my go to spot) as your source of supply.  That relay board, e.g., is about 1/2 the Amazon price and there are all sorts of similar boards including ones with WiFi, BT etc.  There are also good sources of Arduino compatible controllers for $2-3.  The only downside I have found is that the delivery time will be about 2.5-3 weeks rather than 2 days.  However, the quality is generally fine and the options are nearly limitless.

[DrLumen]

Worst case is that a heat strip or condenser is running with no airflow. In terms of failing-safe, an air flow detector in the main duct would help prevent that possibility.

 

Yeah, I realize it may be more critical in some parts of world and I understand the need for back up heat or AC for that matter. Heat stroke is no fun either. I guess I'm just not impressed or awed by them as some seem to be. If I go forward with it and it turns out to be a bust, I'll be here saying I was wrong and with some more experience and insights. And, if all else fails, I will still have my old thermostat to throw back into the mix.

 

Speaking of junky thermostat controls, does anyone remember one of the old X10 t-stat controllers that was a small heat strip that you mounted below your standard t-stat? It only worked for cooling too. lol

 

kck, I'll check it out. i have seen some of that kind of stuff on alibaba but haven't had the guts to try to order anything.

 

mwester, how is the geo-thermal working for you? I was considering it instead of solar but it was just too danged expensive here. In what part of the world are you?

[mwester]

The closest large city is Minneapolis...  so in terms of latitude, I'm north of some of the Canadians on this thread, but south of at least one other...

 

Technically, the geothermal system is performing wonderfully.  It's a dual system -- heats hot water (for radiant heat), and can also do forced air (heating and cooling), and it also has an extra heat exchanger for the domestic hot water (especially useful in the summer, where the heat taken out of the air when in A/C mode gets pumped into the hot water tank before whatever heat remains is pumped into the ground loop).

 

Economically, it's been a poor choice.  It was spec'd into the construction when gas was at $4/gal and easily made economic sense at that price point for fossil fuels.  But with the current fuel prices,  it won't break even for us during it's expected lifetime -- unless prices rise dramatically.  On the other hand, if one doesn't heat with it, it's an absolutely awesome air conditioner -- so it might offer a return that way (we didn't actually factor cooling costs into the ROI model when we bought it).

 

I guess I'm on the fence in general -- I'd encourage those who have the money to go with geothermal; they save energy and are clearly the "green" thing to do.  But they're expensive, and I realize that few folks are ever going to find a geothermal to be more cost efficient than the traditional natural gas or even propane furnace.

 

Final note wrt to automation and a geo -- the two don't mix well.  Geothermal systems are slow to respond so even something as simple as a daily set-back program are problematic.  You want your living quarters raised a couple degrees by 7AM?  Better start the geothermal working on that at 5AM!  (Cooling is better, but in general, with a geothermal system, you're better off just maintaining a temperature/humidity level than trying to bounce it all over the place.)

[G W]

I came from an area where people died from heat stroke and died from extreme cold. I understand and that's why I have a main thermostat as a fail safe. It won't let the temperature go above 90 or below 50.

 

The idea is to keep a comfortable temperature and keep air circulation.

[larryllix]

<snippage>

 

Speaking of junky thermostat controls, does anyone remember one of the old X10 t-stat controllers that was a small heat strip that you mounted below your standard t-stat? It only worked for cooling too. lol

<snipped>

I remember those things. I never used one, but it was probably the first setback thermostat.

[larryllix]

The closest large city is Minneapolis...  so in terms of latitude, I'm north of some of the Canadians on this thread, but south of at least one other...

 

Technically, the geothermal system is performing wonderfully.  It's a dual system -- heats hot water (for radiant heat), and can also do forced air (heating and cooling), and it also has an extra heat exchanger for the domestic hot water (especially useful in the summer, where the heat taken out of the air when in A/C mode gets pumped into the hot water tank before whatever heat remains is pumped into the ground loop).

 

Economically, it's been a poor choice.  It was spec'd into the construction when gas was at $4/gal and easily made economic sense at that price point for fossil fuels.  But with the current fuel prices,  it won't break even for us during it's expected lifetime -- unless prices rise dramatically.  On the other hand, if one doesn't heat with it, it's an absolutely awesome air conditioner -- so it might offer a return that way (we didn't actually factor cooling costs into the ROI model when we bought it).

 

I guess I'm on the fence in general -- I'd encourage those who have the money to go with geothermal; they save energy and are clearly the "green" thing to do.  But they're expensive, and I realize that few folks are ever going to find a geothermal to be more cost efficient than the traditional natural gas or even propane furnace.

 

Final note wrt to automation and a geo -- the two don't mix well.  Geothermal systems are slow to respond so even something as simple as a daily set-back program are problematic.  You want your living quarters raised a couple degrees by 7AM?  Better start the geothermal working on that at 5AM!  (Cooling is better, but in general, with a geothermal system, you're better off just maintaining a temperature/humidity level than trying to bounce it all over the place.)

The general idea here, in the rural, about the same latitude as you, is geothermal is much cheaper where NG is not available, over propane and electricical resistance heating.

 

NG beats them all for economy and probably ecologically too,  if all the factors are considered creating electrical enegy and losses in the delivery producing heat as well.

 

I heat my basement slab with hydronic, as well as an air handler, all running from a tankless hot water heater. All this fancy "Follow Me" and "setbak when no motion" stat  BS doesn't work for me either. At about the freezing point outside (0C = 32F) my home rises about 1 degree C per hour when the stat temperature is raised. I do setback for sleeping by about 1.5C but I start throwing full heat into the basement slab at 5 AM and it reaches living temperature about 3-4 PM each day, just in time to set it back again.

 

ISY programs ave been a big help in adaptive intelligent setback as well as adaptive intelligent recovery. Stats never support the first. I don't do all this crap to save a few pennies per year, I only do it for comfort. I factor in the square of the wind speed to attempt to determine the cooling speed of the house to start my nightly setback between 3:00 PM to 11:00 PM, that the stat would override at that time anyway. I don't sleep if it is too hot by even 1C. We are spoiled.

 

Needless to say I have disabled all the fancy stat features, as they just don't work here. By the time the stat warmed up one room I would be gone the next day. Might be good for Florida where 180,000 BTUHR is never heard of. **SIGH** The negatives of economy in HVAC!

[DrLumen]

...

I guess I'm on the fence in general -- I'd encourage those who have the money to go with geothermal; they save energy and are clearly the "green" thing to do.  But they're expensive, and I realize that few folks are ever going to find a geothermal to be more cost efficient than the traditional natural gas or even propane furnace.

 

Final note wrt to automation and a geo -- the two don't mix well.  Geothermal systems are slow to respond so even something as simple as a daily set-back program are problematic.  You want your living quarters raised a couple degrees by 7AM?  Better start the geothermal working on that at 5AM!  (Cooling is better, but in general, with a geothermal system, you're better off just maintaining a temperature/humidity level than trying to bounce it all over the place.)

 

Green wise, IMO, geo-thermal would be the best solution. When I was looking into it I really didn't know what to expect cost wise. I figured it would be relatively cheap as there are drilling companies and wells all around here. When I got a quote, WOW, talk about sticker shock!

 

I wasn't aware of any inherent delays. Is it the pump flow rate that causes the delays or something else?

 

I came from an area where people died from heat stroke and died from extreme cold. I understand and that's why I have a main thermostat as a fail safe. It won't let the temperature go above 90 or below 50.

 

The idea is to keep a comfortable temperature and keep air circulation.

 

Considering the latest cold snap, I heard that some homeless guy died here a couple of days ago. Doesn't happen often though. Quite a bit of heat frustration and heat stroke.

 

The general idea here, in the rural, about the same latitude as you, is geothermal is much cheaper where NG is not available, over propane and electricical resistance heating.

 

NG beats them all for economy and probably ecologically too,  if all the factors are considered creating electrical enegy and losses in the delivery producing heat as well.

 

I heat my basement slab with hydronic, as well as an air handler, all running from a tankless hot water heater. All this fancy "Follow Me" and "setbak when no motion" stat  BS doesn't work for me either. At about the freezing point outside (0C = 32F) my home rises about 1 degree C per hour when the stat temperature is raised. I do setback for sleeping by about 1.5C but I start throwing full heat into the basement slab at 5 AM and it reaches living temperature about 3-4 PM each day, just in time to set it back again.

 

ISY programs ave been a big help in adaptive intelligent setback as well as adaptive intelligent recovery. Stats never support the first. I don't do all this crap to save a few pennies per year, I only do it for comfort. I factor in the square of the wind speed to attempt to determine the cooling peed of the house to start my nightly setback between 3:00 PM to 11:00 PM, that the stat would override anyway. I don't sleep if it is to hot by even 1C. We are spoiled.

 

Needless to say I have disabled all the fancy stat features as they just don't wrk here. By the time the stat warmed up one room I would be gone the next day. Might be good for Florida where 180,000 BTUHR is never heard of. **SIGH** The negatives of economy in HVAC!

 

Yeah, NG is hard to beat cost wise. If I had gas service here I would love to have a tankless water heater plus other gas appliances. Most developers around here won't even put in gas service anymore. You have to specify it for a custom built home. That whole 70's 'total electric home' paradigm bull that stuck.

 

Yep, the learning stuff like Nest t-stats, just serves to irritate me. Our schedules are too chaotic. X10 had something, I don't remember the name, that would learn your habits and then follow those schedules. It was useless. A trip to the bathroom at 4:00AM would trigger it at the same time the next night. It turned out not to be so much predictive as self-fulfilling. Once I was woken up by the light I then needed to go.

[apostolakisl]

Regarding the geothermal.  I think it is very dependent on your local conditions.  I got a quote when I built my house.  It was absolutely CRAZY expensive.  No way in the world it would ever even come close to paying off.  Even if it were so effiiient that it cut my hvac energy use to zero, it would not pay for itself.  I think it was like $80k more expensive than the SEER 19 Carrier infinity system I put in.

 

Having said that, if you live somewhere where you can drill a single well and pump ground water up maybe 30 feet and then you have someplace to dump that ground water, then I think you would totally be in business.  That sort of well is very cheap and if you have ground water between 40 and 60, it would be really efficient.

 

But where I live groundwater is 500 feet down.  So they wanted to drill like 6 or 8 holes in the ground and run loops to cool/warm a circuit of antifreeze they pump through the system.  Furthermore, I have read that toward the end of the season, the ground around the holes warms/cools to the point where it is hotter/colder than the outside air.  

[LFMc]

Sometimes people do something just because they can, the thrill of accomplishment, etc. Then they can clean up the mess they made later. :-9

 

I was studying this early this morning and then ran across this discussion so it seemed appropriate to share it. Seems like a fun project, if you are somewhat south of the Arctic circle. It would be an easy jump from here to tie it into your ISY I would think. 

 

BTW, I would think that a common old mercury switch thermostat from Lowes or Home Depot for $20 can be parallel wired into some/most 4/5 wire systems as a fail safe in case of a "smart" thermostats failing in winter by setting it a lower "fail safe" temperature to turn on the heat. 

 

https://www.raspberrypi.org/forums/viewtopic.php?t=191336

 

 

 

[KeviNH]

I wouldn't trust anything important to a Raspberry Pi.

 

 

One reason I like the Honeywell (TH8320ZW1000) Z-Wave thermostat is that the (hidden, not Z-wave settable) installer settings include "range stops" ( high and low limits for setting heat and cooling target temperatures), as well as safeguards for "Compressor Protection" and cycles per hour (CPH) to avoid short-cycling.   This all makes it a little less likely that end-user error will cause major problems.

 

Additionally, if the network connectivity drops out or Z-Wave module stops talking, the thermostat defaults back to acting as a normal programmable thermostat.

[apostolakisl]

The comment about using Inteon thermostats to me is spot on.  For whatever reason, SH is selling them for sometimes as little as $30.  At that point, you use your ISY to set the thermostat.  You let the thermostat be a thermostat and use ISY to make all the higher level decisions about when it should be set to what temp.  That is what I did for my church.  We have 9 thermostats all being set by ISY.  But if ISY should go offline or whatever, the thermostats are still going to work as thermostats.  ISY programs are quite capable of doing pretty much anything you might want a thermostat to do (though perhaps not as elegantly as some other programming language).

 

For example, I have ISY always leave the thermostats in "auto" mode.  ISY simply chnages the heat and cool setpoint as per my algorithms.  My heat set point is never lower than 50 and cool is never higher than 90.  So worse case is that ISY goes offline and the place ends up 50 or 90.  If you were to have your ISY turn the thermostat off, then you would run the risk of a freeze.  Not sure that the risk of getting too hot really amounts to anything.  It isn't like there are debilitated people living there who might have a heat stroke. 

[LFMc]

The comment about using Inteon thermostats to me is spot on.  For whatever reason, SH is selling them for sometimes as little as $30.  At that point, you use your ISY to set the thermostat.  You let the thermostat be a thermostat and use ISY to make all the higher level decisions about when it should be set to what temp.  That is what I did for my church.  We have 9 thermostats all being set by ISY.  But if ISY should go offline or whatever, the thermostats are still going to work as thermostats.  ISY programs are quite capable of doing pretty much anything you might want a thermostat to do (though perhaps not as elegantly as some other programming language).

That's what I do also. Makes it real simple to manage. 

 

One reason I like the Honeywell (TH8320ZW1000) Z-Wave thermostat is that the (hidden, not Z-wave settable) installer settings include "range stops" ( high and low limits for setting heat and cooling target temperatures), as well as safeguards for "Compressor Protection" and cycles per hour (CPH) to avoid short-cycling.   This all makes it a little less likely that end-user error will cause major problems.

 

All the HVAC systems I have ever owned have compressor short cycle delay built into the main system, not the thermostat. I would imagine that is so they can use an inexpensive, dumb, wet switch mercury thermostat and not suffer from the A.D.D. 7 year old kid that decides it would be fun to switch the AC on and off 30 times a minute. Like I did when I was that age. 

 

Ooops.... correction, I didn't have AC until I was 9, I stand corrected. (-;