HVAC Management Options

[TomL]

I have seen the mention of HVAC management in multiple posts as I have perused past postings.  I am interested in trying to institute some type of management system other that just changing the setpoint at different times of the day.  I am at a loss though as to exactly what is being done differently than just what a programmable thermostat can accomplish,  It would be greatly appreciated if anyone would be willing to take time to explain what they are doing with ISY to create a management, what it accomplishes and possibly how to go about creating it.  I have written a few short programs that query the 7 temps measured through the house and averaged them, but then not sure what that helps me achieve in doing and/or how often the measurements should be taken and averaged.  Any suggestions or direction would be greatly appreciated.

Thanks

Tom

[mwester]

You'll get lots of opinions on this.

There seems to be a school of thought that says your home automation system should keep track of absolutely everything about your schedule and movements and preferences and should adjust and tweak the HVAC to suite you.  There's another that says your HVAC system should be isolated from your home automation system, either because it's not necessary, and/or because the risk that a failure in the programming or the hardware of the home automation system may result in damage to the house due to the HVAC failure or mis-control.

I'm in the latter camp -- where I live, a failure of the heating system could do massive damage to the house in below-freezing weather, so I prefer to have no direct control of the HVAC by the ISY.  However, the house is also new, with radiant heat in the floors, and lots of stone and tile -- the point being that it's actually more efficient to have a single set-back per day, and that being just a minor couple-degrees tweak.  So, put all together, there's just no compelling reason to connect the HA and the HVAC systems, and there's actually a very good reason to NOT connect the two together.

I can envision, however, a more southerly-located house with less thermal mass -- and such a house might be different.  If it were practical to cool the house by 6 - 10 degrees in an hour, then perhaps being able to have a geo-fence at your work location trigger when you leave work, and start the A/C might be useful if don't have a predictable work schedule (if it is predictable, well, then a set-back thermostat would work equally well).  Perhaps if the HVAC is not well-tuned, or perhaps undersized for a house, or perhaps if there were add-ons to the house, then automating duct boost fans might be useful.  Perhaps if the windows were not solar-reflective glass, and lacked an awning, then a light/lux sensor might be useful to compensate in advance for the heat gain through the glass -- or perhaps it could automatically draw the curtains.

So my personal thought -- if your house is newer, well-constructed, and has a well-tuned and properly-sized HVAC system, then you're only going to screw it up by automating it... on the other hand, if it's not all of the above, then there may well be things you do better with some "smarts".

[paulbates]

I have venstar colortouch thermostats. It’s  full featured from an hvac perspective including schedules, humidity and controlling stages. I do as much as possible on the the thermostat for reasons mwester pointed out. I don’t change temps with the ISY.

Here’s how the ISY helps

- gathering and tallying cycle counts and runtime stats for heat by stage, cooling and humidity. I use a customized Home Automation Dashboard HAD page to review it.  This was more important a few years ago when I replaced my 2 hvac systems and also insulated and needed to see how runtimes changed. Also for tuning how to configure the venstars for triggering second stage.

- fan cycling. I want to cycle the fans twice an hour for 5 minutes each during spring and fall when the systems don’t run much. When it’s really hot or cold out I want the fans on full time - my house is older and this helps hold the temp longer. But if key doors and windows are open, I want no cycling at all. 

- I have a keypad key by the back door to set “away” when leaving. I have the locative app on my phone that works through the ISY portal to set “home” when I’m back with  ~50 miles so the house is ready when we’re back.

- pushover notifications to my phone for fan and humidity pad replacements. 

Paul

[lilyoyo1]

I'm with MWester and Paulbates in regards to keeping my HVAC separate fromy isy. I have the Ecobee3's and allow them to run themselves with minimum input from me.

I have recently added mine to the isy via nodeservers for additional capabilities but not to actually control anything. For example, if a door or window is open too long, the AC will turn off. If a particular room gets warm (but not enough to turn down the AC then the fan will automatically turn on if its occupied. The Ecobee does a great job on its own but the ISY give me additional things I would not have otherwise

[larryllix]

I also use ecobee thermostats and for the most part they do everything very well.

I do not control temperatures from ISY, however I do control their "climate schedule" somewhat. I pre-empt the night time climate schedule change early, when needed.

IOW I implement Adaptive Intelligent Setback, which no thermostat I have ever heard of has. Many have Adaptive Intelligent Recovery.

Eg: Today it was about 32 degrees C and my A/C is schedules to setback at 10:30 PM. My ISY detects the outside effects upon the HVAC system and sets the ecobee stat to "Sleep" climate about 8:30 PM so that the house is getting somewhat cooler by the time I get into bed. If I changed the climate schedule on the stats to 8:30 PM I would be watching TV with a blanket on cooler days outside.

I do the same thing with heating by letting the temperature "drift" down to the desired temperature for bedtime based on how fast the house will cool down. I also assist cooling with my HRV ventilation system. You need some fresh air in a well sealed home and you may as well get it when it is efficient to use.

For my external house effects I incorporate windspeed as well as air temperature. Soon I will add solar heat gain to my calculations.

So my HA plays with climate schedules but never setpoints. I tried it for a while and it is too dangerous, as you can cause setpoint runaways, and I did a few times.  

ecobee stats do have security options so that stats can never be adjusted  remotely outside of a locally programmed range allowance.

[hart2hart]

I use 3 Venstar Colorpoint thermostats. I use a predefined schedule in ISY to set the set-points on two systems with one being a split zone system. I use ISY for this function so I can program all thermostats in one place and not need to recall the functions on the thermostat or have to reprogram it if replaced. I use Fan settings to apply whole house humidifier to the zoned system.

 

I have override functions tied to keypad buttons so each thermostat can stay at manually set set-points and ignore its program.

 

Back to days before the auto mode on thermostats, I still have programs that set heat, auto, and cool based on combination of outside temp and couple other data points. I’ve thought of removing them (and likely will) but the dead-band between heat and cool set-points creates some limits I don’t like. In my region during late spring you often need heat at night and early morning and then cooling by the time you arrive home from work.

 

[apostolakisl]

I don't see much point in having automation of home thermostats, especially in homes with families.  The lag time between changing a thermostat and the temp changing is just too long to be useful.  If you live alone, and have a sizable commute, it would be reasonable to use automation with geo-fencing to, for example, trigger your system when you leave work.  But with a family that is in and out of the house all day long, it is pointless.

I have found it very helpful at my church.  Again, this is a location that spends good chunks of time empty and everything doesn't happen on a regular schedule.  So it is very helpful to be able to quickly (and remotely) change the schedule and be able to manually trigger things from afar when a usage that wasn't on the schedule comes up.  I also have different algorithms that are triggered depending on the type of use and I have staged the system based on outside temp, inside temp, and humidity.  For example, if you turn on the system and conditions are mild, only 2 units will come on.  If conditions are nasty, 5 units come on.  If 2 units trigger, but after 30 minutes things aren't coming around, my algorithm adds more units. 

[jec6613]

I use IFTTT with a Schneider Electric Wiser Air thermostat for basic control, and the ISY only fires off a few things to it:

1) It will disable the HVAC and send an alert if the smoke alarms go off.  This is the only condition which triggers an HVAC shut-down and it's very carefully programmed.

2) It moves between Home, Away, and Sleep programs based on both time of day and home/away status.  It's controlled from keypads and the garage door sensor, and none of the programs are so out of whack as to cause problems.

3) If the outside temperature goes too high so that the cooling system is maxed out, it will raise the setpoint to allow the A/C some breathing room.

4) If the temperature sensors (built into USB powered motion sensors) in any part of the house exceed thresholds (55 degrees at the low end, 88 at the high end), it will send a notification to me so that I can take corrective action as required.

So it's pretty simple: a basic setback program that responds to ISY state, and a manual shutoff tied to the smoke alarms.  I'd actually like to also install a relay to the manual switched oil burner shutoffs in the event of a smoke alarm as well, but I'm still working on how to make that work and be code compliant and secure.

[TomL]

Thanks for all the responses..  I am surprised at the overwhelming sentiment that HVAC control is best left to the tstat.  I would have guessed that most would have leaned towards having it run by HA.  Very glad I asked before committing a serious faux pas.  I do like the idaesof shutting down ventilation when smoke alarms go off and possibly doing some kind of warning or setback if windows or doors have been left open for too long a period.   I really appreciate all the input and thoughts on the matter.

[paulbates]

25 minutes ago, TomL said:

Thanks for all the responses..  I am surprised at the overwhelming sentiment that HVAC control is best left to the tstat.  I would have guessed that most would have leaned towards having it run by HA.  Very glad I asked before committing a serious faux pas.  I do like the idaesof shutting down ventilation when smoke alarms go off and possibly doing some kind of warning or setback if windows or doors have been left open for too long a period.   I really appreciate all the input and thoughts on the matter.

There's not necessarily a right or wrong answer, its more about what you want to accomplish and capabilites of the thermostat. The capabilities of the Insteon thermostat are limited, where thermostats like the Venstar Colortouch and Ecobee are robust. 

[jgcharlotte]

I didn't read every word of every post, but in scanning I didn't see any mention of 'compressor protection'.  If you turn A/C off and then on again right away, the high pressures can damage the compressor.  That's why thermostats have a built in delay.  If one were to use the ISY for control and did not program that in, there could be trouble.

I installed 2 Honeywell Z-Wave thermostats and so far have been very happy with them.  Setup took a couple of seconds literally for each one.

I do all scheduling in the ISY, along with modes (set by state variable) for 'vacation' (out of town, set to 85 and leave it there), 'suspend' (turn off all scheduling), etc etc.

Also, the setup in Alexa was a breeze.

I also added air flow switches to my return vents, so if the system is running and there is no air flow, I can take action to prevent damage.

Haven't done the winter programming yet, but it will be similar, except for the fact that we rarely use the furnace in the winter.

[paulbates]

10 minutes ago, jgcharlotte said:

I didn't see any mention of 'compressor protection

Very good point and that's one of the things my thermostats do as an internal function (and does't matter if its due to automation or not) and displays a message with minutes left until it will start again so the occupants don't revolt.

[larryllix]

1 hour ago, jgcharlotte said:

I didn't read every word of every post, but in scanning I didn't see any mention of 'compressor protection'.  If you turn A/C off and then on again right away, the high pressures can damage the compressor.  That's why thermostats have a built in delay.  If one were to use the ISY for control and did not program that in, there could be trouble.

I installed 2 Honeywell Z-Wave thermostats and so far have been very happy with them.  Setup took a couple of seconds literally for each one.

I do all scheduling in the ISY, along with modes (set by state variable) for 'vacation' (out of town, set to 85 and leave it there), 'suspend' (turn off all scheduling), etc etc.

Also, the setup in Alexa was a breeze.

I also added air flow switches to my return vents, so if the system is running and there is no air flow, I can take action to prevent damage.

Haven't done the winter programming yet, but it will be similar, except for the fact that we rarely use the furnace in the winter.

Squirrel cage type blowers cannot be damaged by blocking the air flow. If you block the air flow to this type of blower the air load is removed, the electrical load drops, as there is no air flowing. Most blowers come with a shutter to close off excess airflow so that the motor is sized properly for smaller applications than the blower capability. This is why all vents can be closed with this type of fan. This does not apply to turbine style fan blade types, which are opposite.

I had my A/C compressor start backwards once, due to fast cycling. Luckily I was about 15 feet across the yard from it and heard this awful growling sound and it started banging inside the case. I ran over and shut off the safety breaker on the wall beside it. The thermostat had no second stage compressor protection and I had it wired to that stage, with simple fan circulation to bring up cool air from the cold well water I run through my basement floor.

Be very careful with this compressor protection. It is important to the health of your system and could cost you big bucks!!

[jgcharlotte]

4 minutes ago, larryllix said:

Squirrel cage type blowers cannot be damaged by blocking the air flow. I

Actually, the damage I was referring to is to the coil.  Without air flow it will probably eventually freeze up and, according to my AC guy, can crack the coil.  I had a capacitor go out recently in my upstairs blower.  It's hard on the compressor, too, but they are pretty robust.

 

[larryllix]

8 minutes ago, jgcharlotte said:

Actually, the damage I was referring to is to the coil.  Without air flow it will probably eventually freeze up and, according to my AC guy, can crack the coil.  I had a capacitor go out recently in my upstairs blower.  It's hard on the compressor, too, but they are pretty robust.

 

Ohh. Yeah that. I requested a thermal sensor cut-off for my A/C. When the cold coils get below 38F? the compressor cuts out. I noticed it did cut out a few times at the beginning. I had the fan speed turned down a bit due to ducts howling and rumbling. Since then, I have added plenum insulation, and built a 5" duct muffler, where it was worst. Now the fan is on it's highest speed.

The temperature cut-out covered my a$$ in those situations.  They are simple to install and cheap. My guess it about $10 and it just clipped into the cold coil fins. It has a built in temperature differential to avoid fast cycling of the compressor should it ever cut-out.

[jgcharlotte]

6 minutes ago, larryllix said:

 I requested a thermal sensor cut-off for my A/C. When the cold coils get below 38F? the compressor cuts out. I noticed it did cut out a few times at the beginning. I had the fan speed turned down a bit due to ducts howling and rumbling. Since then, I have added plenum insulation, and built a 5" duct muffler, where it was worst. Now the fan is on it's highest speed.

The temperature cut-out covered my a$$ in those situations.  They are simple to install and cheap. My guess it about $10 and it just clipped into the cold coil fins. It has a built in temperature differential to avoid fast cycling of the compressor should it ever cut-out.

Good move, I may actually look into that.  
The program just looks for the return register flow while the system is running.  If not it sends a text and can shut the system down.  Right now I don't have it set up to shut down.  You really have quite a bit of time.  The only time I got the alarm is when the flow sensor signal (open/close sensor) didn't get to the ISY.  Imagine that  
I'm having some intermittent noise problems, bought a few more FilterLincs to add to the collection.

[Mustang65]

2 hours ago, jgcharlotte said:

..........  If you turn A/C off and then on again right away, the high pressures can damage the compressor.  That's why thermostats have a built in delay.  If one were to use the ISY for control and did not program that in, there could be trouble.

 

The PAYNE HVAC system I have (14 years old) has its own internal timer that will not let the AC start up again until it has been idle for 5 minutes. It doesn't care what the thermostat is requesting, which is the way I like it.

I really wish that thermostats had interactive communications between it and the HVAC system.

Example, the Payne HVAC system we have goes into defrost mode every 30 minutes (of run time), which after actually watching it over a period of time, determined that here in Florida it was unnecessary (for a AC/heating cycle) and increased the time  on the mother board to 40 minutes. I could probably increase it more, but there are to many variables that could make that a bad idea. The defrost mode runs for 2 minutes to insure that the coils are not freezing over. The problem is, the thermostat just keeps telling the  HVAC sys to keep the AC/Heat running, which is what is should be doing, but does not post a message on the thermostat that it is in "Defrost mode". This also affects the ecobee's green mode into activating the AUX heat source (electric coils $$$) to kick in, not always but it has happened a few times.

The issue I have is that there is a different sound (with all of the PAYNE systems like mine) that it makes and of course the air temperature is affected by this cycle. So, the wife automatically says that the AC/Heat is not working, and I have to go to the back bedroom and listen to the heat pump to hear what sound it is making.

It would be nice if the ecobee 4 and Payne would display that it is in "Defrost mode", and I would not get my brain going. I am currently working on a thermostat enhancement that will have 2 LED's on the ecobee,  Green will show NORMAL operation RED to show "Defrost Mode". I  have the DS18B20 temperature sensors in place (attached to the coils) and currently wired to Home Automation box where the ISY, GEM Dash Box, Arduino and Raspberry Pi are located. I am adding circuits that will tell me if the reversing valves are active or inactive (heat or cold). I would like to install a pressure sensor to monitor the coolant, but that would mean purging the entire system (still a Freon based HVAC). So I guess I will just monitor the existing system's pressure switches. The data will be stored in a dB for trouble shooting if needed. When I need to replace the existing HVAC system, I will try to find one that has a Thermostat that is interactive (probably not available yet), or uses sensors that can be used for more information.

As a reference, the data from the GEM energy system and the ecobee data that gets downloaded each month helped isolate a thermostat programming issue that would have cost me AT LEAST $500. Somehow, and I never mess around with the settings once they are set, the Heat Pump low temperature cutoff was raised and the AUX heat set point was changed. Between the stored data from the 2 systems I was able to isolate the problem, but here is why an HVAC system controlled by a 3rd party system would not be recommended... trouble shooting could become a nightmare. 

 

[jgcharlotte]

2 hours ago, Mustang65 said:

I am adding circuits that will tell me if the reversing valves are active or inactive (heat or cold). I would like to install a pressure sensor to monitor the coolant, but that would mean purging the entire system (still a Freon based HVAC). So I guess I will just monitor the existing system's pressure switches.

Seems like you could just put a relay in parallel with the reversing valve coil and use a dry contact to indicate defrost mode.

An interactive thermostat would be great, but it will probably never happen.  They try and keep it simple for the typical consumer, not geeks like us!

 

[Mustang65]

The ecobee SMART (Commercial) thermostat I originally had, until the humidity circuit died and caused the firmware to do weird things, had an option for notifying a HVAC repair service if things were outside their normal settings. Never activated that feature. If you think about it, if the thermostat/HVAC processors sense that the coolant level is dropping it could send the ecobee an alert and the ecobee could send the home owner an alert. Maybe averting a cooling system disaster ($$$). Also, if the coils are constantly freezing up it could also let you know and readjust the defrost cycle time. Maybe some day, but not in my life time.

There are a lot of things that could be monitored:

Duct air flow (dirty filter), compressor temperature (overheating), excessive amount of compressor load on the electrical, the list goes on.. but the HVAC and Thermostat would have to make some standard decisions based on all that data and alert the user. But it would have to take the "THINKING" part out off the consumers  decision making

Dream on.... 

[jgcharlotte]

34 minutes ago, Mustang65 said:

Duct air flow (dirty filter)

I built an air flow switch from a sail switch from Amazon, cut out piece of a styrofoam plate to increase the sail size and an insteon open/close sensor.  It sits next to the return register and when the blower turns on the sail get sucked onto the grill surface. activating the switch.  I guess I could calibrate the sail to give dirty filter, but that would be a pain.  So it just gives me flow/no flow.  Ain't pretty, but it works.

[mwester]

Love the sail switch -- that's an excellent example of a simple "hack" to effectively create a new insteon device type!

[jgcharlotte]

20 minutes ago, mwester said:

Love the sail switch -- that's an excellent example of a simple "hack" to effectively create a new insteon device type!

One of the smartest things the Insteon engineers did was to put a terminal strip in that sensor so you can use just the contact without the magnet.  I use it like that all the time.