Which Thermostat to buy?

[QuakeTen]

Hello,

 

I am considering adding thermostat control to my current Insteon network and wanted to ask which is the preferred unit? I am considering the two offerings from SmartHome. Both are the Venstar Thermostats with the difference being a 1-day or 7-day programmable unit. If I am controlling with an ISY99i (via iLinc Pro app for iPhone and Cinemar's MainLobby), I don't see the need for a 7-day unit but perhaps there is a good reason to pay the extra money for the flexibility.

 

Are there any other units I should consider at this time and is SmartHome the preferred vendor for these units?

 

Many thanks,

QuakeTen

[intellihome]

I too was asking myself this question. I ended up with the Venstar 1 day.

 

Using the ISY for control, I can think of no reason to have a 7 day programmable T-stat (Heck, we don't need the 1 day either).

 

According to Venstar the communications port is for several other control options besides the Insteon adapter.

 

I'd imagine if your schedule was always the same you could rely on the Venstars programming to set the climate and just use Insteon for temp alerts or changing the temp via a remote or KPL during uncommon conditions.

 

IMO the 1 Day programmable is all you need for unlimited control with the ISY.

Mine has been working flawlessly.

[MikeB]

One thing to note is that I don't believe the 1-day model accepts the humidity sensor module from Venstar if that matters to you.

[intellihome]

Mike, thanks for the info. I thought the only difference was the number of programming days. Turns out there are a few more differences. I collected the following info from Venstar's site. The humidity module appears in the standard list but then is highlighted in the 7-Day unit's features. I'll call Venstar for confirmation.

 

Standard Features for both 1-Day and 7-DAY ...

 

Heat pump compatible

Backlit, color-coded keys and legends

Large, easy to read backlit display

Configurable programmable or non-programmable

Configurable manual or auto changeover

LED indicator glows green or red to indicate cooling or heating

Service filter and UV light indicators

Fahrenheit or Celsius display

Non-volatile memory

Keypad lock

Accepts the IR remote control accessory

Accepts the humidity module accessory

Accepts the EZ Programmer Accessory

Accepts the Comfort Call Telephone Accessory

 

 

Model T1700 (1 Day)

All of the standard features

1-Day Programmable with up to 4 time periods

Auto changeover 2-stage heat, 1-stage cool for use with gas/electric, heat pump, electric & hydronic heat

 

Model T1800 (7 Day)

All of T1700 features plus

7-day programmable

3-Heat/2-Cool

Controls to, or monitors a 2nd sensor

3-configurable outputs

Hi/Low outdoor temps of the day

Programmable fan

Accepts humidity module

Energy Save

Energy-Star rated

[tome]

The T1800 can accept the humidity module but it is an add-on you must purchase. The T1900 comes with the module installed.

 

BTW, for those that might care...This thermostat (T1700, T1800, T1900) does NOT yet control Carrier Infinity 2-speed heat pumps. They will control dual fuel, two-stage furnaces but not a multi speed compressor in a heat pump.

 

I spoke with Venstar tech support and was told that sometime in the beginning of 2010 there will an update to (at least) the T1900 that will allow it to control a 2-speed heat pump.

[Illusion]

Besides Humidity, the 7 day is compatible with multi-stage systems. Even if you do not have a multi-stage system, this may be a consideration for future-proofing. 2 days after installing my 2 t-stats I had my annual AC check-up. My AC guy tells me it is time for a new system, and that this will be the last summer with this unit. Now I am looking into multi-stage systems and of course I bought the 1 day which is not multi-stage compatible.

 

Tome, as far as multi-stage heat pumps...

 

I am installing a multistage heat pump and I intend to use these t-stats. I have done extensive bench testing and I believe I will be able to make them work for me. The t-stat does energize W2 instead of Y2 on a second stage heat call, but by wiring W2 to Y2 at the unit, this should work fine, as the reversing valve, and fan are already being properly called for as stage 1 is running at this point.

 

Further, in my application I also have the advantage of using a very well designed Honeywell HZ432 zone controller. This device, even if I were to connect W2 to W2 instead of Y2, converts it to a second stage compressor call before sending the signal to the unit.

 

But I do believe that by just connecting W2 to Y2 at the unit (or jumpering it in the back of the t-stat) would accomplish the goals on a single zone system. Then you set up W3 as your aux heat call. This does leave you with the problem of no way to call for emergency heat with these t-stats though. Of course, my zone panel fixes that issue as well.

 

EDIT: Okay Tome, one more issue. I guess you are correct that they will not work. I just realized that my method is not fool proof. If you were to force the t-stat into emergency heat, it would ask for W2 alone, which would be like asking for a second stage compressor call. Not a good idea. In my case the zone control panel also fixes this issue. It really is a brilliant piece of engineering... that Honeywell HZ432.

[tome]

Tome, as far as multi-stage heat pumps...

 

I am installing a multistage heat pump and I intend to use these t-stats. I have done extensive bench testing and I believe I will be able to make them work for me. The t-stat does energize W2 instead of Y2 on a second stage heat call, but by wiring W2 to Y2 at the unit, this should work fine, as the reversing valve, and fan are already being properly called for as stage 1 is running at this point.

 

Further, in my application I also have the advantage of using a very well designed Honeywell HZ432 zone controller. This device, even if I were to connect W2 to W2 instead of Y2, converts it to a second stage compressor call before sending the signal to the unit.

 

But I do believe that by just connecting W2 to Y2 at the unit (or jumpering it in the back of the t-stat) would accomplish the goals on a single zone system. Then you set up W3 as your aux heat call. This does leave you with the problem of no way to call for emergency heat with these t-stats though. Of course, my zone panel fixes that issue as well.

 

EDIT: Okay Tome, one more issue. I guess you are correct that they will not work. I just realized that my method is not fool proof. If you were to force the t-stat into emergency heat, it would ask for W2 alone, which would be like asking for a second stage compressor call. Not a good idea. In my case the zone control panel also fixes this issue. It really is a brilliant piece of engineering... that Honeywell HZ432.

 

You are a bit out of my league in HVAC control I don't know the nomenclature for the various abbreviations or what function they perform (or how to hack them). I was asking one of the tech guys from Venstar and was told it wouldn't control a 2-speed heat pump. The diagram I have for my system is below:

 

[tome]

It really is a brilliant piece of engineering... that Honeywell HZ432.

 

I looked at this controller. It is nice indeed. But at $270+ it is pretty pricy to do what the t-stat should handle on it's own. I may consider this if Venstar takes too long to modify the T1900.

 

This made me think of something else...This controller, and probably the Venstar t-stat will require programming (or configuration) to control my system. My current Carrier supplied t-stat works well, as far as I can tell from the perspective of comfort and cost to operate. How can I figure out what algorithm is used in the current t-stat in order to configure the new one to match it or is this operation already built-in and it will just do the right thing?

 

Tome

[Illusion]

Tome,

 

First off, I was not suggesting that you get a zone controller to do what the t-stat should do right out of the box....however, if you were going to go that route, Honeywell also makes some smaller (fewer zones) controllers for less $$ that should do it.

 

If you are interested, and dying to automate your t-stats with Insteon, here is how I would do it:

 

The first thing to understand is how this stuff works. Conventional t-stats are basically variable contact closure devices. You supply a power line ® and it connects that power line to various outputs (G) fan (Y) compressor.

 

The 1900, and by implication the 1800, are indeed a little funky for use with multi-stage heat pumps. Based on my extensive bench testing with the 1900 t-stat configured to have W3 heat and Y2 second stage compressor here is what happens:

 

First Stage Heat Call:

Energize:

( reversing valve energize to heat (not on your system, Tome, you have an (O) energize to cool valve

(G) Fan

(Y1) First stage compressor

 

Second Stage Heat Call: (T-Stat will display as AUX heat)

(

(G)

(Y1)

(W2) Here is the big issue, this should be (Y2). In theory, you could just hook this wire up to the (Y2) of the unit shown in your schematic

 

Third Stage Heat Call:

(

(G)

(Y1)

(W2)

(W3) This would be hooked up to your W/W1 in the schematic

 

First Stage Cooling Call:

(O) reversing valve energize to cool (This would be used on Tome's system)

(G)

(Y1)

 

Second Stage Cooling Call:

(O)

(G)

(Y1)

(Y2) Second stage compressor call

 

As you can see, all we need to do is make the t-stat energize Y2 on the unit when the t-stat energizes W2. A simple connection does that. So in your application, you would have two wires connected to the Y2 terminal at the unit, or alternately the Y2 and W2 would be jumpered at the back of the t-stat.

 

But I stand by my earlier concern: This t-stat thinks W2 is aux heat, not a second stage compressor call. So, if you tell the t-stat locally to engage emergency heat, it is only going to energized W2 and G when a heat call is executed. Bad deal. So it would work, as long as you do not force the t-stat into e-heat.

 

As far as an algorithm for energy efficient operation. That is too complex. It totally depends on how you use setbacks, how much you setback, and how often. Then we have to ask the question of how do you define "comfort" and "efficiency".

 

The t-stat comes with some pretty generic settings for the average joe, and that is probably where you current t-stat falls as well. Also, Tome, these are not algorithms. It is as simple as time and temperature differentials before the t-stat calls for the next stage. And truthfully, none of these settings will have a massive cost impact except the time and temperature differential before the t-stat calls for aux heat. {True aux heat (W3) not what it thinks is aux heat.}

 

See also: http://forum.universal-devices.com/view ... 6546#26546

 

Disclaimer: I am not an HVAC professional. I actually have nothing to do with the industry. This is just a recounting of my personal research for my own personal use. Use this info at your own risk and risk to HVAC equipment.

[tome]

Tome,

 

First off, I was not suggesting that you get a zone controller to do what the t-stat should do right out of the box....however, if you were going to go that route, Honeywell also makes some smaller (fewer zones) controllers for less $$ that should do it.

 

Thanks, and good to know.

 

If you are interested, and dying to automate your t-stats with Insteon, here is how I would do it:

 

I have a vacation house and I want to be able to remotely control the t-stat before we arrive or after we leave. Dying to do it right away, no, but I am going to do this and want to in the next few months at the latest. I hope Venstar updates the T1900 in that timeframe and I can use it as is.

 

The first thing to understand is how this stuff works. Conventional t-stats are basically variable contact closure devices. You supply a power line ® and it connects that power line to various outputs (G) fan (Y) compressor.

 

The 1900, and by implication the 1800, are indeed a little funky for use with multi-stage heat pumps. Based on my extensive bench testing with the 1900 t-stat configured to have W3 heat and Y2 second stage compressor here is what happens:

 

First Stage Heat Call:

Energize:

( reversing valve energize to heat (not on your system, Tome, you have an (O) energize to cool valve

(G) Fan

(Y1) First stage compressor

 

Second Stage Heat Call: (T-Stat will display as AUX heat)

(

(G)

(Y1)

(W2) Here is the big issue, this should be (Y2). In theory, you could just hook this wire up to the (Y2) of the unit shown in your schematic

 

Third Stage Heat Call:

(

(G)

(Y2)

(W2)

(W3) This would be hooked up to your W/W1 in the schematic

 

First Stage Cooling Call:

(O) reversing valve energize to cool (This would be used on Tome's system)

(G)

(Y1)

 

Second Stage Cooling Call:

(O)

(G)

(Y1)

(Y2) Second stage compressor call

 

As you can see, all we need to do is make the t-stat energize Y2 on the unit when the t-stat energizes W2. A simple connection does that. So in your application, you would have two wires connected to the Y2 terminal at the unit, or alternately the Y2 and W2 would be jumpered at the back of the t-stat.

 

But I stand by my earlier concern: This t-stat thinks W2 is aux heat, not a second stage compressor call. So, if you tell the t-stat locally to engage emergency heat, it is only going to energized W2 and G when a heat call is executed. Bad deal. So it would work, as long as you do not force the t-stat into e-heat.

 

Excellent! Thanks for this, it clears things up a bunch.

 

A couple questions. What is considered emergency heat? I had a geothermal system prior to this and emergency heat (forced air over electric coil -YIKES!) came on if the system couldn't heat using geothermal. My current system uses the heat pump down to about 25 degrees, and then brings on the gas furnace. Is the gas furnace considered emergency heat or just stage three heat? Maybe I don't have e-heat...?

 

Is it...

Stage 1 -> heat pump compressor lo

Stage 2 -> heat pump compressor hi

Stage 3 -> gas furnace

 

Are the 2 stages of fan speed on the furnace separate from the stages?

 

As far as an algorithm for energy efficient operation. That is too complex. It totally depends on how you use setbacks, how much you setback, and how often. Then we have to ask the question of how do you define "comfort" and "efficiency".

 

The t-stat comes with some pretty generic settings for the average joe, and that is probably where you current t-stat falls as well. Also, Tome, these are not algorithms. It is as simple as time and temperature differentials before the t-stat calls for the next stage. And truthfully, none of these settings will have a massive cost impact except the time and temperature differential before the t-stat calls for aux heat. {True aux heat (W3) not what it thinks is aux heat.}

 

Ok, I understand t-stat programming for time-of-day setbacks, etc., etc. I was thinking that in order to have the t-stat call for the proper mode of the furnace (stage 1, stage 2, etc) and/or heat pump (compressor speed 1 or 2), it may have to be programmed to do it differently for different systems. You are telling me that they are all basically the same and the t-stat will do the right thing with some possible minor tweaking time between stages and temp differential. Good!

 

See also: http://forum.universal-devices.com/view ... 6546#26546

 

Disclaimer: I am not an HVAC professional. I actually have nothing to do with the industry. This is just a recounting of my personal research for my own personal use. Use this info at your own risk and risk to HVAC equipment.

 

Thanks again. I will talk to the guy who installed my system when I go to do this and might even have him come and help me install it if I run into problems.

 

Tome

[Illusion]

A couple questions. What is considered emergency heat? I had a geothermal system prior to this and emergency heat (forced air over electric coil -YIKES!) came on if the system couldn't heat using geothermal. My current system uses the heat pump down to about 25 degrees, and then brings on the gas furnace. Is the gas furnace considered emergency heat or just stage three heat? Maybe I don't have e-heat...?

 

Is it...

Stage 1 -> heat pump compressor lo

Stage 2 -> heat pump compressor hi

Stage 3 -> gas furnace

Tome

 

Emergency heat from the perspective of the t-stat should be the same as your aux heat. You have what is called a duel fuel system. Switching over to the gas furnace at 25 degrees is something called the economic balance point. It is not that the air source heat pump cannot heat your home, it is that now it is cheaper (not more efficient) to heat it with gas.

 

A heat pump is basically always the most efficient option. Efficiencies range from about 400% down to 101% based on outdoor temp. So for 1 unit of energy, we move 2 existing units of energy (heat) from outside to inside. That is 300% efficient.

 

A gas furnace may be 70-95% efficient. Electric heat strips are 100% efficient. While the gas furnace is less efficient than the heat pump, the units of energy cost less, so at some point it is better to switch to gas from a cost standpoint. (25d in your case)

 

If you are really interested, this can be adjusted. There are calculators online that you input your electricity cost, gas cost, unit efficiencies and it will output the best economic balance point. Bear in mind, this changes whenever the price of utilities change.

 

So yes, in your case, emergency heat is the gas furnace. The problem is, if you have a failure of your compressor, you will not be able to force the system to skip the first two stages and jump right to the gas furnace if using the Insteon t-stats.

 

Are the 2 stages of fan speed on the furnace separate from the stages?

Tome

 

I am not an HVAC guy, but from looking at your schematic, it looks like the furnace fan speed is determined by the furnace looking at what calls are being made and adjusting itself. That is probably why Y2 goes through the furnace before making its trip to the compressor. I am guessing that a fan call makes it run is low speed, and a fan call plus Y2 makes it step up the fan speed.

[brad77]

Just wanted to chime in that threads like these are why I check this forum so often. Great info. I've bookmarked this for future reference.