Thermostat for Modulating Furnace

[wmcneil]

I am preparing to get quotes on a new HVAC system. I see that Trane calls out that only their XL1050 and XL850 thermostats will provide full functionality with a modulating furnace. I'm wondering if anyone has any experience with whether either of these will connect to ISY (via ZWAVE). I'm not sure if I want to step all the way to a modulating furnace, but I want to know what my options are (or are not, as the case may be) if I did....I'm not expecting any other vendor's thermostat would work with a modulating system, but if anyone has knowledge of that, I'd be interested in that as well.

[lzieg]

I did a lot of research on this when I first set up my ISY, and unfortunately the answer is no -- there is no integration with the XL1050 or XL850. Although Trane advertises the thermostat as supporting Z-Wave, it does so only as a hub for Nexia and not as a client. The only available remote control is through Nexia, although the account is free if you have only thermostats.

In my case, my wife and I like our Trane system enough that we simply accepted the limitation. We went with a variable speed compressor and air handler, and it really does an excellent job of keeping the house at a comfortable temperature. The system is so quiet we don't even notice when it's running unless it's responding to a sudden thermostat change of more than a couple of degrees. (Of course, the system we replaced was 40+ years old, so just about anything would have been an improvement.) We use Nexia to control it remotely using the free account (they have a decent mobile app), while the rest of our home automation is done using the ISY.

Although there is apparently no way to interface with the thermostat locally, in my research into this issue I discovered a couple of folks had written Python libraries to interface with Nexia via the web to control thermostats. In theory someone could write a Polyglot nodeserver to do that. It's not an ideal solution since it would depend on an active Internet connection and Nexia's undocumented API to control your own thermostat (insert sounds of weeping and gnashing of teeth), but unfortunately there does not appear to be any other option.

[wmcneil]

Izieg, thanks for all the detailed information. It's too bad that Trane (and other manufacturers, it appears) are going down the road of proprietary thermostats for their highest end modulating solutions. IMHO, it seems that a better architecture would be to have the thermostat become a very simple device, and locate the smart controls for modulation at the furnace/air handler. Failing that, it would be far better to have a standardized interface.....I suspect the "group think" at the HVAC companies is "we can charge an arm and a leg for our proprietary thermostat." Unfortunately for us, perhaps that is more true at the "top" of the market where the modulating systems live.

I'm glad you are enjoying the comfort level of the system you chose, and it is helpful to know that you are happy with it, and find the workaround for remote access at least tolerable. I'm at the beginning of my process to get quotes, so we'll see what the tradeoffs and differences in price are. Thanks again!

[wmcneil]

An update for other users that may looking at Trane thermostats: All of the zwave thermostats Trane is currently selling will only allow connectivity to the thermostat controls if the thermostat is allowed to be the primary controller (a.k.a Nexia Bridge). This includes the newest models of all of the following: XL1050, XL850, XL824, XL724, and XL624. I just had two new Trane HVAC systems installed, and have confirmed this with my own testing with the XL824.  There is no way for the thermostats to simply be a slave device with the ISY as the primary controller.

The alternative I ended up using was the Honeywell T10 Pro. (I ended up not going with a full modulating furnace, so I am not loosing any capability in the HVAC system.) The T10 pro is a wifi only thermostat, but the Harmony Home connection allows an API connection to the Honeywell Home Polyglot Cloud node server, which I am using and am happy with. The T10 Pro can use multiple wireless indoor sensors as well. 

Another alternative would have been using the Honeywell Prestige thermostat, which uses the Honeywell Total Connect connection, which is different than Honeywell Home. There is also a Total Connect node server, which I do not have any experience with. The Prestige thermostat also requires the Honeywell redlink home gateway (additional hardware) to communicate outside the home, as well as the Honeywell EIM (additional hardware) in order to communicate with the HVAC equipment. 

[wmcneil]

One further cautionary note:  If you want your ISY to remain the primary controller of your zwave network, do not attempt to include any of the newest Trane zwave thermostats. These thermostats are not capable of any zwave role other than primary controller, and attempting to include them may remove your ability to include zwave devices using the ISY. Do not be lured by this text in the Trane documentation: "If you already have a Z-Wave bridge on your account, the XLxxx will automatically function as a Z-Wave repeater..."