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Updated November 29, 2007 12:00 PST

Stay Warm This Winter With Z-Wave Thermostats

By David Powell

You most likely want to stay warm this winter and one way to keep control of your thermostat is with some of the currently available Z-Wave enabled thermostats. There are, however, a few "gotchas" to look out for.

Figure 1

The ACT ZTT000 is a thermostat that I currently have installed in my home (see Figure 1). It's designed to work with all types of air conditioners including heat pumps. The thermostat was originally designed for RVs and mobile homes and now contains a Z-Wave transceiver. It's powered using the existing 24Vac, which your existing thermostat uses to control the relays in your system.

Typically programmable thermostats are battery powered to reduce the heat put off by the power supply. So as you might imagine the ZTT000 does put off some heat, which affects the temperature reading. However, this is only an issue when you are changing setting on the thermostat. After a few seconds of inactivity the heat from the power supply is gone and the thermostat functions normally. Installation of this thermostat is fairly easy but you will need to do a little research or hire a professional. Installing a thermostat wrong will likely cause your AC or heater to malfunction.

The ACT ZTT000 is now listed as obsolete and a replacement ACT ZTT010 is listed on ACT-Solutions website as coming soon. Hopefully ACT will fix the issues listed above.

Figure 2

Next, on my list of Z-Wave enabled thermostats is the RCS TZ16 from Home Controls (see Figure 2). The control unit supports up to two stages of heating and cooling for both standard systems and heat pump systems. This Z-Wave thermostat seems to be a crowd favorite in the DIY community but that may change when some of the newer units ship. The RCTZ16 thermostat consists of three parts, a Wall Display Unit (WDU), the HVAC Control Unit and the ZWBT Z-Wave Thermostat adapter.

The Wall Display Unit offers functions like a traditional thermostat and connects to the Control Unit by a four-wire cable. The Control Unit connects at the HVAC system using the standard thermostat connections and provides the thermostatic temperature control of the system. The ZWBT provides connection to your Z-Wave network. This is easily retrofitted into existing homes using the existing thermostat wiring.

Finally, a company called Zykronix has a product called the Magic Box, which includes controls for most HVAC systems, including heat pump versions. Analog inputs can interface to powered or unpowered sensors while four damper outputs provide for multiple zone control. Along with the Z-Wave wireless network, the MagicBox has an RS-232/RS-485 serial interface and four infrared LED driver outputs, which can be used to control remote devices. On board temperature and humidity sensors are also available.

In some ways, you might be better off sticking with your existing thermostat through this winter while the manufacturers work to get these new products on the market. But if you need something now there are two options available. The RCS RCTZ16 from Home Controls, which is currently shipping and the ACT ZTT000, which you will have to find in stock since they are discontinued.

Figure 3

Coming up, HAI, a privately held manufacturer of integrated automation and security products, recently announced its new Z-Wave enabled thermostat called the RC-80BZ (see Figure 3). One thing to consider about the HAI is that, according to the company, it's for single-stage heating and cooling systems, non heat pump. Although I need to dig into this a little more, I interpret that statement to mean that the thermostats are not to be used with heat pumps.

While you have only a few options for automating your heating system this winter, there are definitely more on the horizon. I'll be exploring this topic further in upcoming columns.

David Powell is the Technology Editor for


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