Place Device – ZEN Thermostat

ZEN Installation Tips and Tricks

Precautions and Safety

As with all electrical equipment, the first step in installation should be to turn off the main breaker.

The ZEN thermostat works on low voltage systems rated at 24 volts, with a maximum current rating of 2A per relay. This is the common voltage for most furnaces, heat pumps and air conditioning systems.

ZEN will not work on line voltage systems of 110 volts or higher. These systems are typically European systems or electric baseboard systems.
If the wiring is installed in a junction box, it is also likely to be 110V or higher.

Usually, these systems will have thick black, white or red wires connected with wire nuts on the thermostat.

If the HVAC system is not compatible with ZEN, please return ZEN to the place of purchase.

Removing the existing thermostat main display

Most thermostats allow you to remove the main unit and provide access to a wall plate which holds the wiring terminals

    Removing the existing thermostat differs between models. It usually requires:
  • snapping it off the wall with moderate pressure
  • undoing small screws
  • lifting locking tab and rotating the thermostat
  • If you are unable to pull it off, please refer to your thermostat manufacturer's website or manual for removal instructions.

Some old thermostats contain mercury in a sealed tube. Contact the Thermostat Recycling Corporation at http://www.thermostat-recycle.org/ for information on how and where to properly and safely dispose of your old thermostat.

Wire labelling

There is no single standard for wire colours and thermostat connections. However, most thermostats have terminal blocks with wire labels.

The way in which the old thermostat is wired and labelled is one of the best guides for how to wire up the ZEN thermostat. Correctly identifying the wires that exist ensures that all the functions of your heating and cooling system will be able to be controlled by the ZEN thermostat.

If you are unsure or your wire terminals are unlabelled, tracing the wires back to the HVAC system is the best way to determine what each wire does.

ZEN provides wire labels in the package, which should be used to label the wire before they are removed from the old thermostat terminals.

The ZEN online installation guide provides a detailed description of which label should be applied to which wire.

Once the old thermostat is removed, the best way of identifying wires is through the ZEN labels.

The wiring diagrams provided by ZEN are all based on the ZEN labelling format.

The basic connectors for a home thermostat can be found in the table below:

Terminal Description Alternate labelling
R Power side of 24V transformer V
Rh Power side of 24V heating switch 4
Rc Power side of 24V cooling switch
C Common side of 24V 24C, 24
Y Switched power for cooling Y1
W Switched power for heating W1
G Switched power for fan
Y2 Switched power for second stage cooling
W2 Switched power for second stage heating
E Emergency heat enable AUX
O/B Reversing valve activatoin O, B

Wire preparation and insertion

Disconnecting the wires from the existing thermostat may require a screwdriver to undo the terminals.

Once removed, it is important to check that the wires are in good condition so that they make good electrical contact.

Check wires have between 5/16 - 3/8in (8-10mm) exposed core. If they don’t, you may need to cut and re-strip them.

If you have stranded wire, ensure that all strands are safely captured in the terminal.

If the installation guide has specified that some wires should not be connected, ensure that they are properly insulated.

Link removal and insertion

Many thermostats use links to connect common circuits together.

ZEN does not require re-use of old links. It comes complete with 2 links, which are located on the rear of the main unit.

The links can be removed by pulling gently and inserted by pushing them into place.

Configuration of the links is determined based on the information entered into the online install guide. The function of each link configuration is shown below:

Link 1 and Link 2

  • Rc and Rh connected to common return
  • Aux connected to same return as Rh
  • Applies to most single stage systems and heatpump systems

Link 1 only

  • Rc and Rh on separate return circuits
  • Aux connected to same return as Rh
  • Applies to systems which have separate heating and cooling equipment

Link 2 only

  • Rc and Rh connected to a single return circuit
  • Aux connected to separate return circuit
  • Applies to most heatpump systems where the auxiliary heat system is separate equipment

No links

  • This configuration is never used

Mounting the ZEN wallplate

The ZEN wallplate should be mounted so that the bundle of wires comes out through the centre of the wallplate.

Use a level to help align the wall plate, then mark the mounting holes on either side.

The mounting hardware supplied in the ZEN package consists of 2 wall anchors and 2 screws. The wall anchors are suitable for use on both drywall and plaster.

Use a 1/4in (6mm) drill bit to drill holes for the wall plugs. Ensure that the wires are kept out of the way when drilling.

Insert the wall anchors into the holes. Attach the wallplate using the screws provided. Take note of the orientation arrow which should point upwards.

If your previous thermostat was larger, you may choose to use the blanking plate to cover any unsightly areas.

The blanking plate is sandwiched between the wall plate and the wall and does not require any extra screws to attach.

The blanking plate can be used in either portrait or landscape orientation

Attaching the main display

ZEN requires 4 AA batteries to operate the main display, even when a C-wire is connected.

If a C-wire is available, the batteries are only used when the unit is off the wall and will last indefinitely.

If no C-wire is present, the batteries will last for 2 years under typical use conditions.

The main display attaches to the wall plate by magnets located at each corner.

Once located, the electrical connection is made between the terminals on the wall plate and the main display.

There is also a small push switch on the rear of the main unit which is used to determine if the main display is on the wall.

When the main display is on the wall, the ZEN user interface allows for setting the temperature and mode of the HVAC system

When the main display is removed from the wall, it enters PREFS mode which allows setting of the thermostat preferences.

Configuring ZEN

ZEN uses a configuration code to set the important working parameters required by a thermostat. These include the type and number of heating and cooling stages. A detailed description of the ZEN configuration codes is given in the following section.

When first installed, ZEN does not have any configuration set. The display will show “ZEN” until the CONFIG button is pressed and configuration is entered.

This sequence is intended to force the user or installer to determine the correct configuration of the device before they can operate the heating or cooling. This reduces the likelihood of damaging the HVAC system through incorrect installation.

Some existing thermostats have dipswitches that may change the configuration of the existing wire labels. If the thermostat you are replacing has multiple rows of wire labelling, make sure to check for dipswitches that may alter the configuration. Finding the original installation manual will assist you in getting the configuration set up correctly.

ZEN HVAC Configuration System

ZEN uses a configuration code to set the important working parameters required by a thermostat. These include the type and number of heating and cooling stages.

Basic configuration is suitable for most installations and is highly recommended for DIY installs.

Basic configuration allows the user to enter a 3-digit code which provides all the information required to configure the thermostat.

The first step in setting the basic configuration is to remove ZEN from the wall, turn it over so the rear of the display is accessible, then press the CONFIG button once.

    The ZEN online installation guide automatically determines the required configuration code based on the following items entered by the user:
  • Wiring of the old thermostat
  • Type of heating system

The configuration code is a 3 digit alpha-numeric code. Each digit has a distinct function:

Changing the Basic Configuration


Effect on User Interface

The ZEN thermostat user interface automatically adjusts to only show the heating and cooling options that are available in the configuration.

As an example, if the configuration is set to 10A (1 stage heating, no cooling, no fan control), then the user will be able to select Heating mode but not Cooling or Fan Control mode.

If the configuration is set to 31P (heatpump heating and cooling with emergency heat and fan control), then the user will be able to select Heating, Cooling, Emergency Heat and Fan Control mode.

Heating Type

The most important heating control parameter that is affected by the heating type is the maximum cycles per hour (CPH) that is used for each heating type. In particular, heatpump systems require fewer cycles per hour to ensure that the compressor is not cycled too often which can cause it to lock up.

Digit Heating Type Cycles per Hour
0 No heating N/A
1 Single Stage, Fuel (Gas or Oil) 6
2 Single Stage, Electric 12
3 Single Stage, Heatpump 3
4 Single Stage, Hydronic 3
5 Not used N/A
6 2 Stage, Fuel (Gas or Oil) 6
7 2 Stage, Electric 12
8 2 Stage, Heatpump 3
9 2 Stage, Hydronic 3

Cooling Type

Digit Heating Type Cycles per Hour
0 No cooling N/A
1 Single Stage, Heatpump, Evaporative or Hydronic 3
2 Not used N/A
3 Not used N/A
4 Not used N/A
5 Not used N/A
6 2 Stage, Heatpump, Evaporative or Hydronic 3
7 Not used N/A
8 Not used N/A
9 Not used N/A

Heatpump and Fan Options

Third Digit Fan Control Has Emergency Heating? Switching changeover valve cools Has a changeover valve
A N N N N
B Y N N N
C N Y N N
D Y Y N N
E N N Y N
F Y N Y N
G N Y Y N
H Y Y Y N
I N N N Y
J Y N N Y
K N Y N Y
L Y Y N Y
M N N Y Y
N Y N Y Y
O N Y Y Y
P Y Y Y Y

Advanced Settings

Advanced configuration allows a professional HVAC installer to set more detailed system parameters.

Any changes made in advanced configuration will override basic configuration settings, so it recommended that only a knowledgeable HVAC installer use the Advanced settings.

The first step in setting the advanced configuration is to remove ZEN from the wall, turn it over so the rear of the display is accessible, then press the CONFIG button 5 times.

Resetting the Advanced Settings

The Advanced Settings are retained even when batteries are replaced or an OTA upgrade is made.
If the basic configuration is changed, the Advanced Settings will be lost.
The Advanced Settings can be reset to the factory default by pressing the CONFIG button 20 times.

Typical wiring configurations

Wiring Diagram Links CONFIG Code
1 stage heating 10A-10B
20A–20B
30A–30B
40A–40B
1 stage heating with emergency heat 10C-10D
20C–20D
30C–30D
40C–40D
2 stage heating 60A-60B
70A–70B
80A–80B
90A–90B
1 stage heating and 1 stage cooling 11A-11B
21A–21B
31A–31B
41A–41B
1 stage heating and 1 stage cooling with emergency heating 11C-11D
21C–21D
31C–31D
41C–41D
1 stage heating and 1 stage cooling (Separate Rh and Rc wires) 11A-11B
31A–31B
21A–31B
41A–41B
1 stage heating, 1 stage cooling and emergency heat (separate Rh and Rc wires) 11C-11D
31C–31D
21C–21D
41C–41D
2 stage heating and 1 stage cooling 61A-61B
71A–71B
81A–81B
91A–91B
2 stage heating and 2 stage cooling (Separate Rh and Rc wires) 66A-66B
76A–76B
96A–96B
1 stage heating and 2 stage cooling 16A-16B
26A–26B
46A–26B
1 stage heating and 2 stage cooling, with emergency heat 16C-16D
26C–26D
46C–26D
1 stage reversible heat pump (heat and cool) 31I
31J
31M
31N
1 stage reversible heat pump (heat and cool) with emergency heat 31K
31L
31O
31P
2 stage reversible heat pump (heat and cool) 86I
86J
86M
86N
2 stage reversible heat pump (heat and cool) with emergency heat 86K
86L
86O
86P
2 stage reversible heat pump (heat and cool) with emergency heat (separate Aux and Rh return) 86K
86L
86O
86P

Network Connectivity

Compatibility

ZEN Thermostat is ZigBee HA 1.2 compatible and is continually being integrated into new home automation platforms. For the latest list of compatible platforms, please refer to the website – www.zenthermost.com

ZEN supports only standard ZigBee clusters and should, in theory, work with any ZigBee HA compatible system.

However, in practice, some integration effort may be required by the HA platform to ensure reliable operation.

If you are attempting to connect ZEN to a home automation platform which is not in the list above, and there are issues in the connection process, please contact the home automation platform support line.