MrCool MST03 User manual

MRCOOL ®Universal WiFi Thermostat
®

Contents
APPLICATION ----------------------------------------------------- 1
FEATURES ------------------------------------------------------- 2
SPECIFICATIONS -------------------------------------------------- 3
INSTALLATION ---------------------------------------------------- 5
WIRING -------------------------------------------------------- 13
POWERING THE THERMOSTAT
-------------------------------- --------- 30
INSTALLER SETUP------------------------------------------------ 32
OPERATION ----------------------------------------------------- 44
PROGRAMMING-------------------------------------------------- 64
FCC Note ------------------------------------------------------- 70
TROUBLESHOOTING ---------------------------------------------- 72

1
APPLICATION
MRCOOL® Wi-Fi touchscreen programmable thermostat is a 7-Day programmable thermostat that provides universal
system compatibility, precise comfort control and effortless programming.
MRCOOL® provides temperature control for gas, oil, electric and heat pumps for up to 3 heating and 2 cooling systems.
Not only can you remotely monitor and control the heating and cooling system in your home or business — you can stay
connected to your comfort system wherever you go.

2
FEATURES
• Large, clear display with backlight shows temperature, set temperature and humidity.
• Menu-driven programming makes setup effortless.
• Beautiful ergonomic design is smart and sophisticated to match your lifestyle.
• Touchscreen capability.
• Connect to the Internet to monitor and control your heating/cooling system
• Compressor protection

3
SPECIFICATIONS
Temperature Setting Range:
Heating: 40°F to 90°F ( 4°C to 32°C).
Cooling: 50°F to 99°F (10°C to 37°C).
Operating Ambient Temperature:
32°F to 122°F (0°C to 50°C).
Shipping Temperature:
14°F to 140°F ( -10°C to 60°C).
Operating Relative Humidity (Non-condensing):
IRS –1: 5% to 95%.
ORS -1: 5% to 95%.
Humidity Display Range:
0% to 99%.
Clock Accuracy:

4
+/- 2 minute per month.
Cool Indication:
Show "Cool On" on the screen when Cool is activated.
Heat Indication:
Show "Heat On" on the screen when Heat is activated.
Auxiliary Heat Indication:
Show "Aux On" on the screen when Auxiliary Heat is activated.

5
INSTALLATION
When Installing this Product
1.Read these instructions carefully.Failure to follow the instructions can damage the
product or cause hazardous conditions.
2.Check the ratings given in the instructions to make sure the product is suitable for your
application.
3.Installer must be a trained, experienced service technician.
4.After completing installation, use these instructions to check out the product operation.
Selecting Location
Install the thermostat about 5 feet (1.5m), above the floor in an area with good air
circulation at average temperature.See Fig.4.
Do not install the thermostat where it can be affected by:
---Drafts or dead spots behind doors and in corners.
---Hot or cold air from ducts.

6
---Radiant heat from sun or appliances, concealed pipes and chimneys.
---Unheated or uncooled areas such as an outside wall behind the thermostat.
Mounting Means:
Mounts directly on the wall in the living space using mounting screws and anchors
provided.
Dimensions:
1.MRCOOL® dimensions: see Fig.1.
2.MRCOOL® back case: see Fig.2.
3.MRCOOL® cover plate: see Fig.3.

7
Fig.1. Thermostat Dimensions in inches. (mm)

8
Fig.2.Thermostat back case dimensions in inches. (mm).

9
Fig.3.Thermostat cover plate dimensions in inches.(mm).

10
Fig.4. Selecting thermostat location.

11
Installing Wall plate
CAUTION
Electrical hazard can cause electrical shock or equipment damage.
Disconnect power before wiring.
The thermostat can be mounted horizontally on the wall.
1. Position and level the wall plate (for appearance only).
2. Use a pencil to mark the mounting holes.
3. Remove the wall plate from the wall and drill two holes in the wall as marked.
Gently tap anchors (provided) into the drilled holes until flush with the wall.
4. Position the wall plate over the holes, pulling wires through the wiring opening.
See Fig.5.
5. Insert the mounting screws into the holes and tighten.

12
Fig.5. Mounting wall plate.

13
WIRING
All wiring must comply with local electrical codes and ordinances.
1.See Table 1 and Fig.6 for terminal designation descriptions.Insert wires in the terminal
block under the loosened screw. See Fig.7.
2.Securely tighten each screw.
3.Push excess wire back into the hole.
4.Plug the hole with nonflammable insulation to prevent drafts from affecting the
thermostat.

14
Table 1. Terminal Designation Descriptions.
Terminal Designation Description
RC (see Note 1)
Power for cooling--connect to secondary side of cooling system
transformer
R (see Note 1)
Power for heating--connect to secondary side of heating system
transformer
C (see Note 2) Common wire from secondary side of cooling system transformer
Y Compressor contactor
G Fan relay
Y2 Second stage cooling
O/B/W (see Note 3) Changeover valve for heat pump systems or heat relay
AUX/W2 Auxiliary heat relay for heat pump systems or second stage heat relay
E Emergency heat relay for heat pump systems
L (see note 4) Equipment monitor for heat pump systems

15
NOTES:
1.When used in a single-transformer system, leave metal jumper wire in place between
RC and R. If used on a two -transformer system, remove metal jumper wire between RC
and R.
2.If thermostat is configured for a heat pump system, configure changeover valve forcool
or heat.
3.L terminal is an input port as system monitor.
Fig.6.Terminal identifications for system.

16
Fig.7. Inserting wires in terminal block.
IMPORTANT: Use 18 gauge thermostat wire.