3-WIRE
THERMOSTATS
for Radiant Heating
APPLICATION
Wirsbo Thermostats are the first digital thermostats
designed specifically for use in hydronic radiant
heating applications. Wirsbo provides a specific
model for 3-wire operation.
A3030103 – Heat Only, 3-wire
DEFINITION
The 3-wire version eliminates voltage drop through
the thermostat and provides a full 24 volts to the
associated control device (relay, zone valve, etc.). The
3-wire thermostat can be used in any installation
where power-stealing thermostats pose operational
or compatibility issues. The R and C terminals
provide a continuous power supply to the thermostat
at all times. The heat demand is switched through
terminals R and W and is a “dry” contact. See Wiring
Schematics for additional information.
TOOLS REQUIRED
• Small, flat heat screwdriver
• Phillips screwdriver (mounting hardware)
• Wire cutter/stripper
SPECIFICATIONS
• Operating Voltage
24VAC+/-10%
• Maximum Load
1.3A @ 24VAC
(4 MVAs, p/n A3020522)
(6 TVAs, p/n A3010522)
• Display Range
32 to 99°F (0 to 37°C)
• Setpoint Range
40 to 99°F (4 to 37°C)
• Resolution
1° Displayed
0.25° Calculated
• Temperature Ranges
14 to 158°F, Shipping
(-10 to 70°C)
32 to 104°F, Ambient
(0 to 40°C)
• Humidity
40-90% non-condensing
• Size
5.0"H x 2.72"W x 0.91"D
• Weight
0.22 lbs.
INSTALLATION
Prior to installing a Wirsbo Thermostat:
a. Familiarize yourself with the product by
reading the instructions. Failure to do so could
result in damage to this product, yourself or create
a potentially hazardous situation.
b. Make sure that the function and rating of this
product are suitable for the intended use.
c. The installer must be an experienced, trained
professional familiar with low voltage wiring
d. Wirsbo recommends using 18AWG wiring for all
low voltage wiring connections.
LOCATION
Thermostat placement is extremely important. Install
Wirsbo Thermostats approximately 5 (five) feet
above the floor on a smooth, flat surface. Avoid
mounting the thermostat in the following locations:
• Near or around windows
• On outside walls
• Near fireplaces
• In the corner of a room
• Behind doors
• On interior walls susceptible to solar gains
• Near stoves, lamps, televisions, etc.
• Damp areas
• Dimmer Switches
Typical Wiring Schematic
NOTE: For the most common applications,
please review the schematics in this
document. For additional help, please call
our Technical Department @ 888-594-7726.
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