wirsbo WT Series User Manual

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.

wirsbo WT Series Specifications

General

Brand	wirsbo
Model	WT Series
Category	Thermostat
Language	English

Summary

Specifications

Operating Voltage

Provides 24VAC+/-10% for operation.

Maximum Load

Supports 1.3A @ 24VAC, with specific ratings for MVA and TVA control devices.

Display and Setpoint Ranges

Displays room temperature from 32-99°F and allows setpoints from 40-99°F.

Temperature and Humidity Ranges

Handles shipping temps from -10-70°C and ambient temps from 0-40°C, with 40-90% non-condensing humidity.

Physical Dimensions and Weight

Compact size of 5.0"H x 2.72"W x 0.91"D, weighing 0.22 lbs.

Application and Definition

Application Overview

Digital thermostats specifically for hydronic radiant heating applications, with a 3-wire model (A3030103) for heat only.

3-Wire Operation Benefits

Eliminates voltage drop, provides full 24V, and uses a dry contact for heat demand switching (R & W terminals).

Installation and Location Guidelines

Installation Preparation

Requires familiarity with product, suitability check, professional installation, and use of 18AWG wiring.

Optimal Thermostat Location

Install 5 feet above floor on smooth surface, avoiding windows, outside walls, fireplaces, corners, and drafty areas.

Operation and Adjustment

Mounting and Wiring

Instructions for separating plates, mounting wallplates, and wiring connections, emphasizing power disconnection.

Thermostat Adjustment

Use '+' and '-' buttons to adjust room temperature; changes are accepted after 5 seconds.

Mode Selection

Switch between heating and off modes by pressing both buttons simultaneously.

Radiant Heating Control Methods

Utilizes Differential (1°F below setpoint) and Pulse Width Modulation (PWM) for nuanced temperature management.

Digital Filtering

Smoothes temperature readings by filtering erratic values, ensuring stable operation and display.