wirsbo DuoMix 201, Installation Instructions Manual

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OUTDOOR RESET
In order to maintain occupant comfort with a hot water heating system, the
heat supplied to the building must equal the heat lost by the building.
• The heat supplied to a building is proportional to the temperature of the
water and the surface of the heating area. A small surface area such as
baseboard radiators requires a higher water temperature than a larger
surface area such as radiant floors.
• The heat supplied to a building/space can be changed by increasing or
decreasing the supply water temperature. As the outdoor temperature
falls the supply water temperature rises.
Control Strategy
The WIRSBO DuoMix 201 provides control of two variable speed injection mixing devices in order to satisfy a two temperature system.
The system may consist of a two temperature radiant floor heating application, or a combination of snow melting and radiant floor heating.
The control is designed for use with radiant systems but can be easily integrated to other hydronic applications (baseboard, fan coil).
The control is capable of providing boiler return protection in order to prevent boiler flue gas condensation.
The DuoMix 201 includes a large Liquid Crystal Display (LCD) which provides temperature read-out and adjustable settings.
For building space heating applications the control includes features such as Warm Weather Shut Down (WWSD), outdoor reset, pump
exercising, and maximum supply temperature adjustment. In the snow melting mode the control protects the slab against thermal shock,
has idling capabilities, Warm Weather Shut Down (WWSD), and Cold Weather Cut Off (CWCO).
Constant
Room Temperature
Outdoor
Temperature
Drop
Heat
Loss
Increase
A3030005
DuoMix 201
Installation Instructions
-10
(-23)
70
(21)
°
F
(
°
C)
70
(21)
150
(65)
50
(10)
30
(-1)
10
(-12)
90
(32)
110
(43)
130
(54)
Design
Outdoor
Temp.
Design
Room
Temp.
Outdoor Air Temperature
90
(32)
Supply W
ater
T
emperature
Design
Supply
Temp.
WWSD
60 (15.5)
Theory
The calculated heat loss of a building or space is based on the coldest weather conditions the
area experiences over the heating season. If the heat demand is analyzed as a percentage of
the heating systems capacity, the heating system operates at or near maximum capacity for
a small portion of the heating season. If the water temperature is controlled using a non-weather
responsive tempering device, shown as the dotted line, the line is flat and does not flucuate with
the demand for heat. Resetting the supply water temperature (solid line) allows for the supply
water temperature to adjust itself to the demands on the heating system. Lowering the supply
water temperature in warmer times of the heating season will allow the radiant zones to be open
and run longer, providing increased comfort and efficiency.
Water Temperature Optimization
The Wirsbo DuoMix 201 uses actual data to program the control on start-up, eliminating the
unknowns. Until now, resetting the supply water temperature to a radiant panel meant using
terminology such as "curves" and "shifts". The DuoMix now eliminates manually selecting the
proper curve based on the design data. From the user inputted data, the control creates a
relationship (or ratio) between the outdoor temperature and the water temperature supplied to
the radiant application. The control automatically adjusts the supply water temperature for
every 1
°
F drop in outdoor temperature. In order to correctly reset the supply water temperature,
a few parameters are required:
Outdoor Design Temperature
The Outdoor Design Temperature is used to calculate the heat load required at the most severe
weather conditions expected during a normal heating season.
Design Supply Water Temperature
The Design Supply Water Temperature is the temperature of water supplied to the radiant
panel(s) to meet the requirements of the heat load calculated at the outdoor design termperature.
Design Room Temperature
The Design Room Temperature is the indoor air temperature used in the heat loss calculations.
Warm Weather Shut Down (WWSD)
When the outdoor air temperature is warmer than the Warm Weather Shut Down setting, no
additional heat is supplied to the building; therefore, the heating system can be shut down. The
WWSD setting has no effect on the heating curve slope.