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Mixing Operation
The Application Mode should be set to Mixing when a mixing
valve or a mixing injection pump is installed with a shared
boiler plant. Four mixing options are available:
• Floating action mixing valve
• Variable-speed injection pump
• Analog mixing using 0-10 V (dc)
• Analog mixing using 4-20 mA
The control calculates the Slab Target temperature based on
the outdoor air temperature and the Melting, Idling or Storm
Setpoint. The control then determines the Mix System Target
based on the Slab Target requirements. The Mix Maximum setting
limits the upper temperature of the Mix System Target. The
Mix System Target is shown in the System Status menu.
For design and sizing of the variable-speed injection mixing
pump, please refer to the Essay E021.
Relay operation:
• System pump — operates continuously during melting,
idling or storm
• Heat relay — closes when the mixing valve is open or the
variable speed injection pump is operating.
• Boiler stage 1 — turns on when the valve is open or the
variable speed injection pump is operating.
• Boiler stage 2 — not used
If using Floating Action Mixing
• Floating action open — contact closes momentarily when
pulsing actuator open
• Floating action closed — contact closes momentarily when
pulsing actuator closed
If using Variable Speed Injection Mixing
• Injection Mixing Output — a variable speed signal is
supplied to the pump
If using Analog Mixing
• Analog Mixing Output — a signal ranges between 0-10 V
(dc) or 4 -20 mA
Post Purge
Exercising
In a hydronic snow melting system, the control operates the
system, primary, boiler, variable speed injection mixing pump
and mixing valve every 3 days to prevent pump and valve
seizure.
The boiler or heat source is shut off and the snow melting
system continues to operate for 20 seconds to post purge heat
from the boiler to the load.
Boiler and Mixing Operation
The Application Mode should be set to Mix when a
mixing valve or a mixing injection pump is installed to regulate
the supply water temperature to the snow melting system with
a dedicated boiler plant. In this case, the control operates both
the mixing device and the dedicated boiler at the same time.
The control calculates the Slab Target temperature based on the
outdoor air temperature and the Melting, Idling or Storm Setpoint.
The control then determines the Mix System Target based on
the Slab Target requirements. The control then determines the
required Boiler Target that is required to meet the Mix System
Target. Refer to the Boiler and Mixing Operation sections for
detailed information on the boiler and mixing operation.
Relay operation:
• System pump — operates continuously during melting,
idling or storm
• Heat relay — not used
• Boiler stage 1 — cycles on/off based on boiler target
• Boiler stage 2 — cycles on/off based on boiler target when
using a two-stage boiler, otherwise off.
If using Floating Action Mixing
• Floating action open — contact closes momentarily when
pulsing actuator open
• Floating action closed — contact closes momentarily when
pulsing actuator closed
If using Variable Speed Injection Mixing
• Injection Mixing Output — a variable speed signal is supplied
to the pump
If using Analog Mixing
• Analog Mixing Output — a signal ranges between 0-10 V
(dc) or 4 -20 mA
Outdoor Sensor
The outdoor air temperature is required for all application
modes. The control has the option to measure an outdoor air
sensor or the outdoor temperature can be provided through
the tekmarNet system or through the Internet weather service.
This is selected by the Outdoor Sensor setting in the System
Setup menu.
