MIXING PUMP (P1) OPERATION
• Mixing pump (P1) contact (terminals 11 and 12) closes
whenever there is mixing demand and the SYSTEMpro 311
is not in WWSD
• After mixing demand is removed, Mixing Pmp P1 contact
remains closed for 20 seconds
• During WWSD, the mixing pump (P1) is operated based on
EXERCISE function
BOILER MINIMUM PROTECTION (Boil MIN)
(See fig. i)
• The SYSTEMpro 311 can offer boiler protection from
cold mixing system return water temperature entering the
boiler while firing. This helps reduce possible flue gas
condensation.
• If boiler water temperature is cooler than Boil MIN setting
while boiler is firing, control reduces output from mixing
device (limits amount of cool return water to boiler and
allows boiler water temperature to recover)
MIXING DEVICE SELECTION (MIXING)
• The SYSTEMpro 311 can supply a lower water temperature
to part of the heating system by varying the speed of an
injection pump or modulating a mixing valve.
• This selection is made under the MIXING item in the Adjust
Menu.
VARIABLE SPEED INJECTION (VAR) (See fig. j)
• A standard wet rotor circulator is connected to the
SYSTEMpro 311 on Cls/P4 terminal (19)
• Control increases or decreases power output to circulator
when there is mix demand
• Circulator speed varies to maintain correct mixed supply
water temperature at mix supply sensor
• For correct sizing and piping of variable speed injection
driven circulator, refer to essay Appendix I, Variable Speed
Injection Mixing on page 85.
• A visual indication of current variable speed output is
displayed in the LCD as a segmented bar graph. Two small
indicators at the top of the graph indicate whether the output
is increasing or decreasing.
Section D2: Mixing Devices
69
CONTROL FUNCTION
OVERVIEW
CONTROL FUNCTION OVERVIEW - Section D - Mixing Zones
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