tekmar 423 Universal Reset Module - Manual (Page 26)

© 2007 D 423 - 08/07 26 of 36
DHW During UnOccupied
When using a Powered DHW Demand, the control has a
DHW Exchange UnOccupied setting that allows the installer
to select On or Off. When set to On, and the control receives
a DHW Demand during an UnOccupied or Sleep period,
the control continues operation of the DHW system as it
would during the Occupied and Wake periods. When set to
Off, the control can ignore a DHW Demand for the duration
of the UnOccupied and Sleep periods.
When using a DHW Sensor, a second DHW temperature setting
can be made for the UnOccupied or Sleep period.
DHW Mode and Priority Operation
The control has four different settings available for DHW
Mode that affect pump operation. The required DHW Mode
setting will depend on the piping arrangement of the DHW
tank and whether or not priority for DHW is necessary. DHW
Priority stops or limits the delivery of heat to the building
heating system while the DHW tank calls for heat. This
allows for quick recovery of the DHW tank.
•
• Locate the DHW Mode setting in the Adjust Menu.
DHW MODE 1 - DHW in Parallel no Priority
When a DHW Demand is present, the DHW Pump and
DHW Valve contacts close. The primary pump does not
turn on, but may operate based on either Boiler or Mixing
requirements or a Setpoint Demand.
It is assumed that the DHW Device will provide adequate
flow through the heat exchanger and the boiler.
Mode = 1
DHW
Pump
Primary
Pump
DHW MODE 2 - DHW in Parallel with Priority
When a DHW Demand is present, the DHW Pump and
DHW Valve contacts close. The primary pump can operate
when a Boiler Demand is present. If the boiler is unable
to maintain the boiler target temperature, space heating
zones are shut off sequentially using tN4 communication
in order to provide priority to the DHW tank. This is known
as zone load shedding.
It is assumed that the DHW device will provide adequate
flow through the heat exchanger and the boiler.
DHW MODE 3 - DHW in Primary / Secondary no Priority
When a DHW Demand is present, the DHW Pump and
DHW Valve contacts are closed and the primary pump is
operated.
Mode = 2
DHW
Pump
Primary
Pump
OFF
Mode = 3
DHW
Pump
Primary
Pump
DHW MODE 4 - DHW in Primary / Secondary with Priority
When a DHW Demand is present, the DHW Pump and
Valve contacts are closed and the primary pump is operated.
Priority over space heating zones is achieved by shutting off
the zone pumps or zone valves through tN4 communication.
This is known as zone load shedding.
Mode = 4
OFF
DHW
Pump
Primary
Pump