tekmar 423 Universal Reset Module - Manual (Page 28)

© 2007 D 423 - 08/07 28 of 36
Primary
Pump
Setpoint
Mode = 3
Setpoint
Primary
Pump
OFF
Mode = 4
Setpoint
Primary
Pump
OFF
Mode = 2
Primary
Pump
Setpoint
Mode = 1
Setpoint Mode 2 - Setpoint in Parallel with Priority
When a Setpoint Demand is present, the boiler is operated
to maintain the setpoint target. The primary pump (P1)
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 for the setpoint
load. This is known as zone load shedding.
It is assumed that the setpoint pump will provide adequate
flow through the heat exchanger and the boiler.
Setpoint Mode 3 – Setpoint in Primary / Secondary
Whenever a Setpoint Demand is present, the primary
pump is turned on and the boiler is operated to maintain
the setpoint target.
Setpoint Mode 4 - Setpoint in Primary / Secondary
with Priority
Whenever a Setpoint Demand is present, the primary
pump is turned on and the boiler is operated to maintain
the setpoint target. Space heating zones will be shut off
using zone load shedding if the boiler is unable to maintain
the boiler target temperature.
Setpoint Temperature Operation Section J
Setpoint
The control can operate to satisfy the requirements of a
setpoint load in addition to a space heating load and a
DHW load. A setpoint load overrides the current outdoor
reset temperature and WWSD setting in order to provide
heat to the setpoint load.
Setpoint Demand
A Setpoint Demand is required in order for the control to
provide heat to a setpoint load.
The control registers a Setpoint Demand when a voltage
between 24 and 230 V (ac) is applied across the Setpoint
Demand terminals (77 and 78). Once voltage is applied,
the Setpoint Demand segment turns on in the LCD.
Boiler Target During Setpoint
The boiler target temperature during a Setpoint Demand is
increased to at least the Setpoint setting. This temperature is
maintained as long as the control has a Setpoint Demand.
Setpoint During UnOccupied
The control has a Setpoint UnOccupied setting that allows
the installer to select On or Off. When set to On, and the
control receives a Setpoint Demand during an UnOccupied or
Sleep period, the control continues operation of the Setpoint
system as it would during Occupied and Wake periods. When
set to Off, the control can ignore a Setpoint Demand for the
duration of the UnOccupied and Sleep periods.
Setpoint Modes
The Setpoint Mode determines the operation of the primary
pump. The Setpoint Mode setting is found in the Adjust
Menu.
Setpoint Mode 1 - Setpoint in Parallel
Whenever a Setpoint Demand is present, the boiler is
operated to maintain the setpoint target. The primary pump
does not turn on, but may operate based on either a Boiler,
Mixing or a DHW Demand.
It is assumed that the Setpoint pump will provide adequate
flow through the heat exchanger and the boiler.