Watts tekmar 294 - Constant Setpoint Operation; Setpoint Call Methods; Setpoint Priority and Override; Constant Setpoint Post Purge

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IOM-T-294 2205 © 2022 tekmar
Setpoint Call
A setpoint call operates the boilers to a constant temperature set-
point. The setpoint call status is displayed in the System Inputs on
the display. There are two ways to create a setpoint call:
Setpoint Call Input
A dry contact or 24 V (ac) signal is applied across the Setpoint
Call terminals. The setpoint call operates at the Constant
Setpoint Target.
tekmarNet
®
Setpoint Control
A tekmarNet
®
Setpoint Control 161 or 162 creates a call
through tekmarNet communication bus. The setpoint target is
determined by the setpoint control.
Programmable Schedule and Away Scene
When a programmable schedule is On, the Constant Setpoint
Target Unoccupied selects if the control responds to setpoint
calls during the unoccupied time period.
During the Away scene and the schedule is Off, the control
responds to the Constant Setpoint call.
During the Away scene and the schedule is On, the Constant
Setpoint Target Unoccupied selects if the control responds to
setpoint calls.
System Pump
The Constant Setpoint System Pump setting selects whether
or not the system pump is on during setpoint heating.
Off
The system pump does not turn on during setpoint heating. It
is assumed that the setpoint load pump will provide adequate
flow through the setpoint load and the boiler system loop.
Setpoint
System
On
The system pump turns on during setpoint heating.
System
Setpoint
Setpoint Priority
The Constant Setpoint Priority setting selects whether or not
priority of setpoint over central heating is required. Setpoint
priority stops or limits the delivery of heat to the central heating
system while the setpoint load calls for heat to allow for quick
recovery of the load.
Off
Setpoint priority is not provided and the system pump can
operate when a Heat Call is present.
On
Setpoint priority is provided over the central heating system.
When there are simultaneous constant setpoint and central
heating calls, the system pump shuts off to provide priority to
the setpoint load.
When there are simultaneous constant setpoint and tekmarNet
calls, the system pump can continue to operate. If the boilers
are unable to maintain the boiler target temperature, the tek-
marNet zones are sequentially shut off using tekmarNet com-
munication to provide priority. The sequence order shuts off
the thermostat with address 24 first and address 1 last.
Priority Override
The control includes a Priority Override to prevent the building
from cooling off too much or a potential freezing condition in
the event of a faulty setpoint call signal. It uses the Indirect
DHW Priority Override to determine the priority duration. The
time is adjustable from 20 to 240 minutes. Once the allowed
time for priority has elapsed, the control overrides the constant
setpoint priority and resumes central heating. Setpoint priority
does not resume until the central heating or setpoint calls are
removed and then reapplied.
Conditional Setpoint Priority
If the boiler supply temperature is maintained at or above the
required temperature during setpoint heating, this indicates
that the boilers have enough capacity for setpoint and possibly
central heating as well. As long as the boiler supply tempera-
ture is maintained near the target, setpoint and heating occurs
simultaneously.
Setpoint Post Purge
After a Setpoint Call from a tekmarNet device is removed, the
control performs a post purge. The control shuts off the boilers
and continues to operate, if applicable, the system pump. This
purges the residual heat from the boilers into the setpoint load.
The control continues this purge until one of the following condi-
tions are met:
1. A Heat Call is detected.
2. The boiler supply drops 20°F (11.0°C) below the setpoint target
temperature.
3. Two minutes elapse.
Constant Setpoint Operation