tekmar 284 Boiler Control - Manual (Page 13)

© 2014 284_D - 08/14 13 of 60 A Watts Water Technologies Company
Priority Override --------------------------------- ---------------------------------
Priority Override applies when Setpoint Priority is set to ON. It
prevents the building from cooling off too much or the possibility
of a potential freeze up during setpoint priority.
When set to auto, the priority time is calculated based on outdoor
temperature. At or below the design outdoor temperature, 15
minutes are allowed for setpoint priority. At or above the Indoor
Design temperature, 2 hours are allowed for setpoint priority.
The time allowed for setpoint priority varies linearly between
the above two points. There is a manual setting also available
in the Setup menu.
The priority timer does not start timing until priority is selected
& both a Setpoint Call & a Heat Call exist together. Once the
allowed time for priority has elapsed, the control overrides the
setpoint priority & resumes space heating.
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 & possibly
space heating as well. As long as the boiler supply tempera-
ture is maintained near the target, setpoint & heating occurs
simultaneously.
Setpoint Post Purge ------------------------------ ------------------------------
After a Setpoint Call from a tN4 device is removed, the control
can perform a post purge. The control shuts off the boilers &
continues to operate, if applicable, the primary pump. This purges
the residual heat from the boilers into the setpoint load. The
control continues this purge until one of the following occurs:
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.
Energy Management System (EMS) Operation
The control can accept an external DC signal from an Energy
Management System (EMS). The control converts the DC
signal into the appropriate boiler target temperature for the
space heating system.
EMS is available by setting the APP MODE in the Setup Menu
to EMS.
Indirect Domestic Hot Water (IDHW) & setpoint are both
available during EMS operation.
Heat Call ----------------------------------------- -----------------------------------------
A Heat Call is required in order for the control to provide a
target water temperature for the space heating system. Once
the control registers a Heat Call, it will display the “Heat” icon
under the Calls in the display.
A Heat Call is provided by:
Input Signal
An external signal is generated by applying a voltage between
0 V (dc) & 10 V (dc) across the EMS (+) In & Com (-) terminals
(16 & 19). Voltages that exceed 10 V (dc) will still be considered
a 10 V (dc) signal.
If the EMS signal goes below the minimum voltage, the “Heat”
icon under the Calls in the display is turned off. The boiler target
temperature is displayed as “– – –” to indicate that there is no
longer a call for heating.
External Heat Call terminals are not operational.
EMS Signal --------------------------------------- ---------------------------------------
The control can accept either a 0-10 V (dc) signal or a 2-10 V
(dc) signal. The EMS SGNL setting must be set to the proper
setting based on the signal that is being sent to the control.
0 - 10 V (dc) or 0 - 20 mA
When the 0-10 V (dc) signal is selected, an input voltage of
1 V (dc) corresponds to a boiler target temperature of 50°F
(10.0°C). An input voltage of 10 V (dc) corresponds to a boiler
target temperature of 210°F (99.0°C). As the voltage varies
between 1 V (dc) & 10 V (dc) the boiler target temperature varies
linearly between 50°F (10.0°C) & 210°F (99.0°C). If a voltage
below 0.5 V (dc) is received the boiler target temperature is
displayed as “– – –” indicating that there is no longer a call
for heating.
A 0 - 20 mA signal can be converted to a 0 - 10 V (dc) signal
by installing a 500 Ω resistor between the EMS (+) In & Com
(-) terminals (16 & 19).
2 - 10 V (dc) or 4 - 20 mA
When the 2 - 10 V (dc) signal is selected, an input voltage of
2 V (dc) corresponds to a boiler target temperature of 50°F
(10.0°C). An input voltage of 10 V (dc) corresponds to a boiler
target temperature of 210°F (99.0°C). As the voltage varies
between 2 V (dc) & 10 V (dc) the boiler target temperature varies
linearly between 50°F (10.0°C) & 210°F (99.0°C). If a voltage
below 1.5 V (dc) is received the boiler target temperature is
displayed as “– – –” indicating that there is no longer a call
for heating.
A 4 - 20 mA signal can be converted to a 2 - 10 V (dc) signal
by installing a 500 Ω resistor between the EMS (+) In & Com
(-) terminals (16 & 19).
CONVERSION TABLE 0 - 10
0 - 20 mA* 0 - 10 V (dc) Boiler Target
0 0 – – – (OFF)
2 1 50°F (10.0°C)
4 2 68°F (20.0°C)
6 3 86°F (30.0°C)
8 4 103°F (39.5°C)
10 5 121°F (49.5°C)
12 6 139°F (59.5°C)
14 7 157°F (69.5°C)
16 8 174°F (79.0°C)
18 9 192°F (89.0°C)
20 10 210°F (99.0°C)
*Requires 500  Resistor in Parallel