tekmar 284 Boiler Control - Manual (Page 14)

© 2014 284_D - 08/14 14 of 60 A Watts Water Technologies Company
*Requires 500  Resistor in Parallel
CONVERSION TABLE 2 - 10
4 - 20 mA* 2 - 10 V (dc) Boiler Target
0 0 – – – (OFF)
4 2 50°F (10.0°C)
6 3 70°F (21.0°C)
8 4 90°F (32.0°C)
10 5 110°F (43.5°C)
12 6 130°F (54.5°C)
14 7 150°F (65.5°C)
16 8 170°F (76.5°C)
18 9 190°F (88.0°C)
20 10 210°F (99.0°C)
EMS Offset
For external input operation, the boiler target (determined
from the external input signal) may be fine tuned. The EMS
OFFST setting is used to provide the fine tuning. The setting
may be adjusted ±10°F (±5.5°C). When set to 0°F (0.0°C), if
the temperature determined from the external signal is 140°F
(60.0°C), the boiler target will be 140°F (60.0°C). When set
to +5°F (+3.0°C) & with the same external signal represents
140°F (60.0°C), the boiler target will be 145°F (63.0°C).
Example
Range
= 0 - 10 V (dc)
Input = 7 V (dc) 157°F (69°C)
Offset = +5°F (3°C) + 5°F (3°C)
Boiler Target = 162°F (72°C)
The minimum & maximum settings also apply for external input
operation. For example, if a boiler minimum of 140°F (60.0°C) is
set & the external signal received represents 80°F (27.0°C), the
boiler target will be 140°F (60.0°C). MIN will also be displayed
in the status field to indicate that a limiting condition is in effect.
This also applies for the MAX limit.
Indirect Domestic Hot Water (IDHW) Operation
IDHW operation is applicable during the following application
modes: outdoor temperature reset, fixed setpoint & EMS.
DHW Call ----------------------------------------- -----------------------------------------
A DHW Call is required in order for the control to provide heat
to an indirect DHW tank. Once the control registers a DHW
Call, it will display the “DHW” icon under Calls in the display.
A DHW Call can be provided in three ways:
DHW Tank Aquastat
If a DHW Tank Aquastat (mechanical switch) is used to apply
a DHW Call, the tank is heated to the aquastat temperature
setting. A dry contact or 24 V (ac) signal is applied across the
IDHW Call terminals 7 & 8.
IDHW Sensor must be set to Off.
DHW Sensor
A DHW Tank Sensor provides superior temperature control
of the tank compared to an aquastat. The control can register
a DHW Call when a DHW Sensor is wired to terminals 21
& 22. Once the DHW Sensor temperature drops 1/2 of the
IDHW Differential setting below the iDHW Setpoint, the control
registers a DHW Call.
The IDHW Sensor must be set to On. There cannot be
an external IDHW Call when using a DHW sensor.
tekmarNet ® Setpoint Control with Sensor
A DHW Call is provided through the tekmarNet ® system. This can
be done through the tN4 Boiler Bus terminals with a tekmarNet ®
setpoint device such as a Setpoint Control 161.
DHW Differential --------------------------------- ---------------------------------
Due to large differences between the heating load & the DHW
load, a separate DHW differential should be used whenever a
DHW Call is present. This will improve staging & boiler cycling.
When using a DHW Sensor, a DHW Call is registered when the
temperature at the DHW sensor drops the IDHW DIFF setting
below the IDHW Setpoint setting. The DHW Call is satisfied
once the temperature at the DHW Sensor rises to the IDHW
Setpoint setting.
IDHW
Differential
DHW Target
ON
OFF
Boiler Target Temperature during a DHW Call ------ ------
When a DHW Call is present, a boiler target is determined.
When using a DHW Tank Aquastat, the boiler target is set
to the IDHW Exchange setting.
When using a DHW Tank Sensor, the boiler target is fixed
at the IDHW Setpoint setting plus 40°F (22.0°C).
When using a tekmarNet
® Setpoint Control, the boiler target
is set to the devices Exchange Supply setting.
If there are multiple devices calling for heat, the boiler target
is set to the highest temperature requirement.
IDHW During UnOccupied ------------------------ ------------------------
When using a DHW Tank Aquastat, a second IDHW Exchange
setting is available for the UnOccupied or Sleep period.
When using a DHW Sensor, a second IDHW Setpoint setting
is available for the UnOccupied or Sleep period.
DIP Switch must be set to Setback to view UnOccupied items.
During the Away Scene, DHW Calls are ignored.
•
•
•