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Section D: External Temperature Target Input
When modes 5 or 6 are selected, the control allows for an external control to operate the boiler temperature through an
external input signal provided by a Building Management System (BMS), Energy Management System (EMS), or tekmar
tN4 System Control. When in modes 5 or 6, the external heat demand (CD and Ht D) are disabled.
INTERNAL HEAT DEMAND
An internal heat demand is generated when an analog positive 0-10 V (dc) or 2-10 V (dc) signal is applied to the +V(in)
input. The negative V (dc) signal is applied to the Com/- input.
0-10 V (dc) or 0-20 mA External Input Signal
The external input signal can be selected to be either 0-10 V (dc) or
2-10 V (dc) range. When the 0-10 V (dc) range is selected, an input volt-
age of 1 V (dc) corresponds to a boiler target temperature of 50°F
(10°C). An input voltage of 10 V (dc) corresponds to a boiler target tem-
perature of 210°F (99°C). As the voltage varies between 1 V (dc) and 10
V (dc), the boiler target temperature varies linearly between 50°F (10°C)
and 210°F (99°C). If a voltage below 0.5 V (dc) is received, the boiler tar-
get temperature is displayed as " – – – " indicating that there is no
longer an internal heat demand.
A 0-20 mA signal can be converted to a 0-10 V (dc) signal by installing
a 500 Ω resistor on the external input signal device's terminals.
2-10 V (dc) or 4-20 mA External Input Signal
The external input signal can be selected to be either 0-10 V (dc) or
2-10 V (dc) range. When the 2-10 V (dc) range is selected, an input volt-
age of 2 V (dc) corresponds to a boiler target temperature of 50°F
(10°C). An input voltage of 10 V (dc) corresponds to a boiler target tem-
perature of 210°F (99°C). As the voltage varies between 2 V (dc) and 10
V (dc), the boiler target temperature varies linearly between 50°F (10°C)
and 210°F (99°C). If a voltage below 1.5 V (dc) is received the boiler
target temperature is displayed as " – – – " indi cating that there is no
longer an internal heat demand.
A 4-20 mA signal can be converted to a 2-10 V (dc) signal by installing
a 500 resistor on the external input signal device's terminals.
OFFSET
The Offset setting allows the boiler target temperature to be fine tuned to the external input signal. The control reads the
external input signal and converts this to a boiler target temperature. The Offset setting is then added to the boiler target tempera-
10
Model SF-10 Control Instructions Manual
Example
Range
Input
Offset
B
l i o
r e
a T
g r
t e
0-10 V (dc)
2-10 V (dc)
* requires a 500
=
0-10 V (dc)
=
7 V (dc)
=
+ 5°F (3°C)
=
0-20 mA*
Boiler Target
0
0
– – – (OFF)
1
2
50°F (10°C)
2
4
68°F (20°C)
3
6
86°F (30°C)
4
8
103°F (39°C)
5
10
121°F (49°C)
6
12
139°F (59°C)
7
14
157°F (69°C)
8
16
174°F (79°C)
9
18
192°F (89°C)
10
20
210°F (99°C)
4-20 mA*
Boiler Target
0
0
– – – (OFF)
1
2
– – – (OFF)
2
4
50°F (10°C)
3
6
70°F (21°C)
4
8
90°F (32°C)
5
10
110°F (43°C)
6
12
130°F (54°C)
7
14
150°F (66°C)
8
16
170°F (77°C)
9
18
190°F (88°C)
10
20
210°F (99°C)
resistor.
157°F (69°C)
+ 5°F (3°C)
6 1
° 2
F
7 (
° 2
) C
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