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DC3 - BMS Slave Unit
  
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© 2004 by CapeSoft Electronics (Pty) Ltd
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The DC3 is a very cost effective extension of the Siemens Building Technologies System 600 BMS. It acts as a remote extension of the MBC or RBC. The system 600 programmer has access to the 11 points on the DC3. Each point can be unbundled and used in the usual manner including trending etc.

All connections to the DC3 are by means of plug-in screw terminal connectors which provides for quick, convenient installation, commissioning and maintenance.

Features
  4 Digital outputs  
2 Digital inputs
3 Analog inputs
2 Analog outputs
BMS communications support (Siemens Building Technologies System 600 compatible)
Accepts 10k, 47k and 100k NTC thermistor temperature sensors
Analog inputs can be individually selected as 0-10 Volt or NTC sensor
     


Technical Data

  Operating voltage 24 VAC, 2 VA  
Temperature sensors
Sensing elements - NTC thermistors 10k, 47k or 100k
Temperature range -10 to 50 EC, 0.25 EC Resolution
0-10 Volt analog input 0 to 10 Volt, 0.04 Volt Resolution
0-10 Volt analog output 0 to 10 Volt, 0.0476 Volt Resolution
Source - sink current 1 mA max
Digital outputs 220 VAC, 1 Amp running - 4 Amp max
Digital inputs 24 VAC, 20 mA current
     


Controller Setup
The controllers must each be programmed with an address for BMS operation. The address is set by means of the dip switch on the controller. The dip switch settings have the following values.

Controller Setup
  Switch Number OFF Value ON Value  
1 0 1
2 0 2
3 0 4
4 0 8
5 0 16
     


DC3 Dip Switch The address is calculated by adding the values together.

The dip switch shown here has switches 1 & 2 OFF while 3,4 & 5 are ON. The address is calculated as 4 + 8 + 16 = 28
The analog inputs can be individually configured. Each input can be selected as either 0-10 Volt, or a NTC thermistor sensor input. There are 2 jumper settings for each input.
DC3 Jumper The first jumper selects either 0-10 Volt or NTC thermistor input.
DC3 Jumper The second jumper selects either 0-10 Volts or which value of NTC thermistor is attached.

 
 

DC3 Connections


DC3 Connections



Dimensions

DC3 Dimensions




DC3 Points List (MBS) Version A - Application 140
  Pnt Description Units On / Off Slope Intercept Type  
1 DI 1   ON.OFF 1 0 LDI
2 DI 2   ON.OFF 1 0 LDI
3 DO 1   ON.OFF 1 0 LDO
4 DO 2   ON.OFF 1 0 LDO
5 DO 3   ON.OFF 1 0 LDO
6 DO 4   ON.OFF 1 0 LDO
7 TEMP 1 DEG C   0.25 -10 LAI
8 TEMP 2 DEG C   0.25 -10 LAI
9 TEMP 3 DEG C   0.25 -10 LAI
10 0-10V IN 1 VOLTS   0.04 0 LAI
11 0-10V IN 2 VOLTS   0.04 0 LAI
12 0-10V IN 3 VOLTS   0.04 0 LAI
13 0-10V OUT 1 VOLTS   0.05 0 LAO
14 0-10V OUT 2 VOLTS   0.05 0 LAO
     


DC3 Points List (MBS) Version B - Application 141
  Pnt Description Units On / Off Slope Intercept Type  
1 DI 1   ON.OFF 1 0 LDI
2 DI 2   ON.OFF 1 0 LDI
3 DO 1   ON.OFF 1 0 LDO
4 DO 2   ON.OFF 1 0 LDO
5 DO 3   ON.OFF 1 0 LDO
6 DO 4   ON.OFF 1 0 LDO
7 TEMP 1 DEG C   0.25 -10 LAI
8 TEMP 2 DEG C   0.25 -10 LAI
9 TEMP 3 DEG C   0.25 -10 LAI
10 0-10V IN 1 VOLTS   0.04 0 LAI
11 0-10V IN 2 VOLTS   0.04 0 LAI
12 0-10V IN 3 VOLTS   0.04 0 LAI
13 0-10V OUT 1 VOLTS   0.05 0 LAO
14 0-10V OUT 2 VOLTS   0.05 0 LAO
29 DAY.NGT   NIGHT.DAY 1 0 LDO
     


Special Notes:

There are a few items to bear in mind when using the DC3.

Note 1
The standard DC3 only supports SI units. Non SI can be supplied on request.

Note 2
The points numbered 17 to 24 and those numbered 25 to 32 are both representations of the same physical analog inputs. When the analog input is connected to a NTC thermistor temperature sensor, then unbundle the point from the points 17 to 24. When using the analog input as 0 to 10 Volts then unbundle the point from the points 25 to 32. The points 17 to 24 are corrected, by the DC3, to allow for the non-linearity of the thermistor curve.

Example:
If analog input 1 is connected to a 100k NTC thermistor then you would unbundle the point as address TCCLDD17 with a slope of 0.25, an intercept of -10 and the type L.

Example:
If the analog input 2 is connected to a 0 to 10 Volt device then you would unbundle the point as address TCCLDD26 with a slope of 0.04, an intercept of 0 and the type L. This would return the value 0 to 10. If the 0 to 10 Volt device is, for instance, a pressure sensor with the range 0 to 500 Pa, you might prefer to unbundle the point as address TCCLDD26 with a slope of 2.0, an intercept of 0 and the type L. This would return the values 0 to 500.

The slope to use is calculated as follows:
SLOPE = 0.004 X RANGE

The range was 500 so the slope became:
SLOPE = 0.004 X 500 = 2.0

Note 3
The Siemens Building Technologies 10k NTC sensor has an internal diode which offsets the value read by the DC3. These sensors can be used. The intercept must be changed from -10 to -5 to correct for effect of the internal diode. The BMS standard report will however show a value which is 5 Deg C lower that actual. The unbundled point will show the correct value.

Note 4
The DC3 is fabricated without any non-volatile (permanent) memory. Due to this design any "OPERATOR" priority commands will be lost during a power failure.

Example:
So for instance if you were to unbundle a digital output as FANRUN. Then if you commanded FANRUN to ON, your point FANRUN would appear in the point log as:

FANRUN ( ) ON -N- P:OPER

Should the power to the DC3 become interrupted or the communication to the DC3 be lost for more than 30 seconds, then when the DC3 returns from failure, the point log would show the following:

FANRUN ( ) OFF -N- P:OPER

The FANRUN would default to OFF and remain as such until it is changed by another operator command or be released from OPERATOR priority and change under program control.

The points can be commanded using POINT COMMAND LCTLR SET etc. These commands will be restored by the BMS when the DC3 returns from failure.


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