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ECLYPSE APEX
Because the 24V COM terminal on ECB series controllers is the signal reference point for the data
bus, ground lift offsets the data bus voltage reference that is used to interpret valid data levels sent on
the data bus. If the ground lift is more than 7 volts peak, there is a risk of data corruption and offline
events due to the device being incapable of correctly reading data signals from the data bus. Thus, it
is important to keep the power supply (transformer) as close to the controller as possible or use a
power connection of 3 wire when possible.
Techniques to Reduce Ground Lift
Reduce the impact of ground lift as follows:
£
Use a heavier gauge wire.
£
Add more wire runs. Connect these wire runs to the power supply in a star pattern.
£
For controllers that accept DC power (that is, models without triac outputs): Specify a 24VDC
power supply. The continuous and even voltage of a DC power supply makes more efficient use of
the power handling capabilities of a power run. A 24VDC power supply eliminates the 2.5 multipli-
cation factor associated with the peak AC current being 2.5 times the average RMS AC current.
See below.
£
The functional ground terminal available on some controller is intended to eliminate the ground lift
(when using the 3 wires connection)
About External Loads
When calculating a controller’s power consumption to size the 24VAC transformer, you must also add
the external loads the controller is going to supply, including the power consumption of any connected
subnet module (for example, for Allure series communicating sensors). Refer to the respective mod-
ule’s datasheet for related power consumption information.
A controller can support a maximum of two Allure series sensor models equipped with a CO
2
sensor.
Subnetwork Module Compatibility and Supported Quantity Charts
for how many Allure series com-
municating sensors are supported by a given controller model. The remaining connected Allure series
sensor models must be without a CO
2
sensor.
Transformer Selection and Determining the Maximum Power Run Length
To determine the power requirements and supported quantities of connected subnet modules for the
ECY Series controllers, see the Product Selection Tool available in Builder: https://builder.distech-con-
trols.com.
Please refer to the corresponding controller’s Installation Guide for specific information on power
wiring.
Recommended 24V Power Cable
The table below lists Distech Controls’ recommended power cable.
Cable Type
AWG - Number of Conductors
Non-Plenum Applications(FT4)
Plenum Applications (FT6)
Part Number
O.D. (Ø)
Part Number
O.D. (Ø)
18-2
CB-W181P-1002
5.0mm / 0.20in.
CB-W181P-2051
5.0mm / 0.20in.
16-2
CB-W161P-1031
4.8mm / 0.19in.
CB-W161P-2062
4.8mm / 0.19in.
14-2
CB-W141P-1081
7.2mm / 0.29in.
CB-W141P-2013
7.2mm / 0.29in.
Table 18: Distech Controls Recommended 24V Power Cable
BACnet MS/TP Communication Data Bus Fundamentals
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