Techniques To Reduce Ground Lift; About External Loads; Transformer Selection And Determining The Maximum Power Run Length - Acuity Controls nLight ECLYPSE User Manual

Techniques to Reduce Ground Lift

Reduce the impact of ground lift as follows:
Use a heavier gauge wire.
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Add more wire runs. Connect these wire runs to the power supply in a star pattern.
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For controllers that accept DC power (that is, models without triac outputs): Specify a 24VDC power supply. The con-
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tinuous 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 multiplication factor associated with the peak AC current being 2.5
times the average RMS AC current. See below.

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 com-
municating sensors). Refer to the respective module's datasheet for related power consumption information.

Transformer Selection and Determining the Maximum Power Run Length

To conform to Class 2 installation requirements, only use transformers of 100VA or less to power the device(s).
It is recommended to wire only one controller per 24VAC transformer.
For VAV devices, if only one 24VAC transformer is available, determine the maximum number of daisy-chained VAVs that
can be supplied on a single power cable supplied by a 100 VA transformer based on the controller's expected power con-
sumption including external loads, the cable's wire gauge, and the total cable length, using the following table. Any installa-
tion condition that is outside of the parameters of the following table should be avoided.
Daisy-chaining controllers is not permitted when a VAV controller's expected power consumption including external loads
is over 15VA. In this case the controller must be connected to the 24VAC transformer in a star topology. The transformer
must be installed in close proximity to the controller.
AWG Power Run Total
Cable Length
14 75 m (250 ft.)
1
14 60 m (200 ft.)
14 45 m (150 ft.)
14 30 m (100 ft.)
16 60 m (200 ft.)
16 45 m (150 ft.)
16 30 m (100 ft.)
18 45 m (150 ft.)
18 30 m (100 ft.)
Table 11: Maximum Number of 24VAC VAV Devices on a Power Run with a 100 VA Transformer (Daisy-Chained)
1. Device terminals are not capable of accepting two 14 AWG wires (when daisy-chaining devices). Use a wire nut with a pig tail to make such a connection.
For non-VAV devices, determine the appropriate size transformer for the job as follows:
Add up the power requirements of all devices plus all external loads (see
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power needed by a multiplier of 1.3, as a security 164margin. For example, to power five devices (15 VA each), the to-
tal load is 75 VA multiplied by 1.3 is 98 VA. Choose a size of transformer just over this amount: For example, a 100 VA
model.
When the total load of a number of devices requires a transformer with a rating greater than 100 VA, use two or more
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transformers. Ensure that the load to be connected to each transformer follows the guideline of Step 1 above.
nLight ECLYPSE
Maximum Number of Devices @ 7
VA per device
4
5
5
5
3
5
5
3
5
BACnet MS/TP Communication Data Bus Fundamentals
Maximum Number of Devices @
10 VA per device
2
3
4
5
0
3
4
2
3
About External
Maximum Number of Devices @
15 VA per device
1
2
3
4
1
2
3
1
2
Loads). Multiply the total
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