Honeywell W7761A specifications Power Wiring, Power Budget Calculation Example

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Fig. 10. Bus wiring layout for two singly terminated E-Bus segments.

NOTE: See the E-Bus Termination Module section for wiring details.

IMPORTANT

Notes on communications wiring:

∙All field wiring must conform to local codes and ordinances.

∙Approved cable types for E-Bus communications wiring is Level IV 22 AWG (0.34 mm2) plenum or non-plenum rated unshielded, twisted pair, solid conductor wire. For nonplenum areas, use Level IV 22 AWG (0.34 mm2), such

as U.S. part AK3781 (one pair) or U.S. part AK3782 (two pair). In plenum areas, use plenum-rated Level IV, 22

AWG (0.34 mm2) such as U.S. part AK3791 (one pair) or U.S. part AK3792 (two pair). See Tables 9 and 10 for part numbers. Contact Echelon® Corp. Technical Support for the recommended vendors of Echelon® approved cables.

∙Unswitched 24 Vac power wiring can be run in the same conduit as the E-Bus cable.

∙Do not use different wire types or gauges on the same E-Bus segment. The step change in line impedance characteristics causes unpredictable reflections on the bus. When using different types is unavoidable, use a Q7751A Router at the junction.

∙In noisy (high EMI) environments, avoid wire runs parallel to noisy power cables, or lines containing lighting dimmer switches, and keep at least 3 in. (76 mm) of separation between noisy lines and the E-Bus cable.

∙Make sure that neither of the E-Bus wires is grounded.

Power Wiring

A power budget must be calculated for each Excel 10 W7761 Device to determine the required transformer size for proper operation. A power budget is simply the summing of the maximum power draw ratings (in VA) of all the devices to be controlled by an Excel 10 W7761 Device. This includes the device itself, the equipment actuators (ML6161, or other motors) and various contactors and transducers, as appropriate, for the Excel 10 configuration.

Power Budget Calculation Example

The following is an example power budget calculation for a typical W7761A Excel 10 Device.

Device	VA	Information Obtained from the
Excel 10 W7761	6.0 VA	W7761
Device		Specification Data

20 74-2699