Honeywell W7750A specifications Power Wiring, Power Budget Calculation Example

EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

T7770

EXCEL 10

VAV

LONWORKS

BUS

ACCESS

LONWORKS BUS

SEGMENT NUMBER 1

EXCEL 10	EXCEL 10
CVAHU	CVAHU

209541B209541B

TERMINATION TERMINATION

MODULEMODULE

•Do not use different wire types or gauges on the same LONWORKS Bus segment. The step change in line impedance characteristics causes unpredictable reflections on the bus. When using different types is unavoidable, use a Q7751A,B 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 LONWORKS Bus cable.

•Make sure that neither of the LONWORKS Bus wires is grounded.

Power Wiring

LONWORKS BUS

SEGMENT NUMBER 2

EXCEL 10

Q7750A

ZONE

MANAGER

EXCEL 10	EXCEL 10	Q7751A
VAV	VAV	FTT
		LONWORKS
		BUS
		ROUTER

TO C-BUS (SEE FIG. 1)

LONWORKS BUS

SEGMENT NUMBER 2

T7560A,B

A power budget must be calculated for each Excel 10 W7750 Controller 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 W7750 Controller. This includes the controller 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 Excel 10 W7750B Controller.

Assume a W7750 unit with a fan, two stages of D/X cooling, modulating steam valve for heating, and modulating

EXCEL 10

EXCEL 10

EXCEL 10

economizer dampers. The power requirements are:

CVAHU

CVAHU

CVAHU

M17497

DeviceVA	Information Obtained from
Excel 10 W7750B,C	12.0	W7750 Specification Data
Controller

Fig. 20. Wiring layout for two singly terminated

LONWORKS® Bus segments.

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

IMPORTANT

Notes on communications wiring:

•All field wiring must conform to local codes and ordi- nances or as specified on installation wiring dia- grams.

•Approved cable types for LONWORKS Bus communi- cations wiring is Level IV 22 AWG (0.34 mm2) ple- num 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 11 for part numbers. Contact Echelon Corp. Technical Sup- port for the recommended vendors of Echelon approved cables.

•Unswitched 24 Vac power wiring can be run in the same conduit as the LONWORKS Bus cable.

ML6161	2.2	TRADELINE
Damper Actuator		Catalog
R8242A	21.0	TRADELINE
Contactor for fan		Catalog in-rush rating
D/X Stages	0.0

NOTE: For this example, assume the cooling stage outputs are wired into a compressor control circuit and, therefore, have no impact on the power budget.)

M6410A Steam	0.7 TRADELINE
Heating Coil Valve	Catalog, 0.32A at 24 Vac

TOTAL: 35.9 VA

The Excel 10 System example requires 35.9 VA of peak power; therefore, a 40 VA AT72D Transformer is able to provide ample power for this controller and its accessories. Alternatively, a 75 VA AT88A Transformer could be used to power two Excel 10 Systems of this type, or a 100 VA AT92A Transformer could be used to power two of these Excel 10 Systems and meet NEC Class 2 restrictions (no greater than 100 VA). See Fig. 22 and 23 for illustrations of power wiring details. See Table 8 for VA ratings of various devices.

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