Honeywell W7750A Manual

A SERVICE OF

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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER

74-2958—126

available throu

g

h Hone

y

well, or directl

y

from the

manufacturer, Mamac S

y

stems

(

see Table 11 for orderin

g

information

)

.

Fi

g

. 17 depicts a t

y

pical W7750 S

y

stem with modulatin

g

heatin

g

valve usin

g

a pneumatic valve actuator. Also see Fi

g

.

36 for wirin

g

an MMC325 Pneumatic Transducer to a

W7750A,B,C Controller and Fi

g

. 37 for wirin

g

a RP7517B

Pneumatic Transducer to a W7750C Controller.

NOTE: When choosin

g

the pneumatic pressure ran

g

e, make

sure that the close-off pressure is 2 to 3 psi

g

reater

than that of the sprin

g

ran

g

e. When usin

g

a sprin

g

ran

g

e of 5 to 10 psi with 10 psi as the closed posi-

tion,

do not

use the 0 to 10 psi model of the MMC325

Transducer; use the 0 to 20 psi transducer as the

recommended selection.

Fig. 17. Modulating heat with pneumatic valve actuator.

MIXED-OUTPUT-TYPE CONTROL

The W7750B,C Controller provides control for mixed-output-

t

y

pes of applications such as PWM heatin

g

and sta

g

ed

coolin

g

control occurrin

g

simultaneousl

y

with Series 60

Floatin

g

Economizer Damper Control.

Occupancy Sensor

Excel 10 W7750 Controllers provide a di

g

ital input for

connection to an occupanc

y

sensor. This is a device, such as

a passive infrared motion detector, that contains a dr

y

contact

(

see followin

g

NOTE

)

closure to indicate whether or not

people are present in the space. The Excel 10 W7750

Controller expects a contact closure to indicate the space is

Occupied. See Fi

g

. 27 throu

g

h 35 in Application Step 4,

Prepare Wirin

g

Dia

g

rams, for details on wirin

g

connections.

The control al

g

orithm in the Excel 10 Controller uses the

occupanc

y

sensor, if confi

g

ured, to determine the Effective

Occupanc

y

(

see Table 5

)

mode of operation. If the Time Of

Da

y

(

TOD

)

schedule indicates an Occupied state, and the

occupanc

y

sensor contact is closed, the Effective Occupanc

y

mode is Occupied. However, if the TOD schedule indicates an

Occupied state and the occupanc

y

sensor contact is open,

then the Effective Occupanc

y

mode is STANDBY. The

temperature control al

g

orithm is then controlled to the

STANDBY Coolin

g

and Heatin

g

Setpoints.

If the occupanc

y

sensor is not confi

g

ured, a local controller

can be put in the STANDBY mode onl

y

b

y

either a one-to-one

association of the occupanc

y

sensor from another Excel 10

Controller to the local controller, or b

y

receivin

g

the STANDBY

mode si

g

nal via the L

ON

W

ORKS

Bus.

NOTE: The Excel 10 Controller has limited power available

(

onl

y

9 mA at 4.8 volts

)

for checkin

g

the di

g

ital inputs

for contact closures. It is ver

y

important that the

device used contains hi

g

h

q

ualit

y

, noncorrodin

g

contacts with resistivit

y

that does not de

g

rade; that

is, increase over time. Use noble metal

(

such as

g

old

or silver

)

, or pimpled or sealed contacts to assure

consistent, lon

g

-term operation.

The recommended devices for use with the Excel 10 W7750

Controllers are the EL7628A1007 Ceilin

g

Mounted Infrared or

the EL7680A1008 Wall Mounted Wide View Infrared

Occupanc

y

Sensors. If ultrasonic sensors are re

q

uired, the

EL7611A1003 and the EL7612A1001 Occupanc

y

Sensors are

recommended. An EL76XX Power Suppl

y

/Control Unit is

re

q

uired for use with these occupanc

y

sensors. The

EL7630A1003 can power up to four sensors, and is multi-

tapped for several line volta

g

es. The EL7621A1002 can

power three sensors and it connects to 120 Vac line volta

g

e.

The EL7621A1010 can also power three sensors but it

connects to 277 Vac line volta

g

e.

Window Open/Closed Digital Input

A di

g

ital input is also provided for detectin

g

whether a window

in the space was opened. The Excel 10 W7750 Controller can

be connected to a dr

y

contact

(

see the followin

g

NOTE and

Fi

g

. 27 throu

g

h 35 in Application Step 4. Prepare Wirin

g

Dia

g

rams, for details

)

or a set of contacts wired in series

(

for

monitorin

g

multiple windows

)

to verif

y

that the window

(

s

)

are

closed. The al

g

orithm expects a contact closure to indicate

the window is closed. If an open window is detected, the

al

g

orithm chan

g

es the mode of operation to

FREEZE_PROTECT, which shuts down the control functions,

and watches for low space temperature conditions. The frost

protection setpoint is 46.4

°

F

(

8

°

C

)

, and the frost alarm occurs

at 42.8

°

F

(

6

°

C

)

.

NOTE:

(

This is the same NOTE as in the Occupanc

y

Sensor

section.

)

The Excel 10 has limited power available

(

onl

y

9 mA at 4.8 volts

)

for checkin

g

the di

g

ital inputs

for contact closures. It is ver

y

important that the

device used contains hi

g

h

q

ualit

y

, noncorrodin

g

contacts with resistivit

y

that does not de

g

rade; that

is, increase over time. Use noble metal

(

such as

g

old

or silver

)

, or pimpled or sealed contacts to assure

consistent, lon

g

-term operation.

Wall Module Options

As previousl

y

discussed, there are four basic varieties of the

T7770 Wall Modules and two of the T7560 Di

g

ital Wall Module

(

see the Product Names and the Construction sections

)

. Also,

a T7770 and T7560 Wall Modules can be shared amon

g

two

or more W7750s. The control al

g

orithm must be

g

iven this

wall module information when confi

g

urin

g

the W7750

(

see

Excel E-Vision User’s Guide, form 74-2588

)

.

VALVE

PNEUMATIC

ACTUATOR

PNEUMATIC

TRANSDUCER

MMC325

M

1

1

PNEUMATIC MAIN OR BRANCH LINE MUST BE 1/4 IN. (6 MM)

OR LARGER TUBING. A MINIMUM OF 6 FT (1.8M) OF TUBING

IS NEEDED IN A BRANCH LINE.

MIXED

AIR

HEAT

COIL

DISCHARGE

AIR

+

FAN

FAN

STARTER

M17495

T7560A,B OR T7770