Honeywell perfect climate comfort center control system Manuale Utente

68-0173—3

outdoor temperature, humidity, current setpoint, system mode,

alarm out on High-Low temperature, filter status and

equipment failure. See separate instructions on CM8900A

and W88735B for more detailed information.

Minimum-Off Timing

A minimum-off timer in the Comfort Center™ control systeml

assures that the cooling compressor or heat pump

compressor does not come on again for at least five minutes

after it turns off. The minimum-off timer is triggered when the

compressor goes off and when the system switch is changed.

If the compressor turns off when the setpoint is changed, then

the minimum-off timer is triggered. The minimum-off timer

operates during the first stage of cooling on the W8900A

and C. The minimum-off timer operates during the first stage

of both heating and cooling on the W8900B. The minimum-off

timer can be disabled in the installer setup mode and can be

overridden in the checkout mode.

Fan Control

The fan comes on when any of these conditions are present (it

can take up to 20 seconds for the fan to turn on).

NOTES:

FAN ON: This setting means the fan runs 100

percent of the time during this period.

FAN AUTO: The AUTO setting means the fan runs

only with the heating or cooling system.

FAN CIRC: When the fan is set to CIRC, the fan runs

at least 30 percent of the time, including the time the

fan is on while the heating or cooling system is run-

ning. When the heating or cooling system is not

running at all, the fan runs for ten minutes on, and 20

minutes off. Protection against fan short cycling is

built into the device.

The installer setup has the ability to extend fan operation

following a cooling cycle. When selected, the fan run time at

the end of a cooling cycle is extended 80 seconds.

Ventilation Control

When the Comfort Center™ program is configured for

ventilation, the ventilator contacts are closed, activating high

speed ventilation equipment in response to any of the

following conditions:

• Ventilation request from the user.

• High CO

condition (measured by CO

monitor).

• High humidity condition while in the heating mode.

• Programming.

The ventilation control is set for a 20-second cycle so the user

can wait up to 20 seconds for the ventilation to start after the

request is made.

When the Comfort Center™ program is configured for no

ventilation, the system fan is activated in response to a call for

ventilation. When the Comfort Center™ system is configured

for a VNT damper, calls for ventilation close the VNT damper

contacts and activate the system fan.

NOTE: Each period can have a ventilation program.

Humidity Control (W8900A and B)

IMPORTANT

The humidity configuration can only be set for heat or

cool by the installer. If configured for both, the

Comfort Center™ control system ignores both set-

tings and no humidity control is activated.

Heat Mode

Heat humidification is activated when the sensed RH is below

the setpoint RH and the fan is on. When a ventilator is

installed and configured and the RH is above the setpoint, the

Comfort Center™ program calls for ventilation to lower the

humidity.

Cool Mode

Cool dehumidification is activated when the sensed RH is

above the setpoint. This can cause overcooling; see W8900C

Humidity Control section.

Dehumidification equipment can be controlled in many ways.

See Installation section for hookup drawings.

Humidity Control with Fan

Select models of the W8900A-C can be configured to control

humidity levels while the fan is energized. This type of

humidity control does not require the heat output to be

energized. In order for the humidity terminals (“HUM”) to

energize, the following conditions must be met:

1. System switch must be in the heat mode or in Auto

mode with heat being the last call.

2. There must be a call for humidity (sensed relative

humidity [RH] is below RH setpoint).

3. Fan terminal (“G”) must be energized through program-

ming or by pressing the fan button on the PC8900A.

Frost Control

The frost Control needs an outdoor sensor to be activated.

The Comfort Center™ control system calculates the

possibility of condensation or frost forming by using the

outside temperature and inside temperature to determine the

dewpoint. When the dewpoint would cause frost or

condensation, the humidification request will not be honored.

The frost setting has a value range of zero to ten with zero

representing glass with poor insulation and ten representing

glass with perfect insulation.

NOTE: Set the frost setting to 10 to severely limit the frost

control.

W8900C Humidity Control

The W8900C can be configured to control humidity levels in

both the heat and cool modes. A humidifier is connected to

the HUM terminals. The HUM contacts close and activate a

humidifier when the sensor RH is below the setpoint RH.

Dehumidification equipment is controlled by the Y1,Y2, and G

terminals. These contacts close to activate the air conditioning

equipment when the sensed RH is above the setpoint RH.

The reheat feature is designed to keep the occupants

comfortable. If the cooling setpoint is reached, but the

dehumidification setpoint is not satisfied, the Comfort

Center™ program turns on the heat. When the heat raises the

temperature so there is a call for cooling and the