Honeywell T7350 Benutzerhandbuch

63-2605—5

20

NOTE: The setpoint used during the cool recovery period is 

similar to the heat mode in Fig. 11, except the slope 

of the line reverses for cooling.

Advantages:

• Comfort setting is achieved at the programmed time and 

maintained regardless of weather conditions; occupants 

are comfortable.

• Drafts from low-temperature discharge air are minimized 

during Occupied periods.

• Use of the more economical first stage of heat is 

maximized during recovery, minimizing use of the 

expensive later heat stage(s).

• Comfort and energy savings can be achieved in both 

heating and cooling.

• Heat cycling reduced, extending equipment life.

The auxiliary relay can be used with a variety of controls:

• Time-of-day (TOD).

• Economizer minimum position control.

• Dehumidification (see Dehumidification section).

Time-of-day (TOD) is the Auxiliary Relay default configuration. 

TOD logic operates strictly according to programming:

— Occupied: Relay contacts closed.

— Not Occupied: Relay contacts open.

— Standby (Scheduled): Relay contacts closed.

Mechanical cooling is often used with outside temperatures in 

the 50°F (10°C) to 60°F (16°C) range and humidity below 50 

percent. In central and northern climates, hundreds of hours 

fall into this temperature category. By permitting 80 to 100 

percent outside air into the system, mechanical cooling may 

not be needed at all, particularly during Spring and Fall.

Economizers take advantage of outside air. The typical 

economizer consists of an outside air damper, motor, outdoor 

air changeover control and a minimum position potentiometer. 

The motor controls the dampers. Suitability of the outside air 

for cooling is determined by the outdoor air changeover 

control. The potentiometer adjusts the minimum position of 

the economizer dampers, which provide a minimum amount 

of fresh air for ventilation.

The economizer reduces compressor run time, thereby saving 

energy and extending compressor life. The drawback to using 

the economizer is that during the Not Occupied period, if there 

is no call for cool or outdoor air is not suitable for free cooling, 

the economizer is controlled to minimum position. This 

position allows some percentage of outdoor air to enter the 

building, regardless of air suitability. The situation can cause 

the heating or cooling to run more often than when only 

suitable air is permitted to enter the building.

The T7350 can take advantage of an economizer by closing 

the auxiliary relay contacts to control the economizer 

minimum position potentiometer. (See Table 16 for details.)

— Powered: Allows normal economizer operation.

— Unpowered: Disables the economizer minimum position. 

The lack of power causes the economizer to drive dampers 

fully closed instead of staying at minimum open position. 

This reduces the possibility of unsuitable outdoor air 

entering the building, which lowers the internal load on the 

HVAC system and saves additional energy.

a

Unless otherwise noted, Economizer logic ignores calls for 

heat. TOD logic always observes calls for heat.

b

With fan set to AUTO and call for neither heat nor cool, the 

relay is open in order to disable damper minimum position.

Examples of other uses of the auxiliary relay are hot water 

heaters, lighting, or baseboard heat. The additional loads are 

connected to the auxiliary relay contacts on the subbase. The 

contacts are rated for 1.5A at 30 Vac, but can be adapted to 

higher current applications using an external relay. 

(See Fig. 14 through 16.)

COOL RECOVERY 
RAMP RATE
(DEGREES/HOUR)

MaxClRamp

MinClRamp

OaTempMinClRamp

OaTempMaxClRamp

OUTDOOR AIR
TEMPERATURE

M10111A

—

Occupied

 

—

Closed

b

Closed

 

Occupied

Standby

Yes

Closed

Open

Occupied

Standby

No

Open

Open

Standby

 

Standby

 

—

Closed

b

Closed

—

Not Occupied

Yes

Closed

Open

—

Not Occupied

No

Open

Open