Honeywell T7350 ユーザーズマニュアル

63-2605—5

18

Upon initial thermostat powerup, a startup and initialization 

program begins. This startup occurs only on initial powerup. 

After total loss of power for an extended period, the current 

time and day can be lost (requiring reset). However, the 

thermostat retains the user program.

NOTE: With no program set, the thermostat controls to the 

Occupied default setpoints of 70°F (21°C) for heat 

and 75°F (24°C) for cool.

All T7350 model thermostats contain four switching relays. In 

conventional applications, the relays control first stage cooling, 

first stage heating, fan, and auxiliary. In heat pump 

applications, the relays control the heat pump compressor, 

changeover, fan, and emergency heat.

NOTE: Models T7350B,D, T7350H1009 have subbases with 

more relays to accommodate extra stages.

Logic with Modulating Outputs (T7350H1017, M, only)

The specific relay logic depends on whether or not staging is 

employed. See Table 14.

NOTE: The modulating outputs always provide a signal.

a

See Table 15 for modulating output signal details.

To display the status of the modulating outputs:

1. Cycle through information displays using the info key.

2. The device displays a percentage value for each output:

a. MODHEAT on one screen.

b. MODCOOL on another screen.

The O/B terminal controls heat pump changeover. The default 

operation is for the terminal to be powered when calling for 

heat (or while the most recent call was for heat). This 

corresponds to a typical O terminal.

NOTE: The O/B terminal can be configured to operate as a 

typical B terminal (powered on call for cool).

(select T7350 Thermostats only)

With the system set for Em Heat, auxiliary heat serves as 

stage one; compressor stages are locked off. The fan cycles 

with the auxiliary heat.

As part of the operational sequence, the T7350 

microprocessor incorporates cycle rate, and minimum on and 

off times for all heating and cooling stages. This extends 

equipment life as it prevents rapid cycling of equipment.

NOTE: Minimum on and off times are fixed.

The thermostat control algorithm maintains the temperature by 

cycling stages of heating or cooling to meet setpoint. Cycle 

rates, in cycles per hour (cph) are set using a PDA.

NOTE: Defaults are: heat: 6cph, cool: 3cph.

The T7350 microprocessor-based control requires that the 

user understands temperature control and thermostat 

performance. A conventional electromechanical or electronic 

thermostat does not control temperature precisely at setpoint. 

Typically, there is an offset (droop) in the control point as the 

system load changes. This is a phenomenon that most people 

in the industry know and accept.

All adjustments to Loop Tuning parameters should be gradual. 

After each change, allow the system to stabilize to accurately 

observe the effects of the change. Then, as needed, make 

further refinements until the system operates as desired.

If adjustment of PID parameters is required, use the following:

NOTE: In the items that follow, the term “error” refers to the 

difference between the measured space temperature 

and the current actual space temperature setpoint:

— The Throttling Range (TR), also called Proportional Gain, 

determines the impact of the error on the output signal. 

Decreasing TR amplifies the error effect; that is, for a given 

error, smaller TR causes higher output signal.

— The Integral Time (IT), also called Integral Gain, 

determines the impact of the error-over-time on the output 

signal. Error-over-time has two components making up its 

value: amount of time the error exists; and size of the error. 

The higher the IT, the slower the control response. In other 

words, a decrease in IT causes a more rapid change to the 

output signal.

On 

(1 to 100 

percent)

0

On

Output reaches 10%: On

Output falls below 5%: Off

1 or 2

Staged 

Cycling

On/Off matches equipment 

stage operation

Off 

(0 percent)

0,1, or 2 Off

Off

Direct

4 mA

20 mA

Reverse

20 mA

4 mA