Bryant F Bedienungsanleitung PDF herunterladen (Seite 70)

Cooling

The compressor out puts are controlled by the Cooling

Control PID Loop and Cooling Stages Capacity algorithm.

They will be used to calculate the desired number of

stages needed to satisfy the space by comparing the Space

Temperature (SPT) to the Occupied Cool Setpoint plus the

T56 slider offset when occupied and the Unoccupied Cool

Setpoint (UCSP) plus the T56 slider offset, if unoccupied.

The econom izer, if available, will be used for cooling in

addition to the compressors. The following conditions

must be true in order for this algorithm to run:

S Indoor Fan has been ON for at least 30 seconds.

S Heat mode is not active and the time guard between

modes equals ze ro.

S If occupied and the SPT >(occupi ed cool setpoint plus

the T56 slider offset).

S Space Temperature reading is available.

S If it is unoc cupied and the SPT > (unocc upied c ool

setpoint plus the T56 slider offset). The indoor fan will be

turned on by the staging algorithm.

S If economizer is available and active and economizer

open > 85% and SAT > (SAT low limit + 5_F) and SPT >

effective setpoint + 0.5_F.

Economizer is avai lable , but not active

Economizer is not a vailable

S OAT > DX Lockout temperature.

If all of the above conditions are met, the compressors

will be energized as required, otherwise they will be

de--energized.

There is a fixed 3--minute minimum on time and a

5--minute off time for each compressor output and a

3--minute minimum time delay between staging up or

down.

Any time the compressors are running the RTU--MP will

stage down the compressors if the SAT becomes less than

the cooling low supply air setpoint.

After a compressor is staged off, it may be started again

after a normal time--guard period and the supply air

temperature has increased above the low supply air

setpoint.

Economize r

The Economizer dampers are used to provide free cooling

and Indoor Air Quality, if optional CO

sensor is installed,

when the outside conditions are suitable.

The following conditions must be true for economiz er

operation:

S Indoor Fan has been on for at least 30 sec onds.

S Enthalpy is Low if the Enthalpy input is enabled.

S SAT reading is available.

S OAT reading is available.

S SPT reading is available.

S OAT <= High OAT economizer lockout configurati on

(default = 75).

S OAT <= SPT

If any of the mentioned conditions are not true, the

economizer will be set to its configured minimum

position. The minimum damper position can be

overridden by the IAQ routine described later in this

section.

If the above conditions are true, the Economizer Control

Master Loop will calculate a damper position value based

on the following calculation:

Damper Position = minimum position + PID (SPT -- econ

setpoint). Econ setpoint is half way between the effective

cool and heat setpoints. If the SAT drops below the

cooling low supply air setpoint (+ 5_F), the ec onomizer

will ramp down to minimum position.

Power

Exhaust

If RTU--MP is also controlling an exhaust fan, it can be

enabled based on damper position or by occupancy. If

configured for continuous occupied operation, it will be

energized whenever the controller is in the occupied mode

and disabled when in the unoccupied mode. If configured

for damper position control, it will be energized whenever

the economizer exceeds the power exhaust setpoint and

disabled whe n the economiz er drops below the setpoint by

a fixed hysteresis of 10%.

Heating

The heating outputs are controlled by the Heating Control

PID Loop and Heating Stages Capacity algorithm. They

will be used to calculate the desired number of stages

needed to satisfy the space by comparing the SPT to the

Occupie d Heat Setpoint plus the T56 slider offset when

occupi ed and the Unoccupied Heat Setpoint plus the T56

slider offset if unoccupied. T he following conditions must

be true in order for this algorithm to run:

S Indoor Fan has been ON for at least 30 seconds.

S Cool mode is not active and the time guard between

modes equals ze ro.

S If occupied and SPT <(occupied heat setpoint plus T56

slider offset)

S SPT reading is available

S If it is unoc cupied and t he SPT < (unocc upied heat

setpoint plus T56 slider offset). The indoor fan will be

turned on by the staging algorithm.

S OAT < High OAT lockout temperature.

If all of the above conditions are m et, the heating outputs

will be energized as required, otherwise they will be

de --energized. If the SAT begins to exceed the high supply

air setpoint, a ramping function will cause the Heat Stages

Capac ity algorithm to decrease the number of stages until

the SAT has droppe d below the setpoint.

There is a fixed one minute minimum on time and a one

minute off time for each heat output. Heat staging has a 3

minute stage up and 30 second stage down dela y.

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