Simplicity 1004 Manuel d'utilisateur télécharger pdf (Page 8)

97585-UAI-A-1004

Unitary Products Group 8

When the control is running the fan and the APS has already

been proven, and then it opens, the control will wait 2 sec-

onds before shutting down heating, cooling, and locking out.

It will alarm and retry as if it happened during start-up.

FAN DELAYS - There are separate Fan ON and OFF delay

periods for heating and cooling, to reduce the momentary

change in SAT.

COMFORT VENTILATION MODE

Comfort Ventilation is a control mode that uses the econo-

mizer to modulate SAT. Where possible, the economizer will

modulate the outside / return air mix to keep SAT within the

upper and lower Comfort Ventilation setpoints. The control

will modulate the economizer, and energize cooling or heat-

ing, to keep SAT within the Comfort Ventilation setpoints,

even though space temperature may be satisfied. For exam-

ple, minimum economizer position can take SAT out of the

Comfort Ventilation range, requiring heat or cooling that the

thermostat isn’t calling for.

The result of comfort ventilation control is less variation of

SAT, and fewer on-off cycles of mechanical cooling or heat-

ing.

If turning off a cooling stage raises SAT above the upper set-

point, but leaving it running will take SAT below the lower set-

point - then the compressor is left on, and warmer outside air

is brought in to raise SAT to the lower setpoint to keep a com-

pressor from cycling off. Similarly, if leaving a heat stage on

will raise

SAT above the Upper setpoint, the control will leave

heat on and modulate cooler outside air into the airstream to

maintain proper SAT.

The Comfort Ventilation temperature-band minimum width is

five degrees. Comfort Ventilation high and low setpoints will

be within the Cooling Upper and Heating Lower setpoints.

Without

using the Comfort Ventilation mode where available,

when the space temperature control loop is satisfied (zero

demand), all cooling and/or heating stages would be turned

off and the SAT would be allowed to float until the space tem-

perature control loop again generates a call for cooling or

heating. The supply fan may be kept on during the “satisfied”

periods, or may be turned off, depending on thermostat set-

tings, or “Fan ON mode with the Sensor” option setting. If

Comfort Ventilation is selected, it will take priority over supply

fan control and keep it running during the “satisfied” periods,

when there is no call for heating or cooling.

The Comfort Ventilation mode is used to optionally replace

the uncontrolled, floating SAT situation during the “satisfied”

periods with a “loose” SAT control in a fairly wide temperature

band (between specified Comfort Ventilation Upper Setpoint

and Comfort Ventilation Lower Setpoint). This may require

some additional energy, but improves space comfort (e.g.

instead of bringing a very hot and humid ventilation / outdoor

air into space during the “satisfied” periods, the ventilation air

temperature is “trimmed” to be within the specified SAT con-

trol band).

Comfort Ventilation mode terminates when there is a call for

heating or cooling from the space temperature control.

• Comfort Ventilation can be used only on units

equipped with an Economizer.

• Comfort Ventilation only operates in an Occupied

mode.

• “Comfort Ventilation Mode” must be set to ON

(default setting is OFF).

The modulating range of the economizer dampers are limited

by a specified Economizer Minimum Position and by a speci-

fied Comfort Ventilation Maximum Economizer Setpoints.

The Economizer capability to control SAT may be further lim-

ited in case the Demand Ventilation Operation is enabled and

overrides the economizer to a more-open position in order to

satisfy space IAQ requirements. The values of “Comfort Ven-

tilation Upper Setpoint” and “Comfort Ventilation Lower Set-

point” would typically be set such that they are centered

around an expected return air temperature. The band

between the two setpoints should be set wide enough so that

SAT changes due to staging / destaging compressors, or

heating stages, can be compensated for by the economizer

control so that staging / destaging is minimized. Also, a wider

band minimizes use of additional energy during unit’s “satis-

fied” periods.

ECONOMIZER CONTROL DURING COMFORT VENTILA-

TION - Economizer control uses a Proportional-Integral (PI)

control algorithm that maintains SAT within the specified SAT

band by modulating the economizer dampers. The PI algo-

rithm setpoint is calculated as a midpoint between the pro-

grammed "Comfort Ventilation Upper Setpoint" and "Comfort

Ventilation Lower Setpoint". As the controller uses outside air

to maintain the SAT at the setpoint, it must be capable of self-

configuration for Direct or Reverse action, depending on the

relationship of the OAT to the specified SAT control band:

FIGURE 3 -COMFORT VENTILATION ECONOMIZER

CONTROL

High Supply Air Setpoint

Economizer Control Setpoint

(Middle of SAT Control Band)

Low Supply Air Setpoint

SAT Control Band

(Gray Area)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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Simplicity 1004 Manuel d'utilisateur Page 8

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