Carrier /50HC 04-28, Управление, запуск, эксплуатация и устранение неисправностей, Страница: 40 / 144

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OCCUPANCY
The ERV will not be allowed to run unless it is determined to
be occupied. The ERV monitors the rooftop’s occupancy point
( Run Status
→
MODE
→
OCC ) to determine when it is occu-
pied. The ERV watches the rooftop’s indoor fan state point
( CCN Point = IDFSTATE ) to know when its indoor fan has
started. When the rooftop is occupied and its indoor fan is on,
the ERV is considered to be occupied and allowed to run.
The ERV can also operate during the rooftop’s unoccupied peri-
od. If the ERV is configured for unoccupied operation ( Configu-
rations
→
OAU
→
U.RUN = YES ), then it will ignore the
building occupancy of the Comfort Link controller and allow oc-
cupancy any time the rooftop fan is on. If not configured for un-
occupied operation but there is a CO
2
sensor or switch installed
and the Comfort Link controller is configured to turn on its in-
door fan for CO
2
ventilation at any time ( Configuration
→
AIR.Q
→
IA.FN = 2 , or Configuration
→
AIR.Q
→
II.FN
= 2 ), the ERV will be occupied any time the CO
2
needs the fan.
MODES OF OPERATION
The ERV has 3 basic functions: Auto, Off, or Test. These are
defined as System run states and displayed in the OAU run sta-
tus menu ( Run Status
→
OAU
→
OA.RN ). The ERV will al-
ways operate in one of the following operating modes depend-
ing upon the Comfort Link controller mode and outside condi-
tions: Off, ERV (DCV) Free Cooling, OA Tempering, Defrost,
or Test. The ERV monitors the Comfort Link CCN point
NVO_MODE to determine the rooftops operating mode. The
NVO_MODE values tell the ERV what the rooftop operating
mode is in a numeric form. The ERV’s operating mode is dis-
played numerically as OAU Operating Mode ( Run Status
→
OAU
→
OA.OP ). These modes and their corresponding
numbers are described below.
Off Mode (OA.OP = 0)
The ERV will be set to the Off mode whenever the rooftop in-
door fan is turned off, ERV is unoccupied, NVO_MODE
equals 6, or if communication fails. During Off Mode, the ERV
2 position dampers will be closed and the wheel, outside air
fans(s), and exhaust fan(s) will be off.
Test Mode (OA.OP = 5)
If at any time during operation, the rooftop is put in Service
Test mode (NVO_MODE equals 7) the ERV will be set to Test
Mode. Refer to Start-Up section for Test mode operation.
Free Cooling Mode (OA.OP = 2)
Free Cooling Mode is only available if an optional economizer
damper is factory-installed in the ERV ( Configuration
→
ECON
→
EC.EN = Yes ). Free Cooling Mode will be active
when the rooftop unit is in Unoccupied Free Cooling Mode,
Free Cooling Mode, or in Cooling Mode and the economizer
damper position ( Outputs
→
ECON
→
EC.CP ) is greater than
5% ( NVO_MODE = 10 or 3 ). ERV occupancy tells the control
which speed to start the outside air fan(s) during free cooling,
because the outside fan(s) are needed to assist the indoor fan in
bringing in outside air.
When in Free Cooling Mode, the ERV’s 2-position damper will
be open and the wheel will be set to stop/jog operation. The
rooftop unit will modulate the economizer damper to provide
free cooling as if an ERV was not installed. As the economizer
damper opens the ERV outside air fan(s) will maintain a speed
that produces minimum outside air CFM. Once the economizer
damper position passes that percent fan speed of the outside air
fan(s), the fan(s) speed will ramp up directly with the econo-
mizer damper position, up to 100%. The exhaust fan(s) will run
at a speed equal to the required offset CFM. Refer to Exhaust
Control for details on determining offset CFM.
Defrost Mode (OA.OP = 4)
Defrost Mode is only available when the optional Frost Protec-
tion is factory-installed in the ERV. The ERV will be set to de-
frost mode any time the ERV wheel is running and frost is de-
tected on the wheel. The EXCB D14 LED will turn on to indi-
cate the frost switch is active. Defrost Mode runs for at least 2
minutes but continues to run until the frost is removed. The
frost protection device senses a pressure differential across the
wheel and trips when that differential is greater than the set-
point (default 2.0 in wg). For information on the frost protec-
tion device, refer to the Major Component section.
When in Defrost Mode, the ERV 2 position damper will be
open and the wheel will be rotating. The outside air fan(s) will
ramp down to 0% speed (shut-off). The exhaust fan(s) will run
at a speed equal to the required offset CFM. Refer to Exhaust
Control for details on determining offset CFM.
ERV (DCV) Mode (OA.OP = 1)
General ERV Mode
ERV Mode is the basic operating mode of the ERV. With no
options installed on the ERV this will be the only operating
mode besides off and test. ERV Mode will be active when the
rooftop Comfort Link controller mode is Heating, Cooling, Fan
Only, or Dehumidification (NVO_MODE = 1, 3, 9, or 14) and
the ERV is occupied.
When in ERV mode, the ERV 2 position damper will be open
and the wheel will be rotating. The outside air fan(s) will run at
a speed that produces a CFM equal to the minimum outside air
CFM setpoint ( Configuration
→
OAU
→
OA.MN ). The ex-
haust fan(s) will run at a speed equal to the required offset
CFM. Refer to Exhaust Control for details on determining off-
set CFM.
ERV Mode with DCV
If an optional economizer is factory-installed in the ERV (
Con-
figuration
→
ECON
→
EC.EN = Yes ) and an optional CO
2
sensor or switch is installed ( Configuration
→
AIR.Q
→
IA.CF = 1 or 2 ) or ( Configuration
→
AIR.Q
→
II.CF = 1
or 2 ), DCV ERV Mode will be active when the rooftop Com-
fort Link controller mode is Heating, Cooling, Fan Only, or De-
humidification (NVO_MODE = 1, 3, 9, or 14) and the ERV is
occupied.
When in DCV ERV mode, the ERV 2 position damper will be
open and the wheel will be rotating. The outside air fan(s) will
run at a speed that produces a CFM equal to the minimum out-
side air CFM determined by Demand Controlled Ventilation
(DCV). The exhaust fan(s) will run at a speed equal to the re-
quired offset CFM. Refer to Exhaust Control for details on de-
termining offset CFM.
Sensor Demand Controlled Ventilation (DCV) uses the indoor
air quality levels (CO
2
PPM) to determine how much outside air
is required for ventilation. The ERV monitors the IAQ ( Inputs
→
AIR.Q
→
IAQ ) reading from the rooftop’s installed CO
2
sen-
sor and compares it to a hard coded outside air value of 400PPM.
The difference is then weighed on scale between AQ Differential
Low ( Configuration
→
AIR.Q
→
AQD.L ) and AQ Differential
High ( Configuration
→
AIR.Q
→
AQD.H ) to determine the
minimum outside air CFM required for ventilation. The mini-
mum outside air CFM can be equal to or between the Min DCV
outside air CFM ( Configuration
→
OAU
→
DCV.M ) setpoint
and the minimum outside air CFM ( Configuration
→
OAU
→
OA.MN ) setpoint. As the CO
2
differential rises from AQD.L
to AQD.H , the ERV outside air CFM requirement will rise from
DCV.M to OA.MN . The outside air fan(s) will ramp its speed %
IMPORTANT: Refer to the base unit Controls, Start Up,
operation, and Troubleshooting manual for details on how
the rooftop unit modulates the economizer damper for free
cooling.