Carrier Aquazone 50PEC09-18 Installation, Start-Up And Service Instructions Manual page 19

MODULATING OA DAMPER WITH DCV
The control can be configured to operate a modulating ventilation
damper during occupied periods that responds to changing CO
levels from an optional sensor. The control monitors the CO
and compares it to the configured setpoints and adjusts the ventila-
tion rate as required. The control provides proportional ventilation
to meet the requirements of ASHRAE specifications by providing
a base ventilation rate and then increasing the rate as the CO
increases. The control has three user adjustable setpoints; start
ventilation maximum ventilation and maximum damper position.
The control will begin to proportionally increase ventilation when
the CO level rises above the start ventilation setpoint and will
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reach the full ventilation rate (maximum damper position) when
the CO level is at or above the maximum setpoint. A user config-
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urable minimum damper position insures that proper base ventila-
tion is delivered when occupants are not present.
AUXILIARY MODULATING HOT WATER / STEAM
HEATING REHEAT
The control can modulate a hot water or steam valve connected to
a coil on the discharge side of the unit and supplied by a boiler in
order to maintain the desired heating setpoint should the compres-
sor capacity be insufficient or a compressor failure occurs. Unless
the compressor fails, the valve will only operate to supplement the
heat provided by the compressor if the space temperature falls 2°F
or more below the desired heating setpoint. The valve will be con-
trolled so the SAT will not exceed the Maximum Heating SAT
limit.
2-POSITION HOT WATER / STEAM HEATING REHEAT
The control can operate a two position, NO or NC, hot water or
steam valve connected to a coil on the discharge side of the unit
and supplied by a boiler in order to maintain the desired heating
setpoint should the compressor capacity be insufficient or a com-
pressor failure occurs. Unless the compressor fails, the valve will
only open to supplement the heat provided by the compressor if
the space temperature falls 2°F or more below the desired heating
setpoint. The valve will be controlled so the SAT will not exceed
the Maximum Heating SAT limit and subject to a two minute min-
imum OFF time to prevent excessive valve cycling.
SINGLE STAGE ELECTRIC AUXILIARY HEAT
The control can operate a single stage of electric heat connected to
a coil on the discharge side of the unit in order to maintain the de-
sired heating setpoint should the compressor capacity be insuffi-
cient or a compressor failure occurs. Unless the compressor fails,
the heat stage will only operate to supplement the heat provided by
the compressor if the space temperature falls 2°F or more below
the desired heating setpoint. The heat stage will be controlled so
the SAT will not exceed the Maximum Heating SAT limit and
subject to a two minute minimum OFF time to prevent excessive
cycling.
AUTOMATIC FAN SPEED CONTROL
The control is capable of controlling up to three fan speeds. The
motor will operate at the lowest speed possible to provide quiet
and efficient fan operation. The motor will increase speed if addi-
tional cooling or heating is required to maintain the desired space
temperature setpoint. The control increases the motor's speed by
one step for each 2°F above the cooling or below the heating set-
point. Also, the control will increase the fan speed as the Supply
Air Temperature approaches the configured minimum or maxi-
mum limits. Fan speed for PSC motors is controlled by energizing
and de-energizing low, medium and high speed relays. Fan speed
for ECMs is controlled by first energizing the low speed tap. If a
higher speed is required, the low speed tap remains energized
while the medium speed tap is also energized. If high motor speed
is required, all three speed taps are energized. If more than one
speed tap is energized for an ECM, the ECM will default to the
higher speed.
FAN SPEED CONTROL — DURING HEATING
Whenever heat is required and active, the control continuously
monitors the supply air temperature to verify it does not rise above
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level the configured Maximum Heating SAT Limit (110°F Default). As
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the SAT approaches this value, the control will increase the fan
speed as required to insure the SAT will remain within the limit.
This feature provides the most quiet and efficient operation by op-
level erating the fan at the lowest speed possible.
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FAN SPEED CONTROL — DURING COOLING
Whenever mechanical cooling is required and active, the control
continuously monitors the supply air temperature to verify it does
not fall below the configured Minimum Cooling SAT Limit (50°F
Default). As the SAT approaches this value, the control will in-
crease the fan speed as required to insure the SAT will remain
within the limit.
MODULATING WATER ECONOMIZER CONTROL
The control has the capability to modulate a water valve to control
condenser water flowing through a coil on the entering air side of
the unit.
COOLING
The purpose is to provide an economizer cooling function by us-
ing the water loop when the entering water loop temperature is
suitable (at least 5°F below space temperature). If the water loop
conditions are suitable, then the valve will modulate open as re-
quired to maintain a Supply Air Temperature that meets the load
conditions. Should the economizer coil capacity be insufficient for
a period greater than 5 minutes, or should a high humidity condi-
tion occur, then the compressor will be started to satisfy the load.
As the SAT approaches the Minimum Cooling SAT limit, the
economizer valve will modulate closed during compressor
operation.
HEATING
Additionally, the control will modulate the water valve should the
entering water loop temperature be suitable for heating (at least
5°F above space temperature) and heat is required. The valve will
be controlled in a similar manner except to satisfy the heating re-
quirement. Should the coil capacity be insufficient to satisfy the
space load conditions for more than 5 minutes, then the compres-
sor will be started to satisfy the load. As the SAT approaches the
Maximum Heating SAT limit, the economizer valve will modulate
closed during compressor operation.
2-POSITION WATER ECONOMIZER CONTROL
The control has the capability to open a NO or NC, two position,
water valve to control condenser water flow through a coil on the
entering air side of the unit.
COOLING
The purpose is to provide a cooling economizer function directly
from the condenser water loop when the entering water loop tem-
perature is suitable (at least 5°F below space temperature). If the
optional coil is provided and the water loop conditions are suit-
able, then the valve will open to provide cooling to the space when
required. Should the capacity be insufficient for a period greater
than 5 minutes, or should a high humidity condition occur, then
the compressor will be started to satisfy the load. Should the SAT
reach the Minimum Cooling SAT limit, the economizer valve will
close during compressor operation.
HEATING
Additionally, the economizer control will open the water valve
should the entering water loop temperature be suitable for heating
(at least 5°F above space temperature) and heat is required. The
valve will be controlled in a similar manner except to satisfy the
heating requirement. Should the coil capacity be insufficient to
satisfy the space load for more than 5 minutes, then the compres-
sor will be started to satisfy the load. Should the SAT reach the
Maximum Heating SAT limit, the economizer valve will close
during compressor operation.
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