47
JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
ON / OFF
The unit can be switched into the
“ON”
mode by one
of three ways:
1. Placing the
“On / Auto / Off”
toggle switch,
located below the keypad and display, from the
OFF to ON position. If none of the following
faults
(Duct Hi Pres, Freeze, Fan Fail, Unsafe)
are present the unit will initiate the start up se-
quence.
2. Placing the
“On / Auto / Off”
toggle switch,
located below the keypad and display, from the
OFF to AUTO position. In the AUTO position
the unit can be switched to ON using the internal
scheduling function of the control.
3. Placing the
“On / Auto / Off”
toggle switch,
located below the keypad and display, from the
OFF to AUTO position. In the AUTO position
the unit can be switched to ON using a commu-
nicated BACnet command or through the unit
keypad by turning
“Unit Enable”
ON or OFF.
There is a two minute time delay from the time the
start sequence is initiated until the supply fan blower
starts.
When the control receives the start initiation (On,
Internal Clock, or Communicated) the control closes a
set of dry contacts at the DO-6 – terminals 9 and 10 of
the control panel terminal block. This set of contacts
can be used to energize the pump to supply water to
the condenser.
One minute after the control receives the start initiation
(On, Internal Clock, or Communicated) the control
closes a set of dry contacts at the DO-4 – terminals 7
and 8. This set of contacts can be used to open the VAV
boxes. This contact remains closed until the Air Flow
Switch closes.
SUPPLY FAN OPERATION
The following items must be programmed either through
the
“Setpoints”
section of the Keypad / Display or by
communicated input.
“Fan-VAV/CV En”
– This value needs to be set to
“VAV”
for variable air volume or FlexSys operation
and to
“CV”
for constant volume applications. The
default value is
“VAV”.
If the unit is programmed for
“VAV”
the following items
must also be programmed:
“Fan- S/A Pres SP”
– The control will try to maintain
the duct static pressure to this value. The default value
is 1.0 inwc.
“# of SP Sensors”
– The control has the capability to
use one or two duct static sensors. If a single sensor
is used this value would be set to 1. If two sensors are
used this value would be set to 2.
“SP Calc Method”
– If the unit uses two sensors this
value can be set to
“High, Avg, or Low”
. If the control
is programmed to
“High”
, the control will compare the
higher of the two sensor inputs to the
“Fan- S/A Pres SP”
and control the speed of the VFD based on these values.
If the control is programmed to
“Low”
the control will
compare the lower of the two sensor inputs to the
“Fan-
S/A Pres SP”
and control the speed of the VFD based
on these values. If the control is programmed to
“Avg”
the control will compare the average of the two sensors
to the
“Fan- S/A Pres SP”
and control the speed of the
VFD based on these values.
On FlexSys units the following additional parameters
need to be programmed:
“POA DX Prs Drop”
– This value is used by the control
to determine when there is adequate airflow. When the
pressure across the coil is greater than this value, the
unit allows normal operation.
Constant Volume Fan Operation
Two minutes after the unit is placed in the
“ON MODE”
the control will close a contact at DO-3 terminals 5
and 6 on the controller. The closure of this contact
energizes the MSF2 contactor and turns on the supply
air blower.
The unit has an airflow switch to verify blower operation.
If the switch is not closed within two minutes from the
time the blower binary output is energized the control
will initiate a
“Fan Failure Alarm”
. The Air Flow
Switch input enters the control at the IN7 – terminals
13 and 14.
SECTION 5 – SEQUENCE OF OPERATION
5
Summary of Contents for York VERSECON YSWD 012
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