Johnson Controls York VERSECON YSWD 012, Installation Operation & Maintenance

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JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
The control compares the supply air temperature to
the
“HEAT- S/A TMP SP”
set point and generates a
variable percentage output based on the difference and
the amount of change in the supply air temperature to
a change in output.
Return Air Temperature Control
There is a one minute delay from the time the air-
proving switch closes until heating operation is allowed.
Heating operation will be enabled when the return air
temperature is 1.0° F less than the “HEAT- R/A TMP
SP”
set point. Heating operation will be disabled
when the supply air temperature is 1.0° F greater than
the “HEAT- R/A TMP SP” set point. The control waits
one minute from the time the supply air temperature
increases 1.0° F above the set point before it disables
the Heating operation.
The control compares the return air temperature to
the “HEAT- R/A TMP SP” set point and generates a
variable percentage output based on the difference and
the amount of change in the return air temperature to a
change in output.
When both Supply Air and Return Air Control are
enabled, the Unit Control will control the heat operation
to the lower of the two variable percentage outputs.
Staged Heat Operation
The following parameters must be programmed through
the “Setpoints ” section of the Keypad / Display.
“HT STG –1/TRI-2”
– For staged heat this parameter
needs to be set to 1.
The number of steps of capacity will vary with the
type and capacity of the heat. Each of the stages of
operation is assigned a window of operation based on
the percentage of the total operating range 0 to 100%.
To determine the window of operation for each stage
divide 100% by the number of stages.
When the percentage is equal to or greater than 50%,
the control will wait 30 seconds and then initiate a
demand for the first stage of operation. If the percentage
output drops to 30% or below, the demand for first stage
operation would continue for 30 seconds. During this
30 second off delay if the percentage output is equal to
or greater than 50% again, the first stage demand would
continue and the 30 second off delay would be turned
off. If at any time the heating demand is lost for three
seconds the demand for first stage operation would be
turned off.
When the percentage output is equal to or greater
than 100%, the control will wait 30 seconds and then
initiate a demand for the second stage of operation.
If the percentage output drops to 80% or below, the
demand for second stage operation would continue
for 30 seconds. During this 30 seconds off delay if
the percentage output is equal to or greater than 100%
again, the second stage demand would continue and the
30 seconds off delay would be turned off. If at any time
the heating demand is lost for two seconds the demand
for second stage operation would be turned off. The
second stage of heating will not start until the first stage
of heating has been turned on.
Sequence of Operation