53
Next Stage EDT Decrease (ADD.R)
This variable represents (if adding a stage of cooling) how
much the temperature should drop (in degrees) depending on
the
R.PCT
calculation and exactly how much additional capac-
ity is to be added.
ADD.R
=
R.PCT
*
(
C.CAP
— capacity after adding a cooling
stage)
For example: If
R.PCT
= 0.2 and the control would be adding
20% cooling capacity by taking the next step up, 0.2 times 20 =
4°F (
ADD.R
)
Next Stage EDT Increase (SUB.R)
This variable represents (if subtracting a stage of cooling) how
much the temperature should rise (in degrees) depending on
the
R.PCT
calculation and exactly how much capacity is to be
subtracted.
SUB.R
=
R.PCT
*
(
C.CAP
— capacity after subtracting a
cooling stage)
For example: If
R.PCT
= 0.2 and the control would be subtracting
30% capacity by taking the next step down, 0.2 times –30 = –6°F
(
SUB.R
)
Rise Per Percent Capacity (R.PCT)
This is a real time calculation that represents the number of de-
grees of drop/rise across the evaporator coil versus percent of
current running capacity.
R.PCT
= (
MAT
–
EDT
)/
C.CAP
Cap Deadband Subtracting (Y.MIN)
This is a
control variable used for Low Temp Override
(
L.TMP
) and Slow Change Override (
SLOW
).
Y.MIN
=
-
SUB.R
*0.4375
Cap Deadband Adding (Y.PLU)
This is a control variable used for High Temp Override
(
H.TMP
) and Slow Change Override (
SLOW
).
Y.PLU
=
-
ADD.R
*0.4375
Cap Threshold Subtracting (Z.MIN)
This parameter is used in the calculation of
SMZ
and is calcu-
lated as follows:
Z.MIN
=
Configuration
COOL
Z.GN
* (–10 + (4* (
–
SUB.R
)))
* 0.6
Cap Threshold Adding (Z.PLU)
This parameter is used in the calculation of
SMZ
and is calcu-
lated as follows:
Z.PLU
=
Configuration
COOL
Z.GN
* (10 + (4* (
–
ADD.R
)))
* 0.6
High Temp Cap Override (H.TMP)
If stages of mechanical cooling are on and the error is greater
than twice
Y.PLU
, and the rate of change of error is greater
than 0.5
F per minute, then a stage of mechanical cooling will
be added every 30 seconds. This override is intended to react to
situations where the load rapidly increases.
Low Temp Cap Override (L.TMP)
If the error is less than twice
Y.MIN
, and the rate of change of
error is less than –0.5
F per minute, then a mechanical stage
will be removed every 30 seconds. This override is intended to
quickly react to situations where the load is rapidly reduced.
Pull Down Cap Override (PULL)
If the error from set point is above 4
F, and the rate of change
is less than –1
F per minute, then pulldown is in effect, and
“SUM” is set to 0. This keeps mechanical cooling stages from
being added when the error is very large, but there is no load in
the space. Pulldown for units is expected to rarely occur, but is
included for the rare situation when it is needed. Most likely,
pulldown will occur when mechanical cooling first becomes
available shortly after the control goes into an occupied mode
(after a warm unoccupied mode).
Slow Change Cap Override (SLOW)
With a rooftop unit, the design rise at 100% total unit capacity
is generally around 30
F. For a unit with 4 stages, each stage
represents about 7.5
F of change to EDT. If stages could reli-
ably be cycled at very fast rates, the set point could be main-
tained very precisely. Since it is not desirable to cycle compres-
sors more than 6 cycles per hour, slow change override takes
care of keeping the PID under control when “relatively” close
to set point.
Humidi-MiZer
®
Capacity (CAPC)
This variable represents the total reheat capacity currently in
use during a Humidi-MiZer mode. A value of 100% indicates
that all of the discharge gas is being bypassed around the con-
denser and into the Humidi-MiZer dehumidification/reheat coil
(maximum reheat). A value of 0% indicates that all of the flow
is going through the condenser before entering the Humidi-
MiZer dehumidification/reheat coil (dehum/subcooling mode).
Condenser EXV Position (C.EXV)
This variable represents the position of the condenser EXV
(percent open).
Bypass EXV Position (B.EXV)
This variable represents the position of the bypass EXV (per-
cent open).
Humidi-MiZer 3-Way Valve (RHV)
This variable represents the position of the 3-way valve used to
switch the unit into and out of a Humidi-MiZer mode. A value
of 0 indicates that the unit is in a standard cooling mode. A val-
ue of 1 indicates that the unit has energized the 3-way valve
and entered into a Humidi-MiZer mode.
Cooling Control Point (C.CPT)
Displays the current cooling control point (a target value for air
temperature leaving the evaporator coil location). During a Hu-
midi-MiZer mode, this variable will take on the value of the
dehumidify cool set point (
Configuration
DEHU
D.C.SP)
.
Compressors will stage up or down to meet this temperature.
Evaporator Discharge Temperature (EDT)
Displays the temperature measured between the evaporator
coils and the Humidi-MiZer dehumidification/reheat coil.
Units configured with Humidi-MiZer system have a thermistor
grid installed between these two coils to provide the measure-
ment. This temperature can also be read at
Temperatures
AIR.T
CCT.
Heating Control Point (H.CPT)
Displays the current heating control point for Humidi-MiZer coil.
During a Reheat mode, this temperature will be either an offset
subtracted from return air temperature (
D.V.RA
) or the Vent Re-
heat Set Point (
D.V.HT
). During a Dehumidification Mode, this
temperature will take on the value of the original cooling control
point so that the supply air is reheated just enough to meet the sen-
sible demand in the space. The Humidi-MiZer modulating valves
will adjust to meet this temperature set point.
Leaving Air Temperature (LAT)
Displays the leaving air temperature after the Humidi-MiZer
reheat/dehumidification coil.
SumZ Operation
The SumZ algorithm is an adaptive PID style of control. The
PID (proportional, integral, derivative) is programmed within
the control and the relative speed of staging can only be influ-
enced by the user through the adjustment of the
Z.GN
configu-
ration, described in the reference section. The capacity control
algorithm uses a modified PID algorithm, with a self adjusting
gain which compensates for varying conditions, including
changing flow rates across the evaporator coil.
Summary of Contents for Weathermaster 48P2030-100
Page 130: ...130 Fig 19 Typical Power Schematic Sizes 040 075 Shown ...
Page 131: ...131 Fig 20 Main Base Board Input Output Connections ...
Page 132: ...132 Fig 21 RXB EXB CEM SCB Input Output Connections ...
Page 133: ...133 Fig 22 Typical Gas Heat Unit Control Wiring 48P030 100 Units Shown ...
Page 134: ...134 Fig 23 Typical Electric Heat Wiring 50P030 100 Units Shown ...
Page 135: ...135 Fig 24 Typical Power Wiring 115 V ...
Page 136: ...136 Fig 25 Typical Gas Heat Section Size 030 050 Units Shown ...
Page 138: ...138 Fig 27 Component Arrangement Size 030 035 Units ...
Page 139: ...139 Fig 28 Component Arrangement Size 040 075 Units ...
Page 140: ...140 Fig 29 Component Arrangement Size 090 100 Units ...