Building Pressure Configuration; Constant Volume 2-Stage Control; Multiple Power Exhaust Stage Building; Pressure Control Operation - United Technologies Carrier Weathermaker 48A2 Controls, Start-Up, Operation, Service, And Troubleshooting

Building Pressure Integral Gain (BP.I) — This configuration
selects the integral gain of the PID algorithm. This configuration
is only active when BP.CF = 3. It is recommended that this val-
ue not be changed without guidance from Service Engineering.
Building Pressure Derivative Gain (BP.D) — This configura-
tion selects the derivative gain of the PID algorithm. This con-
figuration is only active when BP.CF = 3. It is recommended
that this value not be changed without guidance from Service
Engineering.
Building Pressure Setpoint Offset (BP.SO) — This configura-
tion is the value below the building pressure setpoint to which
the building pressure must fall in order to turn off power exhaust
control. This configuration is only active when BP.CF = 3.
Building Pressure Minimum Speed (BP.MN) — This configu-
ration is the minimum allowed VFD speed during building pres-
sure control. This configuration is only active when BP.CF = 3.
Building Pressure Maximum Speed (BP.MX) — This configu-
ration is the maximum allowed VFD speed during building
pressure control. This configuration is only active when BP.CF
= 3.
VFD Fire Speed (BP.FS) — This configuration is the VFD
speed override when the control is in the purge or evacuation
smoke control modes. This configuration is only active when
BP.CF = 3.
Power Exhaust Motors (BP.MT) — This configuration is ma-
chine dependent and instructs the building pressure control
algorithm as to whether the unit has 4 or 6 motors to control.
The motors are controlled by three power exhaust relays A, B,
and C. These relay outputs are located at the local display un-
 
der Outputs FANS PE.A,B,C.
The following table illustrates the number of motors each
relay is in control of based on BP.MT:
BP.MT PE_A Relay
1 (4 motors) 1 Motor
2 (6 motors) 1 Motor
Building Pressure Sensor (BP.S) — This configuration al-
lows the reading of a building pressure sensor when enabled.
This is automatically enabled when BP.CF = 2 or 3.
Building Pressure (+/–) Range (BP.R) — This configuration
establishes the range in in. wg that a 4 to 20 mA sensor will be
scaled to. The control only allows sensors that measure both
positive and negative pressure.
Building Pressure SETP (BP.SP) — This setpoint is the
building pressure control setpoint. If the unit is configured for
modulating building pressure control, then this is the setpoint
that the control will control to.
Power Exhaust on Setp.1 (BP.P1) — When configured for
building pressure control type BP.CF = 1 (constant volume two-
stage control), the control will turn on the first power exhaust
fan when the economizer's position exceeds this setpoint.
Power Exhaust on Setp.1 (BP.P2) — When configured for
building pressure control type BP.CF = 1 (constant volume two-
stage control), the control will turn on the second power exhaust
fan when the economizer's position exceeds this setpoint.
Modulating PE Algorithm Select (BP.SL) — This configuration
selects the algorithm used to step the power exhaust stages. This
must be set to 1 at all times. The other selections are not used.
Building Pressure PID Evaluation Time (BP.TM) — This
configuration is the run time rate of the multiple stage (modu-
lating) power exhaust algorithm (BP.CF=2).
Building Pressure Threshold Adjustment (BP.ZG) — This
configuration is not used. It currently has no effect on building
pressure control.
PE_B Relay PE_C Relay
2 Motors 1 Motor
2 Motors 3 Motors
High Building Pressure Level (BP.HP) — This configura-
tion is the threshold level above the building pressure setpoint
used to control stages of power exhaust when BP.SL=1.
Low Building Pressure Level (BP.LP) — This configuration
is the threshold level below the building pressure setpoint used
to control stages of power exhaust when BP.SL=1.
CONSTANT VOLUME 2-STAGE CONTROL (BP.CF = 1)
OPERATION — Two exhaust fan relays will be turned on and
off based on economizer position. The two trip setpoints are
BP.P1 and BP.P2. If the economizer is greater than or equal
to BP.P1, then power exhaust stage 1 is requested and a
60-second timer is initialized. If the economizer is 5% below
the BP.P1, then power exhaust stage 1 is turned off. Also, if the
economizer position is less than BP.P1 and the 60-second timer
has expired, power exhaust stage 1 is turned off. The same
logic applies to the second power exhaust stage, except the
BP.P2 trip point is monitored. If the economizer position is
greater than or equal to BP.P2, then power exhaust stage 2
is energized and a 60-second timer is initialized. If the econo-
mizer is 5% below the BP.P2 the second power exhaust
stage turned off. If the economizer is less than BP.P2 and the
60-second timer has expired, second stage power exhaust is
turned off.
For BP.CF=1, the Table 67 illustrates the power exhaust
stages 1 and 2, relay combinations based upon Configuration

BP.MT (4 or 6 motors).

MULTIPLE POWER EXHAUST STAGE BUILDING

PRESSURE CONTROL (BP.CF = 2) OPERATION —
Building pressure control is active whenever the supply fan is
running. The control algorithm to be used (BP.SL=1) is a timed
threshold technique for bringing stages of power exhaust on
and off.
The number of power exhaust stages available for this con-
trol algorithm is a function of the number of motors it supports.
This number of motors is defined by the Configuration

BP.MT configuration. Table 68 illustrates the staging tables
for this control algorithm based on BP.MT.
The following configurations are used in the controlling of
building pressure with this algorithm:

• Configuration BP
high threshold level)

• Configuration BP
low threshold level)

• Configuration BP
timer)
This control function is allowed to add or select power ex-
haust stages at any time, except that a delay time must expire
after a stage is added or subtracted. Any time a stage change is
made, a timer is started which delays staging for 10 * BP.TM
seconds. The default for BP.TM is 1, therefore the delay
between stage changes is set to 10 seconds.
The logic to add or subtract a stage of power exhaust is as
follows:
• If building pressure (Pressures
than the building pressure setpoint (Configuration

BP BPSP) plus the building pressure high threshold level

(Configuration BP
power exhaust.
• If building pressure (Pressures
the building pressure

BP BPSP) minus the building pressure low threshold
level (Configuration
stage of power exhaust.
63
 
B.CFG BP.HP (building pressure
 
B.CFG BP.LP (building pressure
 
B.CFG BP.TM (building pressure
 
AIR.P BP) is greater
 
B.CFG BP.HP) add a stage of
 
AIR.P BP) is less than
setpoint (Configuration
  
BP B.CFG BP.LP) subtract a

BP

