Carrier WEATHERMAKER 48J Started Manual page 65

CONSTANT VOLUME 2-STAGE CONTROL (BRCF = 1)
OPERATION -- Two exhaust fan relays w illbeturned o nand
offbased o neconomizer position. The twotripset p oints a re
BRP! and BRP2. If the economizer is greater than or equal
to BRP1, then power exhaust stage 1 is requested and a
60-second thner is initialized. If the economizer is 5% below
theBRP1, then power exhaust stage 1 is turned off. Also, if the
economizer position is less than BRP1 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
BRP2 trip point is monitored. If the economizer position is
greater than or equal to BRP2, then power exhaust stage 2
is energized and a 60-second timer is initialized. If the econo-
mizer is 5% below the BRP2 the second power exhaust
stage turned off. If the economizer is less than BRP2 and the
60-second thner has expired, second stage power exhaust is
turned off.
For BRCF=I, the Table 82 illustrates the power exhaust
stages 1 and 2, relay combinations based upon Configuration
-9BRMT (4 or 6 motors).
MULTIPLE POWER EXHAUST STAGE BUILDING
PRESSURE CONTROL (BRCF = 2) OPERATION --
Building pressure control is active whenever the supply fan is
running. The control algoritlnn to be used (BRSL=I) 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 algorithin is a function of the number of motors it supports.
This number of motors is defined by the Configuration-9BP
-9BRMT configuration. Table 83 illustrates the staging tables
for this control algorithin based on BRMT.
The following configurations are used in the controlling of
building pressure with this algorithin:
• Configuration-9BP-9B.CFG-9BRHP (building pressure
high threshold level)
• Configuration-9BP-9B.CFG-9BRLP (building pressure
low threshold level)
• Configuration-9BP-9B. CFG-9BR TM (building pressure
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 * BRTM
seconds. The default for BRTM 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-9AIR.P-9BP) is greater
than the building pressure set point (Configuration-9
BP-gBPSP) plus the building pressure high threshold level
(Configuration-gBP-gB.CFG-gBRHP) add a stage of
power exhaust.
Table 81 -- Building Pressure Configuration
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
BP BUILDING PRESS. CONFIG
BP.CF Building Press. Config 0-3 BLDG_CFG O*
BP.RT Bldg.Pres.PID Run Rate 5-120 sec BPIDRATE 10
BP.P Bldg. Press. Prop. Gain 0-5 BLDGP_PG 0.5
BP.I Bldg.Press.lnteg.Gain 0-2 BLDGP_IG 0.5
BP.D Bldg.Press.Deriv.Gain 0-5 BLDGP_DG 0.3
BP.SO BP Setpoint Offset 0.0 - 0.5 "H20 BPSO 0.05
BP.MN BP VFD Minimum Speed 0-100 % BLDGPMIN 10
BP.MX BP VFD Maximum Speed 0-1O0 % BLDGPMAX 100
BP.FS VFD/Act. Fire Speed/Pos. 0-1O0 % BLDGPFSO 1O0
BP.MT Power Exhaust Motors 1-2 PWRM 1*
BP.S Building Pressure Sensor Enable/Dsable BPSENS Dsable*
BP.R Bldg Press (+/-) Range 0 - 1.00 "H20 BP_RANGE 0.25
BP.SP Building Pressure Setp. -0.25 -> 0.25 "H20 BPSP 0.05
BP.PI Power Exhaust On Setp.1 0 - 100 % PES1 35
BP.P2 Power Exhaust On Setp.2 0 - 100 % PES2 75
B.CFG BP ALGORITHM CONFIGS
BP.SL Modulating PE AIg. Slct. 1-3 BPSELECT 1
BP.TM BP PID Evaluation Time 0 - 10 min BPPERIOD 1
BP.ZG BP Threshold Adjustment 0.1 - 10.0 BPZ_GAIN 1
BP.HP High BP Level 0 - 1.000 BPHPLVL 0.05
BP.LP Low BP Level 0 - 1.000 BPLPLVL 0.04
•Some configurations are machine dependent.
Table 82 -- Power Exhaust Staging (BP.CF= 1)
BP.MT= 1 (4 motors) PE.A PE.B PE.C
Power Exhaust Stage 0 OFF OFF OFF
Power Exhaust Stage 1 OFF ON OFF
Power Exhaust Stage 2 ON ON ON
BP.MT= 2 (6 motors) PE.A PE.B PE.C
Power Exhaust Stage 0 OFF OFF OFF
Power Exhaust Stage 1 OFF OFF ON
Power Exhaust Stage 2 ON ON ON
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