Carrier 48/50AJ specifications Building Pressure Configuration, Power Exhaust Staging BP.CF =

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 set points 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 82 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 →BP.MT configuration. Table 83 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→B.CFG→BP.HP (building pressure high threshold level)

•Configuration→BP→B.CFG→BP.LP (building pressure low threshold level)

•Configuration→BP→B.CFG→BP.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 * 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→AIR.P→BP) is greater than the building pressure set point (Configuration→ BP→BPSP) plus the building pressure high threshold level (Configuration→BP→B.CFG→BP.HP) 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	0*
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.Integ.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		"H2O	BPSO	0.05
BP.MN	BP VFD Minimum Speed	0-100		%	BLDGPMIN	10
BP.MX	BP VFD Maximum Speed	0-100		%	BLDGPMAX	100
BP.FS	VFD/Act. Fire Speed/Pos.	0-100		%	BLDGPFSO	100
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	"H2O	BP_RANGE	0.25
BP.SP	Building Pressure Setp.	-0.25 -> 0.25		"H2O	BPSP	0.05
BP.P1	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 Alg. 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		"H2O	BPZ_GAIN	1
BP.HP	High BP Level	0	- 1.000	"H2O	BPHPLVL	0.05
BP.LP	Low BP Level	0	- 1.000	"H2O	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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