Carrier 48/50AJ Staged Gas Configuration, Staged Gas Heat 48AJ,AK,AW,AY Units, Unit Size

Table 68 — Staged Gas Configuration

ITEM	EXPANSION		RANGE	UNITS	CCN POINT	DEFAULTS
SG.CF	STAGED GAS CONFIGS
HT.ST	Staged Gas Heat Type	0	- 4		HTSTGTYP	0*
CAP.M	Max Cap Change per Cycle	5	- 45		HTCAPMAX	45*
M.R.DB	S.Gas DB min.dF/PID Rate	0	- 5		HT_MR_DB	0.5
S.G.DB	St.Gas Temp. Dead Band	0	- 5	^F	HT_SG_DB	2
RISE	Heat Rise dF/sec Clamp	0.05 - 0.2			HTSGRISE	0.06
LAT.L	LAT Limit Config	0	- 20	^F	HTLATLIM	10
LIM.M	Limit Switch Monitoring?	Yes/No			HTLIMMON	Yes
SW.H.T	Limit Switch High Temp	110 - 180		dF	HT_LIMHI	170*
SW.L.T	Limit Switch Low Temp	100 - 170		dF	HT_LIMLO	160*
HT.P	Heat Control Prop. Gain	0	- 1.5		HT_PGAIN	1
HT.D	Heat Control Derv. Gain	0	- 1.5		HT_DGAIN	1
HT.TM	Heat PID Rate Config	60 - 300		sec	HTSGPIDR	90

*Some configurations are model number dependent.

Staged Gas Heat Staging — Different unit sizes will control heat stages differently based on the amount of heating capacity included. These staging patterns are selected based on the mod- el number. The selection of a set of staging patterns is con- trolled via the heat stage type configuration parameter (HT.ST). As the heating capacity rises and falls based on demand, the staged gas control logic will stage the heat relay patterns up and down, respectively. The Heat Stage Type configuration selects one of 4 staging patterns that the stage gas control will use. In addition to the staging patterns, the capacity for each stage is also determined by the staged gas heating PID control. There- fore, choosing the heat relay outputs is a function of the capaci- ty desired, the heat staging patterns based on the heat stage type (HT.ST) and the capacity presented by each staging pattern. As the staged gas control desired capacity rises, it is continually checked against the capacity of the next staging pattern.

When the desired capacity is greater than or equal to the capacity of the next staging pattern, the next heat stage is select- ed (Run Status→VIEW→HT.ST = Run Status→VIEW→ HT.ST + 1). Similarly, as the capacity of the control drops, the desired capacity is continually checked against the next lower stage. When the desired capacity is less than or equal to the next lower staging pattern, the next lower heat stage pattern is select- ed (Run Status→VIEW→HT.ST = Run Status→VIEW→ HT.ST - 1). The first two staged gas heat outputs are located on the MBB board and outputs 3, 4, 5, and 6 are located on the SCB board. These outputs are used to produce 5 to 11 stages as shown in Tables 69A and 69B. The heat stage selected (Run Status→VIEW→HT.ST) is clamped between 0 and the maxi- mum number of stages possible (Run Sta- tus→VIEW→H.MAX) for the chosen set of staging patterns. See Tables 70-73.

INTEGRATED GAS CONTROL BOARD LOGIC — All gas heat units are equipped with one or more integrated gas control (IGC) boards. This board provides control for the ignition sys- tem for the gas heat sections. On size 020-050 low heat units

there will be one IGC board. On size 020-050 high heat units and 051 and 060 low heat units there are two IGC boards. On size 051 and 060 high heat units there are three IGC boards. When a call for gas heat is initiated, power is sent to W on the IGC boards. For standard 2-stage heat, all boards are wired in parallel. For staged gas heat, each board is controlled sepa- rately. When energized, an LED on the IGC board will be turned on. See Table 74 for LED explanations. Each board will ensure that the rollout switch and limit switch are closed. The induced-draft motor is then energized. When the speed of the motor is proven with the Hall Effect sensor on the motor, the ignition activation period begins. The burners ignite within 5 seconds. If the burners do not light, there is a 22-second delay before another 5-second attempt is made. If the burners still do not light, this sequence is repeated for 15 minutes. After 15 minutes have elapsed and the burners have not ignited then heating is locked out. The control will reset when the request for W (heat) is temporarily removed. When ignition occurs, the IGC board will continue to monitor the condition of the rollout switch, limit switches, Hall Effect sensor, and the flame sensor. Forty-five seconds after ignition has occurred, the IGC will request that the indoor fan be turned on. The IGC fan output (IFO) is connected to the indoor fan input on the MBB which will indicate to the controls that the indoor fan should be turned on (if not already on). If for some reason the overtemperature limit switch trips prior to the start of the indoor fan blower, on the next attempt the 45-second delay will be shortened by 5 seconds. Gas will not be interrupted to the burners and heat- ing will continue. Once modified, the fan delay will not change back to 45 seconds unless power is reset to the control. The IGC boards only control the first stage of gas heat on each gas valve. The second stages are controlled directly from the MBB board. The IGC board has a minimum on-time of 1 minute. In modes such as Service Test where long minimum on times are not enforced, the 1-minute timer on the IGC will still be fol- lowed and the gas will remain on for a minimum of 1 minute.

Table 69A — Staged Gas Heat — 48AJ,AK,AW,AY Units

UNIT SIZE	HEAT CAPACITY	UNIT MODEL NO.	Configuration→HEAT→SG.CF→HT.ST
		POSITION NO. 5	ENTRY VALUE
020-035	Low	S	1	=	5 STAGE
	High	T	2	=	7 STAGE
036-050	Low	S	1	=	5 STAGE
	High	T	1	=	5 STAGE
051,060	Low	S	4	= 11 STAGE
	High	T	3	=	9 STAGE

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