Carrier 48/50AJ specifications Economizer Configuration Table, Custom Changeover Curve Example

Table 79 — Economizer Configuration Table

ITEM	EXPANSION			RANGE		UNITS	CCN POINT	DEFAULT
EC.EN	Economizer Installed?	Yes/No					ECON_ENA	Yes
EC.MN	Economizer Min.Position	0	- 100		%		ECONOMIN	5
EC.MX	Economizer Max.Position	0	- 100		%		ECONOMAX	98
E.TRM	Economzr Trim For SumZ ?	Yes/No					ECONTRIM	Yes
E.SEL	Econ ChangeOver Select	0	- 3				ECON_SEL	0
OA.E.C	OA Enthalpy ChgOvr Selct	1	- 5				OAEC_SEL	4
OA.EN	Outdr.Enth Compare Value	18 - 28					OAEN_CFG	24
OAT.L	High OAT Lockout Temp	-40 - 120			dF		OAT_LOCK	60
O.DEW	OA Dewpoint Temp Limit	50 - 62			dF		OADEWCFG	55
ORH.S	Outside Air RH Sensor	Enable/Disable					OARHSENS	Disable
E.TYP	Economizer Control Type	1	- 3				ECON_CTL	1
EC.SW	Economizer Switch Config	0	- 2				ECOSWCFG	0
E.CFG	ECON.OPERATION CONFIGS
E.P.GN	Economizer Prop.Gain	0.7 -		3.0			EC_PGAIN	1
E.RNG	Economizer Range Adjust	0.5 -		5	^F		EC_RANGE	2.5
E.SPD	Economizer Speed Adjust	0.1 -		10			EC_SPEED	0.75
E.DBD	Economizer Deadband	0.1 -		2	^F		EC_DBAND	0.5
UEFC	UNOCC.ECON.FREE COOLING
FC.CF	Unoc Econ Free Cool Cfg	0-2					UEFC_CFG	0
FC.TM	Unoc Econ Free Cool Time	0	- 720		min		UEFCTIME	120
FC.L.O	Un.Ec.Free Cool OAT Lock	40 - 70			dF		UEFCNTLO	50

Custom Psychrometric Curves — Refer to the psychrometric chart and the standard Honeywell A-D curves in Fig. 10. The curves start from the bottom and rise vertically, angle to the left and then fold over. This corresponds to the limits imposed by dry bulb changeover, outdoor enthalpy changeover and outdoor dewpoint limiting respectively. Therefore, it is now possible to create any curve desired with the addition of one outdoor relative humidity sensor and the options for change- over now available. See Fig. 11 for an example of a custom curve constructed on a psychrometric chart.

UNOCCUPIED ECONOMIZER FREE COOLING — This Free Cooling function is used to start the supply fan and use the economizer to bring in outside air when the outside temperature is cool enough to pre-cool the space. This is done to delay the need for mechanical cooling when the system enters the occupied period. This function requires the use of a space temperature sensor.

When configured, the economizer will modulate during an unoccupied period and attempt to maintain space temperature

to the occupied cooling set point. Once the need for cooling has been satisfied during this cycle, the fan will be stopped.

Configuring the economizer for Unoccupied Economizer Free Cooling is done in the UEFC group. There are three configuration options, FC.CF, FC.TM and FC.LO.

Unoccupied Economizer Free Cooling Configuration (FC.CF) — This option is used to configure the type of unoc- cupied economizer free cooling control that is desired.

0 = disable unoccupied economizer free cooling

1 = perform unoccupied economizer free cooling as available during the entire unoccupied period.

2 = perform unoccupied economizer free cooling as available, FC.TM minutes before the next occupied period.

Unoccupied Economizer Free Cooling Time Configuration (FC.TM) — This option is a configurable time period, prior to the next occupied period, that the control will allow unoccu- pied economizer free cooling to operate. This option is only applicable when FC.CF = 2.

A48-7731

Fig. 11 — Custom Changeover Curve Example

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