Carrier 48EK, 48EW, 48EY024-068, 48AW Staged Gas System Components, Stage Gas System Inputs/Outputs

Table 37 — Staged Gas System Components

ITEM	FUNCTION	LOCATION
Heating Controller (SGC)	Logic and Output Relays	Heating section
Supply-Air Thermistors (SAT)	Sense unit leaving-air temperature	Supply duct (factory-provided,
		field-installed)
Cooling Supply Air Set Point	Specify set point for	Heating section, next to SGC
Potentiometer (CLSASP)	tempering heat control
	Set Point Range: 35 to 70 F
Heating Supply Air Set Point	Specify set point for First-Stage	Heating section, next to SGC
Potentiometer (HTSASP)	Heating control
	Set Point Range: 80 to 125 F
Air Flow Switch (AFS)	Prove Supply Fan operation	Fan supply air plenum
		(factory-installed)

Table 38 — Stage Gas System Inputs/Outputs
INPUT	DESCRIPTION
Cool1	Relay in parallel with Compressor #1 contactor
Cool2	Relay in parallel with Compressor #2 contactor
Heat1	24V input from Base Unit control
Heat2	24V input from Base Unit control
Fan	Air proving switch (contact closure on rise in static pressure)
Cool Supply Set Point	Potentiometer, (range 35-70 F)
Heat Supply Set Point	Potentiometer, (range 80-125 F)
Supply Air Thermistor (1, 2 and 3)	Field-installed in supply ductwork (P/N HH79NZ016)

Operating Modes — The SGC will operate the unit in one of the following operating modes:

•no mode

•Cooling Mode

•Heating1 Mode

•Heating2 Mode

No Mode — In this mode, none of the heat stages are turned on. No mode occurs if the Cool, Heat or Fan inputs are off or the Cool input(s) are on.

Tempering (Cool) Mode — In this mode, the SGC tempers in incoming supply air to maintain the cooling supply air set point. Tempering mode occurs if the Fan input is ON and all Cool and Heat inputs are off.

When the SGC determines that the fan is on and the base unit control is not calling for heat or mechanical cooling, the SGC will stage heat to maintain the cooling set point which is set on the CLSASP potentiometer of the SGC. This set point should be slightly below the supply air set point of the base unit VAV control. Note that the supply-air temperature will still be in the “cooling range.”

Heat1 Mode — Heat1 mode is used on VAV applications as they have one heat stage on the base unit control. CV units have two heat stages and will not operate under Heat1 mode.

In this mode, heat is staged to control supply air temperature to HTSASP. Heat1 mode occurs only if Heat1 is ON and Heat2 is OFF and Cool1 and Cool2 are OFF.

When the base unit control calls for first stage of heat, the SGC will stage heat to maintain the heating set point set on the potentiometer of the SGC. The HIR will be energized to com- mand the zone terminals to open to maintain minimum heating airflow.

Heat2 Mode — Heat2 mode is used on CV applications as they have 2 heat stages on the base unit control. VAV units have only 1 heat stage and will not operate under Heat2 mode.

In this mode, when the base unit calls for the second stage of heat, the SGC will turn on all available heat stages. This mode only occurs if Heat1 and Heat2 are ON and Cool1 and Cool2 are OFF.

Accessory Navigator Display — The Navigator Display is a field-installed accessory. See Fig. 60. Navigator Display is to be connected to LEN connections at communication board

which is attached to the heating and cooling supply air set point potentiometers in heating section. The Navigator Display ac- cessory is required for all units with staged gas control.

The display module provides the user interface to the Staged Gas control system. See Fig. 60. The display has up and down arrow keys, an ESCAPE key, and an ENTER key. These keys are used to navigate through the different levels of the dis- play structure. See Table 39. Press the ESCAPE key until the display is blank to move through the top 11 mode levels indi- cated by LEDs on the bottom left side of the display.

Pressing the ESCAPE and ENTER keys simultaneously will scroll a text description across the display indicating the full meaning of each display acronym. Pressing the ESCAPE and ENTER keys when the display is blank (Mode LED lev- el) will return the display to its default menu of rotating display items. In addition, the password will be disabled requiring that it be entered again before changes can be made to password protected items.

When a specific item is located, the display will flash show- ing the operator, the item, item value, and then the item units (if any). Press the ENTER key to stop the display at the item val- ue. Items in the Configuration and Service Test modes are password protected. The display will flash PASS and WORD when required. Use the ENTER and arrow keys to enter the 4 digits of the password. The default password is 1111.

Changing item values or testing outputs is accomplished in the same manner. Locate and display the desired item. Press the ENTER key to stop the display at the item value. Press the ENTER key again so that the item value flashes. Use the ar- row keys to change the value or state of an item and press the ENTER key to accept it. Press the ESCAPE key and the item, value, or units display will resume. Repeat the process as required for other items.

The unit alarms can be cleared through Navigator display. To check the current alarms, enter the Alarms menu. The first submenu is the CRNT submenu. The CRNT function displays the list of current alarms (maximum of 25). The second sub- menu item is the RCRN (Reset All Current Alarms) function. Press ENTER to reset the current alarms. The next submenu item, HIST, displays the list of cleared alarms (maximum of 20). The HIST function can be cleared with the RHIS function.

84