Install Instructions

ManualsBrandsJohnson Controls ManualsA421 Series Temperature ControlsSingle Stage Digital Temperature Control (120/240VAC SPDT)

A421 Series Standard Electronic Temperature Controls Installation Instructions

To exit the Basic menu and go directly into the

Advanced menu, simultaneously press  and , and

hold them for 5 seconds.

Advanced Menu

The Advanced menu allows you to change the

parameter values in the Basic menu and the parameter

values for the Advanced parameter codes; including

Temperature Units (Un), Temperature Setback (tSb),

Sensor Offset (So), High Temperature Setpoint Stop

(HtS), Low Temperature Setpoint Stop (LtS), and

Backlight Level (bLL).

See Parameter Codes and Modes of Operation

and

Table 4 for more information regarding parameter

codes, usable parameter values, and default values.

Viewing and Changing Values in the Advanced

To access the Advanced menu and view and change

the parameter values, follow these steps:

Restricting User Adjustment

You can restrict user adjustment of the A421 control to

either just OFF value (control band) only and limit the

range of this value (Figure 9).

You set the A421 control into the restricted adjustment

mode by positioning the jumper located on the circuit

board next to the TB3 terminal block. See Setting the

Control to Restricted Adjustment Mode.

Note: Setting the A421 control up in the Restricted

Mode prevents casual users from over-adjusting the

control in your application, or from inadvertently

changing the mode of operation from cooling to heating

or heating to cooling (by over-adjusting the On value or

OFF value).

When the A421 control is set up in the restricted

adjustment mode, the following behavior is enforced:

• The restricted temperature adjustment range is

defined by the selected High Temperature Stop

(HtS) and Low Temperature Stop (LtS) values.

Figure 8: Navigating the Advanced Menu

1. With the Main screen displayed,

press and hold  and 

simultaneously for 5 seconds. The

LCD displays Un, which is the first

parameter code screen displayed in

the Advanced menu.

2. Press  or  to scroll through all of

the Advanced parameter codes and

display the preferred code.

3. With the preferred parameter code

displayed, press MENU to display the

current parameter value for the code.

4. With the current parameter value

displayed, press  or  to scroll

through all of the parameter code’s

usable values and display the

preferred value.

5. With the preferred parameter value

displayed, press MENU to save the

displayed value and go to the next

parameter code.

HtS

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