Control Unit PSYSL01000263 MB250 – Enabling Room Thermostat

Control Unit PSYSL01000263 MB250 – Enabling Room Thermostat

On products equipped with control unit PSYSL01000263 (MB250), to correctly enable the operation of the external room thermostat, it is necessary to modify specific configuration parameters.

1. Parameter Modification

Section: “DEFAULT SETTINGS”

• Parameter P12
  • Default value: P12 = 0
  • Required setting: P12 = 1

Function:
Allows inversion of the clean contact from N.O. (Normally Open) to N.C. (Normally Closed).

Section: “ENABLEMENTS”

• Parameter A07
  • Default value: A07 = 1
  • Required setting: A07 = 0

Function:
Enables the management of the external room thermostat.

2. Procedure for Obsolete Stoves with 6-Button Display

For older products equipped with the MB250 control unit and a 6-button display, the “ENABLEMENTS” entry is not immediately visible.

Access to the Secret Menu:

1. Navigate to the SYSTEM MENU.
2. Leave the item highlighted without entering it.
3. Press simultaneously:
   • Button # (hash)
   • Button Power

This grants access to the Secret Menu, where the “ENABLEMENTS” section can be viewed.

3. MB250 / NG21 Parameter Correspondence

Technical note:

• MB250 → P12 corresponds to P99 on NG21
• MB250 → A07 corresponds to A01 on NG21

Instructions for CAT Technicians

• Always verify the type of contact of the installed thermostat (N.O. / N.C.).
• Make changes only when the stove is off.
• After changing parameters, perform a functional start/stop test from the thermostat.
• Record the modification on the service report.