3D Connexion mD4000-b Manual Do Utilizador

Manual 2100-574

Page 

13 of 23

The MD4000 can be used for controlling two (2) air 
conditioners with economizers.

The MD4000 controller can be locked such that 
unauthorized persons cannot make any changes 
to temperature set points or any other selectable 
parameters of the controller system.

The ON/OFF and Comfort buttons remain fully 
active for their normal intent.  The Advance/Change/
Save button remains active for the Advance feature 
only, which allows the position of the lead and lag air 
conditioners to be swapped (reversed).  The Program 
button remains partially active - allowing the review 
of temperature sensor(s) actual reading of temperature, 
and the current settings/choices that have been chosen.  
However, no changes can be made when the controller 
is locked, and if the change button is pressed when in 
the Program mode, the display will come up showing 

“Locd” instead of flashing the selectable choices for 
that parameter.  The default (DEF) reset capability is 
also disabled when the controller is in locked mode.

Locking and Unlocking the MD4000 Controller:

  1. Locking the controller requires using 3 buttons   
  while the controller is in the normal operating (run)  
 mode.

  2. Press and hold the Advance/Change/Save button  
  and the Up and Down arrow buttons simultaneously  
  for 20 seconds until the display shows “Locd”.

  3. To unlock the controller, press the Change, Up and  
  Down arrow buttons simultaneously for 20 seconds  
  until the display reads “uLoc”.

If desired, the MD4000 controller can be signaled 
from a standby generator system to lockout (disable 
operation of the) lag air conditioning system and close 
economizers if active.  This is sometimes mandated if 

the generator size is not sufficient to handle the building 
load (amperage) and that of both air conditioning 
systems.

A normally closed (NC) dry contact as part of generator 
controls is required.  These contacts must open when 
the generator is started, and such action will signal the 
MD4000 controller to this condition and disable lag 
air conditioner run function and close economizers if 
active.

A wire jumper is factory-installed across the Generator 
Run / Economizer Shutdown terminals.  To utilize 
the generator run feature, remove the jumper from 
Generator Run / Economizer Shutdown, and connect 
the generator normally closed (NC) contacts that will 
open-on-run generator condition to the Generator Run / 
Economizer Shutdown terminals. 

There are input connections available for -24VDC or  
-48VDC (-20 to -56V) backup power connection.  Making 
this connection will maintain microprocessor operation, 
front panel display, LED signaling, and alarm relay 
operation during periods of commercial power outages 
and when no standby generator is available.  This circuit 
is protected by a replaceable .5A (500mA) 250V fuse.

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