Danfoss VFD Fire Mode

Call us for help before you try this—seriously.

 Danfoss VFDs have the ability to program an input as a “fire-mode” input—meaning that the drive will ramp up and continue to run regardless of any alarms.  Some people call this “run until destruct” mode. 

This is most frequently used for things like stairwell pressurization fans--- where you don’t want too much pressure that would keep the stairwell doors from opening, but enough pressure to keep the fresh air flowing into the stairwell so people can evacuate.  You want the VFD to ignore all the internal alarms and keep the air flowing as long as possible.

 As you can imagine there are some risks to this, most likely is that during routine testing of this feature that the VFD could be forced to exceed the programmed safeties and cause equipment damage—use caution here!  The manufacturer can’t warranty a VFD that has been overloaded or damaged by fire mode testing. 

 Here are some of the points that are useful:

 24-09 Fire Mode Alarm Handling

Set this point to [2] “trip at all alarms-test” during setup and testing, this will keep you from damaging the VFD or motor during testing

Change to [0] “trip and reset at critical alarms” ONLY when you are ready to arm the system for tenants

 5-11 Digital Input 19 (or pick any available input)

Set to [37] “fire mode”, a contact closure on this input puts the vfd into fire mode

 24-00 Fire Mode Function

Set to [1] “Enabled”

 24-05 Fire Mode Preset Reference

Set this to the value that you want the fan to run—usually the balancer will tell you this value based on pressure measurements from the stairwell

 You can also set a reference to come from an analog signal, call us to help set this up.

Here is an excerpt from the Programming Guide that describes fire-mode:  LINK