Using the Jog Mode on Danfoss VFDs

Hi- A customer recently asked about having a VFD go to a preset speed from a single input, that would pre-empt the speed the drive is being commanded to normally. An example is a exhaust fan that typically ramps up with building pressure, but should go to full speed on a local command from a fire panel or other gas sensor.

This jog mode can also be used in cases where you only have a single input that you want to use to start the motor AND go to a preset speed (no other speed reference is required).

This is different than putting the VFD into “fire mode”, which ignores all alarms and runs the VFD until it burns up— sometimes the sequence doesn’t need that and you want something simple. Jog mode still monitors the safeties and alarms from the vfd and will trip if limits are exceeded.

After the drive is started and running- typical s/s signal on term 12/18 and speed ref on 53/55. You can add the “jog” signal to terminal 29 in this example. (on some new drives terminal 29 may be defaulted to “jog” already)

Set 3-11 “jog speed” to the speed you want the vfd to run

Set 5-13 terminal 29 to [14] “jog”

At that point, a contact closure between 12/29 will put the drive into jog mode and run at the jog speed.

As always, call us if you need any help.


Bacnet and Digital Inputs for VFDs

8-01 parameter.jpg

A customer called today and was asking about a VFD that would only start AFTER a power cycle, run for a while and then would stop.

They were starting the drive with a contact closure on digital input 18, but also connected over bacnet.

In these cases where both comm and hardwired points are connected, it is possible to get multiple start or stop commands conflicting that result in unreliable start/stop behavior. This happens when the bacnet BV start point is placed on a graphic or in the schedule, while the BO is also scheduled or commanded.

Here is how you can fix this:

If you are ONLY going to start the VFD using the hardwired point:

Set parameter 8-01 “control site” to "[1] Digital Only”. Now bacnet commands to start or stop the drive will have no effect, only the hardwire digital point will work.

Saving and Copying VFD Parameters to the Keypad

Copying TO the Keypad

Copying TO the Keypad

In Progress

In Progress

Copying FROM the Keypad into the drive

Copying FROM the Keypad into the drive

Hi- Today a customer was asking how to copy and save Danfoss VFD parameters to the keypad.

This process is very useful as a fast way to program drives— say that you have 1 vfd setup the way you want, and you want to copy those parameters to all of the other vfds exactly.

Heres how you do it:

1. Parameter 0-50 LCP Copy set to [1] “All to LCP”

The “LCP” is Danfoss jargon for the keypad, this saves all the existing parameters TO the keypad

2. Remove the keypad by tilting down from the top, install keypad in the drive that you want to program

If the new drive is the same size as the saved drive then:

3. Parameter 0-50 set to [2] “All from LCP” Takes the saved data FROM the LCP into the drive

If the VFDs aren’t the same sizes:

Parameter 0-50 set to [3] “Size indep. of LCP” meaning that all the parameters except the motor data will be sent to the new vfd. You will have to program the motor info (Motor FLA etc) manually.

Make sure to check the motor rotation and other startup checklist items, this is just a quick way to get the parameters entered.

Danfoss VFD "Common" Start/Stop

Hi-  Recently a colleague asked about "common" start/stop for VFDs that have the integral bypass--  Basically, the drives come wired with the ability for a single start/stop signal to start the motor when the SELECTOR SWITCH IS IN EITHER DRIVE MODE OR BYPASS!

The reason that you would want common s/s--> It allows the operator to select bypass and the motor will NOT take off at full speed, without dampers/valves etc being positioned in the correct place.  Motors running at full speed when the system isn't ready have the bad effect of blowing out ductwork and dampers.   When selector switch is in bypass you MUST also have a s/s from the EMCS as a backup to make sure the system is ready to start.

The reason that you DON'T want common s/s-->  You want operators to be able to select bypass in an emergency, and want the motor to run immediately without any other control signals required.

Below is a picture showing the examples, as well as a section from the manual on how to change it-- WARNING- the manual excerpt says that you should cap off the "red" wire after jumping X55 3/4, that Danfoss wiring is probably blue from the factory.  See the final picture for how it should look in the panel.





manual common ss.jpg


Monitoring Danfoss VFD in "Bypass"


Hi!  Recently a customer asked about a way to tell remotely if a Danfoss VFD was in bypass-  there are probably several ways to do this but here are a couple methods:

1.  Wire the EMCS point to X56 5/6

On 3-contactor bypass drives (ask us WHY we recommend and sell 3-contactor bypass), Danfoss gives you a customer connection board in the bypass section that allows you to monitor the bypass contactor directly.  You have to hunt for the board a bit, on different sizes drives it is in different places but they usually look similar:  a couple rows of small green terminal blocks.  Find the X56 terminal block that has 12 terminals, a contact between 5/6 indicates that the drive is on bypass (see picture and dwg).

This works if your intent is to show that the drive is on bypass.  If you want to show that the drive is "not ready" for ANY reason (major alarms, power failure, disconnect off, fuses blow, OR selector switch in bypass) then try method #2.



bypass connections.jpg

2. Wire the EMCS point to Relay 2 NO (4/5). 

Program Relay 2 parameter 5-40 to [160] "no alarm".  The relay will go high and have a contact closure between 4/5 if everything is OK with the drive.  Contact would be open if power failure, bypass, or alarm.


Program Relay 2 5-40 to [3] "Drive Ready/remote control"  Does the same as above but contacts open if the drive is placed into "manual" control from the keypad.  Might be useful if you are concerned that operators won't return the drive to auto mode-- might be a nuisance alarm if they do manual control a lot.

*Final Notes:  Unfortunately the bypass status can't really be a bacnet point, because the point of a bypass is to take over if there is a critical failure in the drive (and it wouldn't be talking bacnet at that point).  There are "electronic" bypasses that continue to talk while in bypass BUT we like the simplicity of a 3-contactor old school bypass when you need it -- don't add complexity to your backup emergency option.

Running motors ABOVE 60Hz

Traditionally, maximum motor speed has been 60Hz for motors controlled by VFDs.  Sometimes, it is necessary to have a higher upper frequency limit.  Danfoss VFDs can run at output frequencies higher than 60Hz.

This is especially useful if you are just a little bit short of water/air at full speed, but the motor is still running below its nameplate full load amps (FLA).

No matter what-- you don't want to run the motor above the FLA, and you may want to confirm that mechanically it is OK (motor/fan/pump/belts) to spin faster in your application.  The VFD doesn't care as long as you are below its rated outputs.

Here’s an example of changing the maximum output frequency from 60Hz to 75Hz.

To change the maximum frequency output on the VFDs from 60Hz to 75Hz, update the following three parameters:

3-03       Maximum Reference = 75Hz

4-14       Motor Speed High Limit (Hz) = 75Hz

6-15       Terminal 53 High Ref/Feedback Value = 75Hz --- or whatever input you are using for the speed reference.

After you make these changes to the limits, slowly walk the speed up to the max in "Hand", making sure that the motor amps don't exceed the nameplate FLA.

Danfoss VFD Preset Reference Array

Sometimes you want to control a VFD with multiple digital outputs, instead of using a 0-10v or 4-20ma analog speed signal.

Danfoss has a couple of ways to do this:

1. For one preset speed, you can use the "jog" function in the VFD.

Set parameter 5-11 Term 19 (or any open input) to [14] Jog.  When you turn this input on, the drive will automatically go to the speed that you have set in parameter 3-11 Jog Speed--this will happen regardless if you have a regular s/s turned on.

2. For multiple speeds (like a low/high exhaust fan at a potato chip factory- Hi John!) you can use the "preset reference array" giving you up to 8 speeds with just 3 digital inputs.

Set parameter 3-04 to [0] "sum"- basically adding all of the input, external and preset references.

Set parameter 3-10 "preset reference" values-- remember this is an "array" with up to 8 different values.  In the example below we set "preset ref 0" to 30Hz (50%), and "preset ref 1" to 45Hz (75%)-- these are the two speeds that we want the drive to run in this example.



Set 5-11 Term 19 (or any open input) to [16] "ref bit 0" 

When the S/S is received, the drive will ramp up past the min speed to 30Hz, if you turn Input 19 on then the drive will speed up to 45Hz.  You can see that if you added 2 additional inputs you could get access to all 8 different speeds per the matrix below--- just by turning on and off the 3 input points.  As usual call us if you need any help here.

If you just want to activate the speeds with the reference bits only (no separate start/stop input, the drive only runs when you have a speed reference on it, otherwise it stops)

  1. Setup the preset reference array like above.

  2. Test your speed commands by jumpering the reference array inputs, you should see the reference values change.

  3. JUMPER the start/stop so it is always on

  4. Set parameter 1-82 “min speed for function at stop” to be just slightly higher than the minimum motor speed. For example, if the min motor speed is 12 Hz, make 1-82 13Hz. That way, when there are no other references commanded on the drive will go to sleep when it drops below 15Hz.

Danfoss VFD Relay Delay Settings

Hi-  A customer has an isolation damper tied to a relay on the VFD, so that when the VFD is started the relay will open the damper.  When the damper endswitch is made, the signal goes back to the VFD to allow it to start.

It looks like this:


Use the following points:

Set 5-40 relay 1 to [167] "Start Command Active".  This works great for isolation dampers because the drive can open the damper with any start command or local hand operation.

Set 5-11 Terminal 19 (or any open input) to [52] "run permissive".  If you tie a damper endswitch to that input, the motor will not start until there is a contact closure across the input.

Here is the secret sauce:  When the VFD receives a "stop" command, you may not want the damper to close immediately while the fan is still winding down-- you might trip a pressure switch or otherwise damage equipment if the duct is closed while fan is still turning---

Set 5-42 Relay 1 Off Delay ---Set this to a long enough time to allow the motor to completely wind down before damper closure--- it should be at least as long as ramp down time in parameter 3-42-- probably add another 30s or so on top of that and test it.

As always call us if you have any questions!  

Testing Alarms in Danfoss VFDs

Hi-  Recently a customer asked about how to test alarms-- they wanted to commission the system and verify that VFD alarms are being seen at the front end.

We can use an open digital input, and program the vfd to think that there should be a jumper there-- typically used for a smoke detector or freezestat---no jumper means that the VFD would go into alarm.

Here is one way to do it:

1.       Verify Input 29 has no wires connected to it, if so pick another open input.  We used input 29 in this example because it is usually open in both bare drives and drives with bypass.

2.       Change parameter 5-13 “Digital Input 29” from [14] Jog* to [7] External Interlock.   *It might also be currently set for [0] no operation, that’s fine the point is that input 29 isn’t currently being used and has no wires connected to it.

3.       After you hit OK, the drive will immediately go into “Alarm 60, External Interlock”, and the motor will stop.  This alarm is usually used for external devices--smoke detectors or freezestats and would have to be jumpered to stop the alarm from happening.

4.       Verify that the alarm annuciates correctly at the front panel etc.

5.       Set parameter 5-13 setting to [0] no operation.  The VFD alarm should clear.  If it doesn't clear after a few seconds push the reset button on the VFD.  This just means that your parameter 14-20 Reset mode isn't set to automatically reset after the fault clears.

See Video Below


Danfoss VFD Analog output scaling

We had a recent request about using the analog output on the VFD. This is the analog output at terminals 42/39 (42 is the output, 39 is the common).

A couple of notes:.

  1. It is ONLY a 0/4-20ma output, there is no selector switch to change it to voltage.
  2. Depending on which output parameter you select, those values will be either output as 0-20ma or 4-20ma, there are selections for both. 

    An example is [107] Speed is 0-20ma, [137] Speed is 4-20ma

  3. You can select what parameter you want the output to follow using parameter 6-50, here are some of the more common ones:
  • [137] Speed 4-20ma, scaled from 0 to whatever the speed high limit in par 4-13, usually 60Hz
  • [133] Motor Current 4-20ma, scaled from 0 to "Inverter Max", should be motor nameplate FLA but you can verify it from par 16-37.  This would be different for different motors of course.

Please call us if you have any questions on how to use the analog output.

Danfoss Warning 34 Fieldbus Fault

Warning 34 won't hurt anything.

It usually comes up during startup, if the VFD has an communications option card (bacnet) and no communications connected.

After a couple of minutes without communications, you will get "Fieldbus Fault W34", a comm failure on the card.

It has no effect on the operation of the VFD, but if you want it to go away you can do one of 3 things:

1. Connect your bacnet comm (with some bacnet traffic).

2. Power off the vfd and remove the card, restart the drive.  It will tell you that there has been an "option change", clear that alarm and you should be fine.  This works if you are never going to use the card.

3. Change function 8-02 "control source" from Option A to "none".  That way the vfd won't look for control comm from the card and the warning won't come up.

The intent of warning 34 is that if you lost communications on the card you could trigger certain events-- stop/full speed/preset speed-- things you might want to do if comm went down and you lost control of the VFD.  Call us for more info you want to run a sequence like this.  

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


Danfoss Terminal Blocks

We occasionally get questions about how the Danfoss low-voltage terminal blocks work that are on the VFD-- these are the ones mounted under the keypad on the drive.  There are two variations that are both "spring-type" terminal blocks but the way that you release them is different.

See pictures--

For the older style use a flathead screwdriver in either the top or bottom slot (depending on which wire-hole you are using).  Push in until the spring releases and you can insert or remove the wire.

For the newer style use a flat screwdriver into the flat spot IN BETWEEN the wire holes.  Push in and both holes will recess and you can release or insert the wires.