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-- Obsolete -- EF12 VFD Documentation

For referred-to diagrams, see ION, March 8, 2007.

By Rene Tanaja, March 8, 2007


Here are the new EF12/13 VFD procedures from Rob Walker. Please read and check out locally. Nuclear Exhaust

  1. The EF12-13 switchover controls enclosure and the EF12 Variable Frequency Drive (VFD) enclosure are mounted on the wall beside the entrance to the ISAC I penthouse exhaust fan room.

 EF12 VFD with text

Down in the centre of the controls enclosure is a column of amber LED's.
 EF12 VFD Control - close up

These LED's indicate the conditions that cause the fan to switchover. Only one of these LED's will be lit. Record the condition that caused the switchover. The following is a list of conditions that "trip" EF12 and actions to be taken:
             a. "Low Site Air" - Proceed to step


             b. "Fault - VFD"  - The LCD display on the VFD enclosure keypad will show the VFD fault that tripped EF12. Press the red "stop" button on the keypad. If the fault clears, proceed to step 2. If the fault does not clear, contact Building Maintance staff.

             c. "Low Delta P - EF12 Duct Pressure" - Proceed to step 2.

             d. "Stop EF12 - DDC Signal" - Proceed to step 2.


    2. On the top right hand corner of the controls enclosure is a green momentary pushbutton, labelled "Run EF12".

EF12 VFD Control


It is used to start the lead fan, EF12. Push this button in and hold until the button illuminates. This takes about 20 seconds. Then release. EF12 will continue to run. The dampers for the exhaust fans should switch back to the normal state: open for EF12, closed for EF13. If the "Run EF12" button does not illuminate, there is a mechanical problem, ie. broken fan belt, broken sensor, etc. Release the button and EF13 will start again. Contact Building Maintenance staff.

    3. Once EF12 is back on, acknowledge the DDC EF12 alarm.

    4. Other features of the Switchover Controls enclosure:

             a. The toggle switch labelled "EF13" is used to force a switchover from EF12 to EF13. When this switch is set to "ON", EF13 will start. When this switch is set to     "AUTO", the system will switch to EF13 if there are any faults as listed in step 1.

             b. The "EF12 &13 System" toggle switch is used to turn BOTH fans off. The toggle switch lever must be pulled out first in order to switch, to prevent unintended switching. This switch should NOT be used without a work permit. It is only intended for system maintenance.

             c. The "Auto/Manual" selector switch is used to select the VFD speed reference. When set to "AUTO", the VFD takes its speed signal from the DDC output. When set to "MANUAL", the VFD takes its speed signal from its own internal reference, which has been set up to run EF12 at a steady 43Hz.


When switching from "MANUAL" to "AUTO", the system will switch from EF12 to EF13 unless the DDC Speed signal's output bias is set to run the VFD at a nominal speed. This selector switch should not be used without contacting Building Maintenance staff.

    5. If at a switchover EF13 does not start, check that the "EF13 starter breaker" did not trip off due to inrush current (see first picture in the document for breaker location). If the breaker did trip:

             i. put the mode switch (black) from auto to off

             ii. press the Reset button

             iii. flip the breaker to OFF and then to ON

             iv. put the mode switch back in auto - EF13 should start. It it doesn't, call immediately the Building system expert and Electrical Services engineer for assistance.

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