Troubleshooting guide

MAGNUM VERSION 8 MANUAL REVISION 3.1

7.74.3.12. Common VFD Fan w/Bypass

The Common VFD Fan with a Bypass type of condenser has one fan. All circuits will use this fan; make sure that all

circuits in the Circuit Base point to the same common fan bank. The above setup shows that there is one condenser

stage. However this type requires the following three consecutive Relay Outputs to be set up. For example:

This type of condenser requires one condenser fault. If the fault occurs then the VFD will be bypassed and the fan will

run at 100% if needed.

45 CND STG1 ON

(RO Type)

When the discharge pressure is above this value, turn on the first stage of the condenser

fans.

‘Time (sec)’ field: (Applies to compressors with shared condensers) If non-zero, then the

compressor in startup state will not be in sole control of the condenser fans, it will control

off of highest discharge pressure. If zero, then compressor in startup will have sole

condenser control for 5 minutes. This option is selected in in the ‘Newly started Comp

Controls Common Fan Bank’ box in the ‘Condenser Information’ panel under the MAG

V8 screen.

46 CND STG1 OFF

(RO Type)

If stage 1 of condenser capacity is on and the discharge pressure drops below this value,

then turn this stage off.

CND MIN SPD

(RO Type)

Minimum speed percentage for variable speed condenser control.

55 CND MAX SPD

(RO Type)

Maximum speed percentage for variable speed condenser control.

90 COND FAULT For Condensers with Fault Indicators: If Setpoint is active, a condenser fault occurs, and the

Setpoint type is Alarm, then an alarm message will be generated. If the type is Lockout,

and a condenser fault occurs, then all of the compressors associated with this fault will be

locked off.

For Common VFD Fan Condensers with Bypass: Time in seconds before the bypass can be

used when a fault has occurred.

Fan control when there is no fault:

The highest discharge pressure of all the compressors is the control value.

The first relay, VFD LOAD, is on and the second relay, VFD BYPASS, is off.

When the control discharge pressure is greater than the value of Setpoint #45, then the third relay (VFD

ENABLE) will be turned on and the VFD will be set to the value of Setpoint #55. If the control discharge

pressure decreases the VFD will be modulated between Setpoints #54 and #55 based upon the control

discharge pressure.

Assume Setpoint values:

45 CND STG1 ON 250 psi

46 CND STG1 OFF 170 psi

54 CND MIN SPD 20%

55 CND MAX SPD 100%

90 COND FAULT 30s