retrofitting vfds

[pmsbpfjc1]

hello mike,

i primarily retrofit vfds into old installations. i remove old starters to motors and replace with vfd.
vfd has overcurrent and overload protection built in. my question is how do i now size up feeder conductors to drive? must i use old overcurrent protection device that was supplying the starter and size conductors to that?

 

[ptonsparky]

2011 NEC 430.122

Plus the installation manual for the specific vfd. Not to sure that throwing a vfd at every starter replacement is the best idea. Others that know more.should chime in eventually.

Welcome to.the forum.

 

[Jraef]

Also most factory built starters will have MCP (mag only) breakers in them, you cannot use MCPs for anything other than as part of a factory built combo starter, so you will have to replace them anyway if you are gutting the starter.

 

[jafro]

UL listed

UL listed

hello mike,

i primarily retrofit vfds into old installations. i remove old starters to motors and replace with vfd.
vfd has overcurrent and overload protection built in. my question is how do i now size up feeder conductors to drive? must i use old overcurrent protection device that was supplying the starter and size conductors to that?

Are you aware that the MCC that you add the VFD's to loose their UL approval with the VFD in it?

 

[petersonra]

Are you aware that the MCC that you add the VFD's to loose their UL approval with the VFD in it?

You can't "lose" UL approval because UL does not approve anything.

 

[tish53]

As the above contributors have stated you would need to change out the MCP to a CB and we would size the incoming conductors to the VFD size ( not the motor size). One other issue I have seen is cooling. A VFD will generate alot more heat in an MCC bucket then the old starter and if it is not addressed the VFD life will be quite short.

 

[weressl]

As the above contributors have stated you would need to change out the MCP to a CB and we would size the incoming conductors to the VFD size ( not the motor size). One other issue I have seen is cooling. A VFD will generate alot more heat in an MCC bucket then the old starter and if it is not addressed the VFD life will be quite short.

Two other areas are also of concern:

1. Most older motors will not be suitable for inverter application, so their life expectancy after the ASD installation will become unpredictable.
2. Existing conductors may also have a problem with carrying inverter suplied voltage and may prematurely fail.

 

[pmsbpfjc1]

thank you for the info i must have not been extremely clear we don't actually put the vfd in the mcc bucket most of the time they don't fit usually locate it at or near motor. and you answered my second question which would have been about the circuit protection. and to the last yes we usually have to change motor to a high efficiency motor and has to be inverted duty rated and insulation class rated