Application Guide

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INSTALLATION GUIDELINES
General Guidelines
— Do not install a VFD in a hazardous or flameproof area.
— Do not install a VFD to drive motors installed in hazardous areas. This requires special testing and approvals.
— Every Honeywell VFD has a three-phase output.
— Do not assume that all three-phase AC motors can be driven by a general purpose VFD. Some types require a special
VFD.
— Do get full motor name plate details - do not assume anything.
— Do not select VFD on Hp alone - some motors have high current to Hp ratio and the VFD could be too small if selected on
Hp alone.
— On lightly loaded motors, do not select a VFD with capacity more than one frame size less than motor. If you do, expect
problems.
— On very lightly loaded motors, do not select VFD on motor current drawn alone, i.e. 60 Hp VFD drawing 40 amps at 60 Hz
may draw 60 amps at 10 Hz. If this situation arises, an output line reactor will be needed. Make allowance in proposal.
— Do not install a VFD in a hot, dirty or humid environment without special precautions.
— Do use shielded cable between the VFD and motor.
— Do not install control cables in same trunking, conduit as VFD power cables.
— Do include RFI filters on input to VFD.
— Do use shielded control cables as far as possible - and segregate from power cables at every opportunity.
— Do add additional input reactors, if VFD is installed within 92 feet of a power supply of 1 MVA or more.
— Do allow for output reactors if motor cable length is more than 320 feet or always if mineral insulated type cable is used.
— Do allow for correct sized earth cable as described later.
— Do allow for individual motor protection, if the VFD is driving more than 1 motor.
— Do interface any switches, isolators, contactors on output of the VFD, with the VFD control inputs.
— Do not feed a Star Delta starter with a VFD unless the VFD is held off until Delta sequence is complete and use
late
make/early break
contacts.
— Do ensure when using Excel Classic type controllers, that transformers are connected correctly - otherwise 24 Vac can be
output from DC analogue control terminals.
— On first time power up always disconnect VFD output cables. Transposed input and output cables can damage VFD.
— Beware: Installing a VFD on a fan supplying air to direct expansion refrigeration coils. Reduction in air flow could cause coil
icing or liquid floodback to the compressor, which can cause mechanical failure.
— Do not mount sensors close to an electric motor driven by a VFD. The motor emits higher than normal electrical noise
which may interfere with the accuracy of sensors.
Surveying
As with any system, it is crucial that the system is surveyed thoroughly to ensure that the application of the VFD is to be
successful and provide trouble free operation. The survey should encompass six areas:
1. Location for the VFD.
2. The motor, control gear and power supply.
3. Mode of control.
4. Type of load.
5. The effect of varying the motor speed on the performance of the machine or service provided by the machine to be speed
controlled.
6. Discussion with user.
VFD Location: Enclosures and Ventilation
The VFD is, by comparison with the motor, a relatively expensive machine. It should therefore be installed in a suitable
environment. The VFD although very efficient still has some losses which manifest themselves as heat. The VFD should be
installed in a well ventilated area, and obviously if installed within a cubicle, the cubicle must have sufficient through flow of air
to cool the VFD or its surface area must be sufficiently large to provide natural cooling.
The ambient temperature (surrounding the VFD) must be below 122°F in order to provide correct reliable operation of the VFD.
If the ambient temperature is liable to rise above 122°F then either derating of the VFD capacity will be required or additional
cooling fans or possibly even a refrigeration unit will be required.