4120--Supply: ABB HVAC VFD's

The purpose of this amendment is to post the responses to the questions posed. ***Q&A window will close 02/14/2024. ***

Q&A

We will need to know if these are pumps/fans/variable torque loads or constant torque loads.

The VFD s will serve as the power source between the main service panel and fan motors of each air handler, the load varies during a power outage or voltage drop, the fans will constantly run at a set parameter within the VFD.

We also need to know the required short circuit rating desired e.g 65KAIC, etc. and if an input circuit breaker or disconnect is needed as well.

The required short circuit rating desired current rating must be followed by the manufacture s recommendations and specifications chart that s provided with each VFD purchase, current, size, and voltage, we will utilize the I/O terminals for the motor control.

Do you need a circuit breaker or fusible disconnect switch?

ABB ACH550 VFD s has a disconnect switch/Circuit breaker mounted on the VFD, non-Fusible.

What is the required SCCR for the panel?

The required SCCR for the panel 100KA.

Do you want the VFD keypad mounted on the enclosure door?

The VFD will be mounted on the opposite side of the wall or the air handler, designated mounting brackets.

What pilot devices are required (H-O-A switch, VFD-Off-Bypass switch, Run light, Fault light, etc.).

AAB VFD has and, H-O-A switch and VFD bypass switch with run/fault indicators.

Is the application for variable torque or constant torque?

Constant torque, the VFD at times will ramp down however the horse power remains the same.

The specification mentions 0.5Hz to 200Hz as the frequency range. Is this just a typical manufacturer spec or do you really need frequency above 60Hz? If the answer is above 60Hz, then the application details are critical. As you know available torque rolls off linearly above 60Hz, so by the time they hit 200Hz, the motor would theoretically only be able to produce about 60 / 200 = 30% of its rated torque. The real number will be lower because higher speeds increase the friction and windage losses. My best guess is that 20% is more realistic.

This is the manufactures specifications, we operate under 60 hertz we average our motors at 35 to 45 hertz, the manufacture specifies what the VFD capabilities can achieve if needed.

I have a question regarding the VFD s on this request. I am assuming you are replacing existing Installed VFD s, would you happen to know or have the unit information that these VFD s are installed on?

ABB is a manufacturer of VFD drives, but the drives are installed in bigger Air Conditioning assemblies. If the existing unit information is provided, I may be able to locate the exact VFD that works for said unit.

The VFD s are installed on Air Handler #12-2C Service Bay 2-5, building 100.