Amperage draw versus Air flow VFD Fan

In summary: We have ordered an anemometer to measure the actual air flow.In summary, the conversation revolves around a VFD fan that pushes air through a filter. Over time, downstream resistance increases due to the filter, but the fan speed remains constant. The amperage draw has also remained stable, but it is uncertain if this means that the air flow remains constant. It is suggested that the fan curve and filter loading could potentially cause the amperage to stay the same even with a decrease in air flow. The next step is to measure the actual air flow using an anemometer.
  • #1
mattibo
7
1
I have a VFD fan that pushes air through a filter. Over time, downstream resistance gets higher due to the filter. Fan speed remains constant. We have looked at amperage draw and it has remained stable even with this added resistance. Does that mean that air flow remains constant?

Kind of confused that we are getting constant amperage. I'm inclined to think that we should be seeing a decrease in amperage draw since we should be pushing less air to due added downstream resistance.
 
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  • #2
Fans come in many blades some for CFM others for presser . it is probable that your air flow is stalling . This would not show in a amp test. Did you check the static presser downstream . You could remove the filter then if air stalling was the problem the amp should show a higher reading. A stall air flow will still hold a press downstream.
 
  • #3
mattibo said:
I have a VFD fan that pushes air through a filter.

Fan speed remains constant.
What is the VFD doing? Is it under any sort of control?


Over time, downstream resistance gets higher due to the filter.
How much? Are you actually measuring it?
We have looked at amperage draw and it has remained stable even with this added resistance. Does that mean that air flow remains constant?
Not necessarily. Filter loading is not always a linear (or parabolic) relationship between airflow and pressure and the fan curve can have different shapes, so if resistance goes up and airflow goes down, the amperage could stay the same. That's not common, but it is possible.

Do you have a way of reading the airflow?
Kind of confused that we are getting constant amperage. I'm inclined to think that we should be seeing a decrease in amperage draw since we should be pushing less air to due added downstream resistance.
That would be the expected result, yes.
 
  • #4
What is the VFD doing? Is it under any sort of control?
No control. Just for additional operational flexibility.

How much? Are you actually measuring it?
Between 2-3 in. H2O

Not necessarily. Filter loading is not always a linear (or parabolic) relationship between airflow and pressure and the fan curve can have different shapes, so if resistance goes up and airflow goes down, the amperage could stay the same. That's not common, but it is possible.

BHP is constant since P = IV and both voltage and current are constant in my case. I guess that means that my increase in delta static pressure across the fan is exactly proportional to my decrease in air flow no?

Do you have a way of reading the airflow?

That is the next step.
 

1. What is amperage draw and how does it affect air flow in a VFD fan?

Amperage draw refers to the amount of electrical current that a VFD (variable frequency drive) fan motor uses to operate. It is directly related to the amount of air flow that the fan produces. The higher the amperage draw, the more power the motor is using, resulting in increased air flow.

2. How does adjusting the VFD fan speed affect amperage draw and air flow?

Adjusting the speed of a VFD fan can have a significant impact on both amperage draw and air flow. As the speed of the fan decreases, so does the amperage draw, resulting in lower energy consumption. However, the air flow will also decrease as a result of the slower fan speed.

3. Is there a specific ratio between amperage draw and air flow in a VFD fan?

There is no specific ratio between amperage draw and air flow in a VFD fan, as it can vary depending on factors such as the type of motor and fan, the speed setting, and the load on the fan. It is important to consult the fan manufacturer's specifications for the specific amperage draw and air flow relationship for a particular fan.

4. What is the impact of increasing the amperage draw in a VFD fan?

Increasing the amperage draw in a VFD fan will result in higher energy consumption and increased air flow. However, it is important to ensure that the VFD and fan are capable of handling the increased amperage to avoid damaging the motor or electrical system.

5. Can amperage draw and air flow in a VFD fan be controlled independently?

Yes, amperage draw and air flow in a VFD fan can be controlled independently by adjusting the speed and load settings. This allows for greater flexibility and energy efficiency in managing the operation of the fan.

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