CRG
Mechanical
- Sep 28, 2002
- 512
I need two very small centrifugal fans. The problem is that I require explosion proof motors and need two speeds. One fan requires 50 cfm (4 ACH) continuously and 150 cfm (12 ACH) on high. The other fan requires 150 cfm (4 ACH) continuously and 450 cfm (12 ACH)on high. The fans need to be AMCA Type B.
The last time I had a similar problem, I used two fans for each skid where one fan ran continuously and when the LEL raised to 20%, the second fan was started. It made sense then because the required air flow was about 5 times greater.
The air flows this time are small; however, there are about 9000 heating degree days per year here. One solution might be to have 12 ACH continuously. I question the economics of that but I did not do the math.
I could use VFD drives to be able to use one fan per skid, but I suspect that it would cost way more when factoring in the electrical issues/costs.
The other possibility is to use an automated damper to open if/when I require 12 ACH. I could adjust/block the damper to remain partially open for the continuous 4 ACH.
Do any of you have a suggestion of the best way manage the required outside air?
The last time I had a similar problem, I used two fans for each skid where one fan ran continuously and when the LEL raised to 20%, the second fan was started. It made sense then because the required air flow was about 5 times greater.
The air flows this time are small; however, there are about 9000 heating degree days per year here. One solution might be to have 12 ACH continuously. I question the economics of that but I did not do the math.
I could use VFD drives to be able to use one fan per skid, but I suspect that it would cost way more when factoring in the electrical issues/costs.
The other possibility is to use an automated damper to open if/when I require 12 ACH. I could adjust/block the damper to remain partially open for the continuous 4 ACH.
Do any of you have a suggestion of the best way manage the required outside air?