Recent content by Haotranphotomask

I was more worried if one fan fails, air blown from the running fan would travel through the failed fans into the rooms. I have plans to redesign the entire duct work. I am trying to find short-term solutions. I may try to adjust the VFDs as suggested.

Hello, I have a system where two exhaust fans are running simultaneously. However, they both discharge to the same outlet. The suction pressure seems to be quite stable, but the discharge pressure fluctuates between 2" wc to 4" wc frequently. Below is a rough setup of my system. The rectangles...

Hello, I need some help determining what this piece of equipment is. It is currently attached to the inlet of my exhaust fan and controlled by some electrical signal. I am thinking it may be a pressure relief damper, but not sure if I am correct. I could not find any nameplate/set point for the...

About -5.5" WC at the inlet and 0.5" WC at the discharge. I am not sure I can answer that question. The fan design was like this when I started this project and the OG engineer left without much details. Yes, the damper is closed when one fan is running.

Sorry for the confusion. The inlet consists of 200 ft of 8" piping, then expanding tee to 20 ft of 12" piping, and then reduce to 8" to tie into the inlet of the fans. The discharge is another 20 ft of 12" piping.

I am measuring the SP at the red circles. The green circle is a backdraft damper. I don't think the pressure drop through that damper is significant. There is about 20ft of 12" piping on the inlet. But the remaining 8" piping totals up to 200 ft. The inlet ports consist of 1 ft of 3"-5" pipes.

Yeah when I got the measurements, I was very confused. I am thinking it is due to the 8" trunk being restrictive. I cannot figure out what the problem could potentially be.

I was able to measure the rotation of the fan. Motor pulley size: 5.25” Fan Pulley size: 3.75” Center-to-Center: 13.5” The RPM on motor pulley: 1920 RPM The RPM on fan pulley: 2727 RPM The static pressure is ~6”WC, but we are only getting 1050 CFM of flow through with one fan. I was able to...

Yeah it is the tachometer I was talking about. Thank you for this information! I was not focusing on the fan RPM.

I have not measured the actual RPM of the motor. We just ordered a manometer for this purpose. Hopefully we will receive it soon. There is one thing I have not considered. Do I have to factor in the motor efficiency? The nameplate has a motor efficiency of 89.5%. Does that mean that the motor...

The current fan curve I have is for the old system. The manufacturer has not been quite responsive about providing new fan curves.

That configuration is nearly impossible, as how far the fan was built from the tool. The actual static pressure measured is ~5.5 inWC @ 950 CFM. So using the equation you provided, we may need an increased motor for 10 inWC @ 1300 CFM.

Oh these are helpful!

We have a tool that requires 1300 CFM of exhaust that was previously tied to another exhaust system. They were running into problem with that system, so they decided to move that tool's exhaust trunk to the fans (the fans in this thread, one of them is a spare) that are abandoned in place. The...

Thank you everyone for the information. This is the first time I work on an exhaust system, so I have not considered a lot of the information given on here. They were really helpful. Just to give a bit of history: The blowers were previously designed to flow 1500 CFM at 4"WC (based on...