Lab exhaust fan control
Lab exhaust fan control
(OP)
Guys
I am designing a lab ventilation system which uses active pressure control by modulating exhaust volume from each rooms.The exhaust is discharged through a high plume exhaust fan to maintain a discharge velocity of 3000 fpm.There is a bypass damper at the fan inlet to maintain the discharge velocity constant when the room exhaust volume varies due to operational requirements and night setbacks.HEPA filters are provided in the room exhaust duct.I am not sure how to control the fan as the HEPA filters load.I think the bypass damper air flow will go on increasing as the HEPA filters load thereby reducing the room exhaust flow rate.What is the best way to control this system ?Please note that the fan exhaust volume needs to be kept constant to maintain the discharge velocity 3000 fpm.





RE: Lab exhaust fan control
RE: Lab exhaust fan control
That I've caught.
In connection with a condition that you want to ensure
constant flow of exhaust air by means of baypass you will take a part of air passing HERA filters.
In such case it will result in incorrect work of these filters.
Concerning control of the damper I can offer the following
variant. On the side of an output fan duct to cut the
sensor of pressure. At downturn of pressure, PID-controller
develops a signal on opening of baypass' damper.
Regards,
fs
RE: Lab exhaust fan control
RE: Lab exhaust fan control
Many thanksfor your post.I have been advised that the most simple way to control this system is by static pressure control in the fan suction plenum by modulating the bypass damper.Any comments on this suggestion?
RE: Lab exhaust fan control