Return Ducts
Return Ducts
(OP)
This may be a stupid question, but it bugs me: Are return ducts ALWAYS under negative pressure? I must have been taught some simplistic thinking that air moving towards the fan is negative; hence, it is under negative pressure. And yet, trying to picture a return duct under positive pressure just doesn't sit with me right.
I know...it's my upbringing!
- Curiously George
I know...it's my upbringing!

- Curiously George





RE: Return Ducts
You can also have positive return duct by hooking an inline fan to it. When Bag in Bag out HEPAs are used to tackle contamination issues in Pharmaceuticals, the return air fan is a must and the return duct of main AHU after inline fan becomes positive.
Regards,
RE: Return Ducts