STAIRCASE PRESSURIZATION SYSTEM
STAIRCASE PRESSURIZATION SYSTEM
(OP)
We are using stair case pressurization system in one of our sub station project. The capacity of fan is calculated by assumimg that one door(ground floor-opening outwards) is opend and the other door (first floor-opening inwards) closed and to maintain 15 pa inside the stairwell. But when both doors are closed pressure is building up inside the space and we are facing difficulty in opening the first floor door. How can we design a relief damper to maintain a pressure of 50 pa inside thee stairwell when both door are closed.





RE: STAIRCASE PRESSURIZATION SYSTEM
RE: STAIRCASE PRESSURIZATION SYSTEM
The stairwell undergoes changes in pressure in fractions of seconds as doors open and shut during normal operation or during egress. In systems that are maintaining pressure in the right range, say 50 Pa, one door opening will drop that pressure to 15 Pa (give or take), a second door will drop it more. Then both doors shut, and stair pressure is instantly 50 Pa again. If you try to incorporate an HVAC control to respond to this type of rapid fluctuation, you would likely need to use a mechanical response, such as by a spring-loaded or gravity relief. Using electronically controlled dampers and fan variable speed drives will likely not have the response time required. Tuned to operate at that speed, wild setpoint hunting could result.
Re-sheave the fans and adjust stairwell door sweeps to achieve the 50 Pa pressure with the doors shut. Accept the fact that the system will not be at that pressure with doors open, but air flow will still be in the proper direction.
The following is from the Engineered Systems magazine archives and gets into some problems I've found in commissioning these systems and proposed resolutions. See the "description/problem/resolution" section. Some of this advice might help from a design perspective.
http://www.esmagazine.com/es/cda/articleinformation/coverstory/bnpcoverstoryitem/0,2500,65962,00.html
RE: STAIRCASE PRESSURIZATION SYSTEM
Add air to the stairs every other floor.
Be sure the contractor has sealed the stairwell. If the doors do not have seals you can blow a lot of air and not get the pressure needed.
RE: STAIRCASE PRESSURIZATION SYSTEM
Fantastic answers! Ones for my technical Scrap book.
Paul/Goorah
Buddha's advice 2,500 yrs ago (I'm Christian!!???!!): "After deep, careful observation/analysis; and it agrees with reason, is conducive to the common good: accept it and live up to it."
RE: STAIRCASE PRESSURIZATION SYSTEM
RE: STAIRCASE PRESSURIZATION SYSTEM
Of doors are open. The flow rate of air into the stairwell is varied by modulating bypass dampers, which are controlled by one or more static pressure sensors that sense the pressure difference between the stairwell and the building.
When all the stairwell doors are closed, the pressure difference increases and the bypass damper opens to increase the bypass air and decrease the flow of supply air to the stairwell. In this manner, excessive stairwell pressures and excessive pressure differences
between the stairwell and the building are prevented.