thread403-437658 In my current pro

[smali1]

thread403-437658
In my current project, builder has removed the partition wall between staircase / lobby ventilation shaft and plumbing shaft to make it a single shaft. Basically, they have increased the masonary shaft which is serving the staircase pressurization, before this shaft was split between HVAC and PLM. Now they have removed the partition wall and asking us to check whether increasing the shaft will have an effect on ventilation fans. I would greatly appreciate any potential advice related to this matter.

 

[LittleInch]

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[smali1]

@LittleInch..I will send you requested details but can you please advise how much minimum velocity is acceptable in the shaft. I have attached the comparison table.

 

[smali1]

I would greatly appreciate if anybody provide technical advice on this matter.

 

[Snickster]

If I understand you correctly you are combining a smaller plumbing chase with a larger ventilation shaft/plenum. Since you are slightly increasing the flow area then the most that can happen is that the flow of the fans will increase due to a reduction of pressure drop in the shaft due to the increase in flow area.

 

[smali1]

@Sincker...Yes you understood it correctly. As per attached spread sheet, With a shaft velocity reduced to 1.2 m/s, the airflow delivered to the lobby is even slower as compared to the original scenario. This lower velocity may impact the system's ability to maintain the required pressure difference between the protected areas (lobby) and the fire-affected zones. The reduced air velocity in the duct might make it more challenging to effectively counteract pressure changes and smoke infiltration during intense fire conditions. If the system cannot deliver sufficient airflow quickly enough, it may struggle to maintain the desired pressure differential, potentially allowing smoke to enter the protected areas (lobby).

However, I am not yet able to confidently confirm whether such lower shaft velocities will pose real issues during a fire. If anybody has experienced similar scenerio and it has effected the lobby pressurization, please share the experience.

 

[Snickster]

I would need to understand the configuration of the entire system to understand any negative effects on reducing the velocity in the supply shaft. However it seems to me that the flowrate is not decreased and maybe even increased, it is just that the velocity in the supply air plenum is decrease.