Parallel fans in same ducting system

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Discussion Overview

The discussion centers around the operation of two parallel fans within a mechanical ventilation (MV) ducting system, specifically addressing the implications for airflow when both fans are used simultaneously. The scope includes technical explanations of airflow dynamics and fan performance characteristics.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether running both fans simultaneously would result in a total airflow of 14000cmh.
  • Another participant asserts that the total airflow would not simply double and emphasizes the importance of understanding the flow versus pressure relationship.
  • A further contribution suggests that if there is an increase in pressure due to the fixed ducting system, the flow increase might be approximately 1.4 times, noting that fan performance varies and may deviate from ideal conditions.
  • Another participant seeks clarification on the meaning of "mv" and inquires about managing airflow between the duty and standby fans.
  • A participant clarifies that "mv" stands for Mechanical Ventilation.

Areas of Agreement / Disagreement

Participants express differing views on the airflow outcomes when operating both fans, indicating that the discussion remains unresolved regarding the exact airflow increase and the factors influencing it.

Contextual Notes

The discussion highlights the complexity of fan performance characteristics and the potential impact of ducting system constraints on airflow, with no consensus on the exact relationship between pressure and flow in this scenario.

KingMan
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Currently, I have a mv fan ducted system with two fans in parallel, one duty and standby (each with 7000cmh).
If I were to run both fans at the same time, do I get 14000cmh in total?
 
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KingMan said:
If I were to run both fans at the same time, do I get 14000cmh in total?
No. You must study the flow versus pressure relationship first.
The two fans will only double the flow if there is no increase in pressure when the two fans are operated together.
 
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...if there is an increase in pressure due to having a fixed/the same ducting system the flow increase may be somewhere near 1.4x. I say "may be somewhere near" because fan performance follows a characteristic curve that is different for every fan, and may stray from the ideal.
 
Welcome!
What "mv" stands for?
How do you keep the airflow produced by the duty fan from going through the standby fan?
 
MV = Mechanical Ventilation.
 
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