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A two-pipe system uses half the hydronic piping required by a four-pipe system, which results in a lower cost and a shorter installation time. The systems are also more compact that reduce the space requirements of mechanical rooms. Maintenance is also simpler in a two-pipe system, thanks to the reduced number of piping fixtures and valves.

Two-Pipe Pros

  • Great for Condos, Apartments and Hotels.
  • Less Expensive to Install Than a Four-Pipe System.
  • Reasonably Energy Efficient.
  • Simple Design.

Two-Pipe Cons

  •  Cannot Simultaneously Heat and Cool.
  •  Must Be Manually Switched from Heating to Cooling and Vice-Versa.
  •  Seasonal Temperature Fluctuations May Leave the Building Uncomfortable.

Four-Pipe HVAC System

This system configuration uses twice as much piping as a two-pipe HVAC system, and thus it is more expensive and takes longer to install. In addition, a four-pipe system requires more space to accommodate two hydronic piping circuits that run through the building. The increased number of fixtures, valves and connection points also results in a more demanding system in terms of maintenance.

Four-Pipe Pros

  • Can Heat and Cool at the Same Time.
  •  Can Be Customized to the Building.
  •  No Need to Manually Switch the System.

Four-Pipe Cons

  • More Expensive to Install than a Two Pipe System.
  • Can Be More Expensive to Maintain.
  • Proper Calibration is Essential to Maintain Energy Efficiency.

Three-Pipe HVAC System (VRF System)

  • The 3 pipe Heat Recovery system is the equivalent of a 4-pipe chilled water system.
  •  A Heat Recovery system has the ability to provide simultaneous heating AND cooling.
  •  When both heating and cooling occur simultaneously, system and building energy can be better utilized.
  • When demand is met by an indoor unit the unit will work on fan only or the fan will cycle on/off until demand returns.

Rohan Kuldhar is a Project Sales Engineer at Fusion HVAC Solutions Pvt Ltd. He possesses a BE Mechanical degree.

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