Fixture / Load Node / Fire Node

Overview

This guide covers key Node Properties in your plumbing design, including Pressure, Dead Legs, Flow Rate, Fixture Units, and Fire Node settings. Understanding these properties helps ensure accurate system sizing and efficient operation.

Pressure is a fundamental aspect of plumbing design. Two key pressure measurements are Residual pressure and Static pressure.

Residual Pressure

Residual Pressure is the water pressure available at a Fixture after accounting for Pressure Losses in the system.

Factors Influencing Residual Pressure:

  • Upstream Pressure Sources: The initial pressure provided by Flow Sources or Tanks.

  • Pressure Losses: Resistance caused by Pipes, Valves, Fittings, Equipment, and Height Differences.

  • Pressure Reduction Valves: These components can significantly lower pressure at certain parts of the system.

  • Booster Pumps: These add pressure to the system, increasing Residual Pressure downstream.

Troubleshooting Residual Pressure:

Step-by-step

  1. Verify the Flow Source Properties for correct Pressure and Height.

  2. Check Levels and Elevation Differences for accuracy.

  3. Review the Index Node Path for pressure loss areas.

  4. Use Heat Maps to find regions with unexpected Pressure Drops.

  5. Analyze the Design Report for anomalies in Pressure Drop or Flow Rates.

Static Pressure

Static Pressure is the pressure at a Fixture due to elevation differences alone, irrespective of water flow.

Factors Influencing Static Pressure:

  • Height Differences: Variations in elevation between the Fixture / Node and other components.

  • Flow Source: The Static Pressure and Height provided at the Flow Source.

  • Pressure Reduction Valves: These Valves may reduce the Static Pressure in certain parts of the system.

Troubleshooting Static Pressure:

Step-by-step

  1. Check the Height of Pipes and connections to Equipment to ensure they are accurately represented in the design.

  2. Verify the Properties of Flow Sources to confirm they provide the correct Static Pressure and elevation.

  3. Review Levels and Elevation Differences to ensure they are correctly input and aligned with the system design.

Dead Legs

A Dead Leg is a section of Pipe where water stagnates. This can lead to Bacterial Growth and other water quality issues. Managing dead legs is crucial for system hygiene.

Dead leg length is measured from the recirculation main to the furthest fixture. Dead leg volume describes the internal volume of the dead leg.

For Recirculating Systems (e.g., hot water):

  • The Volume is calculated as the Internal Pipe Area multiplied by the Length between the recirculating Pipe and the Fixture.

For Non-Recirculating Systems (e.g., cold water):

  • The Volume is calculated as the Internal Pipe Area multiplied by the Length between the Fixture and the nearest Pipe supplying other Fixtures (common pipe).

Troubleshooting Dead Leg Volume:

  • Verify the Pipe's Internal Diameter along the dead-leg route.

  • Verify the Length of each Pipe along the dead-leg route.

Dead Leg Volume Formula:

TPiV = ฯ€ ร— (Internal Diameter รท 2)ยฒ ร— Length

Where:

  • TPiV = Total Pipe Volume

  • Internal Diameter = The internal diameter of the pipe (consistent units, e.g., mm or in)

  • Length = The length of the pipe (consistent units, e.g., m or ft)

Dead Leg Length

Dead Leg Length represents the Length of Pipe segment that is not actively circulated.

For Recirculating Systems (e.g., hot water):

  • The Length is calculated between the recirculating Pipe and the Fixture.

For Non-Recirculating Systems (e.g., cold water):

  • The Length is calculated between the Fixture and the nearest Pipe supplying other Fixtures (common pipe).

Troubleshooting Dead Leg Length:

  • Verify the Length of each Pipe along the dead-leg route.

Dead Leg Wait Time

Dead Leg Wait Time is the time it takes for water in the dead leg to be cleared at the Fixture, calculated as the dead leg volume divided by the Fixture's Peak Flow Rate.

Troubleshooting Dead Leg Wait Time:

Step-by-step

  1. Verify the Dead Leg Volume.

  2. Confirm the Peak Flow Rate matches the Fixture/Loading Units and conversion from your Peak Flow Rate Calculation Method.

Flow Rate and Fixture Units

Flow Rate and Fixture units are essential for sizing Pipes and other system Components correctly.

Troubleshooting Flow Rate:

Step-by-step

  1. Open the Node settings to verify the inputs are correct.

  2. Check the Properties of the Node to ensure it hasn't been Overridden.

  3. Verify the total Loading Units against the Peak Flow Rate Calculation Method and its associated Diversification settings.

Fixture Units

Fixture Units represent the total Fixture/Loading Units assigned to the Node, summing all connected Fixtures.

Troubleshooting Fixture Units:

Step-by-step

  1. Check the Node in Settings to verify the Fixtures connected are correct

  2. Check the Properties of the Node to ensure it hasn't been Overridden

  3. Verify the total Loading Units against the Peak Flow Rate Calculation Method and its associated Diversification settings

Maximum Simultaneous Operated Nodes

This value defines the maximum number of Fire Nodes that are designed to operate simultaneously. For example, only two Fire Hydrants may be designed to operate simultaneously, even if the system includes 10.

Troubleshooting Maximum Simultaneous Operated Nodes:

  • Review the Node type in the Settings to confirm the simultaneous operation limit.

  • Review the Properties of each Fire Node to ensure the correct Node has been used and the Properties haven't been Overridden.

Pressure Drop Through (Fire) Node's Kv Value

The Pressure Drop through a fire node is calculated using its Kv value, which represents the flow resistance of the Node. This value is determined by the Velocity through the Node and is defined in its Properties.

Troubleshooting Pressure Drop Through Kv Value:

  • Check the Node's Kv value in its Properties to ensure it aligns with design requirements.

  • Verify that the Flow Rate and associated Velocity on the Pipe connecting to the Node match system specifications.