HVAC Pipe Sizer - Gas Low Online Help

The HVAC Pipe Sizer - Gas Low application allows you to quickly size a simple low (less than or equal to 1.5 psi) pressure gas piping system by inputting a number of piping and gas properties.

The HVAC Pipe Sizer - Gas Low application allows you to quickly size a simple low (less than or equal to 1.5 psi) pressure gas piping system by inputting a number of piping and gas properties. This is a universal app that works on both the iPhone and iPad and adjusts its screen accordingly.

This help is mainly geared toward the iPhone version of the HVAC Pipe Sizer - Gas High app, but all of the input explanations also apply to the iPad version.

Quick Start

The following is a list of hints and suggestions to quickly get started using the "HVAC Pipe Sizer - Gas Low" application:
  1. Size pipe by low pressure gas flow: When the application first opens, select the "Low Pressure Gas Pipe (By Flow)" option to open the screen that allows you to specify the total gas flow in ft^3/hr or m^3/hr and one of either pressure drop, velocity, or diameter to display the resulting exact and nominal pipe diameters and remaining properties.
  2. Nominal Pipe Sizing: The Pipe Sizer application includes nominal pipe sizing tables for a subset of all the pipe material types included with this application. Therefore, results for some pipe material types that don't have nominal pipe sizes will display "N/A" under the "Nominal" results column.
  3. Pipe Fitting Equivalent Lengths: The Pipe Sizer application includes fitting equivalent length tables for 11 different fitting types and a limited number of pipe material and connection types. Please see the section titled "Explanation of the Pipe Sizer Formulas" at the end of this help for more details.
  4. Moving the slider control indicator: If you are having trouble moving the little circle (indicator) on any of the slider controls, lightly tap the indicator twice with your finger, and it will "catch" allowing you to slide it to the left or right.

Overview

When you first open the Pipe Sizer application, you will see 3 tabs at the bottom of your screen:
  1. The "Pipe Sizer" tab displays the first screen that appears when you start up the application and allows you to size piping.
  2. The "Global Settings" tab allows you to specify global settings such as whether to use english (imperial) or metric units. Please read the "Global Settings" section below for more details.
  3. The "Help" tab displays this help screen.

Pipe Sizer Tab

This tab automatically appears when you first start the Pipe Sizer application. Two selections appear at the top of the device screen:
  1. Low Pressure Gas Pipe (By Flow): Select this row to open the input screen that allows you to specify total gas flow rate and one of either pressure drop, velocity, or pipe diameter parameters. By specifying any two of these parameters, the app will calculate other relevant results including total equivalent pipe length. For example, if you specify a gas flow amount in ft^3/hr and a pressure drop value in in. wg, the total gas velocity, pipe diameter, and total equivalent pipe length will be calculated. See the section titled "Low Pressure Gas Pipe (By Flow) - Inputs" below for more details.
  2. Low Pressure Gas Pipe (By Dia): Select this row to open the input form that allows you to specify the pipe diameter and one of either velocity or pressure drop parameters to calculate total gas flow rate other relevant results. For example, if you specify an internal pipe diameter and a pressure drop value in in. wg of pipe, the total gas flow rate, velocity, and total equivalent pipe length will be calculated. See the section titled "Low Pressure Gas Pipe (By Dia) - Inputs" below for more details.

Low Pressure Gas Pipe (By Flow) - Inputs

Select this row to open the form that allows you to select the gas flow in ft^3/hr (m^3/hr) and either the pressure drop in in. wg (Pa), the pipe internal diameter in inches (centimeters) or the velocity of gas in feet/second (meters/second). This form is appropriate for sizing new piping systems. The following is an explanation of each of the input controls:
  1. Gas Flow (ft^3/hr or m^3/hr) Textbox: You can input the gas flow value in ft^3/hr (m^3/hr) directly into this textbox. When you tap within this textbox, a keyboard will pop up allowing you to type in a value. Press the 'Done' button on the keyboard to hide it and register the value (Note that this keyboard appears when you tap within any of the active input textbox controls.). The results will automatically update based upon your newly inputted gas flow value. You can input a maximum value that appears on the slider control just below this textbox. If you input a value that is greater than the maximum value, then it will be substituted with this maximum value. Read the section titled "Additional Pipe Inputs" for ways to increase or decrease the maximum allowable gas flow input.
  2. Gas Flow Slider: This slider control allows you to easily change the gas flow value by using your finger to slide the indicator to the left or right. As you slide the indicator along this control, the results will immediately update. Depending upon the step value that you specified in the "Additional Pipe Settings" (see below), it will determine how much the value increases/decreases as you move the indicator. A value of 0 is continuous. Also, the value represented by the position of the indicator on the slider control will appear in the gas flow textbox discussed above. The maximum allowable value for the slider control is displayed at the far right. You can change this value in the "Additional Pipe Inputs" form described below.
  3. Pressure Drop/Diameter/Velocity Selector: This selector allows you to specify which type of value to input into the textbox discussed in #4 below. If you select "Pressure Drop", you are able to input the pressure drop in in. wg (Pa). If you select "Diameter", you are able to input the internal pipe diameter in inches (centimeters). If you select "Velocity", you are able to input the gas velocity in feet/second (meters/second). The units are displayed to the right of the text box. In addition, the slider control described in #5 below will update.
  4. Pressure Drop/Diameter/Velocity Textbox: This textbox allows you to input a pressure drop, diameter, or velocity value depending upon the selection made in the control described in #3 above. The results will automatically update based upon your newly inputted value. You can input a maximum value that appears on the slider control just below this textbox. If you input a value that is greater than the maximum value, then it will be substituted with this maximum value. Read the section titled "Additional Pipe Inputs" for ways to increase or decrease the maximum allowable value.
  5. Pressure Drop/Diameter/Velocity Slider: This slider control allows you to easily change the pressure drop, diameter, or velocity value by using your finger to slide the indicator to the left or right. As you slide the indicator along the control, the calculated results will immediately update. Depending upon the step value that you specified in the "Additional Pipe Settings" (see below), it will determine how much the value increases/decreases as you move the indicator. A value of 0 is continuous. Also, the value represented by the position of the indicator on the slider control will appear in the pressure drop/diameter/velocity textbox discussed above. The maximum allowable value for the slider control is displayed at the far right. You can change this value in the "Additional Pipe Inputs" form described below.

Low Pressure Gas Pipe (By Flow) - Results

The calculated results are immediately updated as you change values in any of the controls discussed above. Two columns of results are displayed. The column labeled "Calculated" contain results that are precisely calculated without any nominal pipe dimensions involved. However, since most pipes are manufactured to nominal sizes, the "Nominal" column of data is displayed. This column contains dimensions that are rounded to the nearest nominal pipe dimension. These nominal dimensions are derived from tables that take into account the pipe material type and internal pipe diameter. The resulting pressure drop and velocity values are also updated. The following is an explanation of all of the result values:
  1. Nominal Pipe Dia: This result displays the nominal pipe diameter for the particular pipe material type and internal pipe diameter. Only the "Nominal" column contains a value while the calculated column will always display "N/A".
  2. Internal Pipe Dia (in or cm): Under the "Calculated" column, this result displays the calculated (or selected) internal pipe diameter. Under the "Nominal" column, it displays the actual internal diameter of the nominal pipe.
  3. Velocity (ft/s or m/s): This result displays the selected or calculated gas velocity for the calculated and nominal pipe sizes
  4. Pressure Drop (in. wg or Pa): This result displays the selected or calculated pipe pressure drop for calculated and nominal pipe sizes.
  5. Equivalent Pipe Length (ft or m): This result displays the total feet (or meters) of pipe taking into account the actual length of the pipe and the equivalent length of any fittings.

Low Pressure Gas Pipe (By Diameter) - Inputs

Select this option to open the form that allows you to select the pipe diameter in inches (cm) and one of either pressure drop in in. wg (Pa) or gas velocity in feet/s (m/s). This input mode is appropriate for analyzing existing piping systems. The following is an explanation of each of the input controls in this mode:
  1. Internal Pipe Diameter (in or cm) Textbox: This textbox allows you to input the internal pipe diameter value in inches (centimeters). The calculated results will automatically update based upon your newly inputted value. You can input a maximum value that appears on the slider control just below this textbox. If you input a value that is greater than the maximum value, then it will be substituted with this maximum value.
  2. Pipe Diameter Slider: A slider control appears below the textbox described above. It allows you to easily change the diameter by using your finger to slide the indicator to the left or right. As you slide the indicator along the control, the results will immediately update. Depending upon the step value that you specified in the "Additional Pipe Settings" (see below), it will determine how much the value increases/decreases as you move the indicator. A value of 0 is continuous. Also, the value represented by the position of the indicator on the slider control will appear in the diameter textbox just above it. The maximum allowable value for the slider control is displayed at the far right. You can change this value in the "Additional Pipe Inputs" form described below.
  3. Pressure Drop/Velocity Selector: This selector allows you to specify which type of value to input into the textbox discussed in #4 below. If you select "Pressure Drop", you are able to input the pressure drop in in. wg (Pa). If you select "Velocity", you are able to input the gas velocity in feet/second (meters/second). The units are displayed to the right of the text box. In addition, the slider control described in #5 below will update.
  4. Pressure Drop/Velocity Textbox: This textbox allows you to input a pressure drop or velocity value depending upon the selection made in the control described in #3 above. The results will automatically update based upon your newly inputted value. You can input a maximum value that appears on the slider control just below this textbox. If you input a value that is greater than the maximum value, then it will be substituted with this maximum value. Please read the section titled "Additional Pipe Inputs" for ways to increase or decrease the maximum allowable pressure drop/velocity input.
  5. Pressure Drop/Velocity Slider: This slider control allows you to easily change the pressure drop or velocity value by using your finger to slide the indicator to the left or right. As you slide the indicator along the control, the calculated results will immediately update. Depending upon the step value that you specified in the "Additional Pipe Settings" (see below), it will determine how much the value increases/decreases as you move the indicator. A value of 0 is continuous. Also, the value represented by the position of the indicator on the slider control will appear in the pressure drop/velocity textbox discussed above. The maximum allowable value for the slider control is displayed at the far right. You can change this value in the "Additional Pipe Inputs" form described below.

Low Pressure Gas Pipe (By Diameter) - Results

The calculated results are immediately updated as you change values in any of the controls discussed above. Two columns of results are displayed. The column labeled "Calculated" contain results that are precisely calculated without any nominal pipe dimensions involved. However, since most piping is manufactured to nominal sizes, the "Nominal" column of data is displayed. This column contains dimensions that are rounded to the nearest nominal pipe diameter. These nominal diameters are derived from tables that are based upon the pipe material type an the internal pipe diameter. The resulting pressure drop and velocity values are also updated. The following is an explanation of all of the result values:
  1. Nominal Pipe Dia: This result displays the nominal pipe diameter for the particular pipe material type and internal pipe diameter. Only the "Nominal" column contains a value while the calculated column will always display "N/A".
  2. Gas Flow (ft^3/hr or m^3/hr):The same gas flow value in ft^3/hr (m^3/hr) is displayed under both the "Calculated" and "Nominal" columns as the user updates the internal diameter and other properties.
  3. Velocity (ft/s or m/s): This result displays the selected or calculated gas velocity in ft/s (m/s).
  4. Pressure Drop (in. wg or Pa): This result displays the selected (or calculated) pipe pressure drop.
  5. Equivalent Pipe Length (ft or m): This result displays the total feet (or meters) of pipe taking into account the actual length of the pipe and the equivalent length of any fittings.

Additional Pipe Inputs

This screen is accessed by clicking the round button with the "i" inside it located at the top right-hand portion of both the low pressure and high pressure main input screens. The form will flip around and a number of additional pipe inputs will appear. The inputs are similar for both the low- and high-pressure input modes except for a couple of exceptions that are explained below:
  1. Gas Type: This input allows you to specify the type of gas that is flowing through the pipe. Each gas type represents a set of gas properties including heating value and gas viscosity. Select the button inside this input cell to display a new screen that allows you to select from one of the following gas types:
    1. Natural Gas
    2. Propane
    3. Miscellaneous
    As you select each gas type, the heating value and gas viscosity value will update in the text boxes below the picker control. Press the "Back" button to return to the previous form, and the newly selected gas type will appear along with the corresponding gas properties.
  2. Gas Heat Value (BTU/ft^3 or kJ/m^3): This value is automatically updated according to the gas type that you selected above. This value is for reference purposes, only, and is not used in the pipe sizing calculations.
  3. Gas Viscosity (cP): The viscosity is automatically updated according to the gas type that you selected above. It represents the gas resistance to shear or flow. You can override this value for any type of gas.
  4. Gas Temperature (F or C): This input allows you to specify the gas temperature in degrees F or C.
  5. Gas Specific Gravity: This input allows you to specify the ratio of the density of gas relative to the density of air. This is a dimensionless value.
  6. Total Length of Pipe (ft or m): This input allows you to specify the total length of pipe (not including equivalent length of fittings).
  7. Total Fitting Quantities: This input is a read-only value representing the total quantity of fittings that is inputted in the next screen that is accessed by clicking the button within this input cell. This next screen displays a list of 11 common pipe fittings, including:
    1. Regular 90 deg. ell
    2. Long Radius 90 deg. ell
    3. Regular 45 deg. ell
    4. Tee-line flow
    5. Tee-branch flow
    6. 180 deg. return bend
    7. Globe valve
    8. Gate valve
    9. Angle valve
    10. Swing check valve
    11. Coupling/Union
    Each of these fittings represents a pipe equivalent length value for certain types of pipe material types (discussed more below). These pipe equivalent lengths are added to the total pipe length to derive the total downstream pressure in feet or meters.
    You can input quantities up to 1000 for each of the listed fittings. In addition, you can specify the fitting connection type by clicking the button within each input cell to display a picker control that allows you to select either "Screwed" or "Flanged" fitting connection type. As an added feature, you can shake your device (if this functionality is activated in the "Global Settings" form) to reset all of the quantities to 0 and all the fitting connection types to "Screwed". You will be asked for confirmation prior to reset. After you have completed inputting the quantities and selecting the fitting connection types, press the "Back" button at the top of the screen to return to the previous screen. The total quantity of fittings will now display.
  8. Pipe Material: This input allows you to specify the type of pipe material. Each pipe material type represents a pipe roughness value. Select the button inside this input cell to display a new screen that allows you to select from one of the following pipe material types:
    1. Steel, Schedule 10
    2. Steel, Schedule 40 Galv.
    3. Steel, Schedule 80 Galv.
    4. Copper, Type L
    5. Copper, Type K
    6. Brass Tubing, Regular
    7. Brass Tubing, Extra Strong
    8. Other
    9. Cast Iron, Plain
    10. Cast Iron, Tar Coated
    11. Cast Iron, Cement Lined
    12. Cast Iron, Bituminous Lined
    13. Galvanized Iron, Plain
    14. Wrought Iron, Plain
    15. Concrete
    16. Cement - Asbestos
    17. Vitrified Clay
    18. Brick Sewer
    19. Plastic
    20. Fiberglass
    21. PVC (Schedule 40)
    22. PVC (Schedule 80)
    23. Copper, Type M
    As you select each pipe material type, the pipe roughness value will update in the text box below the picker control. Press the "Back" button to return to the previous form, and the newly selected pipe material type will appear along with the pipe roughness value.
    Please note that the pipe material is also important for determining the nominal pipe sizes and the fitting equivalent length values. See the "Explanation of the Pipe Sizer Formulas" section below for more information about the pipe sizing calculations.
  9. Pipe Roughness (ft or m): This input allows you to specify the pipe roughness value in feet or meters. This value is automatically updated according to the pipe material you selected above. However, you can also override this value.
  10. Max Gas Flow (ft^3/hr or m^3/hr): This input allows you to specify the maximum allowable gas flow input. After returning to the main piping input screen, the slider control will update according to the new value. You will not be allowed to specify a value greater than the maximum gas flow.
  11. Gas Flow Step Value: This input allows you to specify the increment/decrement value for the gas flow slider control. As you move the indicator along the slider control, it will increase/decrease the gas flow value by the inputted amount. For example, if you specify 10 ft^3/hr in this input, the gas flow value will increase/decrease by 10 as you move the indicator along the slider control. (Please note that when you convert from English to Metric units (or vice versa), the step units will not convert.)
  12. Max Pressure Drop (in. wg or Pa): This input only applies to low pressure gas pipe sizing. It allows you to specify the maximum allowable pipe pressure drop input. After returning to the main piping input screen, the slider control will update according to the new value. You will not be allowed to specify a value greater than the maximum pressure drop.
  13. Pressure Drop Step Value: This input only applies to low pressure gas pipe sizing. It allows you to specify the increment/decrement value for the pressure drop slider control. As you move the indicator along the slider control, it will increase/decrease the pressure drop value by the inputted amount.
  14. Max. Pipe Diameter (in or cm): This input allows you to specify the maximum allowable pipe diameter input. After returning to the main piping input screen, the slider control will update according to the new value. You will not be allowed to specify a value greater than the maximum pipe diameter.
  15. Pipe Diameter Step Value: This input allows you to specify the increment/decrement value for the pipe diameter slider control. As you move the indicator along the slider control, it will increase/decrease the pipe diameter value by the inputted amount.
  16. Max Velocity (f/s or m/s): This input allows you to specify the maximum allowable gas velocity input. After returning to the main piping input screen, the slider control will update according to the new value. You will not be allowed to specify a value greater than the maximum gas velocity.
  17. Velocity Step Value: This input allows you to specify the increment/decrement value for the velocity slider control. As you move the indicator along the slider control, it will increase/decrease the velocity value by the inputted amount.
As an added feature, you can shake the device and the values in this form will reset to the initial settings that existed when you first installed the Pipe Sizer application. You will be asked for confirmation prior to reset. This feature can be disabled in the "Global Settings" form discussed below.

To return to the main piping input screen, click the button at the top right of the screen, and the form will "flip" over revealing the main piping inputs.

Global Settings Tab

This screen can be accessed by selecting the "Global Settings" tab on the home-page screen that first appears when you start the Pipe Sizer application. The following is an explanation of each of the inputs:
  1. Display Units: This selector allows you to specify whether to display all values in English (Imperial - IP) or Metric (SI) units. When you return to the main piping input screen, all values will reflect the new units.
  2. Where to Display Results on Screen: This selector allows you to specify where to display the calculated results on the device screen. You can display them at the top or the bottom. When you run the program for the first time, the inputs will appear at the botom of the screen and the results will appear at the top.
  3. Shake Device to Reset Values: This selector allows you to specify whether to activate the device "shake" (or accelerometer) functionality in two of the input screens of the Pipe Sizer application:
    1. By shaking the device in the "Additional Pipe Inputs" screen, you can reset the values to the initial settings that existing when you first installed the Pipe Sizer application. You will be asked for confirmation prior to reset.
    2. By shaking the device in the "Total Fitting Quantities" screen, you can reset the quantities to 0 and fitting connection types to "Screwed". You will be asked for confirmation prior to reset.
  4. Copy Values Between Calc. Modes: This selector allows you to specify whether the input/output values are copied between the 2 different input modes (By Gas Flow or By Diameter). If you specify "Yes", the outputs from one mode will be copied to the inputs of the other mode and vice versa. This is useful for doing simple "what-if" analysis. Specify "No", if you want each input mode to maintain separate values.
  5. Digit Group Separator (Thousands Separator): This selector allows you to specify whether a thousands separator (ie - a comma - "1,000.00") should be utilized in all the input and output values. Specify "On" to include it, and "Off" to not include it. This option is important for international users of this application, where a comma is often not used as a digit separator.

Explanation of the Pipe Sizer Formulas

The formulas used to calculate the piping results are derived from the ASHRAE Handbook of Fundamentals and other gas pipe sizing related texts. We use iterative techniques to provide the most accurate results as possible.
Pipe Fitting Equivalent Lengths
The pipe fitting equivalent length tables that come with the Pipe Sizer app are only for steel and cast-iron piping. In addition, they only accomodate sizes up to a maximum of 24" diameter for flanged connections (less for screwed). For pipe material types other than steel and cast-iron, no equivalent lengths will be calculated.
Nominal Pipe Sizes
The nominal pipe sizing tables that come with the Pipe Sizer app are for the following pipe material types, only:
  1. Steel, Schedule 10
  2. Steel, Schedule 40 Galv.
  3. Steel, Schedule 80 Galv.
  4. Copper, Type L
  5. Copper, Type K
  6. Brass Tubing, Regular
  7. Brass Tubing, Extra Strong
  8. Cast Iron, Plain
  9. Cast Iron, Cement Lined
  10. PVC (Schedule 40)
  11. PVC (Schedule 80)
  12. Copper, Type M

In addition, the maximum nominal sizes vary for each pipe material type with the maximum being 24" for several types. For pipe material types other than those listed above, no values will be displayed in nominal diameter results text boxes.

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