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  • GAS PRESSURES LP vs NATURAL GAS - CONTENTS: LP & Natural Gas Pressures, What are the typical pressures found in LP gas or Propane Gas systems. What are the typical pressures found in natural gas systems. Natural gas, Propane, and LP gas piping & regulator pressures. Natural gas, propane, and LP gas gas pressures at appliances
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LP or Propane Gas Pressures & Natural Gas Pressures at common appliances:

Here we give the standard pressure ranges and pressure settings for LP gas, propane gas, and natural gas fuels, including pressures found in the distribution service piping, in the in-building gas piping, and at gas fired appliances such as gas stoves, clothes dryers, furnaces, boilers, and LP gas or natural gas fired water heaters.

What are the common operating pressures of natural gas and LP or "liquid petroleum" gas in the building gas piping and at the appliance? Since there several ways that people express gas pressures we include more than on description of common LP gas or natural gas system operating pressures in this article.



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What are the Typical LP or Natural Gas Set Pressures Found in Residential Systems

Article Series Contents

Natural Gas Appliance Operating Pressures in WC, millibars, Pascals, PSI or ounces of pressure

A common operating pressure for natural gas appliances is around 7 inches of water column (WC) or re-stating this in equivalent measure, that's 14.9 millibars or 1743 Pascals or Pa, or about 0.25 psi (pounds per square inch) or about 4 ounces of pressure per square inch.
See NATURAL GAS APPLIANCE PRESSURES for details.

LP or Propane Gas Appliance Operating Pressures in WC, millibars, Pascals, PSI or ounces of pressure

A common operating pressure for liquid petroleum or LP gas appliance is 10" - 11" of water column (WC) or re-stating this in equivalent measures, that's 27.4 millibars or 2491 - 2739 Pascals or Pa, or about 0.36 - 0.40 psi or about 5.78 to 6.36 ounces of pressure per square inch.
See LPG & PROPANE APPLIANCE PRESSURES for details.

Density of Propane vs Natural Gas

From these three data points you can see that natural gas is lighter than air while propane is heavier (more dense) than air. The density of lighter-than-air gases (natural gas) inside of a closed vertical pipe will be lower at higher heights than at the base of the pipe. Some details are at GAS PRESSURE vs BUILDING HEIGHT

This article continues with more detailed information about the typical pressures and other properties of Butane or of LP gas - liquid propane or "bottled gas", and in a separate section we continue with the properties of natural gas or "piped in gas" used as appliance fuel in buildings.

Typical LP Gas Pressures & Volumes in Residential Appliances

Typically a manufacturer of a home appliance such as gas cooktop will indicate that the LP gas pressure supplied to the appliance regulator inlet cannot exceed 14" WC for LP gas. Manufacturers also say that the inlet gas presure must be at least 1" WC greater than the regulator output pressure setting.

Example Gas Cooktop Pressure Requirements

Finally, just a couple of data points as examples, again borrowing from one of Bosch's Gas Cooktop installation guides (NGM80 series using model NGM8065UC),

  1. The minimum gas supply pressure must be 1" water column (249 pa) above the manifold pressure printed on the appliance data plate
  2. The maximum gas supply pressure must not exceed 14" water column (3487 pa or 34.9 Millibars)
  3. The natural gas supply pressure for this specific appliance, your appliance may be different should be 7" water column (1744 pa) [ the instructions say 14.9 millibars which looks to me like a possible error as 14.9 millibars = about 6" of water column - ed.]
  4. The Propane or LP or LPG gas supply pressure  for this specific appliance, your appliance may be different should be 11" water column (2740 pa or 17.4 millibars)

Natural Gas pressures are described in detail
at NATURAL GAS APPLIANCE PRESSURES

It is important to separate the LP gas (propane gas) pressures that are exerted inside the LP gas storage tank or cylinder from the LP gas pressures that should be delivered to individual appliances.

Watch out: keep in mind that piped-in natural gas found at homes where that service are available will be at different pressures, use a different regulator, and requires changes or adjustment at any appliances that are being changed from LP or Propane gas to Natural gas, or vice versa.

A typical gas regulator used on appliances themselves can be converted to regulate either LP or natural gas delivery pressure in the range required by the appliance over a range of 3-15 inches of water column (WC). Some outdoor gas appliances require higher operating pressures (up to 60 psi). Details are
at CONVERT NATURAL GAS to LP GAS / PROPANE

The following example of LP, Propane, and Natural Gas appliance pressures are excerpted from that article:

Example LP Gas Range Pressure Requirements

Finally, just a couple of data points as examples, again borrowing from one of Bosch's Gas Cooktop installation guides (NGM80 series using model NGM8065UC),

  1. The minimum gas supply pressure must be 1" water column (249 pa) above the manifold pressure printed on the appliance data plate
  2. The maximum gas supply pressure must not exceed 14" water column (3487 pa or 34.9 Millibars)
  3. The natural gas pressure ** for this specific appliance, yours will be different ** should be 7" water column (1744 pa) [ the instructions say 14.9 millibars which looks to me like a possible error as 14.9 millibars = about 6" of water column - ed.]
  4. The Propane or LP or LPG gas pressure ** for this specific appliance, yours will be different ** should be 11" water column (2740 pa or 17.4 millibars)

Why do we Need a Regulator on LP or Propane Gas Systems?

Photograph of a natural gas regulator on a furnace The gas pressure delivered to a heating appliance (gas range, clothes dryer, gas heating furnace, gas fired water heater, etc) needs to be both constant and at the proper pressure for that appliance.

Because of varying outdoor temperatures, the LP gas pressure inside the storage tank may be as low as 10 psi in freezing weather or as high as 200 psi with the tank exposed to sunlight in hot weather.

And in natural gas fuel systems the gas pressure delivered from the gas main in the street can also vary widely by area, season, time of day and for other reasons.

The regulator(s) have to keep gas flowing to the appliance(s) at that pressure even as pressure in the storage tank changes and even when the number of appliances consuming gas changes (as devices turn on and off in the building).


Gas pressure and gas flow rate at individual appliances in a building needs to be maintained at the level needed by each appliance.

See GAS REGULATORS for APPLIANCES for details.

What is pressure LP or LPG "liquid petroleum" gas inside the gas tank?

This topic is now in a separate article
at LPG PROPANE TANK PRESSURES

There is some confusion, even among LP gas service technicians about just what is the pressure inside the gas containers they deliver to or fill at properties. Perhaps this is because the gas laws explain that the vapor pressure of LP-gases varies as a function of temperature.
See BOYLE's LAW discussed at this website.

Gas Cylinder or Tank Regulators: Readers concerned with installing, inspecting, or testing LP Gas regulators which are found on outdoor above ground or buried gas cylinders used for storage of LP Gas on site should also
see GAS REGULATORS for LP TANKS

Effects of Building Height or Piping Length & Diameter on Gas Delivery Flow Rates & Pressures

This topic has moved to a separate article
at GAS PRESSURE vs BUILDING HEIGHT

Articles relating height of a column of water or gas, building height, water pressure, chimney draft, gas pressure include

 

Typical Natural Gas Pressures found at Private Homes & At Appliances

The American Gas Association offers this explanation of typical natural gas pressures, Quoting with significant editing and paraphrasing:

Natural gas runs from the main into a home or business in what's called a one-inch or smaller-diameter natural gas service line. In the service line gas pressure varies by community and other factors, flowing at a pressure range of over 60 pounds to as low as ¼ pound.

When the gas passes through a customer's gas meter and moves inside the home, gas travels to equipment and appliances through piping installed by the home-builder and owned by the customer where it reaches the individual natural-gas-fired appliance(s).

At the customer's gas meter the incoming natural gas passes through another regulator to reduce its pressure to under ¼ pound (0.25 psi) if this is necessary. (Some services lines carry gas that is already at very low pressure.) This is the normal pressure for natural gas within a household piping system. When a appliance such as a natural-gas furnace or stove is turned on, the gas pressure is slightly higher than the air pressure, so the gas flows out of the burner and ignites in its familiar clean blue flame. [1]

Watch out: keep in mind that piped-in natural gas found at homes where that service are available will be at different pressures, use a different regulator, and requires changes or adjustment at any appliances that are being changed from LP or Propane gas to Natural gas, or vice versa. Details are
at CONVERT NATURAL GAS to LP GAS / PROPANE

The following example of LP, Propane, and Natural Gas appliance pressures are excerpted from that article:

Example Gas Cooktop Pressure Requirements

Finally, just a couple of data points as examples, again borrowing from one of Bosch's Gas Cooktop installation guides (NGM80 series using model NGM8065UC),

  1. The minimum gas supply pressure must be 1" water column (249 pa) above the manifold pressure printed on the appliance data plate
  2. The maximum gas supply pressure must not exceed 14" water column (3487 pa or 34.9 Millibars)
  3. The natural gas supply pressure for this specific appliance, your appliance may be different should be 7" water column (1744 pa) [ the instructions say 14.9 millibars which looks to me like a possible error as 14.9 millibars = about 6" of water column - ed.]
  4. The Propane or LP or LPG gas supply pressure for this specific appliance, your appliance may be different should be 11" water column (2740 pa or 17.4 millibars)

LP or Propane Gas Appliance Pressures are given in detail
at LPG & PROPANE APPLIANCE PRESSURES

Gas delivery pressures drop in long or small diameter piping runs

Despite the un-measurable effects of gravity on gas flow in LP or natural gas piping systems, there can be gas flow rate or delivery rate problems due to the pressure drop in long gas piping runs especially with smaller diameter gas piping.

Indeed there are often LP or NG gas flow rate and pressure delivery rate problems in long gas piping runs especially of small-diameter piping systems carrying gases (not liquefied LPG or LNG).

If we are talking about the delivery of appliance pressure (0.4 psi) and whether or not adequate LP gas is being delivered, we would consider the length of piping, even horizontally, as well as the pipe diameter, as well as any gas regulators in that routing.

In that case we would use a primary LPG pressure regulator at the tank to delivery say 10 psi into the gas piping system and we'd step that pressure down to 0.4 psi at or close to the appliance.

See GAS REGLATORS, TWO STAGE

Separately at WATER PRESSURE MEASUREMENT- we discuss the problem of calculating (or measuring) the pressure exerted by a vertical column of a substance (we use water) focusing on pressure at the bottom of the column (a starting point).

In the article above we mention that LP gas operating pressure for typical residential gas fueled appliances is is 10" of water - which is equivalent to about 0.36 psi and which we round-up to 0.4 psi. That is to say, the 0.4 psi figure you cite from our article is the typical operating pressure of LP gas appliances, NOT the pressure of the LP gas (vapor above the liquid) in an LP gas storage tank.

In the storage tank the LP gas vapor pressure ranges from 0-200 psi LP gas pressure depending principally on temperature (and of course having some liquid LPG in the tank. Typical pressures in the tank are at 10 psi (freezing weather) up to about 200 psi (very hot weather and a sun-exposed LPG tank).

You'll see in that article that indeed the temperature effects on LP gas delivery pressure are important in potentially cold-climates.

Reader follow-up:

With natural gas being lighter/less dense than air, I never thought that getting gas up a pipe would be a problem – turn the appliance on and the gas would want to naturally rise and escape. But with LPG being heaver/more dense than air I always thought that there will be a limit that the gas will rise up the pipe before it stops rising.

Using water as an example (and not including all the different losses) if we had a pump delivering water at 0.4psi (about 2.75kpa) than the water would only rise up the pipe 26.9 meters. Would that not be the same with the LPG?

I’m starting to further understand the theory behind your calculations but am not yet totally convinced (maybe that’s just the plumber in me talking)

I guess the question should be asked differently.

At what height above the regulator will the gas no longer flow?

Keeping the number simple and assuming 50/50 propane to butane with an approximate weight of 2kg/m3 and the vapour pipe being 100mm (to overcome the system losses assumed) and a length of 400m I calculate the weight of the gas to be 628kg. being that its denser than air this weight would be exerted on the regulator. Would that much weight on the regulator diaphragm effect the regulator?

This is all new to me and I thank you in advance for any input.

Again keep up your good work with the website.

Reply:

The answer to your question as re-phrased is at EFFECTS of BUILDNG HEIGHT on GAS PIPING SYSTEMS

LP Gas Pressure Testing Procedure for Leak Detection

Reader Question: what is the test pressure used when testing an LPG line?

2016/04/01 Anonymous said:
newly commissioned lpg line what is the required pressure to test the line

Reply: minimum 3 psi, or 1.5 x the gas system's design pressure (low pressure gas testing)

Anon:

Gas systems may be tested at low pressure for low pressure propane installations such as those found at a typical home using LPG. A different, high-pressure gas test procedure is also described.

NFPA 54 (2006), 8.2.3 states that "Immediately after the gas is turned on into a new system or into a system that has been initially restored after an interruption of service, the piping system shall be tested for leakage. If leakage is indicated, the gas supply shall be shut off until the necessary repairs have been made.

Low pressure gas leak tests of the gas piping

This test is performed with a pressure gauge installed on the "downstream" side of the final gas pressure regulator. It is testing the buiding's gas piping and gas appliances for leaks.

When pressure tests are performed on LPG piping, typically the system is sealed, a pressure gauge is installed, and the system is pressurized to 1 1/2 times the maximum design-operating pressure of the system OR a minimum of 3 psi. In some procedures the test period is brief: just 10 minutes for a residential building. But the pressure test interval is increased by 1/2 hour for every 500 feet of piping (that's more likely to occur in a commercial installation).

If the pressure drops during the test period then tools or solutions are used to find the point of gas leakage. Leak testing might be by soap type solution, use of a combustible gas analyzer, or other means.

If the calculated test pressure of 1.5 x the design pressure would exceed 125 psi, then the test pressure should not exceed an amount greater than 50 percent of the pipe strength.

In a low-pressure LP gas system test, the appliance shutoff valves are "ON" (presuming that the appliances are installed) in order to assure that the appliance automatic gas shutoff features are working properly.

High-pressure gas leak tests between the LPG container and the first stage regulator

High pressure tests are made using a 300 psi gauge installed between the gas container (LPG) and the first stage regulator. The gas valve is opened for three seconds and then closed tightly. The system is bled down by at least 10 psi and then tested for 3 minutes, watching for a pressure drop.

A separate test can check for leaks at the gas regulator itself: a 30 psi gauge is installed at the outlet of the first stage regulator. With the pressure gauge installed, the LPG tank's gas valve is opened for 2-3 seconds, just to pressurize the regulator and test gauge. The system is bled down by at least 5 psi and observed for 3 minutes to wat ch for a pressure drop.

Watch out: these general gas leak test descriptions are for illustrative purposes and are not technically complete, detailed, nor exhaustive. Check with the gas testing specifications required where the gas installation is to be tested, and check the gas testing recommendations of the equipment manufacturers.

Watch out: WVPGA (2011) notes that the gas pressure test medium should be air or an inert gas. Never use oxygen.

...


Continue reading at GAS REGULATORS for APPLIANCES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see GAS APPLIANCE CONVERT LP-NATURAL GAS

Or see GAS LAWS & CONSTANTS

Or see GAS PRESSURES LP & NATURAL FAQs

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GAS PRESSURES LP vs NATURAL GAS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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