HPC Fire Inspired fire pits are gaining popularity and transforming outdoor spaces. Planning your installation is a crucial step in the design phase. Selecting the proper fuel source is important to ensuring that the design operates at full capacity.

For the purposes of this article, HPC would like to educate consumers around proper planning when pairing propane with high BTU fire units. HPC’s Tech support have fielded concerns around homeowners attempting to use standard 20lb propane tanks with high BTU units. Doing so, can lead to performance issues as well as safety concerns. When selecting a fuel source for your HPC fire pit, understanding propane’s limitations is crucial to ensuring proper performance and safety. This article will educate consumers to make informed decisions to ensure the chosen HPC designs operate optimally and prevent owners from falling prey to potential pitfalls.

Propane Vaporization: How It Works

Propane is stored in tanks as a liquid under pressure and must convert into a gas before it can be burned. This process is known as vaporization and occurs as heat from the surrounding environment warms the liquid propane, causing it to boil releasing gas.

The key factor here is that the rate of vaporization depends on the surface area of the liquid propane exposed to heat. Larger tanks provide more surface area, allowing for faster and more consistent vaporization.

Why Vaporization Rate Matters:

Each propane tank has a maximum rate at which it can convert liquid propane into usable gas. If a fire pit’s demand for propane exceeds the tank’s vaporization rate, the tank cannot keep up, leading to a drop in gas pressure and performance issues.

How Propane Demand Is Calculated:

HPC Fire Inspired fire pit inserts are sized and rated by the amount of gas consumed rated in BTU (British Thermal Units). BTU (British Thermal Units) measures the heat output of an appliance. In propane fire pits, BTU ratings indicate how much energy the burner consumes per hour.The Larger the fire pit, the higher the BTU rating.

  • A small fire pit insert may be rated around 40,000 – 90,000 BTU/hr.
  • A larger fire fire feature can exceed 100,000 -400,000 BTU/hr.

How Much Energy Does a 20lb Propane Tank Contain

Each pound of liquid propane contains about 21,600 BTUs or 91,500 BTU per gallon of energy. A standard 20lb propane tank contains roughly 430,000 BTUs of potential energy when full.However, this does not mean the tank can supply that energy all at once. The propane must vaporize at a sufficient rate to meet the fire pit’s demand, which is where the limitations of propane come into play.

Limitations Of 20LB Propane Tank For High-BTU Fire Pits:

A 20lb propane tank can only vaporize around 100,000 BTU per hour under ideal conditions (i.e., moderate temperatures around 60°F or higher). If the fire pit’s BTU demand exceeds this rate:

  • The tank cannot supply enough gas, leading to weak flames or intermittent operation.
  • The tank gets colder as propane vaporizes, slowing the process further.
  • In cold weather, vaporization rates can drop to 50,000 BTU/hr or less, worsening performance issues.

The Temperature Factor: Why Cold Weather Makes It Worse

Propane vaporization is highly temperature-dependent:

Ambient Temp. vs Approximate Max BTU Output from a 20lb Tank

Ambient Temp.       Approx. Max BTU Output

70°F (21°C)       ~       100,000 BTU/hr

50°F (10°C)       ~        75,000 BTU/hr

32°F (0°C)          ~        50,000 BTU/hr

10°F (-12°C)      ~        25,000 BTU/hr

At temperatures below freezing, a 20lb propane tank may struggle to provide even enough gas for even a small-sized fire pit.

The Impact of Overdrawing a 20lb Propane Tank

When a fire pit demands more gas than a 20lb tank can supply, several problems occur:

  1. Flame Inconsistency and Sputtering
  • The fire pit may start strong but weaken as the propane supply diminishes.
  • The flames can flicker or die out if the tank cannot maintain
  1. Tank Freezing (Regulator Freeze-Up)
  • When propane vaporizes rapidly, it absorbs heat from the tank’s surroundings.
  • If too much propane is drawn too quickly, the tank becomes extremely cold, causing frost buildup.
  • In severe cases, the regulator may freeze up, completely cutting off the gas flow.
  1. Increased Regulator Stress
  • Regulators are designed to handle a specific gas flow rate.
  • Overdrawing propane forces the regulator to work harder, potentially leading to failure
  1. How to Properly Supply a High-BTU Fire Pit

Option 1: Upgrade to a Larger Propane Tank

  • A 100lb propane tank provides a significantly larger surface area for vaporization.
  • For frequent use, a 250-gallon or larger stationary propane tank is ideal

Option 2: Dual Tank Setup with a Manifold

  • Connecting two 20lb or 30lb tanks using a propane manifold splits the load between tanks, improving vaporization rates

Option 3: Convert to Natural Gas

  • If a natural gas line is available, converting the fire pit eliminates propane supply issues entirely.
  • Natural gas systems deliver fuel at a consistent pressure and flow rate.

When planning and selecting your HPC fire feature remember a 20lb propane tank may not be ideal as a fuel source for higher-BTU fire pits (above 90,000BTU) due to its limited vaporization rate and capacity. While it may be ideal for smaller fire pits (50,000 BTU -90,000BTU), larger models exceeding 100,000 BTU/hr will experience performance issues such as weak flames, tank freezing, and frequent need for refueling. To ensure a reliable and safe fire pit experience, upgrade to a larger propane tank or if possible consider planning for natural gas installation.

Contact HPC at 937-436-9800, to help plan your installation. Our team of certified experts will guide you through the process ensuring optimal performance of every HPC design.