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This article explains LP or Natural Gas Pressure Regulators used on building appliances such as gas fired furnaces, boilers, water heaters, and stoves: How to Inspect & Test LP or Natural Gas Valves Regulators, or Gas Controls at Appliances. We provide descriptions and photographs of unsafe gas piping, regulators, or controls on heating systems, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects. This document also provides free sample draft home inspection report language for reporting defects in oil and gas piping at residential properties. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Gas Regulator or Control Inspection, Testing, & Defect Guide
It's impressive how many important functions are often packed into this little gas valve/regulator: The functions that are typically combined in a modern gas valve/regulator include: If a thermocouple is used you'll see a small copper tube (or in some devices an electrical wire) connecting the flame sensor to the valve. The thermocouple and safety shutoff do double duty, since on burners that use a pilot flame the thermocouple senses the pilot flame and won't permit the gas valve to open if the pilot is not lit. (A bad thermocouple itself can prevent a gas furnace or boiler from working - if you can light the flame at the pilot manually but then the flame goes out when you release the manual gas feed valve, the thermocouple is probably bad.) What goes wrong with gas regulators on furnaces or boilers?Gas pressure too high:: Some technicians have informed us that as the gas valve regulator on some gas furnaces or boilers age over several years, the spring inside the regulator (and determining the regulator output pressure) can weaken. A weakened spring inside of a gas regulator can allow the gas pressure to increase beyond the BTU rating of the heat exchanger. This same condition could occur if the regulator is simply not properly adjusted in the first place. Adjustment of a gas regulator might also be necessary if the gas piping from source (meter or tank) to the appliance is long or is too small in diameter. If the gas regulator delivers gas at too high a pressure the gas flame may be also too big (and too hot), which can accelerate rusting and can warp the heat exchanger at its lower joints causing a "crack" to appear. A cracked heat exchanger on a gas appliance is unsafe. Our correspondent, Charles commented that:
Gas pressure too low: if the gas regulator is not properly adjusted or if there are other problems in the gas piping or supply system the gas pressure may be too low, providing an inadequate and possibly unsafe flame. Depending on the cause of the problem, it may be possible to correct this at the regulator, but don't try boosting pressure at a gas regulator unless the pressure has always been too low. Otherwise when the underlying cause for low gas pressure is corrected elsewhere, the flame will be too big and pressure too high at the burner - an unsafe condition. Immediate LP or natural gas safety hazards: if there is evidence of an LP or natural gas leak at a building, gas odors, for example, you should:
What are the Typical LP Gas, Propane Gas, or Natural Gas Pressures Found in Residential SystemsDetails about the different pressures found or set for LP gas, propane, and natural gas including before and after different gas pressure regulators are at LP & Natural Gas Pressures. LP Gas or Propane Pressures:
Natural Gas pressures:
How are Gas Regulator Valves Inspected and Pressure-Tested? Connecting and Using a Gas Pressure ManometerThe pressure delivered to a gas-fired heating boiler or furnace is typically 3" to 3.5" water column for 100K BTU gas fired furnaces or boilers. (LP gas and piped-in natural gas do not provide the same pressures from the source which is why regulators and orifices must be properly installed and adjusted depending on the type of gas fuel in use (Propane or LP gas from a local gas tank vs. natural or piped-in gas). The large screw on top of the gas regulator shown in the photograph above is a "cap screw" which can be removed by (a trained) heating technician when it is necessary to access the LP or natural gas pressure regulator adjusting screw inside. SAFETY WARNING: If you lack the training and equipment, do not attempt to disassemble or mess with a gas regulator as you could create a very dangerous or even fatal problem. Under the "cap screw" on the gas regulator there a plugged NPT tap (usually 1/8") used to install a hose barb and manometer (a very low pressure gage) in order to check gas pressure right at the heating furnace or boiler. [Gas regulator valves such as this one usually have a 1/8" NPT plug which is remove by the technician in order to connect a manometer to measure the gas pressure being delivered right at the appliance.] For connecting the manometer to measure gas pressure, the technician may obtain a hose barb and plastic hose form a hardware store in order to make these connections. The actual gas pressure setting for the regulator is on the gas valve. Inexpensive manometers such as those made by Dywer Instrument CO. are good for checking and setting the regulators. See the 2T650 and 3T292 models, probably best suited depending on the ranges needed. [Available from Granger Corp., a supplier of HVAC testing equipment.] Since the pressures for gas furnaces (and boilers) can vary above or below the 3" water column (WC), the 7" manometer is probably a better one fits all choices when checking gas regulator assemblies. Charles, a fire pump and sprinkler system inspector in Houston Tx, our correspondent on this topic commented:
Checking the pressure delivered to a furnace by a gas regulator valve is beyond the scope of a normal home inspection. However certain clues such as defects in gas flame or rusty gas burners can suggest that there is a problem with the adjustment of the gas pressure (the regulator's job) or with the combustion air supply (potentially a fatal mistake). Debris on Gas Regulators or Furnace Burners can be Dangerous
... Frequently Asked Questions (FAQs)... Ask a Question or Search InspectApediaQuestions & answers or comments about inspecting, diagnosing, repairing, or replacing LP gas regulators and Natural Gas regulators found on heating appliances Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one.
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