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PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
BACKDRAFTING HEATING EQUIPMENT
DRAIN & SEWER PIPING
FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
GAS DETECTION INSTRUMENTS
GAS EXPOSURE EFFECTS, TOXIC
GAS EXPOSURE LIMITS & STANDARDS
GAS FIRED WATER HEATERS
GAS LP & NATURAL GAS SAFETY HAZARDS
GAS PRESSURES LP vs NATURAL GAS
GAS PIPING, VALVES, CONTROLS
GAS BTUH, CUBIC FEET & ENERGY
GAS CONVERSION LP-NATURAL GAS
GAS FLAME & NOISE DEFECTS
GAS IGNITER DEFECTS & REPAIRS
GAS LEAK DETECTION, LP / NG
GAS LIGHTING, PIPES, FIXTURES
GAS PIPING DEFECTS
GAS REGULATORS for APPLIANCES
GAS REGULATORS for LP TANKS
GAS REGLATORS, TWO STAGE
GAS SHUTOFF VALVES
LP GAS TANKS
GAS LP & NATURAL GAS SAFETY HAZARDS
LP & Natural Gas Pressures
METHANE GAS SOURCES
Natural Gas Combustion Products
SPILL SWITCHES - Flue Gas Detection
TYPES OF FUEL GAS SOURCE
MANUALS & PARTS GUIDES - HVAC
METHANE GAS SOURCES
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS, SEPTIC or SEWER
ODORS, SULPHUR SMELL SOURCES
OIL TANK PIPING & PIPING DEFECTS
PIPING IN buildings, Clogs Leaks Types
SEWER GAS ODORS
SHUTOFF VALVE LOCATION, USE
SULPHUR & SEWER GAS SMELL SOURCES
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.
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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 How to Inspect & Test LP Gas Tank or Cylinder Regulators. Readers concerned with changing the fuel type between LP gas and natural gas for a gas fired appliance should see our safety warnings at GAS CONVERSION LP-NATURAL GAS.
Watch out: improper installation and even improper inspection and testing methods involving natural or "LP" gas can involve dangerous conditions and risk fire or explosion. If you smell gas you should leave the building immediately and should do so without doing anything that could create a spark such as operating a light switch or telephone. From a safe location, call your gas company's emergency line and/or your fire department. The text provided here is a working draft and may be incomplete or inaccurate.
The gas fired furnace gas regulator photograph shown here is a typical gas valve assembly such as those used on most older furnaces and boilers. The regulator is shown removed from the appliance where it will be used.
Since the actual gas pressure right at the heating appliance can vary for several reasons (gas type, source pressure, piping distance, piping diameter), the job of the gas regulator includes not just "turning on" the gas when the thermostat calls for heat.
The gas appliance regulator must also deliver gas at the proper gas pressure specified by the manufacturer for the particular appliance.
The photo of the gas regulator shown here and much of the content in this article are thanks to Charles or Mike Trumbature.
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.) See THERMOCOUPLES.
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:
Details 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 Manometer
The 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 at the gas burner: The gas regulator and gas burner photograph shown in this photo has clearly not been inspected, tested, cleaned, measured, nor serviced in some time.
Not only are there dusty cobwebs over the gas regulator, but a chewing gum wrapper and a scrap of green foam have fallen into the furnace and may be blocking air intake to the right hand gas burner tube.
Not only might this interfere with proper burner operation by obstructing combustion air to the burner, but combustible trash at any gas burner is a potential fire hazard.
The gas burner flame color, pattern, height, or the presence of rust on a gas burner can also indicate potentially dangerous operating problems with a gas furnace or boiler. These concerns are discussed in more detail at GAS FLAME & NOISE DEFECTS or select a topic from the More Reading links shown below.
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