Systems Regulators are mechanical devices used in propane vapor distribution systems to reduce a high inlet pressure to a preset lower pressure, and to control the flow of gas to appliances based on operating demand. When operating properly, the regulator stops the flow of gas when there is no appliance demand (system lock-up), and when appliance burners are operating, maintains a steady outlet pressure, despite changes in the inlet pressure and demand.
The proper selection & operation of the propane pressure regulator is vital to the operation of all appliances in the system.
Vent — The vent is a hole or port which allows the regulator to "breathe." During normal regulator operation, air is drawn into or pushed out of the vent. If the regulator’s internal relief valve opens, propane vapor discharges out of the vent.
Vent — Most regulators use a "drip lip" vent to help prevent ice from closing off the vent. The "drip lip" vent is designed to route water away from the vent. This keeps the center of the vent open even when surrounded by ice.
Single-Stage Regulator Systems use one regulator to supply gas to an appliance or (appliance system).
Note:With the exception of outdoor cooking appliances and small portable appliances (100,000 Btu/hr rating or less), NFPA 58, 1995 and later editions, prohibits the installation of single-stage regulators in the fixed piping systems after June 30,1997.
However, if company procedures permit, NFPA 58 provides that a single-stage regulator may be continued in use until it is necessary to replace the regulator.
Half-Pound Two-Stage Regulator Systems In the ½-pound two‑stage regulator system, two regulators are used to reduce the propane storage container pressure to the working pressure of the appliance. The first-stage regulator reduces the container pressure to an intermediate pressure, usually 10 psig. In typical ½ pound residential applications the second-stage regulator reduces the intermediate pressure to 11" water column.
The first-stage regulator reduces container pressure to an intermediate line pressure of approximately 10 psig supplied to the inlet of a 2-psig service regulator installed at an outside service entrance to the home or building.
Propane vapor at 2-psig is supplied to a line regulator at individual appliances or one located at a manifold connected by short tubing runs to several gas appliances.
The line regulator is a third stage in pressure regulation, reducing vapor pressure to 11-14 inches water column.
Satisfying Gas Demand When the service valve is first opened, gas flows into the regulator and the downstream line leading to the appliances Because there is no demand (appliances off), pressure builds up throughout the system and the diaphragm is forced upward. This action completely closes off the orifice (commonly called lock‑up).
Adjusting Outlet Pressure The outlet pressure of many regulators can be changed in the field by turning the adjusting screw in the bonnet. Turning the adjusting screw clockwise increases the outlet pressure of the regulator.
Relieving Excess Pressure A final stage propane regulator reducing the gas pressure down to the appliance pressure must have a relief valve or shut-off device built into it.
Most built‑in relief valves in second-stage regulators are set by the factory to open when the pressure under the diaphragm is between 1.7 and 3 times the outlet pressure setting of the regulator.
DO NOT ATTEMPT TO CHANGE THE SETTING OF A REGULATOR RELIEF VALVE NOR TAMPER WITH IT IN ANY WAY.
Flow Condition As the appliance uses gas, the pressure inside the regulator decreases allowing the regulator spring to depress the diaphragm again. As the diaphragm moves down, the linkage mechanism pulls the seat back away from the orifice allowing more gas to come into the regulator.
Regulator Freeze‑Ups When a regulator "freezes‑up," the operation of the regulator is stopped by moisture freezing somewhere inside the regulator. There are basically two types of freeze‑ups.
Each type has a different cause and different preventative measures that can be applied.
Regulator Freeze‑up Type 1 may be caused by condensation in the upper spring case or by vent blockage. Protection measures include:
1. mounting the regulator under a hood or protective cover
2. installing the regulator with the vent pointed downward
3. (underground tanks) installing a pipe-away adapter that terminates above the anticipated water line with a downward pointed and protected terminating outlet
Regulator Freeze‑up Type 2 As gas expands moving through the regulator orifice, there is a refrigeration effect, causing regulator freeze‑ups when there is moisture in the fuel. Protection measures include:
1. Properly dry and purge all new tanks, cylinders and lines before putting them into service.
2. Ensure valves on "empty" tanks of cylinders are fully closed to help prevent moisture from entering.
If moisture is present, the following will aid in combating freeze‑ups:
1. Add methyl alcohol (about one pint to every 100 gallon capacity. This will lower the freezing point of the water sufficiently to help prevent freezing).
2. If pigtails are "looped," be sure the loop is upward.3. 1st stage regulators: be sure the regulator inlet is higher than the
A two-stage regulator system, an integral two-stage regulator, or a two-psi regulator system shall be required on all fixed piping systems that serve ½ psig appliance systems (normally operated at 11 in. w.c. pressure).
NFPA 58
2001
3.2.12
NFPA 58
2004
6.7.3
If modifications to an existing distribution system are made or the single-stage regulator does not continue to function properly and is replaced, then the existing system must be converted to a two-stage regulated system.
LP-gas regulators in propane two-stage systems are designed to limit distribution line pressures downstream of the second-stage or service regulator, and therefore appliance input pressure, to no more than 2 psig.
Integral 2-stage regulator for half-pound systems. Most frequently used for manufactured homes with relatively small demand loads and short piping runs.
High-Pressure (pounds to pounds) regulator for relatively high Btuh demand systems and unusually long buried piping distribution lines. Used at the container to reduce container pressure to a lower pressure, usually 12 to 15 psig. Downstream first-stage regulator(s) are used to reduce the pressure to 10 psig or less for delivery to one or more second-stage regulators.
First-stage regulator used at the propane storage tank on medium to large Btuh demand systems. It reduces container vapor pressure to approximately 10 psig and delivers it to the buried distribution line(s) connecting it to the second-stage regulator(s).
Second-stage regulator used at building service entrance(s) to reduce the approximately 10 psig vapor pressure supplied by the first-stage regulator to approximately 11 inches water column supply to the half-pound distribution piping. Body styles available are the straight-though body shown to the left, and the back-mount for a 90° change in flow direction for horizontal service entrances.
2-PSI service regulator used at building service entrance(s) to reduce the approximately 10 psig vapor pressure supplied by the first-stage regulator to 2 psig vapor pressure supply to the distribution piping. Line regulators further reduce the 2 psig pressure to the required appliance input pressures, usually measured in inches water column.
Line regulators are used in hybrid pressure systems to reduce the 2 psig outlet pressure from the 2-pound service regulator to required appliance inlet pressures, measured in inches water column. They are installed just before manifold piping or tubing runs, or just before individual appliances. Consult manufacturer brochures to determine appropriate line regulator to meet system Btuh load and pressure requirements.
Automatic changeover regulators combine first-stage and second-stage regulators with a check valve to receive vapor from manifold cylinders. Cylinder vapor pressure is reduced to approximately 11 inches water column at the second-stage regulator outlet.
Step 2: Calculate the total appliance demand on the regulator.
Step 3: Determine the delivery or outlet pressure required for the regulator, and the input pressure required from the first-stage regulator to achieve the required output in Btuh.
Step 4: Select the second-stage regulator required using manufacturers specifications, performance curves and capacity charts.
1. Designated by the manufacturer as a first-stage regulator suitable for residential applications. DO NOT use high-pressure regulators designed for commercial or industrial applications as a first-stage regulator.
2. Rated with an output capacity in excess of total system demand.
3. Designed to supply outlet pressures within the range needed for the second-stage regulator(s) inlet pressures, typically 5 psig to 10 psig.
4. Equipped with adequate relief capacity to meet the requirements of NFPA codes.
Two first-stage regulators can be used in a parallel installation in unusually high-demand systems.
1. Ensure that the first-stage regulator has sufficient Btuh capacity to supply all installed and anticipated future appliances total Btuh demand.
2. Select a 2-PSI service regulator for each required service entrance that has sufficient Btuh capacity to supply all installed and anticipated future appliances the regulator serves.
3. Ensure that suitable line regulators are selected and properly located to supply connected appliances with adequate gas volume (Btuh) and pressure.
