Master Plumber (UPC/IPC) — All Questions

Before pressurizing or testing a solvent-welded PVC water joint, the installer must do what?

• a.Heat the joint with a torch to accelerate the bond
• b.Allow the proper cure/set time per the cement listing✓
• c.Fill immediately; PVC cement sets on contact instantly
• d.Back off the fitting a quarter turn to relieve stress

Solvent-cement joints need primer and adequate cure time, which varies with pipe size, temperature, and test pressure, before they are pressurized. Rushing the cure causes weeping or blown joints. Never apply flame to plastic pipe. IPC §605.10 / UPC §316.0.IPC §605.10 / UPC §316.0

Compared with rigid metal, plastic pipe (PVC/CPVC) generally requires what for support?

• a.Wider spacing because plastic is stiffer than steel
• b.No hangers at all on horizontal runs
• c.Support only at fittings, never mid-span
• d.Closer support spacing because it sags more✓

Plastic pipe deflects more than metal, so hanger spacing is closer, and room must be left for thermal movement. Code tables set the exact intervals by material and size. Too-wide spacing lets plastic sag and pond water. IPC §308.0 / UPC §313.0.IPC §308.0 / UPC §313.0

The vent opening for a trap must be located where relative to the trap's weir?

• a.Above the trap weir✓
• b.Below the weir, so water keeps the vent wet
• c.Inside the trap body, between the inlet and outlet
• d.At the exact level of the weir, sharing the seal

The vent must take off above the trap weir, and the trap arm may not fall more than one pipe diameter, so the vent opening stays clear of the water seal. A vent below the weir would fill with water and be defeated. This prevents siphonage. IPC §909.0 / UPC §1004.0.IPC §909.0 / UPC §1004.0

A potable water storage tank must have its overflow and cover arranged how?

• a.Overflow run submerged into a floor sink to form a tight seal
• b.Overflow to an air gap; cover and vent screened✓
• c.Overflow hard-piped straight into the sanitary drainage line
• d.Cover left loose-fitting so the tank can breathe to atmosphere

A potable storage tank needs a screened, downturned overflow that discharges through an air gap, plus a gasketed or screened cover and vent, so contaminants and vermin cannot enter. A hard or submerged overflow is a cross-connection. The air gap protects the stored water. IPC §608.14 / UPC §603.0.IPC §608.14 / UPC §603.0

A water-heater temperature-and-pressure (T and P) relief discharge pipe may terminate how?

• a.Fitted with a shutoff valve so it can be isolated for service
• b.Trapped and then tied directly into the sanitary drain line
• c.Full-size, ending 6-24 in above the floor/receptor✓
• d.Reduced one pipe size to fit a smaller drain opening neatly

The T and P discharge must be full pipe size, contain no valve or trap, and terminate 6 to 24 in above the floor or an approved receptor where a discharge is visible. A valve could defeat the safety device and a trap would corrode. Visibility signals a problem. IPC §504.6 / UPC §608.5.IPC §504.6 / UPC §608.5

A thermal expansion tank on a closed water system must be pre-charged to what pressure?

• a.Zero (empty), so it fills completely with water
• b.The relief-valve setting of 150 psi for full capacity
• c.The system static (supply) pressure✓
• d.Twice the street pressure to force water back to the main

The expansion tank's air charge is set to match the system static pressure so its full acceptance volume is available as water heats and expands. An empty or over-charged tank cannot absorb the expansion. Correct pre-charge prevents pressure spikes. IPC §607.3 / UPC §608.3.IPC §607.3 / UPC §608.3

A reduced-pressure principle assembly protecting a high-hazard connection must be tested how often?

• a.Only when the water purveyor reports a problem
• b.At least annually (and after any repair)✓
• c.Once at installation and then never again
• d.Every ten years, matching the pipe warranty period

RP and other testable assemblies must be field-tested by a certified tester at installation, after any repair, and at least annually, with the report filed with the authority. Periodic testing confirms the assembly still functions. Backflow protection degrades over time. IPC §312.10 / UPC §603.0.IPC §312.10 / UPC §603.0

An air gap located within three pipe diameters of a single wall must be increased to what multiple of the effective opening?

• a.Equal to the opening (1x), because the wall helps
• b.The same 2x used away from any wall surface
• c.Three times the effective opening (3x)✓
• d.One-half the opening, since the wall shields it

The standard air gap is twice the effective opening, but near a single wall it increases to three times because the wall disrupts the free entry of air. Near multiple walls the multiplier grows further. The wall changes the airflow geometry. IPC §608.15 / UPC §603.4.6.IPC §608.15 / UPC §603.4.6

Non-potable (reclaimed or gray) water piping must be distinguished from potable piping how?

• a.Marked/colored purple and labeled non-potable✓
• b.Left unmarked because location alone identifies it
• c.Wrapped in standard insulation with no special labeling
• d.Painted the same as potable to simplify inventory

Reclaimed and gray-water piping is identified with purple (violet) color and non-potable marking, and valves and outlets are also marked, so no one mistakes it for drinking water. Matching potable color would invite dangerous cross-use. Clear marking prevents mistakes. IPC §1301.0 / UPC §1502.0.IPC §1301.0 / UPC §1502.0

A local jurisdiction has adopted the IPC, but a fixture manufacturer's installation instructions are stricter. Which governs the installation?

• a.Whichever the installer personally prefers on the job
• b.Neither; local custom and past practice control the work
• c.The more restrictive requirement✓
• d.The UPC, because it is the older model code nationally

The adopted model code sets the legal minimum, but where a listed product's instructions are stricter, the more restrictive requirement governs, and listed products must be installed per their listing where the code defers to it. This protects both the listing and code compliance. IPC §102.0 / UPC §301.0.IPC §102.0 / UPC §301.0

A natural-gas furnace is rated at 80,000 BTU/hr. Using a heating value of 1,000 BTU per cubic foot, what gas volume flow must the piping deliver?

• a.80 cfh✓
• b.8 cfh
• c.800 cfh, because you multiply the input by ten
• d.40 cfh, taking half the rated input

cfh = BTU/hr divided by heating value = 80,000 / 1,000 = 80 cfh. Per IFGC 402.4, gas piping is sized in cubic feet per hour, and for natural gas at ~1,000 BTU/ft^3 the cfh equals the input in thousands of BTU. This cfh is carried into the sizing table at the system's longest length.IFGC §402.4

A 50,000 BTU/hr natural-gas water heater is served on its own branch. At 1,000 BTU per cubic foot, what is the required gas flow?

• a.5 cfh, dividing the input by ten thousand
• b.500 cfh, moving the decimal the wrong way
• c.25 cfh, using half the rated input
• d.50 cfh✓

cfh = 50,000 / 1,000 = 50 cfh. IFGC 402.4 sizes each branch for the demand of the appliance it serves, expressed in cfh. The branch to a single water heater carries only that appliance's 50 cfh, while the common section upstream carries the sum of all appliances.IFGC §402.4

A propane pool heater is rated at 200,000 BTU/hr. Propane has a heating value of about 2,500 BTU per cubic foot. What gas flow in cfh must the piping deliver?

• a.200 cfh, using 1,000 BTU per cubic foot instead of 2,500
• b.80 cfh✓
• c.40 cfh, taking half of the correct value
• d.500 cfh, multiplying instead of dividing

cfh = 200,000 / 2,500 = 80 cfh. IFGC 402.4 requires using the correct heating value for the fuel; propane carries about 2,500 BTU/ft^3, roughly 2.5 times natural gas, so the cfh is much lower for the same input. Using 1,000 BTU/ft^3 wrongly inflates the flow to 200 cfh.IFGC §402.4

The standard natural-gas pipe sizing tables in the fuel gas code are published for one assumed gas specific gravity. What specific gravity do those tables assume?

• a.1.52
• b.0.35, a value lighter than any fuel gas used
• c.0.60✓
• d.1.00

IFGC Table 402.4(1) and related tables are based on a natural-gas specific gravity of 0.60. When the actual gas differs, a multiplier from the code adjusts the capacity. Propane tables use a different gravity (about 1.52), so the correct table must match the fuel.IFGC Table 402.4

Liquefied petroleum (propane) gas is heavier than air. Because of this property, where does an LP-gas leak tend to accumulate?

• a.Near the ceiling, because it rises the way natural gas does
• b.It disperses evenly through the room and never collects
• c.It vents itself harmlessly to the outdoors on its own
• d.In low areas such as floors and pits✓

Propane has a specific gravity of about 1.52, so it is heavier than air and settles into low spots like floors, crawl spaces, and pits, per NFPA 58 and IFGC hazard provisions. This is why LP appliances have low-level ignition concerns and LP is not stored below grade without special provisions.IFGC §404

A residential natural-gas appliance operates at a typical delivered inlet pressure. What is that common supply pressure?

• a.About 2 psi measured right at the burner orifice
• b.About 14 inches of water column at the appliance inlet
• c.About 7 inches of water column✓
• d.About 11 inches of water column, which is the propane value

Natural-gas appliances are typically supplied at about 7 in w.c. (with a manifold pressure near 3.5 in w.c.), per IFGC and NFPA 54 appliance data. Propane appliances instead use about 11 in w.c. Matching the delivered pressure to the appliance rating is essential for correct combustion.IFGC §410.3

A propane appliance is set for the fuel it burns. What is the typical delivered inlet supply pressure for a propane appliance?

• a.About 2 psi delivered directly at the appliance inlet
• b.About 7 inches of water column, which is the natural-gas value
• c.About 11 inches of water column✓
• d.About 3.5 inches of water column at the manifold outlet

Propane appliances are commonly supplied at about 11 in w.c., higher than natural gas at about 7 in w.c., per NFPA 54/58 appliance data. The second-stage regulator on an LP system delivers this pressure. Using natural-gas pressure on a propane appliance would underfire it.IFGC §410.3

A gas line operates at 11 inches of water column. Using 1 psi = 27.7 inches of water column, what is 11 in w.c. expressed in psi?

• a.4.0 psi, off by a full factor of ten
• b.3.05 psi, multiplying by 27.7 instead of dividing
• c.0.30 psi, using the wrong conversion constant
• d.0.40 psi✓

psi = in w.c. divided by 27.7 = 11 / 27.7 = 0.397, about 0.40 psi. IFGC recognizes that residential appliance pressures are fractions of a psi, which is why low-pressure systems are measured in inches of water column. Confusing the two units is a common and dangerous sizing error.IFGC §406

Low-pressure natural-gas sizing tables are built around a specified allowable pressure drop across the piping. What pressure drop do the common low-pressure tables assume?

• a.0.3 psi, an elevated-pressure design assumption
• b.3 inches of water column across the whole system
• c.1.0 psi, which is a high-pressure design value
• d.0.5 inch of water column✓

The standard low-pressure sizing tables in IFGC Table 402.4(1) are based on a 0.5 in w.c. pressure drop. A larger allowable drop (a separate table) permits smaller pipe. The design must not exceed the drop the appliance can tolerate while still delivering its rated input.IFGC Table 402.4

A gas system has four outlets; the most remote outlet is 70 ft from the meter. Under the longest-length method, what length sizes the section of pipe closest to the meter?

• a.70 ft (the single longest run)✓
• b.The physical length of that section of pipe only
• c.The average of all four outlet run lengths combined
• d.The length of the run to the nearest outlet

The longest-length (or 'longest run') method in IFGC 402.4 sizes every section of the system using the single longest run from the meter to the most remote outlet. This conservative approach guards against undersizing under simultaneous demand. Each section's own physical length is not used in this method.IFGC §402.4

A gas branch must carry 120 cfh at a longest length of 50 ft. The table at 50 ft lists 3/4 in = 99 cfh and 1 in = 190 cfh. What is the minimum pipe size?

• a.1 in✓
• b.1/2 in
• c.3/4 in
• d.1-1/4 in

The 120 cfh demand exceeds the 99 cfh capacity of 3/4 in pipe at 50 ft, so the next size, 1 in (190 cfh), is required, per IFGC Table 402.4. Gas pipe is chosen as the smallest size whose table capacity at the longest length equals or exceeds the demand. A 3/4 in pipe would be overloaded.IFGC Table 402.4

A common section of pipe upstream of the first tee feeds a furnace (80 cfh), a water heater (45 cfh), and a clothes dryer (25 cfh). What demand must that common section carry?

• a.25 cfh, counting only the last appliance on the run
• b.80 cfh, counting only the single largest appliance
• c.125 cfh, leaving out the clothes dryer load
• d.150 cfh✓

The common section carries the sum of all downstream demands: 80 + 45 + 25 = 150 cfh, per IFGC 402.4. Each branch downstream of a tee is sized for only the appliance it serves, but every upstream section must carry the total it feeds. Undersizing the common run starves all appliances at once.IFGC §402.4

What is the primary consequence of undersizing fuel-gas piping so it cannot deliver the required cfh?

• a.Pressure drop starves the appliance✓
• b.Higher gas velocity always improves the appliance performance
• c.The appliance receives too much pressure and dangerously over-fires
• d.Nothing happens, because the appliances self-compensate for it

Undersized gas pipe produces excessive pressure drop, so the appliance cannot draw its rated cfh, leading to a low firing rate and incomplete combustion that generates carbon monoxide, per IFGC 402.4 sizing intent. Correct sizing keeps the delivered pressure within the appliance's operating range under full demand.IFGC §402.4

Corrugated stainless steel tubing (CSST) is not sized from the standard steel-pipe schedule tables. How is CSST capacity determined?

• a.It does not require any sizing because it is flexible
• b.From the manufacturer's listed EHD tables✓
• c.From standard copper-tube sizing tables in the fuel gas code
• d.From Schedule 40 black-steel tables using the nominal pipe size

CSST is sized using the manufacturer's listed capacity tables keyed to the product's equivalent hydraulic diameter (EHD), not the generic steel tables, per IFGC 402.4 and the listing. Because CSST's inside geometry differs from threaded pipe, only the listed data gives correct capacity. Substituting steel tables can undersize it.IFGC §402.4

Polyethylene (PE) gas pipe is commonly used for underground fuel-gas service. How must it be handled where it comes above grade?

• a.It may be left exposed above grade as long as it is painted
• b.Transition to metallic pipe below grade with an anodeless riser✓
• c.It may be run above grade and continue inside the building freely
• d.It is prohibited underground and may only be used indoors instead

PE gas pipe is approved for underground use but degrades under sunlight and physical exposure, so IFGC 404 requires an anodeless riser transitioning to metallic pipe below grade before it emerges. PE is not permitted inside buildings or exposed above grade. Tracer wire is installed with it for locating.IFGC §404.4

Which material is NOT permitted for interior fuel-gas distribution piping?

• a.Copper tube where the gas has low hydrogen sulfide content
• b.Corrugated stainless steel tubing that is listed for gas
• c.PVC plastic pipe✓
• d.Black steel pipe joined with threaded fittings

PVC is not an approved fuel-gas piping material for interior distribution under IFGC 403; approved materials include steel, CSST, and (for low-H2S gas) copper. PVC and other thermoplastics lack the required fire and pressure ratings indoors. PE is limited to underground service only.IFGC §403

Copper tube is allowed for natural gas only under a specific gas-quality condition. What is that condition?

• a.Copper is never allowed for natural gas under any circumstances
• b.Hydrogen sulfide below 0.3 grains per 100 scf✓
• c.Copper is allowed only for propane service and never for gas
• d.Copper is always allowed for any natural gas without restriction

IFGC 403.4 permits copper for natural gas only where the gas is not corrosive, generally less than 0.3 grains of hydrogen sulfide per 100 scf; sulfur compounds attack copper and form scale. The local gas utility can confirm gas quality. Where H2S is higher, steel or CSST is used instead.IFGC §403.4

Thread sealant used on fuel-gas pipe joints must meet a specific requirement. What is it?

• a.An oil-based sealant is the preferred product for gas threads
• b.Any general-purpose pipe dope from the shelf is acceptable to use
• c.It must be resistant to the gas (LP-gas resistant on propane)✓
• d.No sealant of any kind may be used on fuel-gas threaded joints

IFGC 403.10 requires joint compounds and tape to be resistant to the fuel gas, and specifically LP-gas resistant on propane systems, so the sealant is not dissolved or degraded. Ordinary sealants can soften in the presence of gas and cause leaks. The sealant is applied to male threads only.IFGC §403.10

A flexible appliance connector joins fixed gas piping to a movable appliance. What installation limit applies?

• a.It may pass through a wall as long as it is sleeved for protection
• b.It may be permanently concealed behind or under the appliance
• c.Its overall length is unlimited for any size of appliance served
• d.It must not pass through walls, floors, or concealed spaces✓

IFGC 411.1 prohibits a listed flexible appliance connector from passing through walls, floors, ceilings, or any concealed location, and limits its length; it must serve a single appliance and remain in the same room, accessible. Concealing or extending a connector creates an unseen leak risk.IFGC §411.1

A ground-joint union lets an appliance be disconnected for service. Where is the union placed relative to the appliance shutoff valve?

• a.Downstream of the shutoff, between the valve and appliance✓
• b.No union is permitted anywhere at a gas appliance connection
• c.At the gas meter, so the whole building can be isolated first
• d.Upstream of the shutoff valve, on the supply side of the piping

The union is installed downstream of the appliance shutoff so the valve can isolate gas before the union is broken to remove the appliance, per IFGC 409/411 practice. This lets the appliance be disconnected without shutting the whole system. A union upstream of the valve would leak gas when opened.IFGC §411

May fuel-gas piping be used as the grounding electrode for the building electrical system?

• a.Yes, but only when it is used for lightning-protection grounding
• b.No; gas piping must not be a grounding electrode✓
• c.Yes, and it is required to serve as the building's primary ground
• d.Yes, because it makes an excellent low-resistance primary ground

Fuel-gas piping must not serve as a grounding electrode, per IFGC 310 and the NEC; a fault current on gas pipe could arc and perforate it. CSST additionally requires dedicated bonding to the grounding electrode system to drain induced surges. Grounding electrodes are ground rods, water pipe, and building steel.IFGC §310 / NEC

Combustion air is provided by a single permanent opening communicating with the outdoors. What free-area rule sizes that opening?

• a.1 in^2 per 3,000 BTU/hr of input✓
• b.1 in^2 per 4,000 BTU/hr, the vertical two-opening duct ratio
• c.1 in^2 per 1,000 BTU/hr, which greatly oversizes the opening
• d.1 in^2 per 50 BTU/hr of aggregate appliance input

IFGC 304.6.1 sizes a single combustion-air opening at 1 in^2 per 3,000 BTU/hr of aggregate input, minimum 100 in^2, located within 12 in of the ceiling and communicating with the outdoors. Two-opening and ducted methods use different ratios. Adequate combustion air prevents oxygen depletion and CO.IFGC §304.6.1

When two combustion-air openings connect to the outdoors through horizontal ducts, what free-area ratio sizes each opening?

• a.1 in^2 per 4,000 BTU/hr, which is the vertical-duct ratio
• b.1 in^2 per 1,000 BTU/hr, which oversizes the ducted opening
• c.1 in^2 per 2,000 BTU/hr✓
• d.1 in^2 per 3,000 BTU/hr, the single-opening direct ratio

For two openings communicating with the outdoors through horizontal ducts, IFGC 304.6 requires 1 in^2 of free area per 2,000 BTU/hr for each opening. Vertical ducts use 1 in^2 per 4,000 BTU/hr because a vertical duct promotes flow. The high opening supplies dilution and the low opening supplies combustion air.IFGC §304.6

A single outdoor combustion-air opening serves a 150,000 BTU/hr load at 1 in^2 per 3,000 BTU/hr. What free area does the calculation give?

• a.100 in^2, doubling the correct result
• b.75 in^2, using the wrong 2,000 BTU ratio
• c.30 in^2, dividing by 5,000 by mistake
• d.50 in^2✓

Free area = 150,000 / 3,000 = 50 in^2, per IFGC 304.6.1, though the 100 in^2 minimum for a single opening would then govern. The calculation itself yields 50 in^2; the code floor raises small results. Louvers further reduce net free area and must be compensated for.IFGC §304.6.1

Two vertical combustion-air ducts serve a 240,000 BTU/hr load at 1 in^2 per 4,000 BTU/hr each. What is the free area of each opening?

• a.60 in^2✓
• b.30 in^2, dividing the load by 8,000 instead of 4,000
• c.48 in^2, using a 5,000 BTU per square inch ratio
• d.120 in^2, using the 2,000 BTU horizontal ratio by mistake

Each vertical opening = 240,000 / 4,000 = 60 in^2, per IFGC 304.6. Vertical ducts use the 4,000 ratio because they draft more effectively than horizontal ducts, which use 2,000. One opening is placed high and one low so both dilution and combustion air are supplied.IFGC §304.6

A required net free area of 50 in^2 must pass through a wood louver that is about 25 percent free area. What gross louver opening is required?

• a.200 in^2✓
• b.50 in^2, ignoring the blockage of the louver blades
• c.67 in^2, using a metal-louver 75 percent free-area factor
• d.100 in^2, correcting for only half of the louver blockage

Gross opening = required net area / louver free fraction = 50 / 0.25 = 200 in^2, per IFGC 304.6. Wood louvers are assumed about 25 percent free and metal louvers about 75 percent unless labeled otherwise. Failing to correct for louver blockage leaves the appliance short of combustion air.IFGC §304.6

A Category I gas appliance uses which type of venting?

• a.No vent at all, because Category I appliances are unvented
• b.A Type B gas vent or a lined masonry chimney✓
• c.A sealed PVC vent designed for positive pressure and condensate
• d.A bare single-wall aluminum vent with no clearance to combustibles

A Category I appliance vents with non-positive pressure and non-condensing flue gas, so IFGC 503 allows a Type B gas vent or an approved lined chimney. Condensing (Category IV) appliances instead require sealed plastic venting. Matching the vent to the appliance category prevents condensation damage and spillage.IFGC §503

A single-wall metal vent connector runs from a gas appliance toward the chimney. What minimum clearance to combustibles is required?

• a.6 in✓
• b.0 in, since a metal connector may touch wood framing
• c.1 in, which applies only to a listed double-wall connector
• d.18 in, which is far more than the code requires here

A single-wall metal vent connector requires 6 in of clearance to combustibles, per IFGC 503.10.6, because its outer surface runs hot. Type B double-wall connectors allow reduced clearance (often 1 in) due to their air space. Reduced clearance requires a listed connector, not single-wall pipe.IFGC §503.10.6

For a naturally drafting appliance, the horizontal length of a single-wall vent connector is limited relative to the vent height. What is that limit?

• a.No more than 75 percent of the vent height✓
• b.It may be as much as twice the vertical vent height allowed
• c.It may equal the full vertical height of the chimney or vent
• d.There is no length limit on a horizontal vent connector

IFGC 503.10 limits a single-wall vent connector's horizontal run to 75 percent of the vent or chimney height (Type B connectors allow 100 percent). A long horizontal connector cools the flue gas and robs draft. The connector must also rise toward the chimney to keep gases moving upward.IFGC §503.10

With all appliances operating, a plumber checks the draft hood for spillage. What is being verified?

• a.That flue gases draft up the vent instead of spilling into the room✓
• b.That the vent connector is completely sealed and airtight
• c.That the pilot flame has been extinguished before testing
• d.That the appliance gas valve is fully closed during the test

A spillage (backdraft) test at the draft-hood relief opening, per IFGC 503, confirms the vent is establishing draft and not dumping combustion products into the room. Spillage indicates blockage, undersized venting, or depressurization. Persistent spillage releases carbon monoxide and must be corrected.IFGC §503

A Type B gas vent penetrates and terminates above a roof. What minimum termination height above the roof is required at the penetration?

• a.Below the ridge line so it is hidden from view
• b.6 in above the roof, which is below the code minimum
• c.At least 1 ft above the roof✓
• d.Flush with the roof surface at the point of penetration

IFGC 503.6.4 requires a gas vent to terminate at least 1 ft above the roof it penetrates, with more height on steeper pitches, and clear of nearby walls and openings, using a listed cap. Terminating too low invites downdraft and re-entry of flue gases. Exact height comes from the vent-height chart.IFGC §503.6.4

A direct-vent (sealed-combustion) appliance is installed in a small utility room. What combustion-air requirement applies?

• a.It draws its combustion air from the surrounding room space
• b.None from the room; air comes from outdoors through its sealed intake✓
• c.It needs 50 ft^3 of room volume per 1,000 BTU/hr of input
• d.It requires a lined masonry chimney for its combustion air

A direct-vent appliance is sealed to the room and draws combustion air directly from outdoors through a concentric or separate intake, so IFGC 503 requires no room combustion-air openings. This makes it suitable for tight or confined spaces. Its exhaust also terminates outdoors per the listing.IFGC §503

CSST that requires bonding is connected to the grounding electrode system with a bonding jumper. What is the minimum size of that conductor?

• a.14 AWG copper, which is far too small for the bonding jumper
• b.6 AWG copper✓
• c.No bonding conductor is required for corrugated stainless tubing
• d.10 AWG copper, smaller than the code-required minimum size

CSST bonding uses a conductor not smaller than 6 AWG copper, clamped to a rigid metallic gas component and connected to the grounding electrode system, per IFGC 310.1.1 and the manufacturer's instructions. The heavy conductor drains induced lightning energy so a surge cannot arc through and perforate the thin CSST wall.IFGC §310.1.1

A commercial gas train has a component that automatically stops gas flow if the flame is lost. What is that component?

• a.A vacuum breaker installed on the appliance connector
• b.An automatic safety shutoff valve✓
• c.A simple swing check valve on the appliance supply line
• d.A thermal expansion tank connected to the gas manifold

A commercial gas train includes an automatic safety shutoff valve driven by a flame-safeguard/flame-sensing control that closes on flame failure, per NFPA 54. This prevents raw gas from accumulating when ignition is lost. The train also typically includes manual valves, a regulator, and pressure switches in a defined order.NFPA 54

A commercial gas train has switches that shut the appliance down when supply pressure is outside safe limits. What are these devices?

• a.A temperature-only switch mounted on the appliance cabinet
• b.No such devices exist on a commercial appliance gas train
• c.High- and low-gas-pressure switches✓
• d.A flow meter that records the appliance's gas consumption

High- and low-gas-pressure switches on a commercial gas train, per NFPA 54, prevent firing when supply pressure is too high (risking overfire) or too low (risking incomplete combustion). They are interlocked with the burner control so an out-of-range condition locks out ignition until corrected.NFPA 54

A line-pressure regulator has an atmospheric vent connection. How must that vent terminate?

• a.Capped tightly so that no gas can ever escape from the vent
• b.Into the appliance flue so a leak is carried up the chimney
• c.Inside the equipment room near the regulator for easy access
• d.Outdoors, protected by an insect screen✓

A gas regulator's atmospheric vent must terminate outdoors and be screened against insects, per IFGC 410.3, so a ruptured diaphragm releases gas safely outside. A vent-limiting device may be used where permitted. Capping the vent would prevent the regulator from breathing and operating.IFGC §410.3

When downstream piping and appliances could see pressure exceeding their rating, what protection does the code require?

• a.No protection is required if the regulator looks new
• b.A relief valve that is piped down to the building sanitary sewer
• c.Overpressure protection✓
• d.Only a thermal expansion tank on the gas manifold assembly

IFGC 410.1 requires overpressure protection wherever a regulator failure could subject appliances to pressure above their rating, using relief valves, a monitoring regulator, or a series-regulator arrangement. This protects appliance controls not rated for elevated pressure. Elevated-pressure systems always include such protection.IFGC §410.1

An elevated-pressure (2 psi) gas system serves a dwelling. How is appliance pressure managed?

• a.No regulator is needed because appliances accept any inlet pressure
• b.Only commercial buildings are ever allowed to run at 2 psi service
• c.Elevated pressure is never permitted in a dwelling under any code
• d.A line regulator with overpressure protection reduces it near the appliances✓

IFGC 402.6 permits elevated-pressure (for example 2 psi) systems in dwellings when a line-pressure regulator with overpressure protection reduces the pressure to the appliance's rating near the appliances. The higher trunk pressure lets smaller pipe carry the load; the regulator delivers safe appliance pressure downstream.IFGC §402.6

Compared with the standard 0.5 in w.c. low-pressure table, a 2 psi sizing table lets a given pipe carry how much gas?

• a.More gas✓
• b.Less gas than the low-pressure table for the same pipe size
• c.Exactly the same capacity, since pressure does not affect flow
• d.No gas at all, because 2 psi sizing tables are not published

Because a 2 psi system tolerates a much larger pressure drop than a 0.5 in w.c. system, IFGC 402.4 sizing shows the same pipe carrying more gas (or a smaller pipe serving the same load). This is the advantage of elevated-pressure distribution, paired with a downstream regulator to protect appliances.IFGC §402.4

A 250-gallon aboveground ASME propane container is set beside a dwelling. What minimum separation from the building is required?

• a.25 ft
• b.10 ft✓
• c.3 ft, essentially placing the tank against the building wall
• d.5 ft

NFPA 58 requires an aboveground ASME propane container in the 125 to 500 gallon range to be at least 10 ft from a building and from the line of adjoining property that may be built upon. The separation limits fire exposure and allows for relief-valve discharge. Larger tanks require greater distances.NFPA 58