New Mexico CID MM-2 Natural Gas Fitting Examination

How many years of experience does NMAC 14.6.6 require for the MM-2 natural gas fitting classification?

• AFour years
• BTwo years
• CSix years
• DOne year of classroom training only

Which fuel-gas work is expressly outside the MM-2 classification in NMAC 14.6.6?

• ANatural-gas piping to a listed furnace
• BA listed natural-gas water heater
• CLiquefied-petroleum-gas (LP-gas) systems
• DA warm-air furnace flue connection

An MM-2 contractor is asked to install a hydronic hot-water heating system. What pressure and input limits does NMAC 14.6.6 place on that MM-2 work?

• ANot exceeding 30 psi or 400,000 Btu/h input
• BAny pressure or input, because MM-2 is unlimited mechanical
• CNot exceeding 15 psi and 100,000 Btu/h only
• DSteam systems only; hot-water heating is MM-3 work

When an MM-2 job needs a water connection for a boiler or hydronic appliance, what water-piping work does NMAC 14.6.6 authorize?

• AConnection of water only to existing valved outlets
• BA complete new potable-water service from the meter
• CAny underground water main in the public right-of-way
• DNo water piping of any kind

Which group of warm-air heating items is listed inside the MM-2 scope in NMAC 14.6.6?

• AChimney connections, flues, refractories, burners, fittings, valves, thermal insulation,…
• BOnly the gas valve; flues and insulation belong to MM-3
• CRefrigerant piping, evaporator coils, and condensing units
• DLP-gas tank sets and first-stage regulators

Which control work is inside the MM-2 classification?

• AIncidental controls, control wiring, and pneumatic control systems
• BBuilding service-entrance electrical panels
• CFire-alarm initiating devices throughout the building
• DHigh-voltage motor starters for 480-volt rooftop units

Does the MM-2 classification include excavation needed to install natural-gas piping?

• AYes; the classification includes all required excavating, trenching, and backfilling
• BNo; all digging must be subcontracted to a GS-8 licensee
• COnly hand digging to 6 inches is allowed
• DOnly boring under public streets is allowed

What code does 14.9.2 NMAC adopt as the 2021 New Mexico Mechanical Code?

• AThe 2021 International Mechanical Code with no changes
• BThe 2015 International Fuel Gas Code only
• CThe 2021 Uniform Mechanical Code, as amended by 14.9.2 NMAC
• DNFPA 58 as the mechanical code

Under 14.9.2.10 NMAC, who is the authority having jurisdiction for the New Mexico Mechanical Code?

• AThe local gas utility only
• BAny homeowner on the job
• CCID and the mechanical-plumbing trade bureau chief
• DThe International Association of Plumbing and Mechanical Officials

14.9.2.10 NMAC keeps the UMC definition of listed (third-party certified) and adds which New Mexico rule?

• AOnly UL-listed appliances may be used
• BListing is waived if the contractor has an MM-2 license
• CA manufacturer may select an ANSI-accredited independent certification organization, or a…
• DOwner affidavits replace product listing

A nameplate lists 80,000 Btu/h input. The local natural-gas heating value is 1,000 Btu per cubic foot. What load, in cubic feet per hour, do you enter in a UMC natural-gas sizing table?

• A8 CFH
• B800 CFH
• C80 CFH
• D80,000 CFH

The common UMC low-pressure natural-gas pipe-sizing tables assume which specific gravity unless the utility states otherwise?

• A0.60
• B1.50
• C2.00
• D0.08

Incomplete combustion of natural gas in a furnace or boiler most directly produces which hazardous product?

• APure oxygen
• BLiquid nitrogen
• CCarbon monoxide
• DRefrigerant oil

A house piping system operates at about 7 inches water column. Which statement is correct for UMC fuel-gas test and sizing language?

• A7 inches water column is the same as 2 psi
• B7 inches water column always requires a 60 psi welded-pipe test
• C7 inches water column is a low-pressure utilization pressure, well below the 14-inch wate…
• DWater-column pressure is used only for hydronic boilers

A customer wants one contractor to install a split-system air conditioner with a refrigerant condensing unit and evaporator coil, plus the natural-gas furnace. What is the correct MM-2 limit?

• AMM-2 covers the entire HVAC system, including refrigerant piping
• BMM-2 covers only the thermostat
• CMM-2 covers the natural-gas furnace, gas piping, flue, and listed gas-appliance work; ref…
• DMM-2 may install the condensing unit if the furnace is gas

Which heating plant is expressly inside the MM-2 classification?

• ASteam and hot-water boilers
• BA 50-ton centrifugal chiller
• CA medical-gas manifold
• DAn LP-gas first-stage regulator and tank set

A crew proposes Type L copper pipe for interior natural-gas distribution. What does 14.9.2.21 NMAC require?

• AApprove Type L copper; UMC 1308.5.2.2 still allows it
• BApprove Type K copper only
• CReject it; 14.9.2.21 NMAC deletes UMC 1308.5.2.2 and states that copper and copper-alloy…
• DApprove copper for natural gas and reject it only for LP-gas

Besides the serving supplier’s meter valve, what extra shutoff does 14.9.2.21 NMAC require on a New Mexico natural-gas piping system?

• AAn additional approved gas shutoff valve downstream of the serving supplier gas meter, be…
• BA second utility meter on the roof
• CA fusible-link valve at every connector
• DA curb valve at the property line in every occupancy

A crew wants to bond CSST natural-gas piping using only the bonding method printed in UMC 1311.0. What does 14.9.2.21 NMAC require?

• AUse UMC 1311.0 as printed; New Mexico did not touch bonding
• BSkip bonding if the CSST is yellow-jacketed
• CDelete UMC 1311.0 and apply the New Mexico Electrical Code, subsection G of 14.10.4.11 NM…
• DHave the gas utility, not the electrical code, approve bonding

An underground natural-gas service will be polyethylene. Under UMC Chapter 13 / UPC 1210.1, what is the ordinary minimum cover, and when must cover increase?

• A6 inches of cover in all locations
• B36 inches of cover under every lawn
• C12 inches of cover, increased to 18 inches where external damage from external forces is…
• DNo cover is required if warning tape is used

An underground polyethylene gas line is installed without a tracer. What does UMC Chapter 13 / UPC Chapter 12 require?

• ANothing; polyethylene is locatable with a metal detector
• BA steel messenger cable inside the PE
• CAn electrically continuous corrosion-resistant tracer buried with the plastic pipe, with…
• DA second PE pipe painted orange

Where may polyethylene (PE) fuel-gas pipe be used on an MM-2 natural-gas job?

• AAs the interior house piping above a basement ceiling
• BAs a flexible connector to a range
• CUnderground outside, with an approved transition to metallic pipe or a listed riser befor…
• DThreaded into a steel tee inside a mechanical room

A listed flexible gas appliance connector measures 10 feet between the appliance shutoff and a movable range. What is the correct call?

• AReject it; listed flexible appliance connectors are limited to a maximum length of 6 feet
• BApprove it; any listed length is acceptable
• CApprove it if the connector is CSST
• DApprove it for ranges and reject it only for water heaters

Where the code requires a sediment trap at a furnace, where is it installed?

• AUpstream of the appliance shutoff, anywhere on the house main
• BOn the vent connector
• CDownstream of the appliance shutoff valve, as close to the appliance inlet as practical
• DOnly on LP-gas appliances

A union serving a gas furnace is buried in the wall behind drywall. What is the correct installation?

• ALeave it; unions may be concealed
• BWeld the union closed
• CLocate the union in an accessible location, typically in the same room as the appliance a…
• DReplace the union with a soldered copper coupling

Natural-gas piping will be concealed in a hollow partition. Which fitting arrangement is acceptable?

• AA right-and-left coupling or union hidden in the stud bay
• BCSST with unlisted hose clamps in the wall
• CA plugged tee left for a future appliance inside the wall
• DRunning pipe with listed fittings permitted for concealed locations; do not conceal union…

Threaded steel gas-pipe joints shall be made up with which compound or tape?

• AOrdinary PVC cement
• BNo compound; dry threads only
• CSweat solder
• DAn approved thread compound or tape suitable for the gas used, applied to the male threads

A 1-inch schedule 40 steel gas pipe runs horizontally. The UMC/UPC support table used on the job states a maximum hanger spacing of 8 feet for 1-inch steel pipe. What is the greatest hanger spacing you may use?

• A8 feet
• B12 feet
• C20 feet
• DSupports are optional on steel pipe

CSST is being joined to a steel manifold. Which fittings are acceptable?

• AOnly the manufacturer’s listed CSST fittings, installed to the listing and the code
• BHose clamps and radiator clamps
• COrdinary plumbing compression stops
• DSoldered copper sweat fittings

14.9.2.21 NMAC, after banning copper and copper-alloy pipe, also states which rule for aluminum-alloy pipe?

• AAluminum-alloy pipe shall not be used with gases corrosive to such material
• BAluminum-alloy pipe is required for all underground services
• CAluminum-alloy pipe replaces steel indoors
• DAluminum-alloy pipe is the only legal CSST jacket

An outdoor PE gas service reaches the building wall. What is the correct way to bring gas inside?

• AContinue the PE through the foundation and up the interior wall
• BUse a garden hose for the last 3 feet
• CStab the PE through a masonry hole with no sleeve and no transition
• DTransition outdoors with a listed anodeless riser or approved metallic riser and enter th…

Steel gas pipe is installed where vehicles or stored materials can strike it. What protection is required?

• ANone; steel pipe is strong enough
• BWrapping the pipe with duct tape
• CA coat of latex paint only
• DApproved protection from physical damage, such as posts, guards, or routing out of the tr…

On a piping system that can collect moisture or debris, where should a drip or sediment pocket be placed?

• AAt a high point so gas can vent
• BOnly at the utility meter, never at appliances
• CIn the vent connector
• DAt a low point on the piping, with a cap or plug that can be serviced, so condensate and…

Gas piping passes through a concrete foundation wall. What installation detail is required?

• AEmbed bare steel in the concrete with no sleeve and no coating
• BLeave a 6-inch open hole around the pipe for combustion air
• CUse PE pushed tightly through the wet concrete
• DProtect the pipe at the penetration with a sleeve, wrapping, or other approved method so…

Using the IPT Pipe Trades 45-degree offset constant of 1.414, what travel length of pipe is required for a 16-inch spread (offset) on a 45-degree gas-pipe offset?

• A16 inches
• B11.3 inches
• C32 inches
• D22.6 inches

Convert a 120,000 Btu/h natural-gas furnace to cubic feet per hour if the heating value is 1,000 Btu per cubic foot.

• A12 CFH
• B120,000 CFH
• C1,200 CFH
• D120 CFH

When sizing a low-pressure natural-gas system by the UMC 1315.2 longest-length method, which length is used for every pipe section?

• AThe developed length from the point of delivery to the most remote appliance outlet, used…
• BEach section’s own short length only
• CThe average of all branch lengths
• DThe plan-view horizontal distance, ignoring fittings and risers

A low-pressure natural-gas system is sized from a UMC schedule 40 metallic-pipe table (inlet less than 2 psi, 0.5 inch water-column drop, specific gravity 0.60). Longest developed length is 60 feet. Total connected load is 120 CFH. The 60-foot row of the table used on the exam lists: 1/2 inch = 65 CFH, 3/4 inch = 137 CFH, 1 inch = 257 CFH. What is the smallest pipe that may carry the full 120 CFH main load?

• A1/2 inch
• B2 inch, because every main must be at least 2 inch
• C1 inch is the minimum that can carry 120 CFH
• D3/4 inch

A dwelling has an 80,000 Btu/h furnace and a 40,000 Btu/h water heater on 1,000 Btu/cf natural gas. Longest developed length is 40 feet. The UMC table row at 40 feet lists 1/2 inch = 81 CFH and 3/4 inch = 170 CFH. What is the smallest branch that may serve only the water heater?

• A1/2 inch, because 40 CFH is less than 81 CFH at the 40-foot longest length
• B3/8 inch, because 40 CFH always fits 3/8 inch
• C3/4 inch, because every branch must match the main
• D1 inch, because water heaters require 1-inch connectors

An existing low-pressure house main was sized for 90 CFH. The owner adds a 50,000 Btu/h (50 CFH) decorative appliance. What must you do before connecting it?

• AConnect it; existing mains never need restudy
• BReduce the furnace orifice instead of checking pipe size
• CAlways replace the entire system with 2-inch pipe
• DRecheck the existing piping capacity for the new total load using the same longest-length…

A UMC low-pressure natural-gas sizing table is titled for inlet pressure less than 2 psi, pressure drop of 0.5 inch water column, and specific gravity 0.60. When may you use that table?

• AFor any 2 psi CSST system, because the numbers look similar
• BFor hydronic pipe sizing
• CFor undiluted propane at 11 inches water column
• DOnly when the actual system matches those inlet-pressure, drop, gravity, and pipe-materia…

Developed length for gas-pipe sizing includes which of the following?

• AOnly the straight plan-view run, ignoring elbows and risers
• BTwice the building perimeter
• COnly the vertical rise
• DThe actual centerline length of the piping, including offsets, fittings, and vertical run…

A system has a 100,000 Btu/h furnace, a 40,000 Btu/h water heater, and a 35,000 Btu/h range on 1,000 Btu/cf gas. Longest length is 50 feet. The 50-foot row of the table used on the exam lists: 1/2 inch = 73 CFH, 3/4 inch = 152 CFH, 1 inch = 286 CFH. What is the smallest main that can carry the entire connected load?

• A1/2 inch
• B3/4 inch
• C1 inch
• D2 inch

After you find a table size that meets the load, which size do you install?

• AThe smallest listed size whose capacity is at least the section load
• BThe next size smaller than the table value, to save money
• CAlways the largest size on the page
• DAny size, because the table is only a recommendation

The utility states a heating value of 850 Btu per cubic foot. A furnace is rated 85,000 Btu/h. What CFH do you use for sizing?

• A85 CFH, using 1,000 Btu/cf anyway
• B85,000 CFH
• C850 CFH
• D100 CFH, because 85,000 ÷ 850 = 100

A 2 psi natural-gas CSST system will be reduced to inches-of-water-column at each appliance regulator. How should the 2 psi portion be sized?

• AFrom the same 0.5-inch water-column low-pressure steel table used for 7-inch house piping
• BBy always using 3/8-inch CSST regardless of load
• CBy using water-pipe friction tables
• DFrom the UMC table that matches 2 psi inlet, the stated pressure drop, the CSST or steel…

A branch has 28 feet of pipe plus fittings. The IPT or UMC fitting table used on the exam assigns 3 feet of equivalent length to each of four 90-degree elbows. What developed length do you take to the sizing table?

• A28 feet
• B31 feet
• C40 feet
• D12 feet