Lesson 14: Tests, Inspections, and Course Review

Reading

Thirteen lessons have taught how mechanical and fuel gas systems are designed and installed. Two things prove the finished work. Inspections say who looks, at what point, and what must stay uncovered until they do. Tests say how each system is shown to be tight and safe before it is covered or put in service. Chapter 1 of the 2021 IMC and IFGC sets the inspection and testing rules for both books, and four places set the specific tests: IMC Sections 1011, 1110 and 1208, and IFGC Section 406. Texas cities choose their own mechanical code and Houston enforces the Uniform Mechanical Code (Lesson 1), so treat every number here as a 2021 IMC or IFGC value and confirm the adopted code and any local test rule before you rely on one. This lesson teaches the tests, then reviews the whole course.

The three inspections (IMC 108.2, IFGC 112.2)

Both books name the same three inspections. The underground inspection comes after trenches are excavated and bedded and the piping is installed, and before backfill. The rough-in inspection comes after the roof, framing, fireblocking and bracing are in place and everything to be concealed is complete, and before wall or ceiling membranes go up. The final inspection comes when the installation is complete. The permit holder schedules each one, tells the code official when the work is ready, and provides access (108.2.2, 112.2.2). The official may add other inspections (108.2.1). Two provisions from Lesson 1 belong beside them: a ground-source loop tested under IMC 1210.10 may be backfilled before inspection, and replacement heating equipment may keep running if an inspection is requested within 48 hours and before anything is concealed.

The codes do not tie each test to a named inspection, so the last column is normal practice. It follows from the rule that piping stays exposed until it is tested and from Section 108.2.3.

Who tests, and what a failure means (IMC 108.3, IFGC 112.3)

Tests are made by the permit holder and observed by the code official. New systems, and altered, extended, renovated or repaired parts of old ones, are tested to disclose leaks and defects. The permit holder furnishes the apparatus, material and labor (the IFGC adds instruments). Work that fails is corrected and resubmitted for inspection and testing (108.3.3, 112.3.3). Under 108.2.3 no work goes past an inspection point without approval, and any portion that does not comply is corrected and not covered until the code official authorizes it. The IFGC repeats the same words in 112.2.3, so the rule for both books is short: nothing is hidden until it is approved.

Boilers: the acceptance test (IMC 1011)

When a boiler or pressure vessel is assembled and installed, acceptance tests are run under the ASME Boiler and Pressure Vessel Code or the manufacturer's requirements, and the tests must be approved. Copies of the test documents and the manufacturer's data reports go to the code official (1011.1). The code text prints no test pressure of its own, so the number comes from ASME or the maker. It does control the gauge. An indicating gauge is connected directly to the boiler where the operator can see it throughout the test, it is calibrated and certified by the test operator, and its scale runs from not less than 1.5 to not more than 4 times the maximum test pressure (1011.2).

Refrigerant piping: strength, then vacuum (IMC 1110)

Field-erected refrigerant piping, other than ammonia, is pressure tested for strength and leak tested for tightness after installation and before operation, on both the high and low sides. Listed and labeled equipment such as compressors and condensers need not be tested (1110.1), and field pipe and joints stay exposed until the tests are done (1110.2). The medium is oxygen-free nitrogen, helium or argon, with carbon dioxide allowed for R-744 and water for R-718. Air, oxygen and combustible gases are never used, although a system with tubing not over 5/8 inch outside diameter may test with the refrigerant on its nameplate (1110.3). Two tests are required (1110.5). First, pressure is held not less than 60 minutes at not less than the lower of the design pressures or the relief setting, with no gas added after the start and no pressure loss. Second, a vacuum of 500 microns is pulled, the pump is isolated, and the pressure may not rise above 1,500 microns for at least 10 minutes. Parts inside a duct that carries air to occupied spaces are tested at 150 percent of the higher of the design pressure or the relief setting (1110.5.1). A system holding 55 pounds or more needs a signed certificate of test for the code official (1110.8). These tests are Section 1110, not Section 1108, which covers joints.

Hydronic piping and ground loops (IMC 1208, 1210.10)

Hydronic piping is tested hydrostatically at 1.5 times the maximum system design pressure, but not less than 100 psi, for not less than 15 minutes (1208.1). PEX may be tested with compressed gas only where every manufacturer's instructions for the installed pipe and fittings authorize it and no other rule prohibits it. Radiant piping to be embedded in concrete is tested before the pour and held at operating pressure during it (1209.2). A ground-source loop is tested with water at 100 psi for 15 minutes before the header trenches are backfilled, then flow and pressure loss are compared with the design. A difference of more than 10 percent means the cause must be found and corrected (1210.10).

Fuel gas piping (IFGC 404.20 and 406)

Gas piping is tested gastight before it is put in service or concealed (404.20). Section 406 requires a visual inspection and a pressure test before acceptance and initial operation (406.1). Repairs and additions get a test of the affected piping, but a minor repair needs only inspection and leak-detecting fluid (406.1.2), and a new branch to a new appliance needs only its own test (406.1.3). The medium is air, nitrogen, carbon dioxide or an inert gas, never oxygen (406.2), and the joints stay exposed (406.3). The pressure is not less than 1-1/2 times the maximum working pressure and never below 3 psig (406.4.1). The duration is 1/2 hour for each 500 cubic feet of pipe volume or fraction, 10 minutes for under 10 cubic feet or a single-family dwelling, and never more than 24 hours (406.4.2). The pressure is read with a manometer or a device that shows a loss, and a mechanical gauge's top of scale may not exceed five times the test pressure (406.4). Any drop is a leak unless it can readily be explained by something else (406.5). Lesson 13 covered the leak check when gas is turned on and purging.

Worked example. A Group B clinic has a hydronic loop designed for 90 psi, so the test is 1.5 x 90 = 135 psi for at least 15 minutes, well over the 100 psi floor. Its rooftop unit has a refrigerant coil in the supply duct, with a 300 psi design pressure and a 350 psi relief setting. The coil is tested at 150 percent of the higher value, 1.5 x 350 = 525 psi. The boiler acceptance test runs at 120 psi, so the gauge scale must run from 1.5 x 120 = 180 psi to 4 x 120 = 480 psi, which a 0 to 200 or 0 to 300 psi gauge satisfies. The gas system operates at 2 psig, so 1.5 x 2 = 3 psig, exactly the floor. Its pipe holds 1,300 cubic feet, and 1,300 / 500 = 2.6, which counts as 3 periods, so the test lasts 3 x 1/2 hour = 1-1/2 hours. A mechanical gauge for that test may not top out above 5 x 3 = 15 psi.

Other tests: grease ducts and hoods (IMC 506.3.2.5, 507.6)

A grease duct gets a light test before any part is used or concealed. The permit holder passes a lamp of at least 100 watts through the whole duct so every welded or brazed joint shows it is liquid tight (506.3.2.5). A commercial cooking hood gets a performance test on completion and before final approval. It verifies the exhaust rate, the makeup air and, with the appliances at operating temperature, capture and containment (507.6).

Approval and utility connection (IMC 111 and 112, IFGC 108 and 110)

When the prescribed tests and inspections show that the work complies, the code official issues a notice of approval (IMC 111.1, IFGC 108.1). It can be revoked in writing if it was issued in error (IMC 111.2, IFGC 108.2). No one connects a utility, fuel or power source to a system that needed a permit until the code official authorizes it (IMC 112.1, IFGC 110.1), although a temporary connection for testing may be allowed (IMC 112.2, IFGC 110.2).

Course review

The review walks the six modules in order and repeats the numbers used most often. It teaches nothing new, and every value carries the hedges of its lesson. Where a lesson said to check the adopted code, do the same here.

Module 1: Administration and General Regulations (Lessons 1 and 2)

Every job starts with which code binds. Lesson 1's dated check found that Texas names no statewide mechanical code, that cities adopt their own, and that Houston has enforced the 2021 Uniform Mechanical Code with Houston amendments since early January 2024. This course teaches the IMC and IFGC as the model, so a Houston plan review is written against UMC numbers, not these. Lesson 2 gathered the physical rules for equipment: listing, location, clearances, access and condensate.

Module 2: Ventilation and Exhaust (Lessons 3 to 5)

Lesson 3 built the outdoor air number, Lesson 4 sent air out of the building, and Lesson 5 treated a commercial kitchen exhaust system as one fire safety assembly. The outdoor air rates are Table 403.3.1.1 values and Houston's Uniform Mechanical Code has its own provisions, so the adopted code gives the actual rate.

Module 3: Ducts and Combustion Air (Lessons 6 and 7)

Lesson 6 kept air, smoke and flame moving where the code wants them, and Lesson 7 fed appliances the air they need. Add up shared duct systems before you decide a detector is not required, and size combustion air from the total input of every appliance in the room.

Module 4: Chimneys, Vents, Appliances, and Boilers (Lessons 8 and 9)

Lesson 8 followed flue gas out through the vent, and Lesson 9 covered the boiler, its safety devices and its room. The terminal distances are checked against the appliance's listing and data plate, and boilers already under federal or state inspection may have another authority (Lesson 9).

Module 5: Refrigeration and Hydronics (Lessons 10 and 11)

Lesson 10 asked how much refrigerant is in one circuit compared with the room people occupy, and Lesson 11 moved water through the building. Houston follows the Uniform Mechanical Code, so check the adopted code before you write a correction on either topic.

Module 6: Fuel Gas and Review (Lessons 12 to 14)

Lesson 12 built the gas piping, Lesson 13 sized and tested it, and this lesson gathered every test. The Btu-to-cfh conversion is not stated in the 2021 Chapter 4 text, so use the supplier's heating value, and check the adopted code for lengths between table rows.

The practice exam

The practice exam is the next step. It draws 60 questions, weighted by each topic area's share of the question bank, with a 120-minute time limit. It is a practice tool GCHS built for its own staff development. On an actual project, the locally adopted code, not this course, governs.

Practice questions

Glossary

Acceptance test

The test run on a boiler or pressure vessel after it is assembled and installed, under ASME or the manufacturer's requirements, with the documents sent to the code official (IMC 1011.1).

Hydrostatic test

A leak and strength test that fills piping with water. Hydronic piping is tested at 1.5 times the maximum design pressure, at least 100 psi, for at least 15 minutes (IMC 1208.1).

Micron

A unit of very low pressure used to measure a vacuum. A refrigerant system is pulled to 500 microns and may not rise above 1,500 microns in 10 minutes (IMC 1110.5).

Manometer

A gauge that shows small pressure differences, used to read a pressure loss from leakage during a gas piping test (IFGC 406.4).

Light test

A grease duct leakage test that passes a lamp of at least 100 watts through the duct to show that welded and brazed joints are liquid tight (IMC 506.3.2.5).

Capture and containment test

A hood test run with the cooking appliances at operating temperature to show that the exhaust holds the plume, part of the performance test before final approval (IMC 507.6.1).

Rough-in inspection

The second required inspection, made after framing and fire protection are in place and the concealed work is complete, and before wall or ceiling membranes (IMC 108.2, IFGC 112.2).

Notice of approval

The approval a code official issues after the prescribed tests and inspections show that the work complies (IMC 111.1, IFGC 108.1).