1. The depth is measured from the surface of the ground to the top of the pipe, which would provide the required one foot of earth coverage for the entire pipe, as required by Sections 313.5 and 718.2 of the 2024 Uniform Plumbing Code.

2. It is the opinion of this committee that the clearances would be measured edge to edge.

1. Yes. This exhaust air could be considered as class 4 due to the potential for acid vapor as the lead-acid is corrosive. Hydrogen is flammable, when the hydrogen concentration rises to levels above 4% there is a substantial risk of an explosion.

2. Yes.

3. Section 502.2.2 of the 2024 Uniform Mechanical Code is not the only regulation the termination would need to comply with. Consideration would also need to be given to NFPA 70 section 706.10, with additional reference to the Fire Code and IEEE 1635-2012/ASHRAE 21-2012.

No. The only restriction for the use of DWV copper is found in Section 811.0 of the 2024 Uniform Plumbing Code, which prohibits the use of copper or copper alloy tube for chemical or industrial waste.

CASE COMMENT: We are looking for clarification regarding Section 504.5 which requires ducted heat recovery ventilators to comply with UL 1812. We are looking to utilize a ducted heat recovery ventilator, but it complies with UL 1995 which appears to be more strict (55 tests vs. 25 tests) than UL 1812. UL 1995 appears to contain nearly all of the tests that UL 1812 has. UL 1812 appears to be more focused on smaller type units more suitable for residential applications while UL 1995 is more focused on larger, commercial style HVAC equipment (which we are proposing to use in this instance).

RESPONSE: UL 1995 is not acceptable as a more stringent substitute for UL 1812. Section 504.5 of the 2024 Uniform Mechanical Code only states UL 1812. UL Standard 1812 is specifically applicable to ducted heat recovery ventilators, whereas UL Standard 1995 has a much broader application as it references HVAC in general. The criteria of UL 1812 includes construction and performance standards for equipment listed for outdoor-use where UL 1995 does not.

CASE COMMENT: If I am interpreting or reading this section correctly, section 710.7 allows the use of all materials (pipe and fittings) approved under Table 701.1 (DWV) can also be used for pressurized application? Comment: The dilemma is most materials listed in Table 701.1 is listed to national standards for gravity flow and not pressurized application and therefore, contradict the intended application within the scope of the standard? An example is PVC pipe and fittings listed to ASTM D2665. Therefore, I would like further clarification.

RESPONSE: Section 710.7 of the 2024 Uniform Plumbing Code states that the the use of pipe and fittings for gravity waste systems may be used for “fixtures, sumps, receiving tanks, and mechanical waste-lifting devices.

CASE COMMENT: We have a Chiller Refrigeration Machinery Room with a Natural Gas Fired Water Cooled Chiller that uses R-134A (Safety Group A1. The room also contains various Electrical Equipment for the building, including the main breaker, Automatic Transfer Switch, and the 460 Volt to 120 Volt Transformer that then serves the Chiller. Per UMC 1108.2 the Electrical Equipment install meets the Electrical Code. However, the State Inspector is citing 1109.1 and has indicated that extra electrical equipment may not be in the same room as the Chiller. The City Building inspector is completely fine with the install.

RESPONSE: Yes, Electrical Equipment that serves the Chiller and also other Equipment in the building may reside in the same room as the chiller, provided the refrigerant is Group A1. The electrical equipment that serve the chiller room needs to meet section 1108.2 of the 2024 Uniform Mechanical Code. Electrical equipment that is essential for the refrigeration process, maintenance of the equipment, or for the illumination of the room can be placed in the machinery room as long as the electrical equipment complies with the electrical code, whereas electrical equipment that serves solely other parts of a building cannot be placed in a machinery room. As stated in the comment the chiller uses a safe refrigerant classed A-1 and most of the equipment listed serves the refrigeration process in one way or another therefore the Authority Having Jurisdiction deemed them safe and essential to the process, Exclusion would be applied to equipment, piping, ducts, vents, or similar devices that are not essential for the refrigeration process. If it is not essential for the chiller room it clearly states that it shall not be in the chiller room under the provisions of section 11098.1 of the 2024 Uniform Mechanical Code. In describing this specific Refrigeration Machinery Room the equipment serves both the chiller and other equipment in the building. Sections 1107.1.8, 1108.1 and 1108.2 of the 2024 Uniform Mechanical Code state that the machinery rooms with Safety Group A1 or B1 refrigerants are not required to be classified as a Class1, Division1 hazardous location; and when other refrigerants are used, instances the machinery room would be considered either a Class1, Division1 or Class1, Division 2 hazardous location for the fans and associated equipment to operate the emergency purge of the machinery room. The flammability ratings increase in Safety Group A2 and A3, or B2 refrigerants; while both the flammability along with the toxicity increase in the Safety Group B3 refrigerants. The intent of the UMC is to recognize the use of certain refrigerants if properly treated are not necessarily any more dangerous to work in than other locations. In those machinery rooms where other than Safety Group A1 or B1 refrigerants are used, the electrical components of the fans and associated equipment to operate the emergency purge of the machinery room would need to intrinsically safe.

The rate of “free air” flow has to do with the air compressor. There are several ways to measure the capabilities of an air compressor, CFM, SCFM (Standard cubic feet per minute), FAD (Free Air Delivery). CFM is the imperial method of describing the volume flow rate of compressed air. It must be defined further to take account of pressure, temperature and relative humidity. SCFM is the flow in CFM measured at some reference point but converted back to standard air conditions (Standard Reference Atmosphere) 14.7 psia, 60°F. Free Air (Free Air Delivery FAD) is the actual quantity of compressed air converted back to the inlet conditions of the compressor. The units for FAD are CFM in the imperial system and l/min in the SI system. The units are in general measured according the ambient inlet standard conditions. Table 1305.2 requires the Nitrogen flow rate to be based on the free air delivery rating. The other gases in the Table are to be rated by CFM or SCFM. An example of rating a compressor by FAD.

As an additional bit of information, nitrogen used in medical settings is more apt to be used for powering pneumatic tools than any therapeutic application.

1. Because of the heat generated by the refrigeration equipment, the room temperature needs to remain at a temperature limited to 104°F. This prescriptive requirement is for the machinery to operate at its optimum, as latent heat loads may affect the design of refrigerants and oils used for lubrication of the equipment the temperature is limited.

2. The code does not offer any exceptions to this. This is to be addressed by the design of the machinery room ventilation to maintain a safe temperature and where natural ventilation cannot provide the required temperature, then mechanical ventilation is required.

3. No, this is a total of the 104°F limit addressed earlier plus and the limit of 18°F temperature rise allowed by incoming air introduced into the machinery room for the entry of authorized personnel.

1. Fuel gas, as defined in Section 208.0 of the 2015 Uniform Plumbing Code, includes, “natural, manufactured, liquefied petroleum, or a mixture of these”. LPG gas systems, other than those described in Section 1202.

3, would be tested using the criteria found in Section 1213.3. 2. The regulations found in Chapter 12, per Section 1201.1, only apply to fuel gas systems with pressures of 5 psi or less. Testing for a 10 psi system should be tested using requirements found in NFPA 58.

3. No.

4. Yes. Per Section 6.14.1.1 of NFPA 58 requires piping to be tested at not less than normal operating pressure for the system.

Yes, unvented wall heaters may be installed in accordance with the manufacturers installation instructions, the terms of their listing requirements, and the strict requirements of 2024 UMC section 915.3.1.1 Unvented Room Heaters, and its noted exceptions. Wall heaters shall not be installed in or attached to walls of combustible material unless listed for such installation. Combustion air shall be provided in accordance with Section 701.4.