New low-GWP mildly flammable fluids require modifications to the way metallic utility lines cross classified perimeters. ASHRAE Standard 15 requires new flammability mitigation measures for an A2L refrigerant line break. Legacy dielectric fittings offer basic electrical isolation but fail chemically and mechanically under today’s operating conditions. Modern Direct Expansion ( DX ) systems operate at pressures greater than 600 psig.
ICD 705 requires complete galvanic isolation at all metal crossings. The new SCIF requirements for HVAC penetrations require high-pressure isolation hardware that is both synthetic oil compatible and signal-suppressed.
ASHRAE Standard 34 defines A2L as mildly flammable refrigerants that have a maximum burning velocity of 10 cm/sec or less and an LFL of at least 0.10 kg/m3. Some primary replacements to R-410A are R-32 and R-454B. Both have significantly less global warming potential than R-410A. A2L refrigerants burn much slower than Class A3 hydrocarbons, but still require careful charge calculations, leak prevention, and high-pressure containment.
According to ICD 705, metallic pipes continuously cutting through a secure perimeter are unshielded antennae. Unless acted upon, these conductive lines lose containment of both types of emanations (acoustic and electromagnetic) on which TEMPEST designs are based. Certified designs implement galvanic isolation, ensuring at least 40 dB of RF attenuation within the 10 kHz to 10 GHz frequency range, and are achieved by means of non-conductive breaks. In high-pressure A2L refrigerant line penetrations, mechanical engineers can’t sacrifice structural safety to ensure electrical isolation. The barrier must withstand high levels of mechanical loading, thermal expansion, and vibration, and must not fail by microfractures or leakage.
Incorporating A2L penetration brings additional challenges to the design. Balancing the three aspects of design: Safety, Flammability, and TEMPEST. For classification of occupied spaces, ASHRAE 15-2022 and the Effective Dispersal Volume Charge (EDVC) formula do not consider leak detection and circulation of air; therefore, the Circulation Factor (CF) stays at 1. If a continuous leak detection system is designed to activate air circulation, the CF reduces to 0.5, and the EDVC charge increases by a factor of 2.
A compliant SCIF refrigerant penetration requires that isolation hardware be positioned no more than 6 inches from the secure boundary to minimize disruption of the RF barrier. Mechanical penetrations become an access point for convenient visual inspection and testing of the barrier for leakage.
No. Older water-style dielectric unions rapidly fail with today’s system operating conditions. Standard piping isolates were developed for low-pressure hydronic systems and will not work for operating conditions of 600+ psig. Additionally, these piping isolates do not have certifications for compatibility with aggressive synthetic lubricants and HFC/HFO blends.
Where A2L refrigerants are used, there is a need for a dedicated line break to ensure system compliance for high-pressure conditions and dielectric breakdown due to decomposition of chemical components.
Hydrostatic Burst Strength: Testing ratings > 3,000 psig to be verified for a 5x safety factor with a minimum of 5x the maximum operating limits.
Dielectric Core Integrity: Use solid, non-conductive cores, such as NEMA G10/FR4 or PVDF. Be sure not to use cheap elastomeric gaskets that will deteriorate over time.
Synthetic Oil Resistance: Polyolester (POE) and polyvinyl ether (PVE) type compressor oils are chemically very reactive. Insulators will prevent the seal from becoming brittle.
Electromagnetic Attenuation: No metallic continuity across the isolation gap to satisfy CTTA TEMPEST attenuation requirements (> 40 dB).
A1 (R-22): 300 psig, Mineral Oil, Requires Basic Dielectric Isolation.
A1 (R-410A): >600 psig, synthetic oil, insulation, high pressure, POE Oil
Modern A2L (R-32 / R-454B): 600–700 psig pressure, POE / PVE Oil, requires a non-conductive refrigerant line break with 5x burst rating and ASHRAE 15 compliance.
For secure facilities, a compromise between working pressure and resistance to synthetic oil has to be made when choosing a line break. In comparison to lubricants, PVE has better properties in terms of hydrolytic stability versus POE. Still, both lubricants have the same effect of extracting plasticizers from unrated elastomers. Precision-manufactured dielectric cores paired with copper tailpieces that are factory-brazed provide an insulated length of pipe without reliance on weak interfaces.
There are several factors that engineers need to verify when specifying a SCIF HVAC refrigerant line break. First, they need to make sure that the assembly has factory hydrostatic test certification. Second, at no time should field-installed, uninsulated unions be assembled. Third, the non-conductive core must have a complete galvanic break, and factory-brazed copper tailpieces facilitate rapid, clean installation using the standard silver-solder technique.
Using Hydronic Isolators: Installing low-pressure water unions on high-pressure secure facility HVAC penetrations risks catastrophic burst failures.
Premature Leakage: Assuming legacy seals hold up to POE or PVE means that they will eventually start to swell and leak.
Leaky Construction: Positioning the SCIF HVAC refrigerant line break too far from the interior wall breaks the CTTA perimeter.
Bypassing EDVC Protocols: Assuming that a small VRF charge means that there is no need to follow ASHRAE 15 mitigation in a sensitive compartmented space.
Omitted Exhaust Interlocks: Failing to link mechanical room refrigerant sampling sensors directly to automated emergency exhaust ventilation.
Securing systems for enclosed spaces requires greater engineering discipline to transition secure facility HVAC systems to lower GWP refrigerants. A2L chemistry won’t change the basic tenets of ICD 705, but it will remove all tolerance for poor penetration hardware. It is possible to specify a refrigerant line break for secure facilities.
It is assembled with a strong and reliable G10/FR4 dielectric and a 5x safety margin. Its POE/PVE resistance is also certified, and this protects valuable classified assets from signal exploitation and mechanical failures.