Multilayer composite tube with flame-resistant layers

A refrigeration system comprising:

• a compressor;
• an evaporator coil;
• a composite refrigeration line set coupled between the compressor and the evaporator coil to form a fluid circuit between the compressor and the evaporator coil, the composite refrigeration line set comprising:
• a suction line;
• and
• a return line;
• characterized in that one or more of the suction line and the return line are a composite refrigeration line set tube comprising:
• an inner plastic tube;
• a first adhesive layer external to the inner plastic tube;
• an aluminum layer circumferentially surrounding the first adhesive layer and coupled to the inner plastic tube via the first adhesive layer;
• a second adhesive layer external to the aluminum layer;
• and
• an outer plastic layer circumferentially surrounding the aluminum layer and coupled to the aluminum layer via the second adhesive layer;
• wherein:
• the inner plastic tube is polyethylene of raised temperature;
• the outer plastic layer is polyethylene of raised temperature;
• and
• the outer plastic layer comprises at least one a flame-resistant compound combined with the polyethylene of raised temperature, wherein the at least one flame-resistant compound includes one or more selected from the group consisting of:
• glass fibers, nanoclay, nanofibers, a thermal foaming agent, and a combination thereof;
• the aluminum layer has one or more properties selected from the group consisting of:
• being an alloy having 0.1% or greater magnesium by mass;
• and
• being an alloy selected from the group consisting of:
• AL 3004, AL 3005, AL 5052, AL 6061, and AL 8006;
• and
• the composite refrigeration line set tube has a burst pressure in excess of 1950 pounds per square inch;
• and;
• and
• wherein the composite refrigeration line set tube has a flame and smoke spread rating of no more than 25/50 when tested in isolation using Appendix A1.22 of the CAN/ULC-S102-10 Standard Test Method for Surface Burning Characteristics of Building Materials and Assemblies;
• and
• a refrigerant received within the fluid circuit;
• wherein the refrigerant is an A2L refrigerant defined as:
• (i) exhibiting flame propagation when tested at 140° F. and 14.7 psia;
• (ii) having a lower flammability limit (LFL) >0.0062 lb/ft3;
• (iii) having a heat of combustion <8169 Btu/lb;
• and
• (iv) having a maximum burning velocity ≤3.9 in/s when tested at 73.4° F. and 14.7 psia in dry air.