Does butane refrigerant piping require special protection

[Yikes]

First time working on a 2-story apartment project where the mechanical engineer is proposing butane as the refrigerant. I am unfamiliar with this.
California's code is based on the Uniform Mechanical Code, and he says it has no requirements to place butane line sets inside shafts or other protected areas.
He did say that in areas that have adopted the IMC, butane lines would require some kind of additional protection.
What is the requirement in the IMC? Should I be concerned if the UMC doesn't have a protection requirement?

 

[BN4537]

If you have less than 6.6 pounds of refrigerant per appliance system, no protection is required no matter how flammable or toxic it is. If you have more than that, and you exceed the limit of refrigerant allowed in that space, the room the appliance is in would have to be a "machinery room". (2021 IMC 1104)

Butane is labeled in the IMC Table 1103.1 as R-600, and it is classified as an A3 refrigerant, meaning that it is flammable, but (mostly) non-toxic. You can have up to .15 pounds of this refrigerant per 1000 cubic feet before triggering a "machinery room". Remember though, if you have less than 6.6 pounds you don't have to worry about it.

MACHINERY ROOM. An enclosed space that is required by Chapter 11 to contain refrigeration equipment and to comply with Sections 1105 and 1106.

❖ Machinery rooms serve to accommodate refrigeration equipment but may also be used to house other equipment and appliances in addition to the refrigeration equipment. ASHRAE 15 defines a machinery room as “a space that is designed to safely house compressors and pressure vessels.” Machinery rooms are considered to be special because of the potential hazard associated with leaking refrigerant equipment. Some refrigerants pose flammability and toxicity hazards to the occupants of the structure, and specially designed rooms are necessary to address those hazards. Sections 1105 and 1106 state the requirements for the construction of machinery rooms. The definition simply states that a machinery room is something that can be required by Chapter 11 for the purpose of containing refrigeration equipment.

 

[BN4537]

Machinery rooms have many limitations including requiring refrigerant detection, mechanical ventilation, hot surfaces that might ignite flammable refrigerants, they become a Class I Division 2 hazardous location per NFPA 70, a break-glass or other tamperproof emergency shutoff and ventilation turn-on devices, 1 hour fire separation or automatic sprinklers - and the list goes on.

You would be looking at Table 509.1 out of the IBC, Section 605 of the IFC, and Sections 1104, 1105, and 1106 out of the IMC. There is a lot there, so I don't want to summarize further lest I oversimplify something.

 

[BN4537]

By contrast, the R410A that has been commonly used until recently is an A1, non-flammable, (mostly) non-toxic, and you could have up to 26 lbs per 1000 cubic feet instead of .15 pounds per cubic feet.

 

[BN4537]

The refrigerant lines themselves being protected in a shaft if they penetrate 2 or more floor/ceiling assemblies would be section 1109.2.5 and the shafts have to have continuously ventilation for A3 refrigerants per 1109.4.2.

 

[Yikes]

Thanks so much!

 

[steveray]

Is it actually butane or just the new A2L stuff?