sprinklernotes
Heat Tracing Entire Wet Systems “Over the years the heat trace section has been evolving. Originally, small, unheated spaces were permitted to be protected with heat trace. The verbiage ‘small, unheated spaces’ has been replaced with ‘unheated spaces.’ As worded, it would appear an entire wet pipe system, installed in an unheated space, can be protected from freezing using heat trace. What is the intent as to how much of a system can be protected with heat trace based on the omission of ‘small’?”
We have reviewed NFPA 13, Standard for the Installation of Sprinkler Systems, 2016 edition that you indicated as the applicable standard. Our informal interpretation is that heat tracing is permitted for entire wet systems excluding the system riser and supply piping. Section 7.1.4 prevents you from using heat tracing to protect the system’s risers from freezing. Also, section 8.16.4.1.4.1 indicates that when using heat tracing to protect branch lines from freezing, it must be listed for such use. Also, the heat tracing must be electronically supervised to provide the positive confirmation that the circuit is energized per section 8.16.4.1.4.2. Additional commentary from the handbook’s “Designer Corner” under section 8.16.4.1.1 states, “In recent editions, NFPA 13 has been modified to allow heat tracing on branch lines. Previous editions prohibited heat tracing on branch lines due to concerns over the potential to heat the sprinkler to its operating temperature and the insulation becoming an obstruction to the sprinkler discharge. Underwriters Laboratories (UL) worked closely with the IEEE to make changes to the listing process required for heat tracing. When heat tracing specifically listed for sprinkler system branch lines is used in accordance with its listing, the concerns are minimized, and it is acceptable to NFPA 13.” As such, there are no imposed limits on the size of a system that can be protected with heat tracing (other than economics).
