To provide a composition for a hat cycle system which comprises a working fluid containing 1,1,2-trifluoroethylene, having cycle performance sufficient as an alternative to R410A while suppressing influence over global warming, and a heat cycle system employing the composition.
A composition for a heat cycle system, which comprises a working fluid for heat cycle containing 1,1,2-trifluoroethylene, CF3I and at least one compound selected from a hydrofluorocarbon, a hydrofluoroolefin other than 1,1,2-trifluoroethylene and a hydrocarbon, and having a temperature glide of at most 7° C., and a heat cycle system employing the composition for a heat cycle system.