Urban waste heat from IT infrastructure is increasingly relevant for district heating, but remains largely invisible to non-experts. Situated augmented reality (AR) can make redistribution more legible by placing conceptual routes between source and receiver buildings. We compare three outdoor AR representations: a cutaway pipe (Pipe), floating ribbon (Ribbon), and ground-conforming trace (Trace). In a within-subject study (N = 24), all three enabled accurate receiver-building identification, indicating basic spatial legibility. Subjective and comparative judgments differed more strongly: Pipe was clearer than Trace and ranked highest for perceived support of understanding; Trace was least intrusive but weaker for communicative suitability, especially understanding; Ribbon was intermediate mainly for understanding. These findings highlight a trade-off between explanatory explicitness and visual intrusion in public-facing AR visualizations of urban waste heat redistribution.