The acceptable tolerance for temperature control during functional performance tests depends on the specific application, system design, and industry standards. For example, in food storage applications, a tolerance of ±0.5°C or ±1°F is commonly accepted. In pharmaceutical or laboratory applications, a tighter tolerance of ±0.1°C or ±0.2°F may be required. It’s essential to consult industry standards, system documentation, and manufacturer recommendations to determine the acceptable tolerance for a specific system.