Principal Mechanical Engineer

Role: Principal Mechanical Engineer Location: Paris, France Project: Major data centre programme Salary: Competitive hourly rate Engagement: Contract Start Date: ASAP Responsibilities Lead mechanical engineering activities for facility upgrades designed to support AI compute loads. Develop and optimise liquid cooling systems to manage increased thermal output from high‑density racks. Assess existing mechanical infrastructure and define upgrade paths for chilled water systems, heat rejection equipment, and distribution networks. Produce and review mechanical calculations, specifications, drawings, and technical documentation. Coordinate with electrical, HVAC, BMS, fire safety and architectural teams to ensure seamless integration of upgraded systems. Support commissioning, testing and performance validation of new cooling solutions. Act as a subject‑matter expert throughout the project lifecycle, advising on mechanical resilience and efficiency. Requirements Degree in Mechanical Engineering or Building Services Engineering. Must have Right to Work in France Must have mission-critical Data Centre experience Background in retrofit or upgrade projects involving chilled water, liquid cooling, or advanced thermal management. Ability to collaborate across multiple technical disciplines and manage interfaces. Experience producing and reviewing technical documentation and leading mechanical packages independently. Strong communication skills and confidence in client‑facing environments. With over 90 years' combined experience, NES Fircroft (NES) is proud to be the world's leading engineering staffing provider spanning the Oil & Gas, Power & Renewables, Chemicals, Construction & Infrastructure, Life Sciences, Mining and Manufacturing sectors worldwide. With more than 80 offices in 45 countries, we are able to provide our clients with the engineering and technical expertise they need, wherever and whenever it is needed. We offer contractors far more than a traditional recruitment service, supporting with everything from securing visas and work permits, to providing market-leading benefits packages and accommodation, ensuring they are safely and compliantly able to support our clients.