Design Engineer (Mechanical)

As Design Engineer (Mechanical), you produce the mechanical design for OnZero's data centers, including the cooling and heat rejection systems that make dense AI compute possible. The solutions are scalable, cost-efficient and sustainable, and built to satisfy technical, safety and customer requirements. You maintain the mechanical content of our reference designs, including the mechanical services of the physical buildings.

You translate business, customer and operational needs into mechanical design principles and deliverables, including heat and mass balances, P&IDs, flow and pressure schedules and equipment specifications. You take part in multidisciplinary design reviews, work alongside the A&E (Architecture & Engineering) consultants who produce detailed design, and carry the mechanical scope through the Project Phases: from Site Selection handover to detailed design, and on through construction, flushing and commissioning.

Responsibilities and Duties:

• Produce and develop mechanical design concepts across direct-to-chip liquid cooling, CDUs and the technology and facility water loops, heat rejection plant, and HVAC cooling of white space and support areas.
• Assess and specify the mechanical technologies, systems, materials and installation methods used across cooling and heat rejection.
• Prepare heat and mass balances, P&IDs, flow, pressure and equipment schedules, and technical specifications to procurement quality.
• Review and comment on consultant and vendor mechanical deliverables, and follow non-conformances through to resolution.
• Act as technical responsible for mechanical systems across design, build and commissioning, supporting factory acceptance testing, flushing and thermal performance verification.
• Maintain the mechanical content of the reference designs, technical requirements and engineering frameworks that align with OnZero standards.
• Propose emerging technologies where they improve efficiency, sustainability and resilience.
• Confirm that mechanical design solutions meet their performance, sustainability, safety and environmental targets, including PUE and WUE.
• Propose updates to the Design Requirements as lessons learned, field experience and new technologies accumulate.
• Keep mechanical guidelines and best practice current so that designs stay consistent, high in quality and scalable.
• Take part in multidisciplinary design reviews and coordinate the mechanical scope with the architectural, civil, electrical and ICT disciplines.
• Work alongside internal and external engineering teams and A&E partners on the mechanical scope.
• Carry the mechanical design through every phase of the Project Phases, from Site Selection handover through detailed design, and stay engaged through construction.
• Support Site Selection, Project Managers and Procurement on mechanical feasibility, cost, lead times and quality, including long-lead equipment.
• Contribute mechanical input to the assessment of brownfield and greenfield opportunities, and to Master Planning, including cooling water availability and heat reuse potential.
• Provide the mechanical basis for CAPEX estimates on new builds, expansions and retrofits.
• Evaluate existing mechanical installations when changes are planned, and support Operations through implementation.
• Approve mechanical design deliverables and calculations within your assigned scope and delegated authority.
• Recommend equipment selections and technical platforms, consistent with engineering standards and sustainability requirements.
• Raise and disposition mechanical design changes and controlled deviations within delegated authority, escalating any that affect the reference design.
• Certify mechanical design readiness as input to design freeze and other Gate Process decisions.

Essential

• A Bachelor's or Master's degree in mechanical, energy, or a related field.

• Experience producing mechanical or HVAC design for data centers, industrial facilities or comparable building services, taken through to construction.
• Working knowledge of hydronic systems and heat rejection: pumps, pipework, valves, flow balancing and pressure drop.

• Working knowledge of air-side cooling, white-space airflow, containment and thermal management.

• Ability to produce heat and mass balances, P&IDs and technical specifications to procurement quality.

• Experience on engineering and construction projects, including review of consultant or vendor deliverables.

• Technical knowledge of product design, and the ability to understand client needs and translate them into solutions.

• Detailed design capability and strong technical problem solving.

• Fluent in English. Finnish, German or Swedish a plus.

Strong Advantage

• Experience in data center design, build and commissioning.

• Direct-to-chip or immersion liquid cooling experience, and exposure to GPU or HPC deployments.

• Heat reuse or district heating interface experience, particularly in the Nordics.

• Thermal modeling, CFD or hydronic system simulation.