Mechanical Engineer (Contractor)

What you'll do •

Design, build and commission hydraulic test rigs and prototype products that integrate with heat pumps (buffer tanks, hot water cylinders, heat exchangers, circulation and modulation hardware, and similar).

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Carry out hands-on assembly and plumbing of water-side and refrigerant-adjacent systems - pipework, fittings, pumps, valves, sensors and controls.

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Instrument rigs with temperature, flow and pressure measurement, and run structured test campaigns to characterise both systems and components performance.

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Diagnose and troubleshoot hydraulic, thermal and mechanical issues on live systems, and feed findings back into the design.

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Work closely with the wider R&D team to iterate designs quickly, balancing performance, cost, manufacturability and serviceability.

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Produce clear documentation: test plans, build instructions, results write-ups and design records.

Essential requirements •

Degree in Mechanical Engineering (or a closely related discipline).

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Minimum 5 years' relevant experience in an R&D, product development or test environment.

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Demonstrable heat pump knowledge - you understand how heat pumps work, their operating envelopes, and how the hydraulic system around them behaves (flow, temperature, ΔT, defrost, modulation, etc.).

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Strong hands-on experience - this is the most important requirement. You can build, plumb, commission and fault-find systems yourself, not just specify them. Practical plumbing and pipework skills are essential.

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Experience working with hydraulic systems - pumps, valves, heat exchangers, tanks, pipework and the behaviour of water-side circuits.

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Comfortable instrumenting rigs and interpreting test data to draw engineering conclusions.

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CAD proficiency for designing rig components and prototype parts.

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Able to work independently and using own initiative on-site in Slough and move quickly in a fast-paced R&D environment.

Desirable •

Experience developing products specifically intended to operate with heat pumps (buffer tanks, hot water cylinders, DHW modules, hydraulic interface units, etc.).

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Familiarity with refrigerant-side systems and relevant safety considerations.

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Thermal/fluids analysis skills (thermodynamic modelling, or sizing calculations) to support design decisions.

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Experience in setting up, running, and interpreting FEA (structural/thermal) and CFD analyses on complex systems.

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Relevant trade or industry qualifications (e.g. plumbing, F-Gas, G3 unvented hot water) - not required but valued.

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Experience taking products through prototype into early manufacture.

Why else you'll love it here! •

A genuinely hands-on R&D role at the leading edge of UK heat pump accessory product development.

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A well-equipped facility and the freedom to build and test real hardware.

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A collaborative team that moves fast and values practical engineering judgement.

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Competitive contract day rate, commensurate with experience.

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Octopus Energy is a unique culture. An organisation where people learn, decide, and build quicker. Where people work with autonomy, alongside a wide range of amazing co-owners, on projects that break new ground. We want your hard work to be rewarded with perks you actually care about!

• Visit our perks hub - Octopus Employee Benefits