Writing NBS Specification Text

A good heat pump specification tells the project team what must be provided, how it should perform and what evidence is needed to confirm that the requirements have been met.

For architects and specifiers, writing NBS specification text means turning design decisions into clear instructions that can be priced, installed and verified. That requires more detail than a product name or a headline efficiency figure.

The specification should connect the selected equipment to the building’s heating requirements, installation constraints and commissioning strategy.

Start with the system requirements

Before writing the product clause, establish what the heating system needs to achieve.

Confirm the calculated heat loss, design temperatures, emitter strategy and domestic hot water requirements with the heating designer. Identify whether the heat pump is serving space heating, hot water, cooling or a combination of these functions.

Also agree who is responsible for completing the design, selecting equipment and coordinating the installation. Where elements remain contractor-designed, the required outcomes and submission process should be clear.

Following the principles of clear, consistent specification writing helps turn this information into requirements the project team can use.

Use the appropriate NBS structure

NBS Chorus provides structured specification content and guidance, while NBS Source provides manufacturer product information that can support selection.

Use the relevant system and product content available in your specification library. Check the classification and clause structure against the current content rather than carrying forward an old reference without review.

A product clause should identify the equipment. Related system clauses should address the wider installation, controls, execution and verification requirements.

Keep the distinction clear. Naming an outdoor unit does not define the cylinder, hydraulic arrangement, electrical supply, controls or commissioning responsibilities.

If manufacturer information is unavailable on NBS Source, obtain current technical documentation directly and incorporate the relevant requirements into the project specification.

Decide how equipment will be selected

The specification needs to reflect the project’s procurement route and design responsibilities.

Where the designer has selected the equipment, identify the manufacturer, exact model and required configuration. Where the contractor will select equipment, define the performance criteria and the evidence needed to demonstrate suitability.

A combination may be appropriate: a named product with a clear process for assessing proposed alternatives.

Avoid relying on “or equivalent” without explaining the criteria for comparison. An alternative might match a nominal capacity while differing in minimum output, dimensions, electrical requirements, acoustic performance or control compatibility.

Record the review process and the stage at which a proposed change must be submitted. The wording should align with the project’s contract and procurement requirements.

Make performance requirements measurable

Terms such as “high efficiency”, “quiet operation” and “suitable for the property” are difficult to verify without supporting criteria.

For heat pumps, useful specification information includes:

Check the heating duty against the model’s actual performance data. A nominal capacity or headline SCOP should not be assumed to describe performance under every operating condition.

Assessing heat pump output at the proposed source and flow temperatures helps establish whether the selected equipment can meet the building’s requirements.

For acoustics, distinguish sound power from sound pressure and record the conditions associated with published figures. Assess the proposed installation location alongside the equipment data.

Coordinate installation and system interfaces

The specification should make the relationship between the heat pump and the wider building clear.

Identify the drawings and schedules that define equipment locations, pipe routes, plant space and electrical provision. Allocate responsibility for foundations, supports, condensate drainage, penetrations, insulation and making good.

Installation requirements should follow the current manufacturer instructions for the selected model, including airflow, maintenance access and refrigerant-related safety provisions.

For a Kronoterm system, obtain the documentation for the exact equipment configuration. The ADAPT 2 range includes different model and electrical variants, so a range name alone leaves important details unresolved.

Coordinate the indoor equipment, cylinder and controls as carefully as the outdoor unit. Clear interfaces help prevent gaps between the architectural, mechanical and electrical packages.

An illustrative specification example

The following shows the type of information a heat pump specification should capture. It is original example wording for adaptation within the appropriate NBS structure, with project values completed by the responsible designer.

Equipment: Provide the heat pump system identified in the equipment schedule, comprising the specified outdoor unit, indoor hydraulic equipment, controls and associated components.

Manufacturer and model: Kronoterm; exact model, electrical variant and configuration as scheduled.

Heating duty: Deliver not less than [insert] kW at a source temperature of [insert]°C and heating flow temperature of [insert]°C, supported by manufacturer performance data.

Efficiency: Meet the scheduled seasonal efficiency requirement at the stated test conditions.

Acoustics: Submit sound power data for the selected model and operating mode. Demonstrate compatibility with the project acoustic requirements.

Installation: Coordinate with the referenced drawings and install in accordance with the current manufacturer instructions.

Completion: Provide the scheduled commissioning records, control settings, operating instructions and maintenance information.

Alternatives: Submit proposed substitutions through the project’s agreed review process, with evidence against the scheduled performance and installation criteria.

This wording needs the associated schedules, system requirements and project procedures to make it complete. Resolve the placeholders before the specification is issued for pricing or construction.

Specify commissioning and handover

Commissioning requirements belong in the specification from the outset.

Identify the checks, records and demonstrations needed to confirm that the system has been installed and set up as designed. These should cover the relevant hydraulic, electrical and control arrangements, alongside the manufacturer’s commissioning procedures.

Include the information needed by the homeowner or building operator: operating instructions, agreed settings, maintenance requirements and support contacts.

Where performance verification is required, define what will be measured, over what period and by whom. Avoid promising that a catalogue efficiency value will be demonstrated through an unspecified site test.

Keep decisions and revisions traceable

A specification should remain coordinated as the design develops.

Review changes to heat loss, emitters, flow temperatures, equipment and layouts against the affected clauses and schedules. Check that a product substitution does not leave conflicting information elsewhere in the package.

Using Specification Notes within NBS Chorus Pro can help record why a model, finish or performance criterion was selected. This gives later reviewers context without filling the issued specification with design discussions.

Keep project decisions, technical evidence and published requirements clearly related, and confirm responsibilities through the team’s review process.

Discuss your specification with KronoHP

Writing NBS specification text for heat pumps is easier when the underlying product information is clear.

As the UK distributor of Kronoterm heat pumps, KronoHP can discuss the range and the technical information needed to support your equipment selection.

Share your heating requirements, proposed operating temperatures and installation constraints with our team to discuss the product information for your specification.