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What Should an MCS Heat Pump Design Pack Include?
What should exist before installation starts?
- Last updated: September 2026
- Heat Loss Hub · For Installers
A heat pump design pack should explain how the proposed system has been calculated, selected and specified.
It should allow the installer to understand:
- What the building needs
- What each room requires
- How the emitters will meet that requirement
- What flow temperature has been selected
- Why the heat pump has been chosen
- How domestic hot water has been considered
- How the system should be arranged
- What assumptions have been made
It should not be confused with the later commissioning records or customer handover pack.
KEY TAKEAWAY
A complete design pack is not a collection of documents. It is a traceable set of engineering decisions.
DESIGN PACK CHECKLIST
Use this checklist to review whether a design pack — yours or a supplier’s — is actually complete.
Design Pack vs Installation Pack vs Handover Pack
These are related, but they are not the same thing.
Design Pack
The design pack is produced before installation and defines the intended system. It should contain enough information to show how the system has been designed and what the installer is expected to build.
Installation and Commissioning Records
These are created during and after installation. They record what was actually installed, tested and commissioned.
Customer Handover Pack
The final handover documentation may include as-installed information, commissioning records, manufacturer manuals, warranty information, customer operating instructions, certificates and other final project documents.
KEY TAKEAWAY
The design pack should describe what is intended to be installed. The handover pack should describe what was actually installed.
The Design Pack Should Tell One Consistent Story
A good design should be traceable from the property all the way through to the final equipment specification. The basic chain is:
Property → Room-by-room heat loss → Emitter requirements → Design emitter temperature → Design flow temperature → Whole-property design load → Heat-pump selection → Hydraulic requirements → Domestic hot water → Final system
Each stage should support the next. If the heat loss suggests one requirement, the emitter schedule another and the selected heat pump something different again, the pack may contain plenty of paperwork but still not represent a coherent design.
KEY TAKEAWAY
If the numbers do not agree with each other, more paperwork does not make the design better.
Project and Property Details
The design pack should clearly identify the project. Typical information includes:
- Customer or project reference
- Property address
- Property type
- Project type
- Design outdoor temperature
- Internal design temperatures
- Relevant construction information
- Designer
- Design date
- Revision number
- Current document status
This information creates the context for everything that follows. It should also make it immediately clear which property and which version of the design the reader is looking at.
Design Assumptions
Some heat pump designs will contain assumptions. That is not necessarily a problem. The problem is when assumptions are invisible. Typical assumptions might relate to:
- U-values
- Hidden insulation
- Floor construction
- Air-change rates
- Ventilation
- Pipe lengths
- Occupancy
- Inaccessible areas
- Construction that cannot be confirmed
Where an assumption materially affects the design, it should be recorded. Ideally the design pack should make clear what has been measured, what has been verified, what has been taken from drawings or documentation and what has been assumed.
KEY TAKEAWAY
Assumptions should be visible, not buried.
Room-by-Room Heat-Loss Calculations
The room-by-room heat-loss calculation is one of the foundations of the design. For each room, the pack should make it possible to identify:
- Room name
- Internal design temperature
- Fabric heat loss
- Ventilation heat loss
- Total room heat loss
The design should also show the resulting whole-property design heat loss. The room totals should reconcile logically with the overall building requirement.
The calculation should also clearly state the external design condition used. Without that context, the heat-loss figure has limited value.
Explore: Room-by-Room Heat Loss Calculations for MCS Installers
Emitter Schedule
The emitter schedule should show how each room will actually receive the heat it needs. For every room, it should normally identify:
- Required heat output
- Existing or proposed emitter
- Emitter type
- Emitter size
- Output at the selected design condition
- Whether the existing emitter is retained
- Whether replacement is required
For radiator systems, the output should be considered at the temperature conditions expected from the heat-pump design. A radiator that produces enough heat at traditional boiler temperatures may not provide the same output at a lower heat-pump flow temperature.
The emitter schedule should prove that each room can meet its calculated heat loss at the chosen design condition.
Design Flow Temperature and Emitter Temperature
Flow temperature should follow from the building and emitter design. It should not simply be chosen first and made to fit later. A sensible design process is:
- Calculate each room heat loss
- Assess the available or proposed emitter
- Determine the temperature required by the limiting room
- Establish the design emitter temperature
- Set the heat-pump design flow temperature accordingly
The pack should make this relationship understandable.
KEY TAKEAWAY
Flow temperature should be the result of the building and emitter design, not a number chosen first.
The design flow temperature also affects heat-pump efficiency, available heat-pump output, emitter output, seasonal performance and hydraulic design. So it should be treated as a central design parameter, not just a line on a report.
Heat-Pump Sizing and Model Selection
The design pack should show why the selected heat pump is suitable for the property. That normally means recording:
- Whole-property design heat loss
- Selected manufacturer
- Selected model
- Heat-pump output at the relevant design condition
- Operating flow temperature
- Relationship between available output and design load
- Any supplementary or bivalent strategy where relevant
The important point is that the selected unit should be assessed at the conditions it will actually be expected to operate under.
KEY TAKEAWAY
Nominal model size is not the same as available output at the design condition. A unit described as an 8kW heat pump, for example, should not automatically be assumed to provide exactly 8kW under every outdoor and water-temperature condition.
The design pack should make the actual selection logic clear.
Explore: Heat Pump Sizing
Seasonal Performance Information
The design pack should also include the relevant design-performance information required for the project. This may include:
- SCOP
- SPER
- Design flow temperature
- Relevant climatic basis
- Manufacturer performance data
- Other required system-performance information
These figures should correspond with the heat pump and system actually being designed. A performance figure calculated using one design temperature should not be presented alongside a different final system configuration without review.
Domestic Hot-Water Design
Domestic hot water should form part of the overall heat-pump design. It should not simply be added once the space-heating design is complete. Relevant information may include:
- Occupancy
- Daily hot-water demand
- Cylinder size
- Cylinder manufacturer/model
- Heat-pump-compatible coil
- Recovery performance
- Available plant space
- Immersion heater or backup arrangement where applicable
The cylinder needs to work with the selected heat pump as well as meet the household’s hot-water requirement.
KEY TAKEAWAY
Hot water should be designed as part of the system, not added after the space-heating design is finished.
Hydraulic Design Information
A technically useful design pack should also explain how water is expected to move through the system. Depending on the project scope, hydraulic information may include:
- Required system flow rate
- Primary pipe sizes
- Distribution pipe sizes
- Pump requirements
- Pressure-drop considerations
- Hydraulic separation
- Buffer or volumiser where justified
- Bypass strategy
- Zoning
- Mixing arrangements where applicable
- Existing system constraints
Not every system needs every hydraulic component. A buffer, low-loss header or additional pump should solve a defined system requirement.
KEY TAKEAWAY
Hydraulic components should solve a design problem, not appear automatically on every schematic.
Explore: Heat Pump Hydraulic Design Service
System Schematic
A system schematic turns a collection of calculations into something the installer can understand operationally. Depending on the project, it may show heat pump, cylinder, pumps, valves, emitters, hydraulic separation, buffers or volumisers, flow and return arrangement, controls, sensors, zone arrangements and other key components.
The schematic does not need to show every physical detail of the installation. Its job is to explain the intended system arrangement clearly.
KEY TAKEAWAY
The schematic should make the intended hydraulic arrangement understandable before installation starts.
Pipe-Sizing Schedule
Where pipe sizing forms part of the design scope, a pipe schedule can make the design much easier to follow. It may include:
- Pipe section or reference
- Required design flow
- Pipe size
- Pipe material where relevant
- Velocity basis
- Pressure-drop basis
- Any key restrictions
A pipe-sizing schedule is particularly useful on larger or more complex systems where several different design flows exist. It also helps prevent later site decisions from undermining the calculated hydraulic design.
Equipment Schedule
A good technical pack may also include an equipment schedule. This can list the main specified components, such as heat pump, cylinder, pumps, motorised valves, controls, buffers or volumisers, hydraulic components, radiators or other emitters and other specified plant.
This gives the installer a clear reference for procurement and installation. It also reduces the risk of equipment being substituted without anybody checking the consequences.
Revision History and Document Control
Designs change. What matters is that those changes are controlled. A design pack should clearly show:
- Revision number
- Revision date
- Description of changes
- Who made the change
- Current issue status
Everyone involved in the project should be able to identify the latest version.
KEY TAKEAWAY
Everyone on the job should know which design revision is current. This becomes particularly important where several people work on the project, the installer and designer are separate businesses, design files are emailed between teams, or equipment changes after the initial design.
What Happens When the Installation Changes?
The final installation does not always follow the original proposal exactly. Examples include:
- Different heat-pump model
- Different cylinder
- Smaller radiator
- Different pipe route
- Different pipe size
- Buffer added or removed
- Control arrangement changed
- Design flow temperature altered
Some changes may be minor. Others can materially affect the design. Where a change affects heat output, flow rate, pressure drop, emitter performance, seasonal performance, hot-water performance or heat-pump suitability, the design should be reviewed.
KEY TAKEAWAY
The design pack should describe the system that is actually going to be installed, not the system that was originally proposed.
What Is Design-Stage Information and What Is Good Practice?
It is useful to distinguish between the core design information required by the applicable design standard and additional technical documents that make the job easier to install and review.
Core Design-Stage Information
Depending on the system and applicable requirements, this can include room-by-room heat losses, internal and external design temperatures, emitter information, design emitter temperature, design flow temperature, whole-property design load, heat-pump selection, heat-pump performance at design conditions, domestic hot-water demand, cylinder information, relevant system-performance information and additional ground-source information where applicable.
Good-Practice Technical Additions
These may include hydraulic schematic, pipe-sizing schedule, equipment schedule, assumptions register, design notes, control notes, design flow rates, revision history and change log.
These additions can make the pack significantly more useful to the installer even where they are not all separate mandatory documents.
What Does Not Belong in the Pre-Installation Design Pack?
Some documents belong later in the project. These can include commissioning sheets, as-installed test results, final commissioning settings, warranty documentation, manufacturer manuals, customer operating instructions, final certificates, final as-installed records and payment documentation.
These may form part of the wider job file or customer handover pack. They should not be confused with the pre-installation design information.
Design Pack vs Audit-Ready Project File
The design pack is only one part of the full project record. An audit-ready project file may also contain initial survey, site photographs, customer information, design calculations, design pack, installation records, electrical information, DNO correspondence, commissioning documentation, handover evidence, certificates and final as-installed records.
The exact requirements depend on the project and the installer’s certification arrangements.
KEY TAKEAWAY
The important point is that the design pack should fit into a wider traceable project record.
Outsourced Design: What Should the Installer Expect Back?
If design work is outsourced, the installer should still receive enough information to understand the design. An external design pack should be complete for the agreed scope, traceable, internally consistent, clearly revised, understandable to the installer, based on declared assumptions, clear about equipment selection and clear about outstanding limitations or queries.
KEY TAKEAWAY
Outsourcing the design should not turn the technical reasoning into a black box. Outsourcing the calculation should not mean outsourcing visibility.
Explore: Outsourced MCS Heat Pump Design
Heat Pump Design-Pack Quality Checklist
A useful way to review a finished pack is to ask whether you can answer the following questions.
Heat Loss
- What does each room lose?
- What is the whole-property design heat loss?
- What external temperature was used?
- What internal temperatures were used?
Emitters
- What output does each room require?
- What emitter has been selected?
- Can it meet the room requirement at the selected design temperature?
Flow Temperature
- What is the design flow temperature?
- Why was that temperature selected?
- Which room or emitter governs it?
Heat Pump
- What model has been selected?
- Why was it selected?
- What output does it provide at the design condition?
- How does that compare with the calculated heat load?
Hot Water
- What daily hot-water demand has been used?
- What cylinder has been selected?
- Why is it suitable?
Hydraulics
- What system flow rate is required?
- Are the pipe sizes appropriate?
- How is the system arranged hydraulically?
- Why are any buffers, volumisers or separation components included?
Documentation
- What assumptions were made?
- Which design revision is current?
- Have later changes been incorporated?
KEY TAKEAWAY
If those questions cannot be answered from the design pack, the design may be incomplete or unclear.
Ground-Source Heat-Pump Additions
Ground-source systems need additional design information beyond the heat-pump and emitter design. Depending on the system, this may include:
- Ground-loop sizing
- Ground-array arrangement
- Borehole information
- Trench information
- Collector details
- Brine design information
- Ground-side flow requirements
- Relevant ground conditions
- Design assumptions
The heat-source side of the system needs to be considered as part of the overall design.
Frequently Asked Questions
A complete design pack should normally explain the room-by-room heat loss, emitter requirements, design temperatures, heat-pump selection, hot-water design and relevant system-performance information. Depending on the design scope, it may also include pipe sizing, hydraulic design, schematics, equipment schedules and revision control.
No. The heat-loss calculation is the starting point. A complete design should also show how the building requirement has been translated into emitters, flow temperature, heat-pump selection, hot-water provision and final system arrangement.
An emitter schedule is extremely useful because it shows how each room will meet its calculated heat requirement at the selected operating temperature.
Yes. Flow temperature affects emitter output, heat-pump performance, seasonal efficiency and hydraulic requirements. It should be clearly stated and supported by the design.
The designer should assess the selected unit against the actual design conditions rather than relying only on the nominal model rating.
Relevant system-performance information should be included where required by the applicable design and certification process. It should correspond with the final design configuration.
A schematic is extremely useful where the design includes system hydraulics. It helps the installer understand the intended relationship between the heat pump, cylinder, pumps, valves, emitters and any hydraulic separation.
That depends on the agreed design scope. For a full technical system design, pipe sizing and required flow rates are often valuable parts of the pack.
The design pack defines the intended system before installation. The handover pack records the final installed system and may include commissioning information, manuals, warranties and certificates.
Material changes should be reviewed. If the change affects heat output, emitter performance, flow rate, hydraulics, hot water or heat-pump selection, the design may need revising.
The installer should receive enough information to understand the calculations, selections, assumptions and intended system arrangement within the agreed design scope.
Yes. Where the design changes, each issue should be clearly identifiable so that the installer knows which version is current.
Ground-source systems may require additional information relating to the ground array, boreholes or trenches, brine system and ground-side flow requirements.
Is Your Design Pack Complete?
A good heat-pump design pack should let the installer understand what the building requires, what each room needs, how the emitters will deliver it, why the design flow temperature was selected, why the heat pump was chosen, how hot water has been considered, how the system should operate, what assumptions were made and which design revision is current.
The objective is not to produce the largest possible pack. It is to produce a design that can be followed, checked and installed.
OUTSOURCE THE COMPLETE DESIGN
Send us a project and receive a design pack that’s traceable, complete and ready to install from.
Explore: Heat Pump Design for Installers