What Does The i-HEATPUMP Toolkit Do?
i-HEATPUMP is developing software to assist heating engineers commission, maintain, diagnose and optimise domestic and commercial heat pump systems.
This suite of tooling represents a growing set of field tools being developed into a dedicated heat pump diagnostics platform - this page gives early access to selected features before the full platform release.
We hope you find these tools useful - spotted something off or have a suggestion?
Email info@i-heatpump.com with feedback.
Toolbox
Turn Testo temperature values into valuable consumer insight in seconds.
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What the tool does
Turn raw temperature data into real heat output (kW), energy (kWh) and cost (£) in seconds. Identify under-performance, verify output and prove results with measured data.
Try it in seconds
New to temperature analysis? Download a sample Testo data file and upload it to visualise & interact with the results instantly.
How it works
Attach Testo 115i clamps to flow and return pipework
Record temperature data over your chosen time period
Export the file from the Testo Smart App
Upload the file into the i-HEATPUMP tool
Enter actual or illustrative flow rate to match or simulate system conditions
Instantly view heat output (kW), energy (kWh) and estimated cost (£) for the uploaded temperature data
What you can use it for
Reduce call backs by proving outcomes
Verify system performance during commissioning
Quantify the impact of faults such as low flow or poor heat transfer
Demonstrate performance to customers in clear terms
Compare pre/post intervention results
Support reporting and year-on-year analysis
Output & sharing
Generate a simple summary view to:
support customer discussions
include in reports
retain for performance tracking
evidence improvements over time
Learn more about the Testo 115i - explore the full product details here.
New to temperature analysis?
Download a sample Testo data file and try the advanced tool in seconds.
Advanced Heat Output Calculator
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Don’t have Testo temperature probes? Try the basic heat calculator instead.
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The Basic Heat Output Calculator quickly estimates a heating system’s instantaneous heat output (kW) using three key inputs: flow rate, temperature difference (ΔT) between flow and return, and glycol concentration.
This allows you to translate what the system is doing into a meaningful heat output figure in seconds.
Instantaneous heat output is particularly useful when:
Commissioning – verifying the system is delivering expected output relative to design
Servicing – checking performance hasn’t degraded over time
Fault finding – identifying issues such as low flow, poor heat transfer or incorrect settings
System comparison – understanding how adjustments to flow rate or ΔT impact performance
Rather than relying on assumptions or controller estimates, this provides a quick, evidence-based snapshot of actual system performance.
Basic Heat Output Calculator
Cable Current Capacity Estimation Tool
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Electrical installations should be fully de-energised before inspection - follow safe isolation procedures and lock out the supply before working.
This tool helps you quickly sense-check cable sizing in real-world installations.
Enter a measured conductor diameter and compare it against typical current-carrying capacity based on installation method, cable type and run length. It also highlights voltage drop and gives an indicative protective device range.
Why it’s useful
Cable performance isn’t just about size - it’s about how it’s installed.
Insulation, grouping, ambient temperature and run length can significantly reduce how much current a cable can safely carry. This tool helps you spot when a cable might be borderline or undersized.
When to use the advanced options
Only adjust these if something about the installation isn’t “standard”:
COP (heat pump comparison)
Use when working on heat pumps.
Helps translate electrical load into an approximate heat output so you can sense-check system size.Additional thermal restriction
Use if part of the cable is buried in heavy insulation or tightly enclosed.
Example: cable runs through a loft and is covered by deep mineral wool.Ambient temperature
Use if the cable is in a hot space.
Example: lofts in summer, plant rooms, or near hot pipework.Grouped circuits
Use if multiple cables are bundled together.
Example: several circuits clipped together or installed in trunking.
Important
This is a reference and diagnostic tool for use on site, not a substitute for full design to BS7671 or manufacturer guidance.
Cable Current Capacity Estimation Tool
Advanced Options
Explanation
Used to calculate voltage-drop percentage. The default is 240V because many UK sites measure close to this. Lower supply voltage increases the displayed percentage voltage drop.
Voltage drop limit
Selects the pass/fail threshold. Lighting circuits are commonly checked against 3%; other final circuits are commonly checked against 5%.
Grouped circuits correction
Use when multiple circuits run together and cannot freely dissipate heat. More grouped circuits reduce the allowable continuous current.
Ambient temperature correction
Use when the cable is installed in a hotter environment. Higher ambient temperature reduces the cable’s safe continuous current.
Additional thermal restriction
Use only if there is extra heat restriction not already captured by the selected installation method. For insulation-heavy situations, prefer selecting Method 100, 101, 102 or 103 rather than adding this manually.
COP slider
Used only to estimate equivalent heat pump thermal output from the displayed electrical load. It does not affect cable current rating.
Output Summary
| Cross Sectional Area (CSA) | Solid Diameter | Volt Drop |
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Traditional Solid Stone U-Value Calculator
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Traditional British stone buildings are often assumed to lose far more heat through their walls than they actually do.
This calculator estimates the thermal performance (U-value) and design heat loss of traditional solid stone walls using the latest Scottish Government validated RdSAP 10 methodology. It can help homeowners, surveyors and heating engineers better understand how wall construction influences overall heat loss and heat pump sizing.
Why it's useful
Older guidance frequently assumed that solid stone walls had very poor thermal performance. Recent Scottish Government research has shown that many traditional stone walls perform significantly better than historic assumptions, particularly where original lath-and-plaster finishes remain.
This tool allows you to quickly estimate:
Estimated wall U-value (W/m²K)
Design heat loss through the wall (W)
Heat loss rate per square metre (W/m²)
This can provide a more realistic starting point when assessing insulation improvements or estimating whole-house heat loss.
When to use this tool
This calculator is intended for:
Traditional sandstone, limestone and granite buildings.
Preliminary heat loss assessments.
Comparing different wall thicknesses.
Understanding the effect of internal lath-and-plaster finishes.
Sense-checking assumptions used in EPCs and heat loss calculations.
It is not intended for cavity walls, timber frame construction or insulated modern masonry.
Assumptions
The calculator assumes:
Uniform solid stone construction.
Steady-state heat flow.
Traditional Scottish wall construction.
Overall wall thickness measured from finished internal face to finished external face.
Where selected, an additional thermal resistance for traditional lath-and-plaster or dry-lining.
Real buildings are also influenced by workmanship, moisture content, exposure, air leakage, thermal bridges and the condition of existing finishes.
Research and methodology
This calculator is based on the Scottish Government validated RdSAP 10 equations for traditional stone walls, which were developed following in-situ heat flux testing of occupied Scottish buildings by BRE.
Validation of RdSAP U-value Calculation Methodology for Traditional Stone Walls in Scotland
The calculator applies the published sandstone/limestone and granite/whinstone equations together with the optional internal lining adjustment described within the report.
Important
This is a reference and educational tool intended to help understand the thermal performance of traditional Scottish stone walls.
It does not replace a full room-by-room heat loss calculation or professional building assessment. Window and door losses, roof and floor construction, air infiltration, thermal bridging, orientation, solar gains and heating system design must all be considered before selecting or sizing a heating system.
Traditional Stone Wall Heat Loss Calculator
Calculation details
Refrigeration Term Reference Tool
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The refrigeration industry uses a wide range of technical terms and abbreviations that can be unfamiliar to engineers new to refrigerant systems.
The Refrigeration Term Reference Tool is a searchable glossary designed to provide quick explanations of common refrigeration terminology, components, abbreviations and refrigerants.
Why it's useful
This tool allows you to quickly find:
Refrigeration abbreviations.
Common technical terminology.
Refrigerant circuit components.
Refrigerant names and safety classifications.
Each entry provides a concise, practical definition suitable for study or field reference.
When to use this tool
Ideal for:
Engineers preparing for F-Gas training.
Heat pump engineers developing refrigeration knowledge.
Understanding terms found in service manuals.
Supporting technical discussions and fault diagnosis.
Important
This is a reference and educational tool intended to improve understanding of refrigeration terminology.
It does not replace manufacturer documentation, formal F-Gas training or competent-person procedures when working on live refrigeration systems.
Refrigeration Term Reference Tool
Search refrigeration abbreviations, terminology, components and common refrigerants.
Brief definition only
Use the dropdown to choose which supporting sections also open automatically; all available sections can still be expanded manually. The icons shown below are displayed on each listing card where they apply, and indicate what level of detail is available for that term.
Prototype Room Cooling Load Model
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The Prototype Room Cooling Load Model estimates room-by-room cooling loads using a calculation structure based on the CIBSE Guide A admittance method.
Due to the complexity, the tool will work best on a laptop, large tablet or PC.
It considers solar gain, building fabric, glazing, ventilation, occupancy and internal heat gains, enhanced with i-HEATPUMP features and UX including interactive load visualisation, estimated free-running room temperature, energy and running-cost estimates, and report export.
The underlying methodology is credited to the Chartered Institution of Building Services Engineers (CIBSE). This is an independent i-HEATPUMP implementation and is not a CIBSE product or approved calculation tool.
Estimated room temperature: The free-running temperature curve is an illustrative i-HEATPUMP feature, derived from the cooling-load balance to show how room temperature may vary without active cooling and with changes in occupancy and equipment heat. It relies on simplified assumptions about adjacent spaces and should not be treated as a CIBSE-approved temperature prediction or used as a substitute for dynamic thermal modelling.
It is currently a prototype published for peer review. Feedback, challenge and technical scrutiny are welcomed.
CIBSE Guide A · Admittance MethodPrototype Room Cooling Load Model
Hourly room cooling-load calculation using the CIBSE Guide A admittance-method structure: solar, ventilation, fabric conduction, internal gains and intermittent plant operation.
1 · Room
What do these inputs mean?
- Room dimensions determine floor area and air volume.
- Indoor design temperature is the maintained room condition. Lowering it increases conduction and ventilation gain.
- Design margin is applied only to the final equipment-selection figure.
2 · Design conditions
What do these inputs mean?
- Location sets the latitude used to calculate the sun's position.
- Design date sets the time of year. Sun height and direction change through the year, so the same window can have a different solar gain on different dates.
- Peak dry-bulb is the hottest outdoor temperature used for the design day.
- Daily temperature range is the difference between the coolest and hottest outdoor temperature over the day. For example, a high of 25°C and a daily range of 8 K gives a low of about 17°C. A larger range makes the day start cooler and warm up more strongly.
- Solar condition adjusts how strong the assumed sunshine is. Higher solar intensity increases window and external-surface heat gain.
3 · Cooling operation
What do these inputs mean?
- Plant hours affect the CIBSE intermittent-operation correction: a shorter cooling period can require a higher on-period capacity.
- Temperature control describes what the comfort target represents. Air temperature uses the room air only; operative temperature also allows for the effect of warm or cool surrounding surfaces on how the room feels.
- Nominal unit is used only for the selection comparison.
4 · External fabric
Enter element dimensions rather than calculating m² manually. Orientation is used for the hourly sol-air effect.
What do these inputs mean?
- U-value controls mean transmission gain.
- Orientation affects solar heating of opaque external surfaces.
- Response is how quickly the building fabric passes heat into the room. A lightweight wall warms the room relatively quickly. A heavy masonry or concrete element stores more heat first and releases it more slowly, so the hottest part of the day can affect the room later. Lightweight (Timber frame / Stud wall), Medium (Cavity block / Plasterboard), Heavyweight (Solid brick / Exposed concrete).
5 · Internal surfaces & thermal mass
Add the principal internal walls, floor and ceiling exposed to the room. These surfaces do not create an external transmission load when treated as adiabatic, but their thermal admittance affects storage and damping of radiant gains.
What do these inputs mean?
- Internal surfaces include partitions, floor and ceiling bounding the room.
- Response supplies thermal admittance and surface-response properties. Heavy masonry/concrete absorbs and delays more short-term radiant heat than lightweight construction.
- CIBSE Appendix 5.A10 permits internal surfaces to be treated as adiabatic where adjacent-space temperatures are not explicitly modelled. They still matter to the room response.
6 · Windows & shading
What do these inputs mean?
- U-value affects conductive gain through the glazing.
- g-value controls solar energy admitted by the glazing. Default g-value: 0.70 - representative clear double-glazing value, based on published 3M reference glazing data tested to EN 410. Actual glazing g-value should be used where known.
- External shading reduces the directly exposed glazed area. “None” means no external shade.
- Solar gain is calculated hourly and delayed/smoothed through the room surface response before contributing fully to cooling load.
7 · Internal gains
What do these inputs mean?
- Occupancy hours tell the calculator when people, lights and equipment are assumed to be adding heat to the room.
- Radiant fraction is the share of heat that warms walls, floors, ceilings and furniture before it warms the air. A higher setting means more of the heat is stored briefly by the room surfaces rather than appearing in the air immediately.
- Latent gain is the cooling needed to remove moisture as well as heat. People and humid outside air add moisture, so the air conditioner has to dehumidify as well as lower the temperature.
- Equipment / appliances should ideally use measured or manufacturer input power. For a quick survey estimate, typical figures might be: laptop ~30–90 W, monitor ~20–40 W, desktop PC ~100–300 W, high-performance/gaming PC ~300–600 W, TV ~50–150 W, and fridge/freezer roughly ~50–150 W averaged while operating. Actual consumption can vary substantially by device and workload.
8 · Outside air
What do these inputs mean?
- Air changes/hour (ACH) describes how much room air is replaced each hour. For example, 0.5 ACH means outside air equal to half the room volume enters each hour. More outside air normally increases both heat and moisture load.
- Outdoor RH changes latent load.
- Heat recovery reduces the effective outside-air load.
9 · Daily energy & running cost
What do these inputs mean?
- Cooling COP / EER is how much cooling the system delivers for each unit of electricity used. For example, 3.5 means about 3.5 kWh of cooling for 1 kWh of electricity.
- kWh is energy, not instantaneous power. A 1 kW cooling load sustained for one hour equals 1 kWh of cooling energy.
- Electricity cost is your unit rate in £/kWh.
- Operating days simply multiplies the estimated daily cost to give a rough period cost.
- The energy estimate integrates the calculated hourly cooling load across the day, so it changes automatically with occupancy, plant hours, temperature, glazing, shading and other inputs.
Cooling load result
24-hour cooling load & estimated room temperature
Click any label to show or hide that series. Loads use the left axis (kW); estimated room temperature uses the right axis (°C).
What do the chart lines mean?
- Total cooling load: The calculated sensible cooling requirement from the system at each hour.
- Solar: Cooling load caused by solar energy entering through the glazing.
- Fabric: Heat gain through external walls, roof, floor and glazing.
- Internal gains: Heat added by occupants, lighting and equipment/appliances.
- Outside air load: Cooling load caused by ventilation or infiltration, including positive sensible heat gain and latent moisture-removal load.
- Room temperature without cooling: An illustrative i-HEATPUMP estimate of free-running room temperature with no active cooling. Solar and internal gains are balanced dynamically against fabric, ventilation and adjacent-space heat exchange using the current estimated room temperature at each timestep. Entered thermal admittance provides damping. It is not presented as a CIBSE-approved temperature prediction.
- Occupied-period shading: The shaded background shows the hours when occupancy and associated internal gains are active.
Peak-hour contribution
Indoor-unit check
| Calculated design total | |
| Selected nominal unit | |
| Nominal ratio | |
| Comment |
Final equipment selection must still use manufacturer capacity data at the actual indoor/outdoor design condition, minimum modulation, airflow/throw, multi-split diversity where applicable and dehumidification performance.
Calculation methodology
The sensible calculation follows the CIBSE Guide A admittance-method sequence: hourly solar, ventilation, conduction and internal gains are separated into daily mean and cyclic components; radiant and convective gains are assigned to environmental and air nodes; response factors are applied; and restricted plant hours receive an intermittent-operation correction. Thermal-response presets provide the admittance/decrement/surface-response quantities required by the method. The displayed latent load is added separately for equipment selection. The dashed free-running temperature curve is derived from the same CIBSE admittance-method sensible-load balance by solving for the hourly room temperature at which the calculated sensible cooling requirement becomes zero. Explicitly entered internal surfaces are treated as adiabatic for transmission but contribute to the room thermal-response terms. The temperature curve remains an illustrative i-HEATPUMP estimate rather than a separate CIBSE-approved free-running-temperature calculation.