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A commercial ground source heat pump should not be selected from building area or nominal unit capacity alone. The equipment, ground heat exchanger, building terminals, pumps and control sequence must operate as one system across peak and part-load conditions.

For a broader explanation of water-source and ground-source configurations, procurement responsibilities and commissioning requirements, read the Water and Ground Source Heat Pump System Design Guide.

This article has a narrower purpose. It explains which ground-loop and building inputs are needed to compare commercial solutions and determine when vertical boreholes, horizontal collectors, surface-water loops, open-loop groundwater or hybrid systems are appropriate. It does not replace geological design, borefield simulation, local permitting or the complete procurement process covered by the pillar guide.

CASSKY all-in-one ground source heat pump installed in a mechanical room

What Commercial Buyers Need to Decide First

Before comparing heat pump quotations, the buyer should resolve four questions:

  1. Can the site provide a technically and legally usable heat source or heat sink?
  2. What are the building’s simultaneous peak loads, hourly load profile and annual heat balance?
  3. What water temperatures must the heat pump deliver to the building?
  4. Which party is responsible for the ground loop, equipment, hydraulics, controls and whole-system performance?

These questions are connected. For example, a unit may meet the building’s nominal heating load at 35°C outlet water but fail to provide the required capacity or COP at 55°C. Likewise, a borefield may handle the winter peak yet experience long-term temperature drift if the building rejects substantially more heat than it extracts each year.

Therefore, a valid commercial proposal must connect the equipment selection to both the building model and the ground-side design.


Ground Source System Comparison

The best source configuration depends on land availability, geology, groundwater conditions, annual load balance and project risk. No arrangement is automatically preferable for every commercial building.

Source configurationConditions where it is usually more appropriatePrincipal design inputsConditions that may make it unsuitable
Vertical closed-loop borefieldLimited surface area, multi-storey buildings, campuses and projects requiring a compact ground footprintDrilling logs, undisturbed ground temperature, effective ground conductivity, borehole resistance, depth, spacing, grout and long-term loadsProhibitive drilling cost, restricted drilling access, unsuitable geology, groundwater protection constraints or insufficient borefield area
Horizontal closed loopLow-rise sites with available land and economical excavationSoil type, moisture, burial depth, trench layout, seasonal ground temperature, pipe spacing and future land useHigh load density, dry soil, restricted land, planned construction above the field or unacceptable landscape disruption
Closed-loop pond or lake systemA suitable permanent water body is available close to the buildingWater depth, seasonal temperature profile, anchoring, environmental permissions, ice conditions and maintenance accessInsufficient depth, seasonal drying, navigation conflicts, ecological restrictions or risk of physical damage
Open-loop groundwater systemAn aquifer can provide sustainable flow at a useful temperaturePumping test, water temperature, static and pumping levels, chemistry, sand content, discharge or reinjection capacity and permitsScaling, corrosion, excessive pumping head, unreliable yield, reinjection failure or restrictions on abstraction and discharge
Hybrid ground-source systemCooling- or heating-dominated projects where a smaller borefield can be balanced by another source or sinkHourly and monthly loads, auxiliary equipment capacity, changeover logic, energy tariffs and lifecycle analysisPoor control integration, auxiliary equipment noise or plume restrictions, or no economic benefit after pump and maintenance energy
Energy piles or foundationsNew construction where structural foundations can be integrated with the ground heat exchanger from the design stageStructural design, pile geometry, construction programme, pipe routing, thermal interactions and responsibility allocationRetrofit projects, late design changes or unresolved structural and thermal responsibilities

The U.S. Department of Energy’s purchasing guidance confirms that accurate ground properties are essential and that larger installations often measure them directly. Meanwhile, the current CSA/ANSI/IGSHPA C448:2025 series addresses commercial and residential ground-source design and installation, including newer applications such as energy foundations and district energy systems.

However, local codes take precedence. Drilling, groundwater abstraction, reinjection, antifreeze use and environmental protection requirements must be checked in the project jurisdiction.

exchange-heat-with-the-ground

Start with an Hourly Building Load Model

Peak heating and cooling loads determine plant capacity, but they do not fully determine the ground heat exchanger. A commercial borefield also responds to hourly, monthly and annual energy exchange.

The 2025 ASHRAE Handbook chapter on nonresidential load calculations identifies envelope heat transfer, internal gains, ventilation, infiltration, moisture, schedules and system effects as relevant load inputs. In addition, ISO 52016-1:2017, confirmed as current in 2022, provides hourly and monthly calculation procedures for heating, cooling, internal temperature and sensible and latent loads.

A commercial ground source heat pump study should use the following building information.

Building inputMinimum information requiredStatus at quotation stage
Location and weatherProject city, elevation and applicable design weather fileBuyer to provide
Heating design loadBuilding or plant block load at the stated outdoor and indoor conditionsTo be calculated by the project engineer
Cooling design loadSensible and latent block loads, including outdoor air and system gainsTo be calculated by the project engineer
Hourly load profileAt least a representative annual 8,760-hour heating and cooling profile for borefield simulationRequired for final design
Monthly energyMonthly heat extracted from and rejected to the sourceRequired for annual balance review
Occupancy and schedulesOperating hours, holidays, setbacks and future occupancy assumptionsBuyer to provide
Ventilation and humidityOutdoor-air volume, heat recovery, dehumidification and reheat strategyProject engineer to confirm
Domestic hot waterDaily demand, peak draw, storage temperature and priority sequenceBuyer and engineer to confirm
Heating-water temperaturesDesign supply and return temperatures at peak and part loadProject engineer to confirm
Cooling-water temperaturesChilled-water supply and return temperatures, plus humidity-control requirementsProject engineer to confirm
Minimum loadLowest sustained load and active water volumeTo be calculated for cycling and staging review
RedundancyN, N+1, duty/standby or another required arrangementBuyer to specify
Future expansionAdditional floor area, loads or construction phasesBuyer to identify
Electrical conditionsVoltage, frequency, phase, available capacity and generator limitationsBuyer to provide

Floor area can support an early plausibility check. Nevertheless, it cannot replace these inputs. Two buildings of equal size may have very different loads because of glazing, occupancy, ventilation, operating hours, process equipment and hot-water demand.


Peak Capacity and Ground Load Are Not the Same

The ground does not see exactly the same load as the building.

In heating mode, the compressor adds electrical energy to the heat extracted from the ground. Therefore:

Ground heat extraction = Building heating output − Heat pump electrical input

In cooling mode, both the building heat and the compressor input are rejected to the ground:

Ground heat rejection = Building cooling output + Heat pump electrical input

Consider a hypothetical commercial project—not a CASSKY case study. If the building requires 300 kW of heating and the heat pump COP is 4.0 at that exact operating condition, the compressor input is approximately 75 kW. Consequently, the instantaneous ground extraction is approximately 225 kW.

If the same building requires 240 kW of cooling at a cooling COP of 5.0, the electrical input is approximately 48 kW. The ground must then accept approximately 288 kW.

These calculations illustrate the equipment-to-ground relationship only. They do not determine borehole quantity or length. Final sizing must also include load duration, ground properties, borehole resistance, spacing, fluid temperatures, groundwater movement and long-term thermal interaction.


Why Annual Load Balance Matters

A cooling-dominated office, data-intensive facility or retail building may reject more heat into the ground than it extracts. By contrast, a building in a cold climate may have a large annual extraction imbalance.

For example, suppose a hypothetical building rejects 600 MWh to the ground during cooling but extracts only 350 MWh during heating. The annual net rejection is 250 MWh. Repeating this imbalance can progressively raise borefield temperatures unless the field, operating strategy or auxiliary heat-rejection system is designed accordingly.

Possible responses include:

However, a hybrid system is not automatically cheaper. Its pumps, fans, water treatment, controls, maintenance and replacement costs must be included in the lifecycle comparison.


Ground Data Required for a Vertical Borefield

A desktop geological review is useful for feasibility, but a commercial design normally needs project-specific site evidence.

Ground-side inputWhy it mattersEvidence boundary
Undisturbed ground temperatureEstablishes the starting source temperature for heating and cooling simulationTo be measured or supported by qualified local data
Effective thermal conductivityInfluences the required borehole length and temperature responseMeasure through a thermal response test where justified
Thermal diffusivityAffects transient and long-term ground responseDerive from suitable testing or defensible geological properties
Borehole thermal resistanceIncludes pipe, fluid, grout, geometry and contact effectsCalculate and, where applicable, estimate from the thermal response test
Drilling logIdentifies soil, rock, groundwater and construction conditionsRecord for every production borehole
Borehole depth and diameterAffect heat-transfer area, drilling method and pressureDesigner to specify; contractor to document as built
Borehole spacingControls thermal interaction between adjacent boreholesDetermine through field simulation and site constraints
Pipe and groutAffect heat transfer, durability, pressure and environmental complianceSpecify material, dimensions, joining and verification requirements
Groundwater movementMay alter effective heat transfer and contaminant pathwaysHydrogeological assessment to confirm
AntifreezeChanges freeze protection, heat capacity, viscosity and pump powerType and concentration subject to equipment and local requirements
Allowed entering-fluid rangeConnects the borefield model to heat pump operating limitsExact model supplier to confirm
Source-side flow and pressure lossDetermine pump selection and affect total system efficiencyCalculate for final circuit arrangement and fluid concentration

ASHRAE’s Ground-Source Heat Pumps and Geothermal Energy chapter explains how thermal property testing can be used to estimate effective ground conductivity and borehole resistance. It also warns, through its design methods, that peak and long-term ground responses occur over different timescales.

A thermal response test is evidence for the tested borehole and test setup. It is not proof that every part of a large site has identical geology. Where conditions vary, the designer should determine whether additional investigations or conservative zoning assumptions are required.


Horizontal Loop Inputs Are Different

Horizontal collectors may avoid deep drilling, but they are more exposed to weather and near-surface conditions.

The design must account for:

A horizontal loop is not automatically suitable merely because a site has open land. Dry fill, future development, extensive paving or seasonal drought may undermine the original assumptions.

Conversely, a vertical field is not automatically required for every commercial project. A low-rise building with stable loads and inexpensive excavation may be better served by a horizontal system if the land can remain protected throughout the project life.


Match the Heat Pump to Real Water Temperatures

Heat pump capacity and efficiency change with source-side and load-side temperatures. Therefore, a single headline COP cannot represent annual project performance.

The CASSKY All-in-One Water / Ground Source Heat Pump public page describes a reversible water-to-water platform with:

Published series informationPublic valueEvidence boundary
Heating capacity6–30 kWPreliminary series range; exact model and condition to be confirmed
Cooling capacity5–26 kWPreliminary series range; exact model and condition to be confirmed
Heating outlet waterUp to 60°COperating limit, not proof of capacity or COP at 60°C
Cooling outlet waterDown to 7°CExact source temperature, flow and capacity to be confirmed
Reference heating COPUp to 4.8 at B0/W35Best published series reference, not every model
Reference cooling EERUp to 5.2 at W30/W7Best published series reference; units and test boundary to be confirmed
Electrical supply220–240 V single-phase or 380–415 V three-phaseModel-specific
Control communicationRS485/Modbus RTUModel-specific
Intended public positioningVillas, apartments and light commercial buildingsLarger commercial architecture requires a separate engineering review

Here, B0/W35 means a 0°C brine-side reference and 35°C load-side water reference as stated in the CASSKY system guide. W30/W7 indicates a 30°C source-water reference and 7°C chilled-water reference.

These conditions do not represent every commercial project. In particular, a heating system requiring 50–60°C water creates a larger temperature lift than a 35°C underfloor or low-temperature fan-coil system. As a result, capacity and COP will normally differ.


Request a Multi-Condition Performance Matrix

For each proposed model, request capacity and input power at conditions representing the project’s operating envelope.

Required operating pointData to requestProject purpose
B0/W35Heating capacity, total unit input and COPComparison with the published CASSKY reference condition
Project minimum source temperature / W35Heating capacity, input, COP and operating statusVerify low-source-temperature heating
Project minimum source temperature / project peak outlet temperatureHeating capacity, input and COPTest the most demanding heating condition
W10/W35, if relevantHeating capacity, input and COPCompare operation with a warmer water source
Project source temperature / DHW conditionCapacity, input, COP and recovery timeCheck hot-water production and mode priority
W30/W7Cooling capacity, input and efficiencyComparison with the published reference cooling point
Project maximum source temperature / W7Cooling capacity, input and efficiencyVerify high borefield-temperature cooling
25%, 50%, 75% and 100% loadCapacity, input power, flow and efficiencyEvaluate inverter or staged part-load operation
Minimum stable outputCapacity, minimum flow and cycling restrictionsCheck low-load operation
Standby and crankcase powerElectrical inputImprove annual energy modelling
Pump-inclusive conditionUnit plus source- and load-pump inputCompare whole-system performance

All values should identify the exact model, voltage, frequency, refrigerant, fluid type, antifreeze concentration, flow rate and test standard. Where the manufacturer has not tested a requested condition, the document should identify the value as interpolated, simulated or unavailable.


Laboratory Ratings Are Not Project Yield

ISO 13256-2:2021 establishes testing and rating criteria for factory-made water-to-water and brine-to-water heat pumps. It covers matched equipment assemblies at defined source- and load-side conditions.

Therefore, an ISO 13256-2 test result can substantiate unit capacity, input and efficiency at its stated condition. However, it does not certify:

AHRI also operates a voluntary Geothermal Water-Source Heat Pump certification programme. Its verified ratings can include capacity, EER, COP and certain part-load values. However, the programme’s public page references the 1998 editions of ISO 13256-1 and ISO 13256-2, whereas ISO published revised editions in 2021. Consequently, an RFQ should identify the edition required by the tender or market instead of stating only “tested to ISO 13256.”

In addition, AHRI performance certification is not safety certification. The AHRI programme’s operations manual explicitly excludes safety criteria.


Separate Performance, Safety and Market Compliance

Different documents answer different questions.

Evidence typeWhat it can establishWhat it does not establish
ISO 13256-2 laboratory reportUnit performance under stated water/brine conditionsBorefield performance or annual building energy
AHRI directory listing, if applicableIndependent verification of listed product ratings within programme scopeSafety, installation compliance or suitability outside listed conditions
IEC 60335-2-40 evaluationElectrical and refrigerating-appliance safety within the standard’s scopeHeating capacity, COP or local market acceptance by itself
National or regional conformity documentsCompliance with specified market requirementsGround-loop adequacy or project energy use
Factory quality recordsProduction inspections, serial traceability and test completionIndependent certification or field commissioning
Borefield simulationPredicted loop temperatures for stated loads and assumptionsActual construction quality or future load changes
Commissioning recordsInstalled flow, temperature, power, controls and safety operationLong-term performance outside the tested period

The current international appliance safety reference is IEC 60335-2-40:2024 with Amendment 1:2026. Nevertheless, the project must use the edition adopted by its target market and verify whether the proposed model and configuration fall within its scope.


Commercial Plant Configuration and Model Differences

The public CASSKY range extends to a preliminary 30 kW heating capacity. Therefore, a larger commercial ground source heat pump project may require multiple modules or a different equipment family.

For a modular plant, buyers should verify:

Do not assume that RS485 or Modbus capability automatically provides complete cascade control. A communication port, a controller function and a documented building-management-system interface are different deliverables.

Similarly, do not multiply one module’s headline capacity by the proposed quantity without checking diversity, defrost or changeover logic, flow conditions, control limitations and the capacity at the project water temperatures.

integrated-internal-structure

Terminal-System Compatibility

Low-temperature distribution generally reduces the temperature lift required from the heat pump. Therefore, underfloor heating, appropriately selected fan coils and low-temperature air-handling coils can support better operating conditions than undersized legacy radiators requiring high water temperatures.

However, terminal compatibility must be calculated rather than assumed.

The engineer should confirm:

A unit capable of producing water “up to 60°C” is not automatically suitable for a 60°C commercial heating system. The decisive evidence is its capacity, input power, COP and operating envelope at the specified source and load temperatures.


When a Commercial Ground Source Heat Pump Is a Good Fit

The technology is more likely to be appropriate when:

In addition, campuses with simultaneous heating and cooling may benefit from shared-loop heat recovery, provided the load diversity and control strategy are properly modelled.


When Another Solution May Be More Appropriate

A ground-source system may be a poor fit when:

For example, a small leased building with a short remaining tenancy may not justify a permanent borefield. Conversely, a hospital or campus with long operating hours may justify a more detailed lifecycle analysis even when the initial civil cost is higher.


Minimum Design Deliverables Before Purchase

A commercial order should not be released solely against a product brochure. At minimum, obtain or assign responsibility for the following:

Building and Energy Documents

Ground Heat Exchanger Documents

Heat Pump Documents

A report for a related model is not automatically evidence for the offered model. Check the model number, voltage, refrigerant, compressor, heat exchangers and certification scope.


Commissioning Acceptance Conditions

Commissioning should verify measurable system behaviour, not merely prove that the compressors can start.

The acceptance plan should record:

ASHRAE/IES Standard 202-2024 provides a commissioning framework based on the Owner’s Project Requirements, design documents, verification procedures and system records. The project should convert that process into system-specific acceptance criteria.

If the measured temperatures and flow are used to calculate heat output, the contract should state the required sensor accuracy, measurement method, stabilisation period and allowable tolerance. Otherwise, apparently precise field results may not be comparable with laboratory ratings.


Buyer Decision Checklist

A proposal is ready for serious evaluation only when the buyer can answer “yes” to the following questions:

If several answers remain “no,” comparing equipment prices is premature.


Frequently Asked Questions

How many boreholes does a commercial ground source heat pump need?

There is no universal number of boreholes per kilowatt. The answer depends on ground conductivity, borehole resistance, depth, spacing, peak ground load, annual imbalance, allowable fluid temperatures and project life. A project-specific simulation is required.

Is a thermal response test always required?

Not necessarily. Its value depends on project size, geological uncertainty, borefield cost and risk. However, using generic ground properties for a large commercial field can create significant sizing uncertainty. The engineer should document why a test is required or why verified local evidence is sufficient.

Can the heat pump manufacturer design the borefield?

Only if that service is explicitly included and performed by qualified personnel using appropriate site and load data. Equipment selection and borefield design are separate responsibilities unless the contract combines them.

Is the highest COP model always the best choice?

No. COP must be compared at the same source temperature, outlet-water temperature, flow and test boundary. Whole-system energy must also include ground-loop pumps, load pumps, controls and auxiliary equipment.

Can multiple smaller heat pumps serve a large commercial building?

Possibly. Modular plants can improve staging and redundancy. However, the supplier must confirm cascade limits, common-loop hydraulics, controller functions, electrical demand and performance at the project conditions.

Can a ground loop be sized from peak heating load alone?

No. Peak heating, peak cooling, load duration, monthly energy and long-term heat imbalance all affect the design. Sizing only from the largest peak can overlook long-term ground-temperature drift.

Does a maximum 60°C outlet make the CASSKY platform suitable for high-temperature radiators?

Not by itself. Request the exact model’s heating capacity, input power and COP at the required source and outlet-water conditions. Also verify radiator output and auxiliary-heating requirements.

Submit the Right Inputs for Preliminary Selection

For a preliminary CASSKY equipment review, submit:

CASSKY can then review candidate equipment, operating conditions and the model-specific information that must be requested. Final building, borefield, hydraulic, electrical and controls design must remain with appropriately qualified project professionals.

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