# Ground Source Heat Pump Loop System: Building Code Definition > How the IMC 2009 define ground source heat pump loop system, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/ground-source-heat-pump-loop-system-code-term/ - Last updated: 2026-09-07 - Data source: Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control. ## Key facts | Fact | Value | | --- | --- | | Defined in | IMC 2009 (2009 editions transcribed in this corpus) | | Primary source | IMC 2009 Definitions (model text, not a jurisdiction's adopted text) | | Chapters using the term | 3 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Ground source heat pump loop system is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “Piping buried in horizontal or vertical excavations or placed in a body of water for the purpose of transporting heat transfer liquid to and from a heat pump. Included in this definition are closed loop systems in which the liquid is recirculated and open loop systems in which the liquid is drawn from a well …” No other I-Code in this corpus defines it, so the IMC 2009 definition is the one to work from. The term is used in 3 chapters of this corpus, most often in Hydronic Piping (IMC 2009), Hvdronic Piping (IRC 2009), Definitions (IMC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. *Content and cited inputs reviewed by [Scott Barrington](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.* ## What does this term mean? **Ground Source Heat Pump Loop System** — IMC 2009, Definitions: > Piping buried in horizontal or vertical excavations or placed in a body of water for the purpose of transporting heat transfer liquid to and from a heat pump. Included in this definition are closed loop systems in which the liquid is recirculated and open loop systems in which the liquid is drawn from a well or other source. ![Labeled code-term definition diagram: Ground Source Heat Pump Loop System: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/ground-source-heat-pump-loop-system-code-term/diagram-1344.webp) *How the IMC 2009 define ground source heat pump loop system, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Ground Source Heat Pump Loop System** is defined once in this corpus, in the [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) chapter of the International Mechanical Code (IMC) 2009: > Piping buried in horizontal or vertical excavations or placed in a body of water for the purpose of transporting heat transfer liquid to and from a heat pump. Included in this definition are closed loop systems in which the liquid is recirculated and open loop systems in which the liquid is drawn from a well or other source. ## Where ground source heat pump loop system is used in the code The term appears in 3 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Hydronic Piping](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/hydronic-piping.md) | IMC 2009 | 5 | | [Hvdronic Piping](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/hvdronic-piping.md) | IRC 2009 | 4 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 | ## The terms ground source heat pump loop system is built out of The definition above leans on 4 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what ground source heat pump loop system covers: - **[Heat Transfer Liquid](https://harth.build/resources/glossary/heat-transfer-liquid.md)** — IMC 2009: The operating or thermal storage liquid in a mechanical system, including water or other liquid base, and additives at the concentration present under - **[Heat Pump](https://harth.build/resources/glossary/heat-pump.md)** — IRC 2009: An appliance having heating or heating/cooling capability and that uses refrigerants to extract heat from air, liquid or other sources. - **[Liquid](https://harth.build/resources/glossary/liquid.md)** — IBC 2009: A material that has a melting point that is equal to or less than 68°F (20°C) and a boiling point that is greater than 68°F (20°C) at 14.7 pounds per square inch absolute (psia) (101 kPa). - **[Piping](https://harth.build/resources/glossary/piping.md)** — IRC 2009: Where used in this code, “piping” refers to either pipe or tubing, or both. ## Ground Source Heat Pump Loop System: what to open, and in what order Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows. | Check | Where | Confirmed | | --- | --- | --- | | Read the definition in the adopted IMC | Definitions | | | Re-check the requirement that uses it | Hydronic Piping (IMC 2009) | | | Re-check the requirement that uses it | Hvdronic Piping (IRC 2009) | | | Re-check the requirement that uses it | Definitions (IMC 2009) | | | Confirm the dependent definition | Heat Transfer Liquid | | | Confirm the dependent definition | Heat Pump | | | Confirm the dependent definition | Liquid | | | Local amendment to any of the above | Jurisdiction's amendment list | | **A research aid, not a code determination.** The authority having jurisdiction decides which edition and which amendments apply. ## Where can you explore related guidance? - [Explore all glossary guidance](https://harth.build/resources/glossary.md) - [Heat Transfer Liquid: Building Code Definition](https://harth.build/resources/glossary/heat-transfer-liquid.md) - [Heat Pump: Building Code Definition](https://harth.build/resources/glossary/heat-pump.md) - [Piping: Building Code Definition](https://harth.build/resources/glossary/piping.md) - [Liquid: Building Code Definition](https://harth.build/resources/glossary/liquid.md) ## Sources and method Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control. ### Source links - [codes.iccsafe.org](https://codes.iccsafe.org/codes) - [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/) ## Frequently asked questions ### What is the code definition of ground source heat pump loop system? The International Mechanical Code (IMC) 2009 defines it in Definitions as: “Piping buried in horizontal or vertical excavations or placed in a body of water for the purpose of transporting heat transfer liquid to and from a heat pump. Included in this definition are closed loop systems in which the liquid is recirculated and open loop systems in which the liquid is drawn from a well or other source.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally. ### Which parts of the code depend on ground source heat pump loop system? In this corpus the term is used across 3 chapters, led by Hydronic Piping in the IMC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fground-source-heat-pump-loop-system-code-term%2F - View this page in a browser: https://harth.build/resources/glossary/ground-source-heat-pump-loop-system-code-term/ - All resources for agents: https://harth.build/llms.txt