Open Source Heat Pump BOM

Open Heat Pump Module v1.0

This page documents an open-hardware heat pump module built from **off-the-shelf, serviceable, replaceable HVAC parts**. The design is a **reversible 2-ton (≈24,000 BTU/h) R-410A heat pump** that can be integrated into air-to-water or water-loop hydraulic systems.

Goal

Create a modular, serviceable, repairable heat pump core using standardized refrigeration components that any trained technician can maintain without proprietary parts or black-box controllers.

System Overview

Each module consists of:

• Refrigeration compressor (≈2-ton, R-410A)
• Reversing valve (4-way)
• Brazed plate heat exchanger (refrigerant to water)
• Expansion device (catalog TXV or EEV)
• Filter/drier, accumulator, service valves
• Controls (temperature sensors, relays/PLC)

Four modules in parallel yield ~96,000 BTU/h total capacity.

Bill of Materials (per 2-ton module)

Core Refrigeration Components

• **Compressor (2-ton R-410A scroll)**

 * **:contentReference[oaicite:0]{index=0}** – widely stocked OEM scroll compressor, 208/230 V.  
 * **:contentReference[oaicite:1]{index=1}** – lower-cost alternative option.  
 * **:contentReference[oaicite:2]{index=2}** – budget surplus compressor option.  
 * **:contentReference[oaicite:3]{index=3}** – cost-competitive eBay option.

• **Reversing Valve (4-way)**

 * **:contentReference[oaicite:4]{index=4}** – standard 4-way valve for heat pump duty.  
 * **:contentReference[oaicite:5]{index=5}** – budget valve option.  
 * **:contentReference[oaicite:6]{index=6}** – alternative 2-ton reversing valve.  
 * **:contentReference[oaicite:7]{index=7}** – low-cost generic reversing valve.

Heat Exchanger (Refrigerant-to-Water / Plate HX)

The refrigerant-to-water heat exchanger is a key part that replaces an air-side indoor coil and lets you extract or reject heat to a water loop.

• **Bell & Gossett brazed plate heat exchangers:**

 * https://www.nationalpumpsupply.com/bell-gossett-brazed-plate-heat-exchangers/ – a family of quality brazed plate HXs in a range of sizes suitable for 2-ton service (e.g., BP400-20, BP400-30MT, BP400-40). :contentReference[oaicite:8]{index=8}

• Other brazed plate suppliers (R410A capable):

 * Alibaba R410A brazed plate HX listings – industrial/contractor supply. :contentReference[oaicite:9]{index=9}  
 * Alfa Laval / SWEP BPHE catalogs – high-performance brazed plates. :contentReference[oaicite:10]{index=10}

• Note:* Plate HXs must be rated for R-410A pressures (≈450-650+ psi) and water side pressures typical of hydronic systems. :contentReference[oaicite:11]{index=11}

Other Refrigeration Parts (Standard HVAC)

• Expansion Device (TXV or Electronic Expansion Valve) sized for 2–3 ton R-410A duty (from HVAC wholesaler).
• R-410A bi-flow filter/drier.
• Suction accumulator.
• Service valves and access ports.
• Sight glass (optional) for service diagnostics.

These parts are commodity HVAC parts available from local wholesalers.

Hydronic Components

• Water circulator pump (≈3–8 GPM range depending on module quantity).
• PEX/Tubing, manifolds, IBC tote manifold headers.
• Hydronic buffer tank(s) or thermal battery.
• Load side heat exchangers e.g., fin-coil units or radiant manifolds.

Refrigerant Circuit (Simplified)

1. Compressor discharge → reversing valve. 2. Reversing valve switches flow between:

  * Outdoor air coil (evaporator in heat mode)  
  * Brazed plate water coil (condenser in heat mode).  

3. Liquid line filter/drier and expansion device (TXV/EEV). 4. Evaporator/plate HX → suction accumulator → compressor suction.

• Ensure correct bi-flow filter/drier and proper check valves for bi-directional flow in heat pump mode.*

Line Sizes and Connections

• Suction: ~3/4″ ODF or flare (common for 2-ton compressors). :contentReference[oaicite:12]{index=12}
• Liquid: ~1/2″ ODF or flare. :contentReference[oaicite:13]{index=13}
• Brazed plate HXs: typical 1/2″ to 3/4″ ports depending on model.

Match hose/barb or flare adapters accordingly.

Controls

• Temperature sensors on water inlet/outlet.
• Refrigerant pressure sensors (optional).
• Relays/solid-state drivers for:

 * Compressor contactor.  
 * Reversing valve solenoid.  
 * Outdoor fan motor.  
 * Water circulator pump.  

• Open controller (PLC/ESP32/industrial controller) with basic logic for:

 * Heat/cool mode.  
 * Defrost (if outdoor coil used as evaporator).  
 * High/low pressure protection.

Notes

• This design uses **standard R-410A refrigerant**, which is common in residential HVAC equipment. :contentReference[oaicite:14]{index=14}
• All pressurized refrigeration work must be performed by a certified HVAC technician with proper tools and leak testing.
• Brazed plate heat exchangers for HVAC duty must be rated for R-410A service and hydronic water pressures. :contentReference[oaicite:15]{index=15}
• This open architecture decouples the **heat pump core** from proprietary OEM boards, enabling replacement of compressors, valves, and heat exchangers with catalog parts.

Open Hardware Intent

This repository’s purpose is to define a **modular, repairable heat pump building block** that:

• Uses widely available components.
• Can be maintained without proprietary spares.
• Serves as the basis for higher-level systems (thermal batteries, PV-driven heating, open water heater modules).
• Allows swarm innovation on controls, hydronics, and integration without vendor lock-in.