Heat Pump Cold Climate Defrost Cycle Patents 2026
Heat Pump Cold Climate Defrost Cycle Patents
Frost accumulation on outdoor heat exchanger coils reduces heat transfer efficiency and degrades HSPF and SCOP metrics for residential air-source heat pumps. This dataset spans four decades of defrost control innovation from fixed time-temperature logic to machine learning-driven predictive scheduling.
Defrost Control Innovation Spans Four Decades of ASHP Development
Defrost cycle technology for residential air-source heat pumps encompasses sensing, control logic, thermal strategies, and system architectures used to detect, initiate, execute, and terminate frost removal from outdoor heat exchanger coils. Frost forms under low ambient temperature with sufficient atmospheric humidity, creating an insulating layer that progressively reduces heat transfer rate and airflow through coil fins.
The dominant defrost execution method in retrieved records remains reverse-cycle defrosting, in which refrigerant flow direction is inverted so the outdoor coil temporarily acts as a condenser delivering hot refrigerant gas to melt frost. Literature confirms this is the most widespread defrosting technique adopted by air-source heat pumps during the heating season, modelled across three phases: pre-defrost, active defrost, and post-defrost coil recovery.
Control logic in this dataset spans from fixed time-temperature scheduling — identified as the prevalent industry default in multiple Carrier Corporation patents — through sensor-based adaptive control, to the most recent wave of machine learning and predictive analytics-driven approaches. A performance evaluation framework measuring defrost COP, equivalent heating capacity, and comprehensive system efficiency has also emerged in recent Chinese academic and patent filings.
In retrieved records, ten named assignees are active across this technology sub-area, with Nortek Air Solutions Canada (approximately 13 records) and Carrier Corporation (approximately 12 records) representing the highest filing counts in this dataset, followed by Lennox Industries, Octopus Energy Heating, York International, and a growing cohort of specialised entrants.
Defrost Control Patent Activity Shifts Toward Predictive and AI-Driven Methods
Three distinct innovation phases are identifiable across retrieved records: a foundational sensor-based phase (1982–2001), a development and differentiation phase (2005–2020), and a predictive and AI-augmented phase (2022–2026). The most recent window shows a clear pivot toward machine learning algorithms, weather-forecast integration, and multi-unit coordination logic.
Patent Records by Technology Cluster — Defrost Control (Dataset Snapshot)
Sensor-based threshold and temperature-differential control represents the largest cluster in this dataset, with reverse-cycle defrost and frost factor adaptive methods also prominent among retrieved records.
↗ Click bars to exploreDefrost Control Patent Filings by Innovation Phase (Dataset Snapshot)
Filing activity in this dataset accelerated markedly in the 2022–2026 predictive and AI-augmented phase, with Octopus Energy and Continual Energy driving new ML-based and multi-unit coordination records.
↗ Click bars to exploreCold-Climate ASHP Defrost Control: Key Application Contexts
Defrost cycle technology spans residential space heating, electrification programs, ventilation heat recovery, and industrial cold storage. The residential air-to-air and air-to-water heating context dominates retrieved results, with growing policy relevance tied to HSPF and SCOP regulatory compliance across North America, Northern Europe, and China.
Residential Air-to-Air and Air-to-Water
The dominant application context across retrieved results targets single-family housing with air-to-air and air-to-water heat pumps for hydronic radiant floor or radiator systems. Key patent assignees explicitly targeting residential HSPF optimization include Lennox Industries, Carrier Corporation, Rheem Manufacturing, and Octopus Energy Heating. Italian climate simulations confirmed defrost cycles’ influence on SCOP varied significantly across three climatic locations and eight years of real weather data.
Residential HeatingResidential Electrification and Decarbonization
Multiple literature sources frame defrost performance in the context of residential electrification mandates. A study on rural US cold-climate buildings found that combining PV with heat pumps can reduce residential building GHG emissions by up to 50% immediately, with potential for over 90% reduction long-term. Norwegian deep-renovation studies and Irish housing stock analyses confirm heat pump COP and seasonal performance factor are primary determinants of economic viability, making defrost efficiency a key policy-relevant parameter.
Electrification PolicyVentilation Heat Recovery Systems
Nortek Air Solutions Canada’s patent portfolio covers pre-processing module systems for residential and commercial buildings requiring combined ventilation and heating. In these systems, defrost of the regeneration air heat exchanger is achieved using hot refrigerant directed sequentially through the coil, with the compressor overdriven during defrost to maintain system performance. Filings span 2012–2022 across US, CA, EP, AU, and IN jurisdictions.
Ventilation Heat RecoveryPhase Change Material Thermal Storage Research
Academic literature from 2019–2020 documents growing research interest in using PCM-integrated heat exchangers as thermal buffers to supply defrost energy from stored heat, eliminating the need for full reverse-cycle operation and maintaining indoor thermal comfort during defrost. A 2020 study on defrosting performance improvement combined refrigerant direct-condensation radiant floor heating with PCM. This approach has not yet appeared prominently in filed patents within this dataset but represents a near-term patent filing target based on published research.
Emerging ResearchKey Patent Assignees in Heat Pump Defrost Control (Retrieved Records)
In retrieved records, Nortek Air Solutions Canada and Carrier Corporation account for the highest filing counts in this dataset, with approximately 13 and 12 distinct records respectively. A growing cohort of specialised entrants — including Octopus Energy Heating, Continual Energy Inc., and Schneider Electric — is driving the predictive and AI-augmented innovation wave observed in 2022–2026 filings in this dataset.
Top Assignees by Filing Count — Defrost Cycle Patents (Dataset Snapshot)
↗ Click bars to exploreNortek Air Solutions Canada, Inc.
Nortek Air Solutions Canada holds approximately 13 distinct patent records in this dataset, the highest filing count among retrieved records, spanning 2012–2022 across US, CA, EP, AU, and IN jurisdictions. The portfolio is concentrated on hot-refrigerant direct defrosting and pre-processing module architectures for cold-climate ventilation heat pump systems, with the compressor overdriven during defrost cycles to maintain system performance. Key filings include the heat pump defrosting system and method (US, 2020) and heat pump system having a pre-processing module (EP, 2013).
Canada — CACarrier Corporation
Carrier Corporation holds approximately 12 distinct patent records in this dataset across US, EP, and WO jurisdictions, spanning 1992–2025. The portfolio covers the full spectrum of defrost control approaches: fixed time-temperature scheduling (identified as the prevalent industry default), the 0–100% frost factor algorithm derived from clean-coil performance baselines (EP, 2007), the defrost interval indicatrix X = T1/TMn + T2/TNn (EP, 2019), supplemental electric heat management during defrost (US, 1994), and the most recent demand-signal-based defrost threshold method filed in 2024 across US and EP jurisdictions.
United StatesFour Forward-Looking Directions in Defrost Cycle Innovation (2022–2026)
The most recent filings in this dataset (2022–2026) indicate a clear pivot toward machine learning algorithms, multi-unit cascade staggering with active frost manipulation, demand-adaptive capacity-signal thresholds, and intelligent frost detection integrating weather forecast data for Chinese cold-climate markets.
Machine Learning-Augmented Defrost Prediction
Octopus Energy Heating’s US patent (2024) and GB/WO filings (2022) deploy machine learning algorithms that receive weather forecast feeds, historical defrost cycle data, occupancy patterns, and indoor temperature telemetry to predict the next defrost cycle start time with sufficient lead time to pre-charge thermal storage. This represents a shift from reactive to fully anticipatory defrost management. The architecture is explicitly designed to schedule defrost during low-occupancy and low-demand periods, such as overnight, minimising disruption to domestic hot water supply.
Multi-Unit Cascade Staggering with Active Frost Manipulation
Continual Energy Inc.’s January 2026 US filing extends its 2023 portfolio with a key innovation: deliberately adjusting heat output of individual units within a multi-pump array to accelerate or decelerate frost accumulation, thereby engineering the timing of defrost cycle onset across units. This goes beyond scheduling — it actively manages the thermal physics of frosting to achieve continuous heating output from the array. Only Continual Energy Inc. and Mitsubishi Heavy Industries hold relevant claims in this area in this dataset, making multi-unit cascade coordination an identified patent white space.
Reverse-Cycle Defrost vs. Hot-Gas Bypass Defrost: Key Differences
Click any row to explore further.
| Dimension | Reverse-Cycle Defrosting (RCD) | Hot-Gas Bypass Defrosting |
|---|---|---|
| Mechanism | Refrigerant flow direction inverted; outdoor coil acts as condenser delivering hot gas to melt frost | Compressor discharge gas injected directly into frosted coil without full cycle reversal |
| Industry Prevalence | Most widespread defrosting technique adopted by air-source heat pumps during heating season (per literature in dataset) | Used in Nortek Air Solutions Canada portfolio; described in patents dating to 2014 |
| Indoor Heating Impact | Interrupts space heating during active defrost phase; pre-defrost and post-defrost recovery phases also reduce capacity | Compressor overdriven during defrost to maintain system performance per Nortek filings |
| Representative Assignees | Carrier Corporation, Lennox Industries, Rheem Manufacturing, Octopus Energy Heating, York International | Nortek Air Solutions Canada, Inc. |
| Primary Application | Residential air-to-air and air-to-water heat pumps for space heating; HSPF and SCOP optimization | Residential and commercial ventilation heat recovery systems with combined heating function |
| Defrost Cycle Phases | Three phases: pre-defrost (reduced capacity), active defrost (reversed cycle), post-defrost (coil recovery) | Hot refrigerant directed sequentially through coil; single active phase without full cycle reversal |
| Control Integration | Compatible with sensor-threshold, frost-factor, weather-predictive, and ML-based control logic across multiple assignees | Integrated into pre-processing module architecture in Nortek filings (2012–2022) |
| Jurisdictional Coverage | US, EP, CA, WO, GB, AU — broad multi-jurisdiction coverage across multiple assignees | US, CA, EP, AU, IN — Nortek Air Solutions Canada multi-jurisdiction portfolio |
Frequently Asked Questions: Heat Pump Cold Climate Defrost Cycle Patents
According to literature in this dataset, reverse-cycle defrosting (RCD) is the most widespread defrosting technique adopted by air-source heat pumps during the heating season. In RCD, refrigerant flow direction is inverted so that the outdoor coil temporarily acts as a condenser, delivering hot refrigerant gas to melt the frost layer across three phases: pre-defrost, active defrost, and post-defrost coil recovery.
In this dataset, Nortek Air Solutions Canada holds approximately 13 distinct patent records (2012–2022) and Carrier Corporation holds approximately 12 records (1992–2025). Other active assignees include Lennox Industries (5 records, 2015–2023), Octopus Energy Heating (5 records, 2022–2024), York International Corporation (4 records, 1986–1994), Rheem Manufacturing (3 records, 2020–2021), and Continual Energy Inc. (3 records, 2023–2026).
The frost factor is a 0–100% index derived from clean-coil performance baselines that tracks real-time system performance degradation due to frost accumulation. It was introduced by Carrier Corporation in an EP-jurisdiction filing dated 2007. It avoids the over-defrosting problem inherent in fixed-time scheduling by triggering defrost only when actual performance degradation is detected against the baseline.
Octopus Energy Heating’s GB and WO filings (2022) and US filing (2024) deploy machine learning algorithms trained on weather forecast data, current weather conditions, indoor temperature, and historical defrost cycle data to predict the expected start time of the next defrost cycle. This enables pre-charging of thermal storage before the defrost event and scheduling defrost during low-occupancy periods such as overnight — representing a shift from reactive sensor-based initiation to fully anticipatory defrost management.
Continual Energy Inc.’s January 2026 US filing extends its 2023 portfolio by introducing the ability to deliberately adjust heat output of individual units within a multi-pump array to accelerate or decelerate frost accumulation, thereby engineering the timing of defrost cycle onset across units. This goes beyond scheduling — it actively manages the thermal physics of frosting to ensure at least one unit is always in heating mode, achieving continuous heating output from the array.
Lennox Industries filed weather-data-assisted defrost control in 2015 (US) and 2019 (CA), classifying precipitation type — including freezing rain, snow, sleet, and hail — to select appropriate defrost profiles targeting HSPF optimization. More recently, Octopus Energy Heating integrated weather forecast APIs into ML-based predictive defrost scheduling. Two 2025–2026 CN filings from Chinese assignees also describe intelligent defrost systems that incorporate weather forecast inputs to compute a frost grade trend index for future time windows.
Data and insights on this page are based on a limited patent and literature dataset and are for reference only. Figures may not represent the complete technology landscape.