# Thermostat C-Wire Injector ## Description A simple PCB for interfacing smart thermostats requiring a C wire with a boiler's zone controller by incorporating an auxiliary 24VAC power supply. ## Project Details - **Owner:** nreilingh - **Created:** 2/6/2025 - **Last Updated:** 2/6/2025 - **Visibility:** Public ## Key Components ### 24 VAC — [282844-2](https://www.flux.ai/jecstronic/282844-2.md) - Datasheet URL: https://www.te.com/usa-en/product-282844-2.datasheet.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: TE Connectivity AMP Connectors - Part Type: Connector - Manufacturer Part Number: 282844-2 **Pins:** - P1 [pin 1] - P2 [pin 2] ### T1 — [KF128-5.08-3P-AA](https://www.flux.ai/lcsc/kf128-5p08-3p-aa.md) - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-3P-AA_C474953.pdf - Voltage Rating: 250V - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-3P_C474953.html - Current Rating: 24A - Manufacturer Part Number: KF128-5.08-3P-AA - JLCPCB Part Class: Extended Part - LCSC Part Number: C474953 - Connector Pitch: 5.08mm - Manufacturer Name: KEFA(科发) - Connector Rows: 1 - Package or Case Code: CONN-TH_3P-P5.08_KF128-5.08-3P - Operating Temperature: -40℃~+105℃ - Part Type: Screw terminal **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### T2 — [KF128-5.08-3P-AA](https://www.flux.ai/lcsc/kf128-5p08-3p-aa.md) - Package or Case Code: CONN-TH_3P-P5.08_KF128-5.08-3P - Operating Temperature: -40℃~+105℃ - Part Type: Screw terminal - Connector Pitch: 5.08mm - Connector Rows: 1 - Manufacturer Name: KEFA(科发) - JLCPCB Part Class: Extended Part - LCSC Part Number: C474953 - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-3P-AA_C474953.pdf - Voltage Rating: 250V - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-3P_C474953.html - Manufacturer Part Number: KF128-5.08-3P-AA - Current Rating: 24A **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### T3 — [KF128-5.08-3P-AA](https://www.flux.ai/lcsc/kf128-5p08-3p-aa.md) - Operating Temperature: -40℃~+105℃ - Package or Case Code: CONN-TH_3P-P5.08_KF128-5.08-3P - Part Type: Screw terminal - Connector Pitch: 5.08mm - Manufacturer Name: KEFA(科发) - Connector Rows: 1 - JLCPCB Part Class: Extended Part - LCSC Part Number: C474953 - Voltage Rating: 250V - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-3P-AA_C474953.pdf - Current Rating: 24A - Manufacturer Part Number: KF128-5.08-3P-AA - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-3P_C474953.html **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### Z1 — [KF128-5.08-2P-AA](https://www.flux.ai/lcsc/kf128-5p08-2p-aa.md) - Package or Case Code: CONN-TH_P5.08_KF128-5.08-2P - Manufacturer Part Number: KF128-5.08-2P-AA - LCSC Part Number: C474952 - Connector Positions: 2 - JLCPCB Part Class: Extended Part - Connector Gender: Female - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-2P_C474952.html - Manufacturer Name: KEFA(科发) - Connector Rows: 1 - Connector Pitch: 5.08mm - Connector Type: Screw terminal - Part Type: Screw terminal - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-2P-AA_C474952.pdf - Operating Temperature: -40℃~+105℃ - Current Rating: 24A **Pins:** - 1 [pin 1] - 2 [pin 2] ### Z2 — [KF128-5.08-2P-AA](https://www.flux.ai/lcsc/kf128-5p08-2p-aa.md) - Connector Rows: 1 - Connector Type: Screw terminal - Connector Pitch: 5.08mm - Part Type: Screw terminal - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-2P-AA_C474952.pdf - Current Rating: 24A - Operating Temperature: -40℃~+105℃ - Package or Case Code: CONN-TH_P5.08_KF128-5.08-2P - Manufacturer Part Number: KF128-5.08-2P-AA - LCSC Part Number: C474952 - Connector Gender: Female - JLCPCB Part Class: Extended Part - Connector Positions: 2 - Manufacturer Name: KEFA(科发) - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-2P_C474952.html **Pins:** - 1 [pin 1] - 2 [pin 2] ### Z3 — [KF128-5.08-2P-AA](https://www.flux.ai/lcsc/kf128-5p08-2p-aa.md) - Part Type: Screw terminal - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2408211511_Cixi-Kefa-Elec-KF128-5-08-2P-AA_C474952.pdf - Current Rating: 24A - Operating Temperature: -40℃~+105℃ - Connector Rows: 1 - Connector Pitch: 5.08mm - Connector Type: Screw terminal - Connector Positions: 2 - JLCPCB Part Class: Extended Part - Connector Gender: Female - Product Info Url: https://lcsc.com/product-detail/New-Quadratic-Unclassified-Data_Cixi-Kefa-Elec-KF128-5-08-2P_C474952.html - Manufacturer Name: KEFA(科发) - Package or Case Code: CONN-TH_P5.08_KF128-5.08-2P - Manufacturer Part Number: KF128-5.08-2P-AA - LCSC Part Number: C474952 **Pins:** - 1 [pin 1] - 2 [pin 2] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/nreilingh/thermostat-c-wire-injector](https://www.flux.ai/nreilingh/thermostat-c-wire-injector).* --- *Generated from [https://www.flux.ai/nreilingh/thermostat-c-wire-injector](https://www.flux.ai/nreilingh/thermostat-c-wire-injector)*