Williamson-Thermoflo Boiler Manuals
Select your Williamson-Thermoflo model number below for installation steps, settings, maintenance schedules, troubleshooting and the full specification sheet. Your model number is printed on the rating plate.
Williamson-Thermoflo boilers by model number
| Model | Description | Certified |
|---|---|---|
| FS-120- | 95% AFUE condensing gas boiler | January 2025 |
| FS-155- | 95% AFUE condensing gas boiler | January 2025 |
| FS-80- | 95% AFUE condensing gas boiler | January 2025 |
| GWC-070-N-TGWC | 91% AFUE condensing gas boiler | September 2026 |
| GWC-105-N-TGWC | 91% AFUE condensing gas boiler | September 2026 |
| GWC-140-N-TGWC | 91% AFUE condensing gas boiler | September 2026 |
| GWC-175-N-TGWC | 91% AFUE condensing gas boiler | November 2021 |
| OWB-3-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWB-4-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWB-5-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWB-6-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWT-3-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWT-4-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWT-5-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |
| OWT-6-T-S3-D | 87% AFUE non-condensing oil-fired boiler | September 2026 |