Ruud R951V0403A17M4UCAP furnace filter size
This furnace takes a 15.75 x 25 filter (bottom (RXGF-CB external rack, upflow/horizontal) return) or a 15.75 x 25 filter (side (RXGF-CD external side-return rack, upflow)) or a 14 x 20 filter (downflow top (RXGF-CC external rack) return), depending on where the return air comes in.
The maker lists width and height only. Most filter racks next to a furnace hold a 1-inch filter; a separate filter cabinet usually holds a 4- or 5-inch one. Check the thickness printed on the edge of your old filter before you order.
Every filter option for this model
| Where return air enters | Filter size (inches) | How many |
|---|---|---|
| bottom (RXGF-CB external rack, upflow/horizontal) | 15.75 x 25 | 1 |
| side (RXGF-CD external side-return rack, upflow) | 15.75 x 25 | 1 |
| downflow top (RXGF-CC external rack) | 14 x 20 | 1 |
Where the filter goes
External filter rack accessory. Spec sheet footnote: "*Filter racks are shipped without filters. Filters shipped with furnace may be used or a suitable 1" [25.4 mm] filter." Whether a filter actually ships in the carton is not stated elsewhere in this doc.
How often to change it
General guidance, not from the maker's table: 1-inch filters every 1 to 3 months; 4- and 5-inch filters every 6 to 12 months. Change sooner with pets, smoking or construction dust.
About this model
| Cabinet width | 17.5 in. |
|---|---|
| Airflow direction | multi-position (ultra low NOx) |
| Heat input | 40,000 BTU/hr |
| Efficiency (AFUE) | 95% |
| Model number note | Same furnace as Rheem R951V0403A17M4UCAP, per the maker's document. |
| Also sold as | Rheem R951V0403A17M4UCAP |
How to read a Ruud model number
Source
- Rheem R951V Ultra Low NOx spec sheet, Form G11-675 Rev. 3 (spec sheet, page 8): document. Read 2026-11-03.
- Ruud R951V Ultra Low NOx spec sheet, Form G22-675 Rev. 3 (spec sheet, page 8): document. Read 2026-11-03.
Check that the model number on your furnace label matches, and compare with the size printed on your old filter. If they differ, go by the filter that fits your rack.