Ruud R801V1005A21UHNCAP furnace filter size
This furnace takes a 19.25 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)), 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) | 19.25 x 25 | 1 |
| side (RXGF-CD external side-return rack, upflow) | 15.75 x 25 | 1 |
Where the filter goes
External filter rack accessory; "*Filter racks are shipped without filters." Furnace is not shipped with a filter.
The maker does not ship a filter with this furnace. The size above is the maker's recommended size at the furnace; if your home has a filter grille in a wall or ceiling, that grille sets the size instead.
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 | 21 in. |
|---|---|
| Airflow direction | upflow/horizontal |
| Heat input | 100,000 BTU/hr |
| Efficiency (AFUE) | 80% |
| Model number note | S = standard, N = low NOx Same furnace as Rheem R801V1005A21UHNCAP, per the maker's document. |
| Also sold as | Rheem R801V1005A21UHNCAP |
How to read a Ruud model number
Source
- Rheem Endeavor Line SEER2 furnace brochure + spec sheet bundle (Form M11-6115/M11-6116 with G11-662..G11-678) (spec sheet (bundle of maker spec sheets), page 43): document. Read 2026-11-03.
- Ruud R801V UH Endeavor Line Achiever Series spec sheet, Form G22-663 (spec sheet, page 9): 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.