FitCheckrReplacement comparison
HAC-504 / Filter A vs 35 Water Panel
Honeywell HAC-504 and AprilAire 35 are both humidifier evaporative media, but they fit completely different humidifier types.
Exact model
HAC-504 / Filter A: 2 mo
35 Water Panel: Replace at le...
Official product image references
Use the manufacturer reference images to identify the two parts before comparing model support and usage.
Which replacement should you use?
Honeywell HAC-504 Humidifier Replacement Filter A
Portable Honeywell cool moisture humidifiers that list HAC-504 or Filter A.
Check compatible modelsAprilAire 35 Replacement Water Panel
AprilAire whole-house humidifiers that list Water Panel 35, including 600-series models.
Check compatible modelsRisk summary
Do not buy by the generic words wick, filter, or water panel alone. Portable humidifier wicks and furnace-mounted water panels are not interchangeable.
Main difference between HAC-504 / Filter A and 35 Water Panel
Which one fits which models
Use HAC-504 / Filter A for the model family described on its replacement page. Use 35 Water Panelonly when your device model or manual explicitly lists that part number.
Buyer mistake warning
Do not substitute by shape alone. The most important difference to check here is exact model.
When to choose HAC-504 / Filter A
Portable Honeywell cool moisture humidifiers that list HAC-504 or Filter A.
When to choose 35 Water Panel
AprilAire whole-house humidifiers that list Water Panel 35, including 600-series models.
Frequently asked questions
Are HAC-504 / Filter A and 35 Water Panel interchangeable?
Honeywell HAC-504 and AprilAire 35 are both humidifier evaporative media, but they fit completely different humidifier types.
What is the main difference between HAC-504 / Filter A and 35 Water Panel?
The main difference to verify is exact model. Do not buy by the generic words wick, filter, or water panel alone. Portable humidifier wicks and furnace-mounted water panels are not interchangeable.
When should I choose HAC-504 / Filter A?
Portable Honeywell cool moisture humidifiers that list HAC-504 or Filter A.
When should I choose 35 Water Panel?
AprilAire whole-house humidifiers that list Water Panel 35, including 600-series models.
Can I rely on product photos alone?
No. Product photos help identify packaging and shape, but compatibility should be confirmed by exact model support, part number, replacement type, and manufacturer references.
Official reference pages
Use these manufacturer pages to inspect current product photos, packaging, and model language. FitCheckr's comparison notes summarize fit risk, but the official pages should be used to confirm current product details before buying.
| Fit signal | HAC-504 / Filter A | 35 Water Panel |
|---|---|---|
| Brand family | Honeywell | AprilAire |
| Replacement type | Humidifier wicking filter | Whole-house humidifier water panel |
| OEM status | oem | oem |
| Replacement interval | Replace every 1-2 months during heavy use or when mineral buildup appears | Replace at least once per heating season |