SUNLU FilaDryer S4: problems, parts and running costs
Checked: 2026-10-05
Summary
The structural limitation is one shared chamber temperature, so every roll loaded must tolerate the same setpoint, and the 70°C ceiling rules out materials that need hotter drying. Other reported problems are audible fans with no silent mode, a humidity readout that measures chamber air rather than moisture inside a roll, and drying that did not rescue an old NinjaFlex roll or fully recover a PETG roll. Running cost is electricity at roughly 400 W during heat-up and 80 W to hold, with no cycle energy measured, so the honest approach is a plug-in energy meter.
Common problems and fixes
- One temperature for the whole chamber — all loaded spools must share a single setpoint, so mixed materials cannot be dried together; if you need two zones, the S4 Pro is the relevant model. [3]
- 70°C ceiling — materials needing higher drying temperatures are out of scope, since some nylons list a 100°C schedule; check the filament’s own requirement before loading. [3]
- Audible fans with no quiet mode — one reviewer finds them noticeably loud and another calls the unit better suited to a printing room than a bedroom or a call-taking desk, and neither found a silent mode or fan-speed control. [3] [4]
- Humidity display measures chamber air, not the roll — warm air can show low RH while the filament is still wet, so do not treat the readout as proof of dryness. [3]
- Drying does not rescue every spool — testing left an old NinjaFlex TPU roll unusable and only partly recovered a PETG roll, and matte PLA improved only modestly, so buy it for moisture-sensitive filament, not as a universal fix. [3]
- Direct feeding can add drag — one setup developed excessive filament tension feeding without the guide tube, and direct feeding worked properly only from the outlets nearest the printer; use the supplied PTFE tubes. [3]
- Fits less than the roll count suggests — a bulk 3 kg spool did not fit in testing, standard 1 kg and 750 g rolls were workable, and cardboard spools were awkward when nearly empty; measure your spools including rim adapters, and allow clearance above to open the lids. [3]
- No reliability record — no source provides a failure rate or multi-year owner history, and no replacement heater, fan, door or control-board list was found, so long-term durability is uncharacterised. [3]
Parts and consumables
- Chamber rollers — the rubberised rollers ride on bearings and are described as user-replaceable, but no replacement-parts list or price appears in the sources. [4]
- Desiccant and sealed storage — recommended for rolls kept outside the dryer, since humidity maintenance only works while the unit is powered; no prices appear in the sources. [3]
- No filter or scheduled consumable — nothing else is meant to be replaced as routine upkeep. [1]
Yearly running cost
Not enough data for a yearly figure, because energy per cycle was not measured by any source. The numbers to use are the measured draws rather than the nameplate: about 400 W while heating and about 80 W to hold temperature, with one separate report above 360 W instantaneous. Budget for electricity, desiccant and possibly longer PTFE tubes, and measure a real cycle with a plug-in energy meter. [3] [4]
When it is a good buy
No non-Amazon store price was captured in the sources, so no price threshold can be set. The base S4 is worth buying when three or four rolls regularly need drying, all tolerate one shared temperature, and the unit can live in a permanent, out-of-bedroom spot with workable filament routing. It is the wrong purchase for occasional clean-printing PLA, cramped desks, or any material needing more than 70°C, and a one-roll user is better served by a smaller dryer or sealed storage. [3] [4]
- SUNLU FilaDryer S4 Pro — the better choice when you need two independent temperature zones and an 85°C maximum, which address the base model’s only structural limitation; when the two cost about the same, the Pro wins on flexibility. [3]
- A smaller single-spool dryer — the better choice when only one roll is active, since the S4’s capacity is only economic if it gets used. [3]