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SUNLU Official Filament Dryer S4

SUNLU Official Filament Dryer S4

By SUNLU · Filament Dryers · 3D Printing · More from SUNLU

  • 4 x 1kg spool capacity
  • 350W PTC heater, 70°C max temperature
  • ±3°C temperature uniformity with 3 circulation fans
  • 300W rated power, 458×218×312mm
  • 1.75mm/2.85mm/3.0mm filament support

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Summary

A four-spool hot-air dryer that conditions four 1 kg rolls in one shared 35–70°C chamber, built for workshops running several printers or a multicolor setup. Check the plug and shipping region before you order: the maker’s US-dollar page defaults to an EU-plug, ship-to-Europe variant.

Strengths

  • Four separately supported rolls and eight feed ports cut repeated reloading in a busy workshop.
  • Independent testing dried several damp rolls and reduced bubbling and stringing.
  • A preproduction trial recovered a TPU print after about five hours at 55°C.
  • Bearing rollers and top and side ports let you dry and feed several printers at once.
  • MO2 can restart heat when chamber humidity rises, unlike a purely manual timer dryer.
  • The 70°C ceiling covers typical PLA, PETG and TPU cycles without extreme heat.

Weaknesses

  • One shared chamber means four spools must share a single temperature; PLA beside PA or PC at 70°C can deform.
  • Er3 fan errors recur across 2024–2026 owner reports, though no failure rate exists.
  • The 70°C ceiling falls short of the 75–85°C some PA, PC and PAHT grades call for.
  • The humidity readout measures chamber air, not the moisture inside a tightly wound spool.
  • Hot air has softened PLA spools and printed PETG adapters after hours at 65°C.
  • Two opened lids need more vertical clearance than the closed dimensions suggest.

Verified specifications

ModelSUNLU FilaDryer S4 / S4-FD; manufacturer part S4DRYBOX, retailer UPC 618996783281.
Capacityfour 1 kg spools in one chamber, internal dimensions about 450 × 210 × 211 mm; about 77 mm practical maximum spool width.
Temperature35–70°C, one shared zone for all four rolls.
Heatingthree fans (two side recirculating, one bottom heater/intake), marketed at ±3°C spread; an independent test measured about 5°C across a loaded roll at a 50°C preset.
Powerconflicting first-party labels of 300 W rated input and 350 W PTC heater; an independent test measured about 300–350 W during warmup.
MainsAC 110–240 V, 50/60 Hz.
Display and controlsbacklit LCD with touch controls; presets for PLA, PETG, TPU, ABS, PA and PC.
ModesMO1 timed drying and MO2 humidity maintenance, which restarts heat at a selected 30–50% RH threshold.
Timerup to 99 h.
Filament outputseight ports, four on top and four on the side, for 1.75, 2.85 and 3.0 mm filament.
In the boxdryer body, power lead, user guide, two 100 cm and four 8 cm PTFE tubes, eight port caps and eight metal tube clips.
CertificationsETL, CE-EMC, CE-LVD, FCC and RoHS documents.
Dimensions18.0 × 8.6 × 12.3 in (458 × 218 × 312 mm); 4.8 kg (10.6 lb).
Full research notes and sources

Drying performance and limits

Independent testers loaded standard 1 kg spools and confirmed the rollers, the two latched lids and the eight exits work. Clever Creations photographed roughly 5°C of variation across a loaded roll after an hour at a 50°C preset, against SUNLU’s marketed ±3°C. A preproduction trial recovered a flexible TPU print after about five hours at 55°C, while matte PLA changed little and a degraded old spool could not be rescued.

The chamber runs one temperature for all four rolls. That is fine when everything needs the same moderate setting, but a PA or PC preset at 70°C can thermally deform PLA wound nearby, and printed PLA and PETG spool adapters are at risk too. Two different temperatures at once need two drying batches or a two-zone model.

The humidity readout

The display shows chamber relative humidity, not the water content of the filament. After a warmup the air can read very dry well before the core of a 1 kg spool has released enough moisture, so a low number is not proof the roll is finished. Treat the reading as a guide and dry by time.

Faults, noise and repairs

Er3 fan-fault shutdowns are the most repeated hardware complaint. Owners reported it soon after arrival, after a few months of intermittent use and again in March 2026, sometimes with the side fans apparently working. No published failure rate exists, so treat Er3 as a known risk rather than a measured defect percentage.

Earlier teardown threads mention Er1 after about 13 minutes, no heat and humidity readings stuck near 30%. These are owner diagnoses, not an approved repair procedure, so a unit under warranty should go back to the seller rather than being opened.

The three fans and heater make noise at desk distance, and one early reviewer felt low-frequency vibration through the metal feet. A later owner replaced fans to quiet the unit.

Running costs

No subscription or proprietary cartridge is needed; electricity and occasional wear items are the real cost. The rated labels conflict at 300 W, 320 W and 350 W, and an independent test measured about 300–350 W during warmup that then cycles down. A duty-cycle estimate at an assumed $0.20/kWh runs about $4.61 a year for two eight-hour sessions a month at a hypothetical 120 W average, up to about $40 for twice-weekly use at a 250 W average. Those are planning figures, not a meter reading.

The maker’s US-dollar store lists the original S4 from $116.99 (compare-at $139.99, October 2026), but the captured page defaulted to an EU-plug, ship-to-Europe variant, so confirm a US plug before checkout. Micro Center advertises $129.99 as an in-store pickup item with 30-day returns and a one-year vendor warranty. A reseller page lists a black S4 at $99.44, and one distributor lists it near $199.99; neither was verified for seller authorization or plug.

Which model this is

This is the original SUNLU FilaDryer S4, model S4-FD, sold by Micro Center as SKU 800581. It is not the S4 Pro, the single-spool S2 or the Creality SpacePi X4. The S4 Pro is a different machine with independent left and right temperature zones, an 85°C maximum and a rated 380 W, listed at $139.99 with a US plug; the original S4 can only dry all four spools at one temperature.

Is it worth it?

Under $85 a working unit with genuine returns is excellent value for four-roll drying. At $106–120 it is solid normal value, and $121–135 is reasonable when local pickup and returns matter. Over $150 the original S4 is poor value against the S4 Pro and the Creality SpacePi X4, both of which offer separate heating zones.

Sources

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Independent reviews:

Owner reports:

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