Filament Dryer Box S4 Four-Spool 3D Printer Dehydrator - Rapid Heating

In this review the Filament Dryer Box S4 is evaluated for makers and small print farms that need reliable filament storage and fast drying. The S4 stands out for its four-spool capacity and rapid, even heating driven by a 350W PTC heater and a three-fan layout. For those printing PLA, PETG, ABS or engineering filaments, the S4 combines practical humidity control with enough throughput to keep multiple printers fed, making it a useful tool for anyone frustrated by brittle or moisture-affected filament.

Key Features

• 350W PTC Heater: Delivers rapid heating up to 70 C so spools reach drying temperature quickly and reduce downtime between prints.
• Triple-Fan Circulation: Three fans distribute heat evenly around all spools, lowering the risk of uneven drying or hot spots.
• Four-Spool Capacity: Holds four 1kg spools at once with eight filament ports and PTFE tubes for simultaneous drying and printing.
• Auto Humidity Control: Built-in high-precision humidity sensor displays real-time levels and automatically activates at or above 50% to prevent reabsorption.
• Adjustable Timer and Temp: Temperature from 35 C to 70 C and timing from 0 to 99 hours with preconfigured presets for common materials for easier setup.
• Wide Filament Compatibility: Works with PLA, PLA+, PETG, TPU, ABS, PA, PC and standard diameters 1.75mm, 2.85mm and 3.00mm.

Who It's For

The S4 is best suited to hobbyists with multiple printers, small workshops, or anyone who buys spools in bulk and needs continuous access to dry filament. Its ability to hold four 1kg spools and feed multiple printers makes it a practical choice where throughput and storage matter.

Users who print only occasionally or only use one spool at a time may find the S4 larger and more powerful than necessary, and those seeking a completely silent solution should note the active fan system designed for even drying.

Pros & Cons

Pros

• Large four-spool capacity that supports concurrent drying and printing for multiple machines.
• Fast, even drying from a 350W PTC heater combined with triple-fan circulation.
• Automatic humidity control with a live display helps keep filament ready for use without constant monitoring.
• Simple touch-screen operation with presets reduces setup time for common filaments.

Cons

• Active fans and a powerful heater mean it is not the quietest solution, which may matter in very noise-sensitive spaces.
• Some users report mixed durability experiences, so longer-term reliability can vary by unit.

Specifications

Heater Power	350W PTC heater
Max Temperature	70 C
Spool Capacity	Four 1kg spools
Filament Diameters	1.75mm, 2.85mm, 3.00mm
Humidity Control	High-precision sensor, auto-activate at 50%+
Timer Range	0 to 99 hours
Fans	Triple-fan configuration for even circulation

Our Verdict

The Filament Dryer Box S4 is a strong choice for users who need to dry and store multiple spools reliably; its fast heating, triple-fan circulation and automatic humidity control deliver consistent filament condition and improved print quality. For workshops and multi-printer setups it represents good value, though those needing a quieter or smaller unit should compare alternatives.

Frequently Asked Questions

Can it run while printing?
Yes, the S4 supports feeding filament through PTFE tubes and eight ports so multiple printers can draw filament while the unit maintains drying and humidity control.

What filaments are compatible?
The unit is compatible with PLA, PLA+, PETG, TPU, ABS, PA, PC and other common 3D filaments at 1.75mm, 2.85mm and 3.00mm diameters.

How does the auto humidity feature work?
A built-in high-precision sensor displays interior humidity and automatically starts the dryer when the level reaches or exceeds 50% to prevent moisture reabsorption.