Built for Inrush: The TSC 5x20mm Time-Lag Glass Fuse
If your circuit has a harmless inrush: motor start, transformer magnetizing current, capacitor charging, or an alternator kick: fast-acting fuses can become a nuisance. OptiFuse TSC is a 5x20 mm time-lag (slow-blow) glass fuse designed to ride through brief surges and open only when an overcurrent actually persists.
What it is (and what “time lag” buys you)
TSC is a 20mm long x 5mm diameter glass cartridge fuse, offered with (TSC-P) or without (TSC) axial leads, and UL listed.
Time-lag behavior is the entire value proposition: it helps prevent nuisance openings in circuits that legitimately draw a short inrush above steady-state current.
Key specifications engineers care about
- Size: 5x20mm (ULxCSA)
- Characteristic: Time lag (slow-blow)
- Voltage rating: 250VAC
- Current range: 100mA to 15A
- Interrupt rating: 200A AC
- Visual inspection: clear glass body supports quick filament checks
- Bonus (packaging): Select items available in blister packs.
Where TSC shows up in the field
In practice, it’s a strong fit for:
- Small motors/fans/pumps
- Transformers and power supplies
- Cap-input loads (brief charging surge)
- Industrial control and general electronics needing serviceable 5x20mm protection
What it pairs with (holders, mounting, and solderable options)
A good fuse choice can still fail in the field if the mounting method is sloppy. With 5x20mm fuses, you generally have two clean paths: in-line holders for harness installs, or board-mount / solderable solutions for electronics.
In-line holders for harness installs
OptiFuse offers compatible 5x20mm in-line holders when you want the fuse in the wiring harness:
These are the go-to when you want the fuse accessible without opening the enclosure or when protection needs to be placed close to the source.
Solderable / PCB-friendly mounting
If you need a fuse on a PCB, there are two common approaches:
- Use the leaded version (TSC-P)
The axial leads let you solder the fuse directly into the circuit, which is simple and compact. This is often used in cost-sensitive designs or where service access isn’t critical.
- Use a PCB-capable fuse holder to keep it replaceable
Direct-solder fuses work, but they aren’t fun to replace. For a more robust, serviceable design, use a PCB/panel fuse holder so the fuse can be swapped without rework. A holder like CSC-05 keeps the circuit serviceable while still letting you solder the holder leads/pins to the board.
Related options in the same family
If you need a different time-current behavior or body material, OptiFuse offers additional tube fuse counterparts:
For more information, read our How to Choose a Tube Fuse blog.
For more inquiries, contact OptiFuse at [email protected] and see our Fuse Selection Guide for complete context.
Sebastian Castañeda is a circuit protection specialist and technical writer with application-focused experience in technical support and custom protection design. He contributes practical, application-driven insights to the OptiFuse Blog.