STC6333 – CERAMIC TEMPERATURE FUSE LINK (L333°, ELBOW)

A ceramic-body thermal fuse link with a 90° elbow terminal orientation. Opens at 333°F to protect equipment from overheating. The elbow design fits installations where straight terminals won’t clear nearby components. Ceramic body handles higher ambient temperatures than plastic fuse links.

Specs: 15A, opens at 333°F (167°C), ceramic body, 90° elbow terminals

Replaces: NTCK333, STC6333

Fits: Furnaces, electric heaters, and HVAC equipment using a ceramic 333°F thermal fuse link with elbow (90°) terminals

In stock at Open To Public HVAC Parts in Dallas. We test parts at the counter before you buy. Call or text (214) 340-9421.

Specs

• TypeCeramic temperature fuse link (one-time)
• Trip Temperature333°F
• ShapeElbow
• Type BehaviorOne-time use (replace after trip)
• OEM CompatibilityUniversal

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• NTCK333
• STC6333

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

Fits these models

• Universal ceramic temperature fuse link — safety cutoff for electric air handler heat kits, gas furnace plenums, and heat-strip assemblies
• Match the L-rating (trip temp), shape (elbow vs straight), and connector style to your existing link
• Common applications: First Co, Rheem RHFM/RHGL, Goodman ARUF/AWUF, Trane TWE/TUE, Carrier FB4A/FE4A air handlers with heat strips

What does L333° mean on a temp fuse link?

The L-rating is the trip temperature in Fahrenheit. L333° trips at 333°F. Common ratings: L235°, L257°, L300°, L333°, L377°, L438°, L468°. Match your unit's data plate exactly — these are not interchangeable.

Why does my temp fuse link keep blowing?

On electric heat strips: usually restricted airflow — clogged filter, dirty blower wheel, undersized return, closed-off supplies. The strips overheat without enough air moving across them. On gas furnaces: usually flame impingement from a cracked heat exchanger, misaligned burners, or wrong manifold pressure. Fix the root cause; don't just keep swapping links.

One-time vs resettable — which do I need?

Look at what your existing link is. One-time ceramic / non-ceramic links are SAFETY devices designed to fail permanently — they're catastrophic-failure protection. Resettable breakers are convenience devices for short-cycling. They're NOT interchangeable; match what your equipment was designed for.

Can I bypass the fuse link with a jumper wire?

No. The fuse link is a safety device — bypassing it can cause fires, melted ductwork, CO production from incomplete combustion, or worse. If yours is blown, replace it. Period.

How do I tell if the fuse link is blown?

Use a multimeter on continuity / resistance mode. A healthy link reads near 0 ohms (closed circuit). A blown link reads infinite / OL (open circuit). Visual inspection helps too — blown links often have a visible gap or melted appearance.