Is there a pin-compatible replacement for FTR14D391K?

While several candidates share the 2-pin radial disk package, none match the critical 4500A surge current rating of the FTR14D391K. They are not electrically equivalent for pin-to-pin replacement.

What risks should I check before replacing FTR14D391K?

The main risk is insufficient surge protection. Using a part with a lower surge current (e.g., 400A vs 4500A) or energy rating can lead to premature failure of the varistor and the circuit it protects.

FTR14D391K Alternatives, Datasheet & Cross Reference | FTR Qiaoguang

FTR14D391K is a 14mm, 390V varistor from FTR for overvoltage protection. Finding a direct replacement requires matching its high 4.5kA surge current rating, a key challenge for most alternatives.

AI replacement insight

Electrical riskhigh

Candidates have critically lower surge current ratings (400A-1.2kA vs 4.5kA).

Package risklow

Candidates are also radial leaded disks, but smaller size impacts thermal and surge performance.

Can it be replaced directly?

No direct, fully equivalent replacement was identified. All reviewed candidates have significantly lower surge protection capabilities, posing a high risk if substituted without analysis.

Best replacement path

Search for 14mm disk varistors with a ~390V varistor voltage and a surge current rating of 4.5kA or higher.

Main risk

Inadequate surge current and energy handling capability, which could lead to failure of the varistor and damage to the protected circuit.

Recommended alternatives

Matches varistor voltage but has significantly lower surge current and energy handling capability.

View details

Alternative comparison matrix

Feature / factor	FTR14D391K	VDR-05D391K	VDR-07D431K	Compatibility / risk
Voltage	390V (351V~429V)	390V (351V ~ 429V)	430V (387V~473V)	390V (351V ~ 429V) / 430V (387V~473V) — Varistor voltage matches.; VDR-07D431K: Varistor voltage is ~10% higher.
Current	4500A	400A	1.2kA	400A / 1.2kA — Peak surge current is critically lower.; VDR-07D431K: Peak surge current is critically lower.
Power	100J	12J	-	12J — Energy rating is critically lower.
Package	14mm	5mm	7mm	5mm / 7mm — Disk diameter is much smaller, affecting power dissipation and surge rating.; VDR-07D431K: Disk diameter is smaller.

Application & sourcing insights

Questions & answers

No direct drop-in replacements were found. Candidates like VDR-05D391K match the voltage but have much lower surge ratings (400A vs 4500A), requiring careful circuit analysis before use.