This may be better suited for the Software discussion; if so, let me know:

I'm trying to model a Westinghouse Current Limiter LFB3070R. It attaches onto the load side of an old Westinghouse breaker, and presumably lowers the current. The device doesn't seem to show up in the library of my software (EasyPower), and I can't find any info online about how it works.

I was going to ignore it since it's a (480V, 3 phase) 20a breaker feeding a small heater....but of course, the breaker is only rated for 14kA and the AFC is higher than that. I'm assuming/hoping the current limiter will keep the AFC down to acceptable levels, but since I can't find any info on how the thing works, I'm not sure how to model it. Any ideas?

From Google AI:
LFB3070R "series rated" current limiting fuse
The LFB3070R is a current limiter module designed to be used in a "series rated" combination with specific molded case circuit breakers. It is not a standalone fuse, but an accessory that increases the overall short-circuit interrupting rating (AIC) of the breaker it is installed with.
LFB3070R overview
Manufacturer: Westinghouse, which later became part of Eaton/Cutler-Hammer.
Function: It is a 15-70 Amp, 3-pole, 600 VAC current limiter for use with FB-series circuit breakers.
Mounting: The LFB3070R bolts onto the load side of a standard FB circuit breaker to increase its interrupting capacity.
Interrupting capacity: When used in a series-rated setup, this module can raise the combination's interrupting rating to 200,000 AIC (Amperes Interrupting Capacity).
How "series rated" works
A series-rated system involves two or more overcurrent protective devices (OCPDs) connected in series that have been tested and certified by a Nationally Recognized Testing Laboratory (NRTL) to work together safely.
Higher interrupting rating: The combination of devices can be applied where the available fault current is higher than the interrupting rating of the downstream OCPD alone. The upstream device, typically with a higher individual interrupting rating, assists in clearing the fault.
Upstream protection: In a series-rated system, the LFB3070R acts as the "upstream" protector to the standard FB circuit breaker. For high-level fault conditions, the LFB3070R's current-limiting fuses melt, effectively dissipating the energy and limiting the peak current that the downstream breaker must handle.
Cost efficiency: Series-rated systems are often used for cost savings because they allow for the use of less expensive, lower-interrupting-rated circuit breakers downstream.
Labeling and limitations: The panelboard or electrical enclosure must be clearly marked by the manufacturer to indicate the specific tested combination of devices. There are also limitations on using series ratings where motor loads are connected between the protecting and protected devices.
Note: For a critical system where high-level fault conditions could cause a main device to open and kill power to an entire panel, a fully-rated system is generally preferred over a series-rated one.
AI responses may include mistakes.

As Stevenal points out the 14k FB breaker has a series rating of 200k when used with the limiter so you're good there. As far as ignoring it goes, this goes back to your earlier thread about how far do you take it. Unless the heater had a control panel or a disconnect switch that you needed or wanted to label, I would ignore it if I were modeling. A heater has no fault contribution and if no label is required then no reason for me to include it.

RE: Modeling, I cannot help you with EasyPower but here is how I would model it in SKM if I needed to. The limiter is in the SKM fuse library and looking at the device online it looks like it is a one-and-done fuse module that needs to be replace if it blows.

And the curves:

Ah, thanks guys! In all the research I did, I didn't see the word "fuse" or "element" mentioned anywhere....but it makes sense to treat it that way, since it's good for one use only. And sure enough, while EasyPower doesn't have the Westinghouse Current Limiter in its library, it does include the Cutler-Hammer version. Much appreciated!