2-Wire Smoke and Heat Detector

Average rating:

(based upon one review)

The ESL 521BXT provides smoke and heat detection. It is a 2-wire dual-purpose smoke and heat sensor that is great for residential application. The device uses photoelectric technology to detect smoke, it uses rate-of-rise and fixed temperature for heat. Buy the ESL 521BXT from Alarm Grid.

This product has been discontinued and is no longer in stock.


The ESL 521BXT is a 2-wire smoke and heat detector that works with the NetworX Alarm Control Panels. The 521BXT has a photoelectric smoke detector and a fixed temperature and rate-of-rise heat detector. It is a great hardwired life-safety and fire-protection sensor for residential use.

The photoelectric smoke detector uses an internal light to determine whether or not smoke is in the area. Smoke will cause the light to refract, and the sensor will respond to this change. The rate-of-rise sensor responds to temperature increases of 15 degrees Fahrenheit or higher in a single minute. The fixed temperature sensor actives at 135 degrees Fahrenheit or higher. The sensor measures 5 inches in diameter and has a thickness of 2 inches.

Brand: ESL

Great NetworX Smoke Detector
Submitted on 05/29/2020 Alarm Grid

2-wire smoke detector zone. The unit is a photoelectric smoke detector, and its heat sensor offers both fixed temperature detection and rate of rise temperature detection. The fixed sensor will activate at 135 degrees Fahrenheit or higher, and the rate of rise sensor requires a temperature increase of 15 degrees or higher in a single minute. The sensor has been discontinued, so it can no longer be purchased from Alarm Grid. But we still like this sensor if you are able to find it somewhere else. That is why we give the ESL 521BXT a 5 Star rating.

There are many things to like about the ESL 521BXT. For one, it offers both fixed temperature and rate of rise detection, which is good for ensuring that a fire is properly detected. Since this is a 2-wire smoke detector, you don't need any extra equipment, such as a relay and an external power supply. The smoke and heat detector is reliable, and it has a strong build quality. It is great for anyone with a compatible NetworX System looking to add fire detection. And we like the fact that this is a photoelectric smoke detector, as they are the most reliable.

There are some downsides to the ESL 521BXT that should be kept in mind. The smoke detector is discontinued, and it can no longer be purchased from Alarm Grid. As a 2-wire smoke, it can only be used at the designated 2-wire smoke zone on a NetworX Panel. It cannot be used at a different zone. Also remember that it can only be used with NetworX Panels. You will not be able to use this smoke detector on a different hardwired panel, such as a Honeywell VISTA Panel or a DSC PowerSeries Panel. But these downsides are relatively minor, so we still give the ESL 521BXT a 5 Star rating.

Good: Fixed & RoR Temperature Detection, Photoelectric, No Extra Equipment Needed, Reliable, Good Build Quality

Bad: Discontinued, Only Works @ Designated 2-Wire Smoke Zone, For NetworX Only

Bottom Line: 5 Stars

* Based on a 10% APR with 12 months financing. APR's will vary between 10% - 30% based on credit score and various factors.