3V8
3V8 | |
![]() A 3V8 in Lowndesville, SC. Photo taken by Christopher J. (TrainsAndSirens1) | |
Company | Sentry Siren, Inc. |
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Produced | 1980-present |
Type | Omnidirectional Electromechanical |
Sound output | 107-109 dB @ 100 ft |
Frequency | 60 Hz |
Horsepower | 5 hp |
Voltage | 208-230/460 V AC 1 or 3 ph |
Preceded by | |
Documentation | Product sheet |
The 3V8 is a small omnidirectional siren produced by Sentry Siren, Inc. It is the smallest siren in Sentry's lineup, as well as the cheapest. It has been a mainstay in Sentry's catalogue since its introduction and has seen use in many places for a wide variety of purposes.
History
The 3V8 was introduced in 1980 as part of Sentry's 1980 lineup, which also included the 5V, 10V, and 20V2T, following the success of the earlier 10V2T. The 3V8 is the smallest of that lineup, and is intended for short range use, often by industrial sites or fire stations. As early as the year 1999, a variant of the 3V8 named the 3V8-H was offered with 8 flat-ended horns attached to the stator ports instead of a skirt. In 2003, the Centennial Correctional Facility in Canon City, CO, needed a siren to warn of prison escapes and other serious situations at the facility. Because the facility was relatively small (at 40 acres) and was made of sound-deadening thick concrete, Sentry's standard sirens did not cut it. As a result, Sentry created the 3V8-HC, a variant of the 3V8-H with the 40V2T's pointed horns. It is unknown if this siren is still in service, and only 1 was ever built. The 3V8-HC can be seen as the predecessor to modern 3V8-H units, as in the 2010s the standard 3V8-H gained pointed horns similar to the 3V8-HC's, albeit at a steeper angle. In 2015, the battery-backup variant of the 3V8 was introduced, named the 3V8-H-B. The 3V8 is still in production by Sentry to this day and is a popular option with fire departments and small towns which lack the budget or need for larger sirens. The standard skirted 3V8 is the most popular option due to its low price, though the 3V8-H is also quite common. The 3V8-H-B on the other hand is uncommon due to being new, and its additional cost not being justified by its performance versus Sentry's larger DC offerings such as the 16V1T-B and 14V-B.
Design
3V8
The 3V8 uses a small 8-port rotor and stator which is borrowed from the Sterling Model M, which is driven by a 5 hp AC motor. Like all of Sentry's single rotor sirens, the 3V8's design is very basic, with the rotor and stator being attached to a 6-legged mount which has a cone to project the sound from the intake outwards. The motor itself is placed inside a weatherproof housing, and the siren comes standard with a skirt above the rotor and stator to direct sound outwards. This simple design allows the siren to be both cheap and easy to maintain. The rotor, stator and intake are protected by mesh screens to keep debris out. The 3V8 is available in either 1 or 3 ph AC, with 1 ph units using a centrifugal regenerative brake which slows the rotor down rapidly when the rotor reaches a low enough rpm in order to recharge the motor's capacitor. 1 ph units can be visually distinguished from 3 ph units by their taller motor housings. The siren is able to reach 107 dB at 100 ft. While the siren is normally made of steel by default, Sentry also offers corrosion resistant stainless steel or painted fiberglass (designated as the 3V8-F) housings as an option.
3V8-H
The 3V8-H is a variant of the 3V8 with 8 horns attached to the stator ports instead of a skirt. While the 3V8-H is slightly more expensive, the horns increase the siren's performance to 109 dB at 100 ft. Each horn has a screen to help keep debris out. With the exception of the horns, the 3V8-H is identical to the standard 3V8. These horns make the siren very similar in appearance to the 7V8, but shorter in height due to the 3V8's smaller rotor.
3V8-H-B
The 3V8-H-B is the DC alternative to the 3V8, running on a 4 hp 42 V DC motor rather than a 5 hp AC motor. This allows the siren to run on battery backup if AC power is lost and is rated to run approximately 30 minutes after power is lost. The 3V8-H-B comes with horns as standard and is not offered with a skirt. It uses the same motor housing as the three phase 3V8. The 3V8-H-B can be distinguished by sound from the other 3V8 models by its rapid non-linear windup. It is otherwise identical to a standard 3V8-H, with the same performance.
3V8-HC
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The 3V8-HC is a custom siren built for the Centennial Correctional Facility in Canon City, CO. The 3V8-HC is identical to the 3V8-H but features the horns used on the 40V2T, with each of the siren's 8 horns being significantly pointed at the top. This helps disperse the sound both outwards and downwards to penetrate the thick sound-deadening concrete used by the Centennial Correctional Facility. The siren is otherwise identical to a standard 3V8-H. Only 1 3V8-H-C was ever built.
Gallery
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A 3 ph 3V8-H, located in Stow, OH. Photo taken by Fumikiri06.
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A 3V8-H-B in Frenchburg, KY. Photo taken by Tristan G.