Do duct detectors go in supply or return?

The International Mechanical Code requires a duct smoke detector in the return for units over 2000 cfm and requires a detector in the supply duct for systems over 15,000 cfm. Many designers require duct detectors in the supply and return in an attempt to meet both conflicting requirements.

Where do you put a duct smoke detector?

Installation guidelines Install the duct smoke detector on a flat section of HVAC duct between six and ten duct widths from any bends or obstructions. Install supply-side detectors at a point downstream from the supply fan and after the air filter.

Are duct smoke detectors required on exhaust fans?

Return system smoke detectors are not required where the entire space served by the air distribution system is protected by a system of area smoke detectors. Smoke detectors are not required in exhaust ducts.

How does a duct smoke detector work?

How Do They Work? Duct detectors sample currents in the air handling equipment to determine if smoke or fumes are present. If smoke is detected, the device will close dampers, stop fans and blowers, and trigger an audible and visible signal at the fire control panel, Kapparos explains.

Are duct detectors required to be monitored?

Bottom line is if a building fire alarm system is not installed, duct smoke detectors shall be stand alone and are not required to be connected/monitored by a dedicated function fire alarm system.

What is the largest return air opening that can be protected with a single smoke detector?

2,000 cfm
Smoke detectors shall be installed in return air systems with a design capacity greater than 2,000 cfm (0.9 m3/s), in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.

How far does a smoke detector have to be from a vent?

NFPA 72 recommends that they should not be installed closer than 3 feet from any supply air diffuser or return vent. If they are too close to the supply, smoke may not reach the detector. Also, the air coming out of the vent contains dust and dirt, which can settle in the detector and cause nuisance alarms.

How far does a smoke detector have to be away from a vent?

Do duct detectors need to be monitored?

Are duct detectors life safety?

Therefore, duct smoke detectors are typically considered mechanical equipment devices instead of life safety devices. Both the IMC and NFPA 90A state that, if multiple air handlers serve the same area and the combined air volume is greater than 2,000 cfm, detectors are required.

Can a duct penetrate a fire wall?

The duct shall not terminate at a wall register in the fire-resistance-rated wall. Such walls are penetrated by ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3. 1.1 or 903.3. 1.2.

When are duct detectors needed?

Duct smoke detectors, when installed in HVAC systems, automatically stop their respective fans upon the detection of smoke. For HVAC systems with airflows exceeding 2,000 cfm, duct smoke detectors are required.

Where is the duct detector located?

Duct detectors located on the return side and upstream of any filters or introduction of outside air detect smoke coming from an air conditioned space. This eliminates interference caused by outside smoke or heat-strip dust-accumulation burnoff.

What is HVAC duct detector?

Duct Detectors. Duct detectors are devices installed on ventillation systems ducts that detect the presence of smoke and send out a trouble signal when activated, while shutting down the hvac unit the duct is attached to. In the past these units used to generate alarms, but due to high false alarms, they now are required to send troubles.