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DEDPVs Vs. Duct Boosters: What Builders Need to Know
Reading time: 2 minutes
Safety
Lint ignition in dryer ducts is a serious safety issue, responsible for about 16,000 annual dryer fires in the U.S. each year, according to the National Fire Protection Association. Cleaning the lint screen isn’t enough, as lint can still get through and build up in the ductwork. If homes have long dryer duct runs, installing a mechanical solution - dryer exhaust ventilation - can help more lint escape to the outside. However, some builders have concerns about using dryer exhaust solutions, due to instructions from some dryer manufacturers. Understanding the differences between DEDPVs and duct boosters is an important first step.
Are Duct Boosters Allowed?
You may have been advised against installing a "duct booster" or “dryer booster” by dryer manufacturers. These boosters are not listed under the UL 705 Standard for Safety Power Ventilators. They are not designed specifically for residential clothes dryers and, therefore, may lack important features, such as a pressure switch to sense when the dryer is on and an indicator panel to indicate proper operation automatic shutoff. What UL does recognize are “dryer exhaust duct power ventilators,” such as the DEDPV-705. This solution has a similar function as duct boosters - to increase the flow of air in the duct - but is designed and engineered for the unique needs of the dryer environment.
Dryer Exhaust Under UL 705
In 2012, UL together with CSA developed a supplement to UL Standard 705, Standard for Safety Power Ventilators, that specifically addresses the safety and performance of ventilators used to facilitate proper dryer exhaust and gave the product a new name: Dryer Exhaust Duct Power Ventilator (DEDPV). Consequently, both the 2015 and 2018 International Residential Code and International Mechanical Code require dryer exhaust fans to comply with the UL 705 supplementary addendum for Dryer Exhaust Duct Power Ventilators. The National Building Code of Canada must comply with CSA DEDPV standard 22.2 No. 113-15.
The UL testing standards for DEDPVs help ensure that dryer exhaust ventilators can safely and effectively assist in the ventilation of a residential-capacity dryer. The standard’s tests prove functionality of required safety features, provisions for maintenance, proper air velocities for lint management, etc.
Building inspectors and local code criteria can now require “UL Listed” or “CSA Certified” DEDPVs for installations in their communities, and architects and engineers can specify the same for their projects.
Commentary on the 2015 International Residential Code noted: “Exhaust ducts that exceed the developed length allowed by code are a potential fire hazard, create maintenance problems, increase drying times and cause the dryer to be inefficient and waste energy. Dryer exhaust systems are commonly installed improperly with excessive lengths, too many elbows and the wrong duct materials. Because of the high incidence of reported dryer fires, the code strictly regulates the installation. DEDPVs are listed to a revised version of UL 705 that now contains tests and construction requirements that are specific to these devices. DEDPVs have been around for years, but until recently, were not listed to a national consensus standard that was specific to these devices. The UL 705 standard contains requirements for the construction, testing and installation of DEDPVs and requires them to be equipped with features such as interlocks, limit controls, monitoring controls and enunciator devices to make certain that the dryers or dryer operators are aware of the operating status of the DEDPVs.”
According to some dryer installation instructions and local building codes, adding fans listed to the DEDPV standard are required when the length of the duct run exceeds 35 linear feet. The maximum length of the exhaust duct shall be determined by the dryer exhaust duct power ventilator manufacturer’s installation instructions.
Specifying Dryer Exhaust Duct Power Ventilators
DEDPVs differ from other dryer booster fans in several ways:
DEDPV fan housings must be manufactured from metal, never plastic.
A DEDPV must also shut down in the event of a dryer fire, so as not to facilitate the spread of fire in the home.
A DEDPV must automatically energize when the dryer is operated.
An integral pressure switch is used to sense dryer operation and energize the fan.
A DEDPV must indicate proper fan operation to the dryer operator as well as notify the dryer operator in the event of a fan failure.
DEDPV-705 was the industry’s first dryer exhaust duct power ventilator to be listed to UL-705 standards for both gas and electric residential clothes dryers. DEDPV-705 maintains an exhaust air velocity ideal for keeping lint entrained in the flow of air during its journey to the outside, thereby minimizing the risk of fire due to lint buildup. The unit continues to operate for a short time after the dryer stops, which cools the clothes, and it removes humid air from the dryer and ducting.
Just as important, DEDPV-705 provides visual indication of proper operation and also alerts the homeowner of potential problems such as a locked rotor or duct blockage. This advanced warning allows the user to take action to clean the dryer exhaust duct or seek service.
The Candian equivalent, DPV22-2, is certified by CSA to the DEDPV requirements of C22-2.
Installers also must add a secondary lint trap in addition to the traditional lint screen, inside the dryer. The secondary trap collects additional lint, which can lessen the task of cleaning out the exhaust duct. Builders and remodelers should be sure to educate customers on regular maintenance, including cleaning the secondary lint trap as frequently as the dryer lint screen.
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DEDPV-705
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DPV22-2
To learn more about dryer exhaust, visit our FAQs page or contact your Fantech representative.
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