Dryer Booster Fans White Paper

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A new name for Dryer Booster Fans
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in dryer applications. The tests confirm key safety features and operation,
including redundant safety circuits, adequate air velocities, temperature
sensing mechanisms, cleanout access, etc. These tests go well beyond the
UL standards that were once imposed on dryer booster fans. And while
they may not be required by building codes yet, eventually most if not all
jurisdictions will require the UL marking for fans used in this application.
The primary differences between DEDPVs and other dryer booster
fans are:
1. Under normal operating conditions, the LED panel of a DEDPV, which
should be prominently displayed in a laundry room, will illuminate
when the fan is in operation. This steady state illumination should
correspond with the operation of the dryer for the duration of the cycle.
If the temperature of the exhaust duct rises above a normal operating
temperature of 165°F, the fan will sense this increase and will turn the fan
off. This response cuts off the air supply to the duct, thus starving a fire
should one exist.
2. DEDPV fan housings are made of metal, never plastic.
3. DEDPVs must provide at least one of the following:
a. A means to sense the operation of the clothes dryer, which
automatically turns on the DEDPV. Ventilators using this method must
also include a means to operate a visual indicator and/or audible alarm
to notify the user if the ventilator fails to start. This indicator and/or
alarm must be provided as part of the notification panel that is to be
permanently mounted in the laundry space.
b. An interlocking device that prevents the clothes dryer from being
energized if the DEDPV fails to operate as intended. This method
requires an electrician for installation, adding to the installation cost.
Also, if the homeowner replaces the dryer in the future, they or the
installer must ascertain that the interlocking device is compatible with
the replacement appliance.
Proper Installation of DEDPVs
Although it may be a while before state and local building codes adopt the
latest UL standard for these products, at least one manufacturer has received
approval for a DEDPV. With such products freshly on the market, it is
important that both builders and installers understand a few key points about
their application and operation:
• DEDPVs must be installed at appropriate distances from the dryer and
from the dryer exhaust outlet. Typically this will be a few feet from the
dryer and up to 40 feet from the exhaust outlet. However, these minimum
and maximum allowable lengths are a function of the fan performance, so
installers must refer to the DEDPV manufacturer’s installation instructions
for exact lengths.
• DEDPVs must be installed so that they are fully accessible for
maintenance. Fan impellers can in some cases accumulate lint and should
be checked and/or cleaned every six months, so their location should
allow for reasonably easy access. If this is not possible, a secondary lint
trap can be installed in a more accessible location.
• The indicator panel must be permanently installed within the laundry room
space and readily visible to the homeowner or operator at all times. The
DEDPV must also be used in accordance with the dryer appliance.
• DEDPV operation is always required with the operation of the dryer.
The two are not meant to operate independently of one another.
• Finally, not all dryers are suitable for use with a DEDPVs. Compatibility
must be confirmed with the dryer manufacturer. Specifically, the DEDPV
airflow should not exceed the dryer fan capacity, otherwise dryer fan
cavitation could result.
The interrelated sequence of codes and UL listings has created confusion
about the application of dryer booster fans. But builders can take heart in
the fact that homeowner preference for laundry room location need not be
compromised to meet code – at least not in most jurisdictions. Dryer booster
fans may be applied when exhaust duct length exceeds the limits set by the
IRC.
Those who are conscientious of the latest safety standards for ventilation
equipment also have a choice - UL-listed DEDPV products.