Issue link: http://iaqnet.uberflip.com/i/637209
Standard for Measuring Residential Dryer Exhaust Duct Performance The NADCA Standard • 2014 17 Conditions That May Cause Performance Issues The NADCA Dryer Exhaust Duct Performance (DEDP) Test shall be performed on dryer exhaust ducts that have been visually inspected and confirmed to be clean. The primary function of the performance test is to capture airflow (velocity) and back pressure data combined to determine if the values are within an acceptable range. If the performance test results are below minimum values, there are numerous conditions that may be affecting the outcome. A series of common issues are listed below. This list does not imply that the dryer exhaust contractor must perform some or any of these services. The list does identify most conditions that may be further impacting performance. These are conditions and areas of concern that should be addressed if the NADCA Dryer Exhaust Duct Performance (DEDP) Test results are below minimum values. Many of these items are not the direct responsibility of the dryer exhaust duct service provider. Deficient conditions that may be presented after servicing and noncompliance might include: o The dryer vent pipe developed length is too long in accordance with manufacturer's specification. o The dryer exhaust duct is using a wall cavity as a riser. o The dryer exhaust duct has too many elbows restricting air flow. o The longitudinal seams on the dryer vent snap lock pipe are leaking air. o Elbow and connection joints are leaking or are non-taped. o The termination barrier screen (bird/rodent guard) is too restrictive (it is assumed the technician has serviced this correctly before the test). o The termination device damper is too small. o The termination device damper is restricted by its installed location. o Moisture is condensing on the inside of the dryer exhaust duct and accumulating within the ductwork. o The dryer exhaust duct is pitched incorrectly. o Lint combined with water in the duct has solidified into a cementitious mass that cannot be removed with direct agitation and requires advanced procedures. o The dryer exhaust duct may still be blocked or crushed after servicing procedures were performed. (Recommend to video scope or physically dismantle the ductwork to identify the cause) o Non-code compliant duct materials. Appliance Exhaust Performance The dryer exhaust duct discharge velocity at the termination device may be measured with the dryer appliance in its final installed position and operating empty in the non-heat mode. This information can be used to determine if a significant pressure differential exists between the appliance and the test device. In the event there is a significant pressure differential, the dryer appliance should be evaluated for proper operation by a qualified service provider. This measurement provides supplemental data to the NADCA Dryer Exhaust Duct Performance (DEDP) Test and is not a requirement of this Standard. APPENDIX