8” Start Collar w/ Damper

507DR88 8 Inch Start Collar with Damper is an HVAC air-distribution fitting designed to connect compatible ductboard to 8-inch round ductwork. Its integrated damper provides a convenient way to adjust the airflow moving through the connected duct branch during system setup and balancing.

This start collar is identified as model 507DR88 and is designed for compatible 1½-inch or 2-inch ductboard. Before ordering, verify the ductboard thickness, required duct diameter, planned connection location, and airflow requirements of the complete HVAC system.

507DR88 8 Inch Start Collar with Damper Features

The 507DR88 8 Inch Start Collar with Damper combines a round duct connection and an airflow-control component in a single fitting. It creates a starting point for an 8-inch duct branch while allowing airflow through the branch to be adjusted.

• Model number: 507DR88
• Nominal connection diameter: 8 inches
• Designed for compatible 1½-inch ductboard
• Also designed for compatible 2-inch ductboard
• Integrated damper for airflow adjustment
• Connects compatible round HVAC ductwork
• Suitable for air-distribution applications
• Useful for new installations and replacement projects

The collar forms the transition from the ductboard surface to the round duct branch. Correct positioning, fastening, and sealing help create a stable connection and reduce unwanted air leakage around the opening.

Integrated Airflow Damper

The damper included with the 507DR88 8 Inch Start Collar with Damper allows airflow through the connected branch to be adjusted. This feature can support HVAC system balancing when different rooms or areas require different amounts of supply or return air.

A damper should not be used to compensate for incorrectly sized ductwork. The duct branch, collar, register, grille, and other fittings must be selected according to required airflow and the static-pressure limitations of the complete system.

Damper position should be adjusted carefully during system startup or balancing. Excessive restriction can increase static pressure, reduce delivered airflow, create operating noise, and negatively affect comfort in the connected area.

After adjusting the damper, verify that air continues to move properly through the branch. The damper mechanism should remain accessible whenever possible so future inspections and airflow adjustments can be completed without dismantling the duct system.

Designed for Compatible Ductboard

The 507DR88 8 Inch Start Collar with Damper is listed for use with compatible ductboard measuring either 1½ inches or 2 inches thick. Confirm the actual thickness and condition of the ductboard before cutting the installation opening.

The mounting surface must be strong enough to support the collar and the connected duct. Do not install the fitting on wet, damaged, deteriorated, or structurally weak ductboard because it may prevent the collar from remaining properly secured and sealed.

The collar location should support a short and efficient duct route. Consider seams, reinforcements, fasteners, nearby duct connections, equipment panels, structural components, electrical wiring, and plumbing before selecting the opening location.

Installing the 507DR88 Start Collar

Before installing the 507DR88 8 Inch Start Collar with Damper, verify the planned position and make sure there is enough clearance for the fitting, damper mechanism, connected ductwork, insulation, and sealing materials.

Mark the opening carefully using the correct template or fitting dimensions. Cut the ductboard with tools appropriate for the material and remove loose fibers, sharp edges, and debris from the surrounding area.

Position the collar evenly inside the prepared opening. Secure it according to the applicable ductboard and fitting installation requirements. The completed connection should remain stable without crushing, tearing, or excessively compressing the ductboard.

Seal the complete perimeter of the collar using an approved HVAC sealing product compatible with ductboard. An airtight connection helps prevent conditioned-air loss and limits unfiltered air from entering a return-air system.

Follow all applicable mechanical codes and approved ductboard installation practices. The exact fastening and sealing method may vary according to the ductboard construction, HVAC application, and local requirements.

Connecting Flexible Round Duct

When connecting flexible duct to the 507DR88 8 Inch Start Collar with Damper, pull the flexible inner core completely over the round collar. Secure the core using an approved clamp, band, or fastening method and seal the inner connection.

Pull the insulation back over the completed connection without leaving exposed gaps. Secure and seal the outer vapor barrier around the collar according to the flexible duct manufacturer’s installation instructions.

Flexible duct should follow a smooth and direct route without sharp bends, excessive compression, twisting, unnecessary length, or unsupported sections. These conditions can increase resistance and reduce airflow through the 8-inch branch.

Connecting Rigid Round Duct

When connecting rigid round duct, align the duct and collar properly before fastening the components together. Use approved mechanical fasteners and seal the full circumference of the joint with HVAC-approved mastic, sealant, or listed tape.

Rigid duct sections must be independently supported. The start collar and ductboard surface should not carry the complete weight of long ducts, heavy fittings, transitions, or other air-distribution components.

Inspect the inside of the connection before operating the system. Confirm that screws, excess sealant, or duct edges do not interfere with the movement of the integrated damper.

Airflow and System Compatibility

An 8-inch duct connection is not suitable for every HVAC application. Required duct diameter depends on airflow demand, duct length, fitting resistance, blower performance, static pressure, and the requirements of the connected room or area.

The 507DR88 8 Inch Start Collar with Damper should be selected as part of a complete air-distribution design. Do not determine compatibility only by comparing the collar diameter with existing ductwork.

A qualified HVAC professional can calculate the required airflow and determine whether an 8-inch branch is appropriate. The technician can also adjust the damper while measuring airflow and system static pressure.

Inspection and Maintenance

Inspect the start collar during routine HVAC maintenance. Check for loose connections, damaged ductboard, deteriorated sealant, air leakage, unusual vibration, corrosion, and obstructions around the damper.

Whistling, rattling, or excessive airflow noise may indicate an air leak, restriction, loose fitting, incorrect damper position, or duct-sizing problem. Evaluate the complete duct branch before making additional adjustments.

Professional Installation Recommended

Professional installation of the 507DR88 8 Inch Start Collar with Damper is recommended. Correct placement, fastening, sealing, support, duct sizing, and damper adjustment are essential for dependable airflow and system performance.

This product includes the start collar and integrated damper. Flexible duct, rigid duct, clamps, fasteners, sealants, insulation, supports, and other installation materials may be sold separately. Confirm all required components before ordering.

Browse additional fittings and air-distribution products in the Xpress Supply Ducting & Venting category. For general heating, cooling, and energy-efficiency information, visit the U.S. Department of Energy Energy Saver.