Aprilaire 6908 Installation guide

Brand: Aprilaire

Model: 6908

Type: Installation guide

NOT CORRECT

ZONE CONTROL SYSTEM

MODEL 6908, 6910, 6912, 6914 AND 6916 BAROMETRIC BYPASS

DAMPER INSTALLATION INSTRUCTIONS

CAUTION: Sharp edges may cause serious injury from cuts. Use care when

cutting and handling ductwork.

1. IDENTIFY BYPASS DAMPER POSITION IN SYSTEM

Identify where the bypass damper is to be installed. The bypass damper must be

located downstream of any heating or cooling components and upstream of all

zone dampers.

The damper may be installed in a horizontal or vertical (upflow) position. It is

recommended that the damper be installed horizontally. The location of the

damper should allow for clearance around the

balancing mechanism for free rotation.

2. INSTALL THE BALANCING

MECHANISM

Install the balancing mechanism collar on

either end of the damper blade shaft and lock

in place with bolt provided. Based on the

damper orientation, move the balancing

mechanism to the position appropriate for the

orientation of discharge (see Figure 1). Lock

into place with the nut provided.

3. INSTALL THE DAMPER TO THE DUCTWORK

 Install the damper with crimped end downstream.

 For horizontal installation, rotate the damper

such that the damper blade shaft is parallel to

the floor and located above the damper

centerline (see Figure 2).

 Secure the damper to the duct with ½” long, #8

or #10 sheet metal screws (not included).

 Insulate the damper. Leave clearance for free

rotation of the balancing mechanism.

Figure 1 - Install the Balancing Mechanism

Figure 2 - Horizontal Installation

CORRECT

4. ADJUSTING THE WEIGHTS

A barometric damper maintains a relatively constant pressure drop across itself

until the point that the blade is fully open.

A. Ensure all zone dampers are fully open and that the filter is clean (replace if

necessary).

B. Screw the weights on the balancing mechanism as close to the collar as

possible.

C. Turn on the system blower at high speed. You may need to make a cooling

call to do this. If the outside temperature is below 50°F, do not turn on the

compressor. Disconnect power to the condensing unit by switching off the

circuit breaker or removing the fuse before making a cooling call.

D. Move the weights outward until the barometric damper blade fully closes, then

move the weights out an additional ¼” to ½”.

E. If the damper is installed between the supply and return plenum, then the

pressure drop across the damper is approximately equal to the system

pressure.

The barometric damper will open and close to try and maintain this pressure

drop when individual zones are calling. The blade will open more when a

smaller zone is calling and less when a larger zone or combination of zones is

calling.

F. To ensure that you are not bypassing too much air

, make a heating or

cooling call (depending on outdoor temperature conditions) from the smallest

zone (i.e. the one with the smallest zone damper). After five (5) minutes,

measure the supply air temperature and ensure it is within normal operating

limits. In the cooling mode, the supply air temperature should be above 40-

45°F. In the heating mode, the air supply temperature should be below about

150°F. Refer to the HVAC equipment manufacturer literature or contact the

equipment manufacturer to find out what the limits are. If the supply air

temperature is not within normal operating limits, move the weight further

down the threaded rod to reduce the bypass air.

B2203198B

10006029

Aprilaire 6908 Installation guide

Aprilaire 6908 Installation guide

Aprilaire 6908 Installation guide

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